Raychem Surface Snow Melting
Surface snow melting – MI
Mineral insulated Heating
Cable System
This step-by-step design guide provides the tools necessary to design a Raychem
Mineral Insulated heating cable surface snow melting system. For other
applications or for design assistance, contact your Pentair Thermal Building Solutions
representative or phone Pentair Thermal Building Solutions at (800) 545‑6258. Also,
visit our web site at www.pentairthermal.com.
Contents
Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
How to Use this Guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Safety Guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Warranty . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
System Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Typical System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
MI Heating Cable Construction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
MI Heating Cable Configuration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Approvals. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Surface Snow Melting Applications. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Surface Snow Melting Design. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Design Step by Step. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Step 1 Determine design conditions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Step 2 Determine the required watt density . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Step 3 Determine the total area to be protected. . . . . . . . . . . . . . . . . . . . . . 10
Step 4 Select the heating cable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Step 5 Determine heating cable spacing. . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Step 6 Determine the electrical parameters. . . . . . . . . . . . . . . . . . . . . . . . . 24
Step 7 Select the control system and power distribution. . . . . . . . . . . . . . . 26
Step 8 Select the accessories. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
Step 9 Complete the Bill of Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
Raychem MI System Surface Snow Melting Design Worksheet . . . . . . . . . . . . . . . . 37
Introduction
The Raychem Mineral Insulated (MI) heating cable system is designed for surface
snow melting in concrete and asphalt, and under pavers.
If your application conditions are different, or if you have any questions, contact your
Pentair Thermal Building Solutions representative or contact Pentair Thermal
Building Solutions directly at (800) 545‑6258.
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Surface snow melting – MI Mineral insulated Heating Cable System
How to Use this Guide
This design guide presents Pentair Thermal Building Solutions’ recommendations
for designing a Raychem Mineral Insulated (MI) heating cable surface snow melting
system. It provides design and performance data, electrical sizing information, and
heating cable layout suggestions. Following these recommendations will result in a
reliable, energy-efficient system.
Follow the design steps in the section “Surface Snow Melting Design” on page 6
and use the “Raychem MI System Surface Snow Melting Design Worksheet” on
page 37 to document the project parameters that you will need for your project’s
Bill of Materials.
Other Required Documents
This guide is not intended to provide comprehensive installation instructions. For
complete Raychem MI surface snow melting system installation instructions, please
refer to the following additional required documents:
• Surface Snow Melting – MI Installation and Operation Manual (H57754)
• Additional installation instructions included with thermostats, controllers, and accessories
If you do not have these documents, you can obtain them from the Pentair Thermal
Building Solutions web site at www.pentairthermal.com.
For products and applications not covered by this design guide, including
installations in hazardous locations or where electromagnetic interference (EMI) may
be of concern, such as traffic loop detectors, please contact your Pentair Thermal
Building Solutions representative or call Pentair Thermal Building Solutions at
(800) 545-6258.
Safety Guidelines
As with any electrical equipment, the safety and reliability of any system depends
on the quality of the products selected and the manner in which they are installed
and maintained. Incorrect design, handling, installation, or maintenance of any of
the system components could damage the system and may result in inadequate
performance, overheating, electric shock, or fire. To minimize these risks and to
ensure that the system performs reliably, read and carefully follow the information,
warnings, and instructions in this guide.
This symbol identifies important instructions or information.
This symbol identifies particularly important safety warnings that must be
followed.
WARNING: To minimize the danger of fire from sustained electrical arcing if
the heating cable is damaged or improperly installed, and to comply with the
requirements of Pentair Thermal Building Solutions, agency certifications, and
national electrical codes, ground-fault equipment protection must be used on each
heating cable branch circuit. Arcing may not be stopped by conventional circuit
protection.
Warranty
Pentair Thermal Building Solutions’s standard limited warranty applies to Raychem
Snow Melting Systems.
An extension of the limited warranty period to ten (10) years from the date of
installation is available, except for the control and distribution systems, if a properly
completed online warranty form is submitted within thirty (30) days from the date of
installation. You can access the complete warranty on our web site at
www.pentairthermal.com.
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THERMAL Building SOLUTIONS
System Overview
System Overview
The Raychem MI heating cable surface snow melting system provides snow melting
for concrete, asphalt, and pavers. The copper-sheathed, mineral insulated heating
cables are coated with a high-density polyethylene (HDPE) jacket and are supplied as
complete factory-assembled cables ready to connect to a junction box. The seriestype technology, inherent to all mineral insulated heating cables, provides a reliable
and consistent heat source that is ideal for embedded snow melting applications.
The system includes heating cable, junction boxes, a control system and sensors,
power distribution, and the tools necessary for a complete installation.
Typical System
A typical system includes the following:
• MI heating cable
• Junction boxes and accessories
• Snow controller and sensors
• Power distribution
Power Distribution Panel
Aerial Snow Sensor
Snow Controller
Junction Box
Caution Sign
Flexible Nonmetallic
Conduit
Pavement Snow Sensor
Heating Cable
Hot/Cold Joint
Fig. 1 Typical Raychem MI system
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Surface snow melting – MI Mineral insulated Heating Cable System
MI Heating Cable Construction
Standard surface snow melting MI heating cables are comprised of a single
conductor surrounded by magnesium oxide insulation, a solid copper sheath, and
an extruded high density polyethylene (HDPE) jacket. The HDPE jacket protects
the copper sheath from corrosive elements that can exist in surface snow melting
applications.
Insulation (magnesium oxide)
HDPE jacket
Heating conductor
Copper sheath
Single-conductor
Fig. 2 MI heating cable
construction cable
Custom engineered heating cables are also available for applications outside the
scope of this design guide. For design criteria, including the maximum cable loading
(watts/foot) for installations in concrete, asphalt and paver applications, refer to
the MI Heating Cable for Commercial Applications data sheet (H56990) or contact
Pentair Thermal Building Solutions at (800) 545-6258 for design assistance.
MI Heating Cable Configuration
MI heating cables are supplied as complete factory-fabricated assemblies consisting
of an MI heating section that is joined to a section of MI nonheating cold lead and
terminated with NPT-threaded connectors. Two configurations are available for
standard heating cables:
1. Type SUA, consisting of a looped cable joined to a single 7 ft (2.1 m) cold lead
with one 1/2-in NPT-threaded connector.
2. Type SUB, consisting of a single run of cable with a 15 ft (4.6 m) cold lead and a
1/2-in NPT-threaded connector on each end. Where custom cold lead lengths
are required for the heating cables shown in Table 2, Table 3, Table 4, and
Table 5, contact your Pentair Thermal Building Solutions sales representative for
assistance.
Type SUA
Cold lead length
7 ft (2.1 m)
Heated length
NPT-threaded
connector
Type SUB
Cold lead length
15 ft (4.6 m)
Heated length
Cold lead length
15 ft (4.6 m)
NPT-threaded
connector
Fig. 3 MI heating cable configurations
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THERMAL Building SOLUTIONS
Surface Snow Melting Applications
Approvals
The Raychem MI surface snow melting system is UL Listed and CSA Certified for
installation in nonhazardous locations in concrete and asphalt, and under pavers
where the cables are embedded in concrete. For paver snow melting installations
where the heating cables are embedded in sand or limestone screenings, special
permission is required from the Authority Having Jurisdiction, e.g. the local
inspection authority.
De-Icing and Snow
Melting Equipment
421H
-PS
Surface Snow Melting Applications
SURFACE SNOW MELTING
Surface snow melting systems provide the required heat flux (W/ft2 or W/m2) to melt
snow and ice on ramps, slabs, driveways, sidewalks, platform scales, and stairs and
prevent the accumulation of snow under normal snow conditions.
Application Requirements and Assumptions
The design for a standard surface snow melting application is based on the
following:
Reinforced Concrete
Heating cable
•4 to 6 in (10 to 15 cm) thick
•Placed on grade
•Standard density
•Secured to reinforcing steel, mesh or
with prepunched strapping
•Located approximately 2 in (5 cm) below
finished surface, but not exceeding 3 in
(7.5 cm)
Asphalt
•Install on 1 in (2.5 cm) asphalt base
layer if a concrete base is used in
construction
•Placed on grade
•Secured with prepunched strapping
•Located 2 in (5 cm) below finished
surface
Pavers
•1 ½ to 2 ¼ in (4 to 6 cm) thick pavers
•Minimum 1 in (2.5 cm) limestone
screenings or sand layer
•Placed on an approved compacted
base or concrete slab
•Secured to the compacted base or concrete with mesh or prepunched
strapping
•Located in a minimum 1 in (2.5 cm) layer
of limestone screenings or sand
Nonstandard applications are not covered in this design guide, but are available
by contacting your Pentair Thermal Building Solutions representative for design
assistance. Using proprietary computer modeling based on a finite difference
program for nonstandard applications, Pentair Thermal Building Solutions can
design an appropriate snow melting system.
The following are examples of nonstandard applications not addressed in this design
guide:
•Concrete thinner than 4 in (10 cm)
•Concrete thicker than 6 in (15 cm)
•Lightweight concrete
THERMAL Building SOLUTIONS
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•Ramps, walkways, and stairs with air
below
•Concrete without reinforcing bar or
mesh
•Retrofitting of heating cable to existing
pavement
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Surface snow melting – MI Mineral insulated Heating Cable System
Surface Snow Melting Design
This section details the steps necessary to design your application. The examples
provided in each step are intended to incrementally illustrate sample project designs
from start to finish. As you go through each step, use the “Raychem MI System
Surface Snow Melting Design Worksheet” on page 37 to document your project
parameters, so that by that end of this section, you will have the information you
need for your Bill of Materials.
Design Step by Step
Your system design requires the following essential steps:
 Determine design conditions
 Determine the required watt density
 Determine the total area to be protected
 Select the heating cable
 Determine heating cable spacing
 Determine the electrical parameters
 Select the control system and power distribution
 Select the accessories
 Complete the Bill of Materials
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THERMAL Building SOLUTIONS
Surface Snow Melting Design
Surface Snow Melting
Step 1 Determine design conditions
1. Determine design
conditions
2. Determine the
required watt density
3. Determine the total
area to be protected
4. Select the heating
cable
5. Determine heating
cable spacing
6. Determine the
electrical parameters
7. Select the control
system and power
distribution
8. Select the
accessories
9. Complete the Bill
of Materials
Collect the following information to determine your design conditions:
• Environment
–– Geographical location
• Paving material
–– Concrete
–– Asphalt
–– Pavers
• Size and layout
–– Slab surface area
–– Ramp surface area
–– Stairs
-- Number of stairs
-- Stair width
-- Riser height
-- Stair depth
-- Landing surface area
–– Wheel tracks
-- Track length
–– Concrete joints
–– Surface drains
–– Location of area structures
–– Other information as appropriate
• Supply voltage
• Phase (single-phase or three-phase)
• Control method
–– Automatic snow melting controller
–– Slab sensing thermostat
–– Manual on/off control
Note: Drainage must be a primary concern in any snow melting system design.
Improper drainage will result in ice formation on the surface of the heated area once
the system is de-energized. Ice formation along the drainage path away from the
heated area may create an ice dam and prohibit proper draining. If your design
conditions may lead to drainage problems, please contact Pentair Thermal Building
Solutions Technical Support for assistance.
Prepare Scale Drawing
Draw to scale the area in which the snow melting cables will be installed, and note
the rating and location of the voltage supply. Include stairs and paths for melting
water
runoff.
concrete joints, surface drains, and location of area structures
P
PowerShow
connection
including
post
installations
for railings, permanent benches, and flagpoles.
E
End seal
Measurements for each distinct section of the snow melting application, including
S
Splice
stairs, will allow for an accurate system design, including control configuration. Use
these symbols to indicate the heating cable expansion and crack-control joints:
Expansion joint
Crack-control joint
Expansion
joint kit
Fig. 4 Design
symbols
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Surface snow melting – MI Mineral insulated Heating Cable System
Example: Surface Snow Melting System
Geographical location Philadelphia, PA
Ramp surface area
45 ft x 12 ft (13.7 m x 3.66 m)
Paving material
Concrete
Supply voltage
480 V, three-phase
Control method
Automatic snow melting controller
Example: Surface Snow Melting System for Stairs
Geographical location Philadelphia, PA
Number of stairs
5
Stair width
5 ft (1.52 m)
Riser height
8 in (20 cm)
Stair depth
11 in (28 cm)
Landing surface area 5 ft x 3 ft (1.52 m x 0.91 m)
Paving material
Concrete
Supply voltage
208 V, single-phase
Control method
Slab sensing thermostat
Example: Surface Snow Melting System for Wheel Tracks
Geographical location Philadelphia, PA
8 / 43
Track length
28 ft (8.5 m)
Paving material
Asphalt
Supply voltage
240 V, single-phase
Control method
Automatic snow melting controller
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THERMAL Building SOLUTIONS
Surface Snow Melting Design
Surface Snow Melting
Step 2 Determine the required watt density
1. Determine design
conditions
3. Determine the total
area to be protected
For maximum performance from any snow melting system, you must first take
into account the local snowfall patterns. A system design that works well in one
city may be inadequate in another. The energy required to melt snow varies with air
temperature, wind speed, relative humidity, snow density, and the depth of the snow
on the pavement.
4. Select the heating
cable
Surface Snow Melting
2. Determine the
required watt density
5. Determine heating
cable spacing
6. Determine the
electrical parameters
7. Select the control
system and power
distribution
Table 1 summarizes the required watt density for most major cities in North America
based on typical minimum ambient temperatures and the snowfall patterns. Select
the city from the list, or closest city, where similar climatic conditions exist.
Table 1 Required Watt Density for Surface Snow Melting
Watts/ft2
8. Select the
accessories
9. Complete the Bill
of Materials
City
Watts/m2
Asphalt
Asphalt
Concrete
or
or
Concrete
Concrete pavers
stairs Concrete pavers
stairs
USA
Baltimore, MD
Boston, MA
Buffalo, NY
Chicago, IL
Cincinnati, OH
Cleveland, OH
Denver, CO
Detroit, MI
Great Falls, MT
Greensboro, NC
Indianapolis, IN
Minneapolis, MN
New York, NY
Omaha, NE
Philadelphia, PA
Salt Lake City, UT
Seattle, WA
St. Louis, MO
35
35
40
35
35
35
35
35
50
35
35
50
35
45
35
35
35
35
40
40
45
40
40
40
40
40
50
35
40
50
40
50
40
35
35
40
40
45
45
40
40
40
40
40
55
40
40
55
45
50
45
40
40
45
377
377
431
377
377
377
377
377
538
377
377
538
377
484
377
377
377
377
431
431
484
431
431
431
431
431
538
377
431
538
431
538
431
377
377
431
431
484
484
431
431
431
431
431
592
431
431
592
484
538
484
431
431
484
45
50
40
35
40
45
45
50
45
50
50
40
35
40
50
35
35
50
45
50
45
40
40
45
45
55
45
55
50
45
35
45
55
40
40
55
50
55
45
40
45
50
50
55
50
55
55
45
40
50
55
40
40
55
484
538
431
377
431
484
484
538
484
538
538
431
377
431
538
377
377
538
484
538
484
431
431
484
484
592
484
592
538
484
377
484
592
431
431
592
538
592
484
431
484
538
538
592
538
592
592
484
431
538
592
431
431
592
Canada
Calgary, AB
Edmonton, AB
Fredericton, NB
Halifax, NS
Moncton, NB
Montreal, QC
Ottawa, ON
Prince George, BC
Quebec, QC
Regina, SK
Saskatoon, SK
St. John, NB
St. John’s, NF
Sudbury, ON
Thunder Bay, ON
Toronto, ON
Vancouver, BC
Winnipeg, MB
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Surface snow melting – MI Mineral insulated Heating Cable System
Example: Surface Snow Melting System
Geographical location
Philadelphia, PA (from Step 1)
Paving material
Concrete (from Step 1)
Required watt density
35 W/ft2 (377 W/m2) (from Table 1)
Example: Surface Snow Melting System for Stairs
Geographical location
Philadelphia, PA (from Step 1)
Paving material
Concrete (from Step 1)
Required watt density
45 W/ft2 (484 W/m2) (from Table 1)
Example: Surface Snow Melting System for Wheel Tracks
Surface Snow Melting
1. Determine design
conditions
2. Determine the
required watt density
3. Determine the total
area to be protected
4. Select the heating
cable
5. Determine heating
cable spacing
6. Determine the
electrical parameters
Geographical location
Philadelphia, PA (from Step 1)
Paving material
Asphalt (from Step 1)
Required watt density
40 W/ft2 (431 W/m2) (from Table 1)
Step 3 Determine the total area to be protected
Surfaces
To select the proper heating cable you need to know the size of the surface area
you will be protecting from snow accumulation. For large areas, divide the area
into smaller subsections no greater than 400 ft2 (37.2 m2). For three-phase voltage
supplies, create multiples of three equal areas not exceeding 400 ft2 (37.2 m2) as
shown in Fig. 5. Do not exceed 20 ft (6.1 m) in any direction. If assistance is required
to select heating cables for irregularly-shaped areas, please contact your Pentair
Thermal Building Solutions representative.
Total surface area (ft2/m2) = Length (ft/m) x Width (ft/m)
7. Select the control
system and power
distribution
8. Select the
accessories
9. Complete the Bill
of Materials
A
B
15 ft (4.57 m)
15 ft (4.57 m)
C
12 ft
3.66 m)
15 ft (4.57 m)
45 ft (13.7 m)
Fig. 5 Example for surface snow melting
Joints in Concrete
Many large concrete slabs are constructed with control and expansion joints. There
are three types of joints that can be placed in concrete slabs. An explanation of each
follows:
1. Crack-control joints (sawcuts) are intended to control where the slab will crack.
Their exact location is determined by the concrete installers before the concrete is
poured. Because of the reinforcement in the base slab, there is rarely a shearing
action caused by differential vertical movement between the concrete on either side
of the crack. As a precautionary measure, however, either of the two methods of
crossing control joints shown in Fig. 7 should be used. Minimize the number of times
the joint is crossed as shown in Fig. 7. When installing cables using the two-pour
method, control joints must be placed in both the base slab and the surface slab.
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THERMAL Building SOLUTIONS
Surface Snow Melting Design
2. Construction joints are joints that occur when the concrete pour is going to
stop but will resume at a later date. Therefore their location may not be known
beforehand. However, the rebar is left protruding out of the first pour so that it enters
the next pour and therefore shearing action rarely occurs due to differential vertical
movement between the concrete on either side of the joint. As a precautionary
measure, either of the two methods of crossing control joints shown in Fig. 7 should
be used.
3. Expansion joints are placed where a concrete slab abuts a structure, such as
a building, a slab, or a foundation, etc. Since the reinforcement does not cross
expansion joints, differential movement will occur between the slab and the
adjoining structure. Avoid crossing expansion joints with the heating cable. If this is
not possible, expansion joints can be crossed using a sand filled metal box as shown
in Fig. 6.
Heating
cable
Metal
box
(sand not shown)
Expansion
joint
Heating
cable
Concrete slab
Well drained
gravel base
6 in x 6 in x 4 in
(15 cm x 15 cm x 10 cm)
metal box filled with sand
Fig. 6 Crossing expansion joints
Cold leads may cross expansion joints provided that they are fed through nonmetallic
conduit to protect against shear (see Fig. 7).
Important Points to Remember
• Concrete slabs should have crack-control joints at intervals typically not exceeding 20 ft (6.1 m).
• When crossing crack-control joints, protect the cable as shown in Fig. 7 or design
for a sufficient number of heating cables to avoid crossing control joints altogether.
• Avoid crossing expansion joints. If possible, design for a sufficient number of
heating cables so that the cables do not cross expansion joints.
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Surface snow melting – MI Mineral insulated Heating Cable System
1 x 1 x 12 in
(2.5 x 2.5 x 30 cm)
angle iron filled
with RTV or silicone
rubber caulk
Heating cable
Angle iron
Base slab
Well-drained base
Nonmetallic
conduit
Control joint
Control joints
(cut into both bottom
and top slabs for two
Hot/cold joints pour installations)
Cold leads
Concrete
Heating cable secured
to rebar with plastic
tie wraps
Steel rebar
Fig. 7 Method of crossing crack-control joints with MI heating cable in concrete slabs
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THERMAL Building SOLUTIONS
Surface Snow Melting Design
Example: Surface Snow Melting System
Total ramp surface area
45 ft x 12 ft = 540 ft2 (from Step 1)
(13.7 m x 3.66 m = 50.1 m2)
For three-phase, divide the ramp
into three equal subsections
15 ft x 12 ft = 180 ft2 (see Fig. 5)
(4.57 m x 3.66 m = 16.7 m2)
Continue with “Step 4 Select the heating cable” on page 15, and use Table 2 or
Table 3 to select an appropriate heating cable.
Stairs
Snow melting applications in concrete stairs present a problem distinct from snow
melting on single layer surfaces. Heat loss in stairs occurs from the two exposed
surfaces: the top of each stair and its side. Melting snow and ice from stairs requires
one run of heating cable be installed 2 to 3 in (5 to 7.5 cm) maximum from the front,
or nose, of each stair at a depth of 2 in (5 cm) below the surface of the stair.
Note: Stairs typically require a heating cable that is a specific length. In many
cases, it may not be possible to find a SUA/SUB heating cable of the exact length,
and a custom engineered heating cable will be required. In these cases, or for
elevated stairs or stairs that are not concrete, please contact your Pentair Thermal
Building Solutions representative for assistance in designing a custom engineered
heating cable.
Junction
box
W
5 ft idth
(1.5
2m
ir
Sta pth
de 1 in
1 )
cm
(28
)
R
he iser
igh
t (2 8 i
0cn
m
t
3 f m)
1
9
.
(0
)
Fig. 8 Example for concrete stair
Typically, three runs of cable are used for stairs with a depth of 10.5 to 12 in
(27–30 cm); two runs of cable may be used for stairs with a depth of less than 10.5 in
(27 cm). Riser height is typically 8 in (20 cm). For stairs greater than 12 in (30 cm) in
depth, contact your Pentair Thermal Building Solutions representative.
Use the formulas below to determine the length of cable required for stairs (a) and
for an attached landing (b), if any, where no expansion joint exists between the stair
and landing.
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Surface snow melting – MI Mineral insulated Heating Cable System
(a) Length of cable
for stair (ft/m)
=
(b) Length of cable for
=
attached landing (ft)
Length of cable for
=
attached landing (m)
No. of stairs x [(No. of runs per stair x stair width (ft/m))
+ (2 x riser height (ft/m))]
Landing area (ft2) x 12
4.5
Landing area (m2) x 1000
115
For applications where the landing area is very large or where an expansion joint
exists between the stairs and landing, consider the stairs and landing as two
separate areas. In these cases, determine the length of cable required for the stairs
as shown above and select the cable for the landing as shown for surface snow
melting.
Example: Surface Snow Melting System for Stairs
Number of stairs
5 stairs (from Step 1)
Stair width
5 ft (1.52 m) (from Step 1)
Riser height
8 in (20 cm) convert to 0.7 ft (0.2 m) (from Step 1)
Stair depth
11 in (28 cm) (from Step 1)
Number of cable runs per stair
3 runs (for 11 in (28 cm) stair depth)
Length of cable for stair
5 stairs x [(3 x 5 ft) + (2 x 0.7 ft)] = 82 ft
5 stairs x [(3 x 1.52 m) + (2 x 0.2 m)] = 25 m
Landing surface area
5 ft x 3 ft = 15 ft2 (from Step 1)
1.52 m x 0.91 m = 1.4 m2
Length of cable for attached landing (15 ft2 x 12) / 4.5 = 40 ft
(1.4 m2 x 1000) / 115 = 12.2 m
Total heating cable length required 82 ft + 40 ft = 122 ft
25 m + 12.2 m = 37.2 m
Continue with “Step 4 Select the heating cable” on page 15‚ and use Table 4 on
page 20 to select an appropriate heating cable.
Wheel Tracks
To reduce power consumption for concrete and asphalt driveways, it may be
sufficient to snow melt only the wheel tracks. However, do not snow melt only
the wheel tracks in paver applications because of potential problems with pavers
sinking.
It is not necessary to calculate the area of the wheel track to select the heating
cable. Four runs of heating cable per wheel track spaced evenly over the track width,
typically 18 in (46 cm), will provide sufficient heat for snow melting.
Heated area
10 ft
(3.0 m)
28 ft (8.5 m)
Junction box
Fig. 9 Example for wheel tracks
14 / 43
EN-RaychemMISurfaceSnowMelting-DG-H57045
12/15
THERMAL Building SOLUTIONS
Surface Snow Melting Design
Example: Surface Snow Melting System for Wheel Tracks
Wheel track length
28 ft (8.5 m) (from Step 1)
Typical wheel track width
18 in (46 cm)
Continue with “Step 4 Select the heating cable” on page 15 and use Table 5 on
page 21 to select an appropriate heating cable.
Surface Snow Melting
Step 4 Select the heating cable
1. Determine design
conditions
2. Determine the
required watt density
3. Determine the total
area to be protected
4. Select the heating
cable
5. Determine heating
cable spacing
6. Determine the
electrical parameters
7. Select the control
system and power
distribution
8. Select the
accessories
9. Complete the Bill
of Materials
Three-phase supply voltages, including 208 V, 480 / 277 V, and 600 / 347 V, are
commonly used for snow melting applications for large areas. For small areas, a
single-phase supply voltage must be used. A snow melting system designed for a
three-phase supply uses three identical heating cables in each circuit, resulting in
the following advantages: fewer circuits, reduced distribution system costs, and a
balanced heating system load.
Surfaces
Select a heating cable from Table 2 on page 16 or Table 3 on page 17. When
selecting cables from Table 2, ensure that the selected cable is suitable for use
when embedded in the paving material being used. The heating cables in Table 3
are suitable for surface snow melting applications where the cables will be directly
embedded only in concrete. To select a cable, first calculate the required heating
cable output (watts) by multiplying the watt density by the area or subsection area.
Under the appropriate voltage in Table 2 or Table 3, select a heating cable from the
shaded column with a heating cable output equal to or up to 30% greater than the
calculated wattage. In cases where the surface area has been divided into equal
subsections, select the appropriate number of heating cables.
Required watts
=
Number of cables =
Watt density x Area
Number of subsection areas
Example: Surface Snow Melting System
Supply voltage
480 V, three-phase (from Step 1)
Required watt density for ramp
35 W/ft2 (377 W/m2) (from Step 2)
Subsection area (for 3 equal areas)
180 ft2 (16.7 m2) (from Step 3)
Required watts (for each subsection)
35 W/ft2 x 180 ft2 = 6300 W
377 W/m2 x 16.7 m2 = 6300 W
Heating cable catalog number
SUB20
Cable wattage
6450 W
Cable voltage
480 V (for cables connected in Delta
configuration)
THERMAL Building SOLUTIONS
Heating cable length
340 ft (103.6 m)
Number of cables
3 (one cable required for each subsection)
EN-RaychemMISurfaceSnowMelting-DG-H57045
12/15
15 / 43
Surface snow melting – MI Mineral insulated Heating Cable System
Table 2 Selection Table for Concrete, Asphalt, and Paver Areas Heating cable
catalog number
Heating cable output
Concrete Asphalt
Pavers 1
Heating cable length
(W)
(ft)
(m)
Heating cable
current
(A)
120 V
SUA5
Yes
Yes
Yes
550
40
12.2
4.6
SUA9
Yes
Yes
Yes
1100
66
20.1
9.2
208 V
SUA4
Yes
Yes
No
1600
68
20.7
SUA7
Yes
Yes
No
2300
95
29
7.7
11.1
SUB1
Yes
Yes
No
3100
132
40.2
14.9
SUB3
Yes
Yes
Yes
3900
280
85.3
18.8
SUB5
Yes
Yes
No
5500
260
79.2
26.4
SUB7
Yes
Yes
No
7000
310
94.5
33.7
SUB9
Yes
Yes
Yes
9000
630
192
43.3
SUB10
Yes
Yes
Yes
13000
717
218.5
62.5
Yes
Yes
Yes
2000
140
42.7
8.3
240 V
SUA3
SUA8
Yes
Yes
Yes
3200
177
53.9
13.3
SUB2
Yes
Yes
Yes
4000
240
73.1
16.7
SUB3
Yes
Yes
Yes
5200
280
85.3
21.7
SUB4
Yes
Yes
Yes
6000
320
97.5
25
SUB5
Yes
No
No
7350
260
79.2
30.6
SUB6
Yes
Yes
Yes
7500
375
114.3
31.3
SUB8
Yes
Yes
Yes
9000
550
167.6
37.5
SUB7
Yes
No
No
9250
310
94.5
38.5
SUB9
Yes
Yes
Yes
12000
630
192
50
SUB10
Yes
Yes
No
17000
717
218.5
70.8
277 V
SUA3
Yes
Yes
Yes
2740
140
42.7
9.9
SUA8
Yes
Yes
No
4100
177
53.9
14.8
SUB15
Yes
Yes
Yes
4250
225
68.6
15.3
SUB2
Yes
Yes
No
5300
240
73.1
19.1
SUB16
Yes
Yes
Yes
6180
310
94.5
22.3
SUB3
Yes
Yes
No
6850
280
85.3
24.7
SUB4
Yes
Yes
No
8000
320
97.5
28.9
SUB17
Yes
Yes
Yes
8700
440
134.1
31.4
SUB6
Yes
No
No
10200
375
114.3
36.8
SUB18
Yes
Yes
No
12000
560
170.7
43.3
SUB8
Yes
Yes
No
12200
550
167.6
44.0
SUB9
Yes
No
No
16400
630
192
59.2
Yes
Yes
Yes
4700
245
74.7
103.6
480 V
SUB19
9.8
SUB20
Yes
Yes
Yes
6450
340
SUB21
Yes
Yes
Yes
8700
440
134.1
18.1
13.4
SUB22
Yes
Yes
No
11000
525
160
22.9
1 Cables embedded in sand or limestone screenings.
Note: Type SUA cables supplied with 7 ft (2.1 m) cold lead. Type SUB cables supplied with 15 ft (4.6 m) cold leads. Tolerance on
heating cable length is –0% to +3%.
To modify cold lead length, contact your Pentair Thermal Building Solutions sales representative.
16 / 43
EN-RaychemMISurfaceSnowMelting-DG-H57045
12/15
THERMAL Building SOLUTIONS
Surface Snow Melting Design
Table 2 Selection Table for Concrete, Asphalt, and Paver Areas Heating cable
catalog number
Heating cable output
Concrete Asphalt
Pavers 1
Heating cable length
(W)
(ft)
(m)
Heating cable
current
(A)
600 V
SUB11
Yes
Yes
Yes
4100
225
68.6
6.8
SUB12
Yes
Yes
Yes
5800
310
94.5
9.7
SUB13
Yes
Yes
Yes
8000
428
130.5
13.3
SUB14
Yes
Yes
Yes
11000
548
167
18.3
1 Cables embedded in sand or limestone screenings.
Note: Type SUA cables supplied with 7 ft (2.1 m) cold lead. Type SUB cables supplied with 15 ft (4.6 m) cold leads. Tolerance on
heating cable length is –0% to +3%.
To modify cold lead length, contact your Pentair Thermal Building Solutions sales representative.
The heating cables in Table 3 have been specifically designed for use only in
concrete. Do not use these cables in asphalt or for paver areas because they exceed
the maximum watts per foot loading for these applications (embedded in asphalt 25
watts/foot maximum; embedded in sand/limestone screenings for paver areas – 20
watts/foot maximum). To select a cable, calculate the required heating cable output
(watts) as shown in the example earlier in this section.
Table 3 Selection Table for Concrete Areas Heating cable
catalog number
Heating cable
output
Heating cable
length
(W)
(ft)
1400
50
Heating cable
current
(m)
(A)
15.2
6.7
208 V
SUB1402
SUB1702
1700
64
19.5
8.2
SUB2002
2000
72
22.0
9.6
SUB2402
2400
90
27.4
11.5
SUB2802
SUB3402
2800
3400
103
121
31.4
36.9
13.5
16.3
SUB3902
3900
139
42.4
18.8
SUB4502
4500
160
48.8
21.6
SUB5502
5500
197
60.1
26.4
SUB6402
6400
226
68.9
30.8
SUB7802
7800
277
84.5
37.5
SUB10302
10300
368
112.2
49.5
SUB12802
12800
455
138.7
61.5
SUB16102
16100
576
175.6
77.4
Note: Type SUB cables supplied with 15 ft (4.6 m) cold leads. Tolerance on heating cable
length is –0% to +3%. To modify cold lead length, contact your Pentair Thermal
Building Solutions sales representative.
THERMAL Building SOLUTIONS
EN-RaychemMISurfaceSnowMelting-DG-H57045
12/15
17 / 43
Surface snow melting – MI Mineral insulated Heating Cable System
Table 3 Selection Table for Concrete Areas Heating cable
catalog number
Heating cable
output
Heating cable
length
Heating cable
current
(W)
(ft)
(m)
(A)
SUB1604
1600
59
18.0
6.7
SUB2004
2000
74
22.6
8.3
SUB2304
2300
84
25.6
9.6
SUB2804
2800
103
31.4
11.7
SUB3204
3200
120
36.6
13.3
SUB3904
3900
140
42.7
16.3
SUB4504
4500
160
48.8
18.8
SUB5204
5200
185
56.4
21.7
SUB6404
6400
225
68.6
26.7
SUB7304
7300
263
80.2
30.4
SUB9004
9000
320
97.6
37.5
SUB11904
11900
426
129.9
49.6
SUB14704
14700
528
161.0
61.3
SUB18604
18600
664
202.4
77.5
SUB1807
1800
70
21.3
6.5
SUB2307
2300
85
25.9
8.3
SUB2707
2700
95
29.0
9.7
SUB3207
3200
119
36.3
11.6
SUB3807
3800
135
41.2
13.7
SUB4507
4500
162
49.4
16.2
SUB5207
5200
184
56.1
18.8
SUB6007
6000
213
64.9
21.7
SUB7307
7300
262
79.9
26.4
SUB8507
8500
300
91.5
30.7
SUB10307
10300
372
113.4
37.2
SUB13707
13700
491
149.7
49.5
SUB17207
17200
600
182.9
62.1
240 V
277 V
347 V
SUB2305
2300
85
25.9
6.6
SUB2905
2900
107
32.6
8.4
SUB3405
3400
119
36.3
9.8
SUB4105
4100
148
45.1
11.8
SUB4705
4700
171
52.1
13.5
SUB5605
5600
205
62.5
16.1
SUB6505
6500
231
70.4
18.7
SUB7505
7500
267
81.4
21.6
SUB9205
9200
327
99.7
26.5
SUB10605
10600
380
115.9
30.5
SUB13005
13000
463
141.2
37.5
SUB17205
17200
614
187.2
49.6
Note: Type SUB cables supplied with 15 ft (4.6 m) cold leads. Tolerance on heating cable
length is –0% to +3%. To modify cold lead length, contact your Pentair Thermal
Building Solutions sales representative.
18 / 43
EN-RaychemMISurfaceSnowMelting-DG-H57045
12/15
THERMAL Building SOLUTIONS
Surface Snow Melting Design
Table 3 Selection Table for Concrete Areas Heating cable
catalog number
Heating cable
output
Heating cable
length
(W)
(ft)
SUB3208
3200
SUB4008
4000
SUB4708
SUB5708
Heating cable
current
(m)
(A)
118
36.0
6.7
147
44.8
8.3
4700
5700
163
202
49.7
61.6
9.8
11.9
SUB6608
6600
233
71.0
13.8
SUB7908
7900
278
84.8
16.5
SUB9008
9000
320
97.6
18.8
SUB10408
10400
368
112.2
21.7
SUB12808
12800
450
137.2
26.7
SUB14808
14800
520
158.5
30.8
SUB18008
18000
640
195.1
37.5
SUB4006
4000
147
44.8
6.7
SUB5106
5100
181
55.2
8.5
SUB5806
5800
207
63.1
9.7
SUB7106
7100
254
77.4
11.8
SUB8206
8200
293
89.3
13.7
SUB9806
9800
350
106.7
16.3
SUB11206
11200
402
122.6
18.7
SUB13006
13000
462
140.9
21.7
SUB15906
15900
566
172.6
26.5
480 V
600 V
Note: Type SUB cables supplied with 15 ft (4.6 m) cold leads. Tolerance on heating cable
length is –0% to +3%. To modify cold lead length, contact your Pentair Thermal
Building Solutions sales representative.
Stairs
For stairs, select a heating cable from Table 4. Under the appropriate voltage,
select a cable from the shaded column with a length equal to or up to 20 ft (6.1 m)
longer than the calculated length from Step 3. Next, confirm that the watt density
is equal to, or greater than, the watt density determined from Step 2. If a cable of
the required length is not available, please contact your Pentair Thermal Building
Solutions representative for assistance in designing a custom heating cable.
Anticipate and design for the addition of railings or other follow on construction that
will require cutting or drilling into the concrete as damage to installed heating cable
may occur. Allow for at least 4 in (10 cm) clearance between the heating cable and
any planned cuts or holes.
Example: Surface Snow Melting System for Stairs
Supply voltage
208 V, single-phase (from Step 1)
Required watt density
45 W/ft2 (484 W/m2) (from Step 2)
Total heating cable length required 122 ft (37.2 m) (from Step 3)
THERMAL Building SOLUTIONS
Heating cable catalog number
SUB1
Cable wattage
3100 W
Cable voltage
208 V
Heating cable length
132 ft (40.2 m)
Number of cables
1
Installed watt density
55 W/ft2 (592 W/m2) (from Table 4)
EN-RaychemMISurfaceSnowMelting-DG-H57045
12/15
19 / 43
Surface snow melting – MI Mineral insulated Heating Cable System
Table 4 Selection Table for Concrete Stairs
Heating cable
catalog number
Watt density
Heating cable
length
3 runs cable 1
(W/ft2)
(W/m2)
2 runs cable 2
(W/ft2)
(W/m2)
Heating
cable
output
Heating
cable
current
(W)
(A)
(ft)
(m)
SUA5
40
12.2
40
431
–
–
550
4.6
SUA9
66
20.1
50
538
40
431
1100
9.2
120 V
208 V
SUA4
68
20.7
55
592
55
592
1600
7.7
SUA7
95
29.0
55
592
55
592
2300
11.1
SUB1
132
40.2
55
592
55
592
3100
14.9
SUB3
280
85.3
40
431
–
–
3900
18.8
SUB5
260
79.2
55
592
50
538
5500
26.4
SUB7
310
94.5
55
592
50
538
7000
33.7
SUB9
630
192.0
40
431
–
–
9000
43.3
240 V
SUA3
140
42.7
40
431
–
–
2000
8.3
SUB2
240
73.1
50
538
40
431
4000
16.7
SUB3
280
58.3
55
592
40
431
5200
21.7
SUB4
320
97.5
55
592
45
484
6000
25.0
SUB6
375
114.3
55
592
45
484
7500
31.3
SUB8
550
167.6
50
538
40
431
9000
37.5
SUB9
630
192.0
55
592
45
484
12000
50.0
277 V
SUA3
140
42.7
55
592
45
484
2740
9.9
SUB15
225
68.6
55
592
45
484
4250
15.3
SUB2
240
73.1
55
592
50
538
5300
19.1
SUB16
310
94.5
55
592
45
484
6180
22.3
SUB3
280
85.3
55
592
55
592
6850
24.7
SUB4
320
97.5
55
592
55
592
8000
28.9
SUB17
440
134.1
55
592
45
484
8700
31.4
SUB6
375
114.3
55
592
55
592
10200
36.8
SUB18
560
170.7
55
592
50
538
12000
43.3
480 V
SUB19
245
74.7
55
592
45
484
4700
9.8
SUB20
340
103.6
55
592
45
484
6450
13.4
SUB21
440
134.1
55
592
45
484
8700
18.1
SUB22
525
160.0
55
592
50
538
11000
22.9
225
68.6
55
592
40
431
4100
6.8
600 V
SUB11
SUB12
310
94.5
55
592
45
484
5800
9.7
SUB13
428
130.5
55
592
45
484
8000
13.3
SUB14
548
167.0
55
592
45
484
11000
18.3
1 Based on stairs with a depth of 10.5–12 in (27–30 cm) and 3 runs of cable
2 Based on stairs with a depth of less than 10.5 in (27 cm) and 2 runs of cable
Note:Type SUA cables supplied with 7 ft (2.1 m) cold lead. Type SUB cables supplied with 15 ft (4.6 m) cold leads. Tolerance on heating cable length is –0% to +3%.
To modify cold lead length, contact your Pentair Thermal Building Solutions sales representative.
20 / 43
EN-RaychemMISurfaceSnowMelting-DG-H57045
12/15
THERMAL Building SOLUTIONS
Surface Snow Melting Design
Wheel Tracks
The heating cables shown in Table 5 will allow for four runs of cable in each wheel
track. Under the appropriate voltage, select a heating cable from the shaded column
for the wheel track length required. For wheel tracks outside the scope of this design
guide, please contact your Pentair Thermal Building Solutions representative for
assistance in designing a custom engineered heating cable.
Example: Surface Snow Melting System for Wheel Tracks
Supply voltage
240 V, single-phase (from Step 1)
Wheel track length
28 feet (8.5 m)
Heating cable catalog number
SUB2
Cable wattage
4000 W
Cable voltage
240 V
Heating cable length
240 ft (73.1 m)
Number of cables
1
Table 5 Selection Table for Concrete and Asphalt Wheel Tracks
Heating
cable
catalog
number
Wheel track length
(ft)
Spacing
(inches)
Normal
heat
(m)
High
heat
Heating cable
length
Spacing (cm)
Normal
heat
High
heat
(ft)
(m)
Heating
cable
output
Heating
cable
current
(W)
(A)
208 V
SUA7
8– 11
2.4 – 3.4
7
5
18
13
95
SUB1
12– 15
3.5– 4.6
7
5
18
13
132
29
2300
11.1
40.2
3100
14.9
SUA8
16– 21
4.7– 6.4
4
3
10
8
177
54
2400
11.5
SUB5
22– 31
6.5– 9.5
6
5
15
13
260
79.2
5500
26.4
SUB7
32– 38
9.6–11.6
6
5
15
13
310
94.5
7000
33.7
SUB6
39– 46
11.7–14.0
4
3
10
8
375
114.3
5700
27.4
SUB8
47– 68
14.1–20.7
4
3
10
8
550
167.7
6800
32.7
SUB9
69– 78
20.8–23.8
4
3
10
8
630
192
9000
43.3
SUB10
79– 88
23.9–26.8
5
4
13
10
717
218.5
13000
62.5
240 V
SUA3
8– 16
2.4– 4.9
4
3
10
8
140
42.7
2000
8.3
SUA8
17– 21
5.0– 6.4
5
4
13
10
177
53.9
3200
13.3
SUB2
22– 29
6.5– 8.8
5
4
13
10
240
73.1
4000
16.7
SUB3
30– 34
8.9–10.4
5
4
13
10
280
85.3
5200
21.7
SUB4
35– 39
10.5–11.9
5
4
13
10
320
97.5
6000
25
SUB6
40– 46
12.0–14.0
6
5
15
13
375
114.3
7500
31.3
SUB8
47– 68
14.1–20.7
5
4
13
10
550
167.6
SUB9
69– 78
20.8–23.8
6
5
15
13
630
192
12000
9000
50
37.5
SUB10
79– 88
23.9–26.8
7
5
18
13
717
218.5
17000
70.8
277 V
SUA3
11– 16
3.4– 4.9
6
5
15
13
140
42.7
2740
9.9
SUB15
17– 27
5.0– 8.2
6
5
15
13
225
68.6
4250
15.3
SUB16
28– 38
8.3–11.6
6
5
15
13
310
94.5
6180
22.3
SUB17
39– 54
11.7–16.5
6
5
15
13
440
134.1
8700
31.4
SUB18
55– 69
16.6–21.0
6
5
15
13
560
170.7
12000
43.3
SUB9 1
70– 78
21.1–23.8
7
6
18
15
630
192
16400
59.2
1 Not for asphalt applications; for use when embedded in concrete only
Note: Type SUA cables supplied with 7 ft (2.1 m) cold lead. Type SUB cables supplied with 15 ft (4.6 m) cold leads. Tolerance on
heating cable length is –0% to +3%.
To modify cold lead length, contact your Pentair Thermal Building Solutions sales representative.
THERMAL Building SOLUTIONS
EN-RaychemMISurfaceSnowMelting-DG-H57045
12/15
21 / 43
Surface snow melting – MI Mineral insulated Heating Cable System
Table 5 Selection Table for Concrete and Asphalt Wheel Tracks
Heating
cable
catalog
number
Wheel track length
(ft)
(m)
Spacing
(inches)
Normal
heat
High
heat
Spacing (cm)
Normal
heat
High
heat
Heating cable
length
(ft)
(m)
Heating
cable
output
Heating
cable
current
(W)
(A)
480 V
SUB19
20– 29
6.1– 8.8
6
5
15
13
245
74.7
4700
9.8
SUB20
30– 41
8.9–12.5
6
5
15
13
340
103.6
6450
13.4
SUB21
42– 54
12.6–16.5
6
5
15
13
440
134.1
SUB22
55– 64
16.6–19.5
6
5
15
13
525
160
8700
18.1
11000
22.9
600 V
SUB11
20– 27
6.1– 8.2
6
4
15
10
225
68.6
4100
6.8
SUB12
28– 38
8.3–11.6
6
5
15
13
310
94.5
5800
9.7
SUB13
39– 52
11.7–15.9
6
5
15
13
428
130.5
SUB14
53– 67
16.0–20.4
6
5
15
13
548
167
8000
13.3
11000
18.3
1 Not for asphalt applications; for use when embedded in concrete only
Note: Type SUA cables supplied with 7 ft (2.1 m) cold lead. Type SUB cables supplied with 15 ft (4.6 m) cold leads. Tolerance on
heating cable length is –0% to +3%.
To modify cold lead length, contact your Pentair Thermal Building Solutions sales representative.
Surface Snow Melting
1. Determine design
conditions
2. Determine the
required watt density
3. Determine the total
area to be protected
4. Select the heating
cable
5. Determine heating
cable spacing
6. Determine the
electrical parameters
7. Select the control
system and power
distribution
8. Select the
accessories
Step 5 Determine heating cable spacing
surfaces
Determine the spacing between runs of heating cables using the formula below. For
concrete installations, do not exceed 10 in (25 cm) spacing of cable, and for asphalt
and paver installations do not exceed 6 in (15 cm) spacing. If the cable spacing
for asphalt or pavers exceeds 6 in (15 cm), contact your Pentair Thermal Building
Solutions representative for assistance.
To determine heating cable spacing required for surface snow melting
Cable spacing (in) =
Area (ft2) x 12 in
Heating cable length (ft)
Cable spacing (cm) =
Area (m2) x 100 cm
Heating cable length (m)
9. Complete the Bill
of Materials
Round to the nearest 1/2 in or nearest 1 cm to obtain cable spacing.
Note: If a large area has been divided into subsections or if a three-phase
voltage supply is used, the area in the above equations will be the subsection area
and the heating cable length will be the length of the cable selected for the
subsection area.
22 / 43
EN-RaychemMISurfaceSnowMelting-DG-H57045
12/15
THERMAL Building SOLUTIONS
Surface Snow Melting Design
Example: Surface Snow Melting System
Subsection area
180 ft2 (16.7 m2) (from Step 3)
Heating cable catalog number
SUB20 (from Step 4)
Heating cable length
340 ft (103.6 m) (from Step 4)
Cable spacing
(180 ft2 x 12 in) / 340 ft = 6.4 in
Rounded to 6.5 in
(16.7 m2 x 100 cm) / 103.6 m = 16.1 cm
Rounded to 16 cm
Stairs
For concrete stairs with a depth of 10.5–12 in (27–30 cm), use three runs of cable
with one run 2 to 3 in (5–7.5 cm) maximum from the front edge of the stair (this is
where snow and ice build-up is the most dangerous) and the remaining two runs
spaced equally apart from this run of cable. For stairs with a depth of less than
10.5 in (27 cm), use two runs of cable with one run 2 to 3 in (5–7.5 cm) maximum
from the front edge of the stair and the second run spaced 4 in (10 cm) from this run
of cable. Up to 20 ft (6.1 m) of excess cable may be used up in an attached landing,
preferably, or by adding an extra run to one or more stairs.
For attached landings, space heating cables 4.5 in (11.5 cm) apart; up to 20 ft
(6.1 m) of excess cable may be used up in the landing, decreasing cable spacing as
necessary to accommodate the extra cable.
Example: Surface Snow Melting System for Stairs
Heating cable catalog number
SUB1 (from Step 4)
Stair depth
11 in (28 cm) (from Step 1)
Cable spacing – stairs
3 runs per stair spaced as described above
Cable spacing – landing
4.5 in (11.5 cm)
Wheel Tracks
For wheel tracks, use the spacing shown in Selection Table for Concrete and Asphalt
Wheel Tracksfor “Normal” or “High” heat. Use the spacing for “High heat” for all
asphalt applications, or where a watt density of 45 W/ft2
(484 W/m2) or higher is required.
Example: Surface Snow Melting System for Wheel Tracks
THERMAL Building SOLUTIONS
Paving material
Asphalt (from Step 1) – high heat required
Heating cable catalog number
SUB2 (from Step 4)
Cable spacing 4 in (10 cm) (from Table 5)
EN-RaychemMISurfaceSnowMelting-DG-H57045
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23 / 43
Surface snow melting – MI Mineral insulated Heating Cable System
Surface Snow Melting
1. Determine design
conditions
2. Determine the
required watt density
3. Determine the total
area to be protected
4. Select the heating
cable
5. Determine heating
cable spacing
6. Determine the
electrical parameters
7. Select the control
system and power
distribution
8. Select the
accessories
9. Complete the Bill
of Materials
Step 6 Determine the electrical parameters
DETERMINE NUMBER OF CIRCUITS
For single phase circuits, individual heating cables are generally connected to
separate circuit breakers. Multiple heating cables may be connected in parallel
to reduce the number of circuits with permission from the Authority Having
Jurisdiction. The single-phase heating cable current is shown in the appropriate
selection table.
For three-phase circuits used in snow melting systems, the three heating cables
are generally connected in the Delta configuration shown in Fig. 11 on page 30.
Heating cables may also be connected using the Wye configuration shown in
Fig. 12 on page 31, but this configuration is less common. For both Delta and Wye
configurations, each set of three equal cables form a single circuit.
SELECT BRANCH CIRCUIT BREAKER
The safety and reliability of any snow melting system depends on the quality of
the products selected and the manner in which they are installed and maintained.
Incorrect design, handling, installation, or maintenance of any of the system
components could damage the snow melting system and may result in inadequate
snow melting, electric shock, or fire. To minimize the risk of fire, Pentair Thermal
Building Solutions and national electrical codes require a grounded metallic covering
on all heating cables. Pentair Thermal Building Solutions, agency certifications, and
national electrical codes require a grounded metallic covering on all heating cables.
They also require that all heating cables be protected with ground-fault equipment
protection.
WARNING: To minimize the danger of fire from sustained electrical arcing if
the heating cable is damaged or improperly installed, and to comply with the
requirements of Pentair Thermal Building Solutions, agency certifications, and
national electrical codes, ground-fault equipment protection must be used on each
heating cable branch circuit. Arcing may not be stopped by conventional circuit
protection.
The power output and heating cable current draw for the snow melting cables are
shown in Table 2 through Table 5.
For single-phase circuits, the load current must not exceed 80% of the circuit
breaker rating.
Load current = Heating cable current (for a single circuit)
Circuit breaker rating = Load current x 1.25
For a Delta connected three-phase circuit, shown in Fig. 11 on page 30, the load
current can be determined by multiplying the heating cable current times 1.732 and
it must not exceed 80% of the 3-pole circuit breaker rating.
Load current = Heating cable current x 1.732 (for a single Delta connected circuit)
Circuit breaker rating = Load current x 1.25
For a Wye connected three-phase circuit, shown in Fig. 12 on page 31, the load
current is the same as the heating cable current and it must not exceed 80% of the
3-pole circuit breaker rating.
Load current = Heating cable current (for a single Wye connected circuit)
Circuit breaker rating = Load current x 1.25
Record the number and ratings of the circuit breakers to be used. Use ground-fault
protection devices (GFPDs) for all applications. For three-phase circuits, ground fault
may be accomplished using a shunt trip 3-pole breaker and a ground fault sensor.
Circuit breaker rating (A) ___________Number of circuit breakers ___________
24 / 43
EN-RaychemMISurfaceSnowMelting-DG-H57045
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THERMAL Building SOLUTIONS
Surface Snow Melting Design
Determine Transformer Load
The total transformer load is the sum of the loads in the system. Calculate the Total
Transformer Load as follows:
For cables of equal wattage:
Cable (W) x Number of cables
Transformer load (kW) =
1000
When cable wattages are not equal:
Transformer load (kW) =
Cable1 (W) + Cable2 (W) + Cable3 (W)... + CableN (W)
1000
Example: Surface Snow Melting System
Heating cable catalog number
SUB20 (from Step 4)
Heating cable current
13.4 A (from Table 2)
Load current
13.4 x 1.732 = 23.2 A
Circuit breaker rating
30 A breaker, 80% loading 24 A
Number of circuit breakers
1
Cable power output
6450 W (from Step 4)
Number of cables 3 (from Step 4)
Total transformer load
(6450 W x 3) / 1000 = 19.4 kW
Example: Surface Snow Melting System for Stairs
Heating cable catalog number
SUB1 (from Step 4)
Heating cable current
14.9 A (from Table 4)
Load current
14.9 A
Circuit breaker rating
20 A breaker, 80% loading 16 A
Number of circuit breakers
1
Cable power output
3100 W (from Step 4)
Number of cables 1 (from Step 4)
Total transformer load
3100 W / 1000 = 3.1 kW
Example: Surface Snow Melting System for Wheel Tracks
THERMAL Building SOLUTIONS
Heating cable catalog number
SUB2 (from Step 4)
Heating cable current
16.7 A (from Table 5)
Load current
16.7 A
Circuit breaker rating
30 A breaker, 80% loading 24 A
Number of circuit breakers
1
Cable power output
4000 W (from Step 4)
Number of cables 1 (from Step 4)
Total transformer load
4000 W / 1000 = 4.0 kW
EN-RaychemMISurfaceSnowMelting-DG-H57045
12/15
25 / 43
Surface snow melting – MI Mineral insulated Heating Cable System
Surface Snow Melting
1. Determine design
conditions
2. Determine the
required watt density
3. Determine the total
area to be protected
4. Select the heating
cable
Step 7 Select the control system and power distribution
Control System
Select a control system from the following three options keeping in mind that an
automatic snow melting controller offers the highest system reliability and the
lowest operating cost.
• Manual on/off control
• Slab sensing thermostat
5. Determine heating
cable spacing
• Automatic snow melting controller
6. Determine the
electrical parameters
If the current rating of the control means is exceeded, all three methods will require
contactors sized to carry the load. Each method offers a tradeoff, balancing initial
cost versus energy efficiency and ability to provide effective snow melting. If the
system is not energized when required, snow will accumulate. If the system is
energized when it is not needed, there will be unnecessary power consumption.
Choose the control method that best meets the project performance requirements.
For additional information, refer to “Power Distribution” on page 30 or contact your
Pentair Thermal Building Solutions representative for details.
7. Select the control
system and power
distribution
8. Select the
accessories
9. Complete the Bill
of Materials
Manual On/Off Control
A manually controlled system is operated by a switch that controls the system power
contactor. This method requires constant supervision to work effectively. A manual
system can be controlled by a building management system.
Slab Sensing Thermostat
A slab sensing thermostat can be used to energize the system whenever the slab
temperature is below freezing, but is not energy efficient when used as the sole
means of control. The slab sensing thermostat is recommended for all snow melting
applications, even when an automatic snow controller is used, and is required for
all asphalt and paver installations (for asphalt, it prevents surface damage due
to overheating). The snow melting controllers shown in Table 4 include a slab
temperature sensor.
Automatic Snow Melting Controller
With an automatic snow melting controller, the snow melting system is automatically
energized when both precipitation and low temperature are detected. When
precipitation stops or the ambient temperature rises above freezing, the system
is de-energized. In addition, a slab sensor de-energizes the system when the slab
temperature reaches the slab sensor set point even if freezing precipitation is still
present. Using an automatic snow controller with a slab sensor offers the most
energy-efficient control solution. For additional information, refer to Fig. 10.
For areas where a large number of circuits are required, the Raychem ACS-30 can
be used. The Surface Snow Melting control mode in the ACS-30 includes an External
Device control option. This option allows a Snow/Moisture sensing controller
(from Table 6) to be integrated into the ACS-30 system. Note that sensors (snow
or gutter) cannot be directly connected to the ACS-30 system. Refer to the ACS-30
Programming Guide (H58692) for more information on system setup.
26 / 43
EN-RaychemMISurfaceSnowMelting-DG-H57045
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THERMAL Building SOLUTIONS
Surface Snow Melting Design
Optional
RCU-3 or RCU-4
remote control unit
CIT-1
snow sensor
To additional
SC-40C satellite
contactors
Optional
SC-40C
satellite
contactor
SIT-6E pavement
mounted sensor
To power supply
To heating cable(s)
APS-4C (shown) with SC-40C satelllite
contactor or APS-3C snow controller
To power supply
To heating cable(s)
Note: APS-4C, APS-3C
and SC-40C include an
integral high limit
temperature sensor
Fig. 10 Automatic snow melting control system
Table 6 Control Systems Catalog number
Description
Slab Sensing Thermostat and Accessory
ECW-GF
Electronic ambient sensing controller with 30-mA ground-fault protection. The controller can be programmed to maintain temperatures up to 200°F (93°C) at voltages from
100 to 277 V and can switch current up to 30 Amperes. The ECW-GF is complete with
a 25-ft (7.6-m) temperature sensor and is housed in a Type 4X rated enclosure. The
controller features an AC/DC dry alarm contact relay.
An optional ground-fault display panel (ECW-GF-DP) that can be added to provide
ground-fault or alarm indication in applications where the controller is mounted in
inaccessible locations.
ECW-GF-DP
HE
AT
ER
CY
CL
An optional remote display panel (ECW-GF-DP) that can be added to provide groundfault or alarm indication in applications where the controller is mounted in inaccessible locations.
ETI PD Pro
Automatic snow and ice melting controller for pavement, sidewalks, loading docks,
roofs, gutters and downspouts in commercial and residential environments.
The PD Pro interfaces with up to two sensors, (any combination of CIT-1, GIT-1 or SIT6E) to meet site requirements. The PD Pro is housed in an environmentally-sheltered
Type 4X enclosure and weighs only 3 pounds.
ETI GF Pro
Automatic snow and ice melting controller for pavement, sidewalks, loading docks,
roofs, gutters and downspouts in commercial and residential environments.
The GF Pro interfaces with up to two sensors, (any combination of CIT-1, GIT-1 or SIT6E) to meet site requirements. The GF Pro is housed in an environmentally-sheltered
Type 4X enclosure and weighs only 3 pounds.
E
Features a built-in 30-mA, self-testing Ground-Fault Equipment Protection (GFEP)
capability, digitally filtered to minimize false tripping. A ground-fault alarm must be
manually reset using the Test/Reset switch before heater operation can continue.
THERMAL Building SOLUTIONS
EN-RaychemMISurfaceSnowMelting-DG-H57045
12/15
27 / 43
Surface snow melting – MI Mineral insulated Heating Cable System
Table 6 Control Systems Catalog number
Description
MI-GROUND-KIT
Grounding kit for nonmetallic enclosures.
Automatic Snow Melting Controllers
APS-3C
Automatic snow melting controller housed in a Type 3R enclosure provides effective,
economical automatic control of all snow melting applications. Features include:
120 V or 208–240 V models, 24-A DPDT output relay and an adjustable hold-on timer.
Enclosure dimensions: 11-1/2 in x 9-1/8 in x 6-9/16 in (292 mm x 232 mm x 167 mm)
APS-4C
Automatic snow melting controller housed in a Type 3R enclosure provides effective,
economical automatic control of all snow melting applications. The APS-4C can operates with any number of SC-40C satellite contactors for larger loads. Features include:
277 V single-phase or 208–240, 277/480, and 600 V three-phase models, built-in 3-pole
contactor, integral 30 mA ground-fault circuit interrupter and an adjustable hold-on
timer.
Enclosure dimensions: 11-1/2 in x 9-1/8 in x 6-9/16 in (292 mm x 232 mm x 167 mm)
SC-40C
Satellite contactor power control peripheral for an APS-4C snow melting controller,
housed in a NEMA 3R enclosure. Features include: 277 V single-phase or 208–240,
277/480 and 600 V three-phase models, built-in 3-pole contactor and integral 30 mA
ground-fault circuit interrupter.
Enclosure dimensions: 11-1/2 in x 9-1/8 in x 6 in (292 mm x 232 mm x 152 mm)
Snow Melting Sensors and Accessories
28 / 43
CIT-1
Overhead snow sensor that detects precipitation or blowing snow at ambient temperatures below 38°F (3.3°C). For use with either an APS-3C or APS-4C automatic snow
melting controller.
SIT-6E
Pavement-mounted sensor signals for the heating cable to turn on when the
pavement temperature falls below 38°F (3.3°C) and precipitation in any form is
present. Microcontroller technology effectively eliminates ice bridging while ensuring
accurate temperature measurement. For use with either an APS-3C or APS-4C
automatic snow melting controller.
RCU-3
The RCU–3 provides control and status display to the APS–3C controller from a remote
location. It has a 2, 4, 6 or 8 hour CYCLE TIME adjustment, independent of APS-3C
setting.
RCU-4
The RCU–4 provides control and status display to the APS–4C controller and SC-40C
Satellite Contactor from a remote location. It has a 2, 4, 6 or 8 hour CYCLE TIME
adjustment, independent of the APS-4C or SC-40C setting.
EN-RaychemMISurfaceSnowMelting-DG-H57045
12/15
THERMAL Building SOLUTIONS
Surface Snow Melting Design
Table 6 Control Systems Catalog number
Description
Electronic Controllers
A0
A1
A2
A3
A4
A5
A6
A7
ACS-UIT2
ACS-PCM2-5
The Raychem ACS-30 Advanced Commercial Control System is a multipoint
electronic control and monitoring system for heat-tracing used in various commercial
applications such as pipe freeze protection, roof and gutter de-icing, surface snow
melting, hot water temperature maintenance and floor heating. The Raychem ACS-30
system can control up to 260 circuits with multiple networked ACS-PCM2-5 panels,
with a single ACS-UIT2 user interface terminal. The ACS-PCM2-5 panel can directly
control up to 5 individual heat-tracing circuits using electromechanical relays rated at
30 A up to 277 V.
ProtoNode-LER
ProtoNode-RER
The Raychem ProtoNode is an external, high performance multi-protocol gateway for
customers needing protocol translation between Building Management Systems (BMS)
and the Raychem ACS-30 or C910-485 controllers.
PROTOCESSOR
SERIAL ETHERNET
PROTONODE
B0
B1
B2
B3
S0
S1
S2
S3
By FieldServer Technologies
www.ProtoCessor.com
RS 485 GND
RS 485 RS 485+
The ProtoNode-LER is for LonWorks® systems; and the ProtoNode-RER is for
BACnet® or Metasys® N2 systems.
+PWR
- PWR
FRAME GND
RTD10CS
RTD-200
RTD50CS
THERMAL Building SOLUTIONS
Stainless steel jacketed three-wire RTD (Resistance Temperature Detector) used with
Raychem C910-485 and ACS-30 controllers.
RTD10CS: 10-ft (3 m) flexible armor, with 18-in (457 mm) lead wire and 1/2-inch NPT
bushing.
RTD-200: 6-ft (1.8 m) fluoropolymer with 1/2-in NPT bushing.
RTD50CS: 50-ft (3 m) flexible armor with 1/2-in NPT bushing
EN-RaychemMISurfaceSnowMelting-DG-H57045
12/15
29 / 43
Surface snow melting – MI Mineral insulated Heating Cable System
Power Distribution
Three-phase, 4-wire voltage supplies such as 208 V, 480 V, and 600 V are commonly
used for snow melting applications, especially for large areas. Designing the snow
melting system using a three-phase voltage supply results in a balanced heating
system load, since three identical cables are used in each circuit. In addition, since
three cables are used in each circuit, the result is a system with fewer circuits. For
small areas, it may not be possible to select three cables, and one or two heating
cables, single-phase connected, must be used.
The Delta wiring configuration shown in Fig. 11 is commonly used for three-phase
snow melting circuits. Each circuit comprises three heating cables of equal wattage
and connected as shown.
Fig. 12 shows the less common Wye wiring configuration. In this case, the three
heating cables are also of equal wattage, but most important is that the heating
cable voltage must equal the phase-to-neutral supply voltage.
Ground
A
Supply power
480 V, 3Ø, 4 W
B
Control power CIT-1
120 V
Snow sensor
C
MCB
15 A
Up to
2000 ft
3-pole contactor
120 volt coil
C
APS-3C
Snow/Ice Melting
Controller
APS
blakgb
bllfkldffd
fjsosfnfloo
dl;gffglf
20 A
3-pole circuit
breaker with shunt
trip/external ground
fault sensor
Slab temperature
sensor
20 A
APS-3C
Automatic snow
controller
To ground
fault module
Ground fault
sensor
B
480 V
480 V
Heating
cable sheath,
braid or ground
Note: For Delta connected heating
cables, the current in the supply
feeder, contactor, and breaker is equal
to the “Heating Cable Current” x 1.732.
C
A
480 V
Fig. 11 Typical three-phase DELTA connected heating cables with automatic snow melting
controller
30 / 43
EN-RaychemMISurfaceSnowMelting-DG-H57045
12/15
THERMAL Building SOLUTIONS
Surface Snow Melting Design
Ground A
Supply power
480 V, 3Ø, 4 W
B
Control power
CIT-1
120 V
Snow sensor
C
MCB
3-pole contactor
120 volt coil
15 A
Up to
2000 ft
C
APS-3C
Snow/Ice Melting
Controller
APS
blakgb
bllfkldffd
fjsosfnfloo
dl;gffglf
3-pole circuit
breaker with shunt
trip/external groundfault sensor
20 A
Slab temperature
sensor
20 A
APS-3C
Automatic snow
controller
To ground
fault module
Ground fault
sensor
B
Heating cable
sheath, braid
or ground
277 V
N
277 V
277 V
A
C
Note: For Wye connected heating
cables, the current in the supply
feeder, contactor, and breaker is equal
to the “Heating Cable Current.”
Fig. 12 Typical three-phase WYE connected heating cables with automatic snow melting
controller
Connecting heating cables in Delta or Wye configuration using three-phase voltage
supplies reduces the number of circuits required because three heating cables
are used in each circuit. For example, if you select three heating cables to operate
on 480 V, single-phase (i.e. 480 V across each cable), you need three 2-conductor
feeders, three 2-pole contactors, and three 2-pole breakers (i.e. three circuits)
as shown in Fig. 13. If the same three heating cables are connected in Delta
configuration to the 480 V, three-phase supply, you need one 3-conductor feeder,
one 3-pole contactor, and one 3-pole breaker (i.e. one circuit) as shown in Fig. 11. In
addition, decreasing the number of circuits will reduce the cost of the distribution
system.
THERMAL Building SOLUTIONS
EN-RaychemMISurfaceSnowMelting-DG-H57045
12/15
31 / 43
Surface snow melting – MI Mineral insulated Heating Cable System
C
Supply
B
voltage
A
Ground
C
C
C
Contactor
Contactor
Contactor
Breaker
Breaker
Breaker
JB
JB
Cable 1
Cable 2
JB
Cable 3
Heating cable
sheath, braid
or ground
Fig. 13 Simplified single-phase connected heating cables
Single Circuit Control
Heating cable circuits that do not exceed the current rating of the selected controller
can be switched directly. Fig. 14 shows a typical single-phase circuit where the
heating cable is controlled by a thermostat. When the total electrical load exceeds
the rating of the controller or if a single-pole controller is used to control a threephase circuit, an external contactor is required. In Fig. 11 and Fig. 12, the snow
melting controller is used to control the three-phase connected heating cables
through a contactor.
Heating cable
sheath, braid
or ground
ø
Heating
cable
1 ø supply
N
Temperature
controller
1-pole
GFEP breaker
Ground
Fig. 14 Single circuit control
Group Control
Multiple single-phase or three-phase circuits may be activated by a single snow
melting controller or thermostat (group control).
The SMPG power distribution panel is designed to control snow melting circuits
installed in medium sized areas. This panel is available in single-phase (SMPG1) and
three-phase (SMPG3) versions and includes ground fault protection, monitoring, and
control for snow melting systems. The snow melting system is energized after the
integrated snow controller receives an input from any of the remote sensors.
32 / 43
EN-RaychemMISurfaceSnowMelting-DG-H57045
12/15
THERMAL Building SOLUTIONS
Surface Snow Melting Design
Mounting brackets
Nameplate
HTC energized light
Power on light
Heater cycle
timed control
NP
Snow/Ice
melt controller
Heater thermostat (3R only)
Door lock
handle
NP
NP
G
G
NP
Control power
transformer
EUR - 5A
Main breaker
(optional)
NP
NP
NP
Power distribution
block
ground-fault
sensors
PDB
Alarm acknowledge
C.B. tripped alarm
R
GFS1
GFS2
GFS3 HTC
CB1
CB2
CB3
NP
Control wiring
Heat trace
contactor
NP
Heater (3R only)
NP
NP
Ground bar
Exterior View
Branch
breakers
(3 pole)
Interior View
Fig. 15 SMPG3 power distribution panel
Main circuit breaker (optional)
N
Incoming
power
Ground
Fuse
GIT-1
EUR-5A SNOW SWITCH
24 V
4
AUTOMATIC SNOW/ICE MELTING CONTROL PANEL
Remote annunciation
alarm circuit breaker
with alarm type #3)
Three-pole
main contactor
Three-pole circuit breaker
with shunt trip/external
ground fault sensor
Slab
temperature sensor
Control transformer
6
2
SUPPLY
SNOW/ICE
8
HOURS
60°F
55°F
HEATER
Aerial
CIT-1 snow sensor
10
0
HEATER
CYCLE
50°F
45°F
65°F
Gutter
ice sensor
70°F
75°F
80°F
85°F
TEMPERATURE
To ground fault module
SIT-6E
Junction box
A1
Pavement-mounted
sensor
3 Ø Delta connected
heating cables
B1
Heating
cable
sheath,
braid
or
ground
C1
Current
transformers
Ground
To ground fault module
A
B
C
Junction box
Heating
cables
3 Ø Wye connected
heating cables
Junction box
Three-pole circuit breaker
with shunt trip/external
ground fault sensor
Current
transformers
Ground
Terminal
block
Heating cable
sheath, braid
or ground
Fig. 16 Typical wiring diagram of group control with SMPG3
THERMAL Building SOLUTIONS
EN-RaychemMISurfaceSnowMelting-DG-H57045
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Surface snow melting – MI Mineral insulated Heating Cable System
Table 7 Power Distribution
Catalog number
Description
Power Distribution and Control Panels
SMPG1
NP
Single-phase power distribution panel that includes ground-fault protection, monitoring, and control for snow melting systems. Single-phase voltages include 208 and 277 V.
Refer to the SMPG1 data sheet (H57680) for information on selecting a control panel.
If standard configurations do not meet your requirements, contact your Pentair Thermal
Building Solutions representative for a quotation on a custom SMPG1 panel.
NP
NP
NP
NP
NP
NP
SMPG3
Three-phase power distribution panel that includes ground-fault protection, monitoring, and control for snow melting systems. Three-phase voltages include 208, 480, and
600 V. Refer to the SMPG3 data sheet (H57814) for information on selecting a control
panel.
NP
If standard configurations do not meet your requirements, contact your Pentair Thermal
Building Solutions representative for a quotation on a custom SMPG3 panel.
NP
NP
NP
NP
NP
NP
NP
NP
Contactors and Junction Boxes
E104
Three-pole, 100 A per pole, 600 V maximum contactor housed in UL Listed, CSA Certified, Type 4X enclosure with two 1-inch conduit entries. When ordering, select coil voltage (110–120, 208–240, 277 V).
Enclosure dimensions: 13-1/2 in x 9-1/5 in x 6-11/16 in (343 mm x 234 mm x 170 mm).
E304
Three-pole, 40 A per pole, 600 V maximum contactor housed in UL Listed, CSA Certified
Type 4X enclosure with two 1-inch conduit entries. When ordering, select coil voltage
(110–120, 208–240, 277 V).
Enclosure dimensions: 9-1/2 in x 7-1/5 in x 6-11/16 in (241 mm x 183 mm x 170 mm).
Example: Surface Snow Melting System
Automatic snow melting controller APS-4C
Quantity
1
Pavement-mounted sensor
SIT-6E
Quantity
1
Example: Surface Snow Melting System for Stairs
Slab sensing thermostat
ECW-GF
Quantity
1
Example: Surface Snow Melting System for Wheel Tracks
Automatic snow melting controller APS-4C
34 / 43
Quantity
1
Overhead snow sensor
CIT-1
Quantity
1
EN-RaychemMISurfaceSnowMelting-DG-H57045
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THERMAL Building SOLUTIONS
Surface Snow Melting Design
Surface Snow Melting
Step 8 Select the accessories
A typical Raychem snow melting system consists of several accessories. All of the
accessories work together to provide a safe and reliable snow melting system that is
easy to install and maintain.
1. Determine design
conditions
2. Determine the
required watt density
We recommend using the following as appropriate.
3. Determine the total
area to be protected
4. Select the heating
cable
5. Determine heating
cable spacing
6. Determine the
electrical parameters
7. Select the control
system and power
distribution
8. Select the
accessories
9. Complete the Bill
of Materials
Table 8 Accessories
Catalog
number
Description
Standard
packaging
Usage
HARD-SPACERGALV-25MM25M
Galvanized steel prepunched strapping
82 ft (25 m)
rolls
No. rolls = 0.005 x area (ft2)
No. rolls = 0.05 x area (m2)
HARD-SPACERSS-25MM-25M
Stainless steel prepunched strapping
82 ft (25 m)
rolls
No. rolls = 0.005 x area (ft2)
No. rolls = 0.05 x area (m2)
SMCS
Snow melt caution sign
Dimensions 6 x 4 in (150 x 100 mm)
1
1 minimum per system
D1297TERM4
A cast aluminum junction box (Type 3) for
installation in nonhazardous and CID2 locations. Three 1/2" NPT entries on bottom,
provided with plugs. Includes 4-pole terminal block (CSA - 600 V, 65 A, 18 - 6 AWG;
UL - 300 V, 65 A, 18 - 6 AWG). External
mounting feet. CSA approved for Class I,
Div. 2, Groups A, B, C, and D.
1
Enclosure dimensions: 6 in x 6 in x 4 in
(150 mm x 150 mm x 100 mm).
THERMAL Building SOLUTIONS
EN-RaychemMISurfaceSnowMelting-DG-H57045
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35 / 43
Surface snow melting – MI Mineral insulated Heating Cable System
Example: Surface Snow Melting System
Junction box
Contractor supplied
Prepunched strapping 1HARD-SPACER-GALV-25MM-25M
Quantity3
Snow melt caution sign
SMCS
Quantity2
1
Only required for two-pour slab construction
Example: Surface Snow Melting System for Stairs
Junction box
D1297TERM4
Quantity1
Prepunched strapping 1HARD-SPACER-GALV-25MM-25M
Quantity 1
Snow melt caution sign
SMCS
Quantity1
1
Only required for two-pour slab construction
Example: Surface Snow Melting System for Wheel Tracks
Junction box
D1297TERM4
Quantity1
Prepunched strapping 1HARD-SPACER-GALV-25MM-25M
Quantity1
Snow melt caution sign
SMCS
Quantity1
1
Surface Snow Melting
1. Determine design
conditions
2. Determine the
required watt density
Only required for two-pour slab construction
Step 9 Complete the Bill of Materials
If you used the Design Worksheet to document all your design parameters, you
should have all the details you need to complete the Bill of Materials.
3. Determine the total
area to be protected
4. Select the heating
cable
5. Determine heating
cable spacing
6. Determine the
electrical parameters
7. Select the control
system and power
distribution
8. Select the
accessories
9. Complete the Bill
of Materials
36 / 43
EN-RaychemMISurfaceSnowMelting-DG-H57045
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THERMAL Building SOLUTIONS
Raychem MI System Surface Snow Melting Design Worksheet
Raychem MI System Surface Snow Melting Design Worksheet
Step  Determine design conditions
Application and
environment
T Surface snow melting
Geographical location:
_______________________
Paving material
T Concrete
T Asphalt
T Pavers
Size and layout
Supply
voltage
Phase
Control method
Slab surface area (ft2 / m2):_____________
T 120 V
T Single-phase
Ramp surface area (ft2 / m2):___________
T 208 V
T Three-phase
T Automatic snow melting
controller
Stairs
T 240 V
T Slab-sensing thermostat
T 277 V
T Manual on/off control
Number of stairs:
______________
Stair width (ft/m):
______________
Riser height (in/cm):
______________
Stair depth (in/cm):
______________
Landing surface area (ft2 / m2):________
T 347 V
T 480 V
T 600 V
Wheel tracks
Track length (ft/m):
______________
Concrete joints:
______________
Surface drains:
______________
Location of area structures:____________
Other information as appropriate:
____________________________________
____________________________________
____________________________________
Example:
0 Surface snow melting
Ramp surface: 45 ft x 12 ft
0 480 V
0 Three-phase 0 Automatic snow
melting controller
0 Philadelphia, PA
0 Concrete ramp
Step  Determine the required watt density Surface snow melting system for slabs, ramps, stairs, and wheel tracks: See Table 1
Geographical location:
_______________________________
Paving material:
_______________________________
Required watt density:
_______________________________
Example: Surface Snow Melting System
Ramp surface
Geographical location: Philadelphia, PA (from Step 1)
Paving material:
Concrete (from Step 1)
Required watt density: 35 W/ft2 (from Table 1)
THERMAL Building SOLUTIONS
EN-RaychemMISurfaceSnowMelting-DG-H57045
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37 / 43
Surface snow melting – MI Mineral insulated Heating Cable System
Step  Determine the total area to be protected Total ramp/slab surface area
x
Length (ft/m)
=
Width (ft/m)
Surface area to be protected (ft2/m2)
For large areas and areas using a three-phase voltage supply
Length (ft/m)
/ No. of subsections =
Length of each
subsection (ft/m)
x
=
Width (ft/m)
Subsection area to be protected (ft2/m2)
Note: For three-phase voltage supplies, use multiples of three equal subsections.
Example: Surface Snow Melting System
Ramp
Calculate the surface area of the ramp for three-phase application
45 ft
/ 3 =
Length (ft)
15 ft
Length of each subsection (ft)
x
12 ft
Width (ft)
=
180 ft2
Subsection area to be protected (ft2)
Stairs
Calculate the heating cable needed for stairs and landing
Determine the number of cable runs needed
Stair depth:
< 10.5 in (27 cm): 2 cable runs
Stair depth:
10.5–12 in (27–30 cm): 3 cable runs
Cable runs needed:
Calculate the heating cable length for stairs
No. of stairs
x [(
No. runs per stair
x
Stair width (f/m)
) + (2 x
)] =
Riser height (ft/m)
Length of cable for stairs (ft/m)
Landing (attached to stairs)
Calculate the heating cable length for landing
(
x 12) / 4.5
Landing area (ft2)
(
Length of cable for attached landing (ft)
x 1000) / 115 =
Landing area (m2)
Length of cable
for stairs (ft/m)
=
+
Length of cable
for landing (ft/m)
Length of cable for attached landing (m)
=
Total heating cable length required (ft/m)
Wheel tracks
Wheel track length:
38 / 43
EN-RaychemMISurfaceSnowMelting-DG-H57045
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THERMAL Building SOLUTIONS
Raychem MI System Surface Snow Melting Design Worksheet
Step  Select the heating cable Surfaces: See Table 2 and Table 3.
Supply voltage:
(from Step 1)
Required watt density:
(from Step 2)
Subsection area:
(from Step 3)
Watt density (W/ft2) (W/m2)
x
Area (ft2/m2)
=
Required watts for area (W)
Heating cable catalog number:
Cable wattage:
Cable voltage:
Heating cable length:
Number of cables = Number of subsection areas
Example: Surface Snow Melting System
Supply voltage:
480 V, three-phase (from Step 1)
Required watt density for ramp:
35 W/ft2 (from Step 2)
Subsection area (for 3 equal areas):
180 ft2 (from Step 3)
Required watts (for each subsection):
35 W/ft2 x 180 ft2 = 6300 W
Heating cable catalog number:
SUB20
Cable wattage:
6450 W
Cable voltage:
480 V (for cables connected in Delta configuration)
Heating cable length:
340 ft
Number of cables:
3 (one cable required for each subsection)
Stairs: See Table 4
Supply voltage:
Required watt density:
Total heating cable length required:
Heating cable catalog number:
Cable wattage:
Cable voltage:
Heating cable length:
Number of cables:
Installed watt density:
______________________________________ (from Step 1)
______________________________________ (from Step 2)
______________________________________ (from Step 3)
______________________________________
______________________________________
______________________________________
______________________________________
______________________________________
______________________________________ (from Table 4)
Wheel Tracks: See Table 5
Supply voltage:
Wheel track length:
Heating cable catalog number:
Cable wattage:
Cable voltage:
Heating cable length:
Number of cables:
THERMAL Building SOLUTIONS
______________________________________ (from Step 1)
______________________________________
______________________________________
______________________________________
______________________________________
______________________________________
______________________________________
EN-RaychemMISurfaceSnowMelting-DG-H57045
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39 / 43
Surface snow melting – MI Mineral insulated Heating Cable System
Step  Determine the heating cable spacing Surfaces
Imperial (
Surfaces Surface area (ft2)
x 12 in) /
Imperial
Metric ((
Surface area (ft2)
Surface area (m2)
x 12 in) /
x 100 cm) /
Heating cable length (ft)
Heating cable length (ft)
Heating cable length (m)
in or
1 cm
Metric ( Round to the nearest x1/2100
cm)
/ to obtain cable spacing.
Surface area (m2)
Heating cable length (m)
=
Heating cable spacing (in)
=
=
Heating cable spacing (in)
Heating cable spacing (cm)
=
Heating cable spacing (cm)
Example: Surface Snow Melting System
Round to the nearest 1/2 in or 1 cm to obtain cable spacing.
Subsection area:
180 ft2 (from Step 3)
Cable spacing
Heating
cable catalog number:
180 ft2
Heating cable length:
(
Cable spacing
Surface area (ft2)
(
180 ft
SUB20 (from Step 4)
340 ft
340 ft (from Step 4)
x 12) /
Heating cable length (ft)
2
Surface area (ft )
2
x 12) /
340 ft
Heating cable length (ft)
6.4 in rounded to 6.5 in
=
Heating cable spacing (in)
6.4 in rounded to 6.5 in
=
Heating cable spacing (in)
Stairs
Stair depth:
Cable spacing – stairs:
Cable spacing – landing:
______________________________________ (from Step 1)
______________________________________ (refer to Step 5)
______________________________________ (refer to Step 5)
Wheel Tracks: See Table 5
Paving material:
Heating cable catalog number:
Cable spacing:
______________________________________ (from Step 1)
______________________________________ (from Step 4)
______________________________________ (refer to Step 5)
40 / 43
EN-RaychemMISurfaceSnowMelting-DG-H57045
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THERMAL Building SOLUTIONS
Raychem MI System Surface Snow Melting Design Worksheet
Step  Determine the electrical parameters Determine circuit breaker rating and number of circuits
Number of circuit breakers
Circuit breaker rating (A)
For single-phase circuit
Load current = Heating cable current (from selection tables)
(
Load current (A)
x 1.25 ) =
Minimum circuit breaker rating (A)
=
Circuit breaker rating (A)
For Delta connected three-phase circuit
Load current = Heating cable current (from selection tables) x 1.732
(
Load current (A)
x 1.25 ) =
Minimum circuit breaker rating (A)
=
Circuit breaker rating (A)
For Wye connected three-phase circuit
Load current = Heating cable current (from selection tables)
(
Load current (A)
x 1.25 ) =
Minimum circuit breaker rating (A)
=
Circuit breaker rating (A)
Determine transformer load
For cables of equal wattage
(
Cable (W)
x
Number of cables
) / 1000
=
Transformer load (kW)
When cable wattages are not equal
(
Cable1 (W)
+
Cable2 (W)
+
Cable3 (W)...
+
CableN (W)
) / 1000
=
Transformer load (kW)
Example: Surface Snow Melting System
For Delta connected three-phase circuit
(
(
Heating cable catalog number:
SUB20 (from Step 4)
Number of heating cables:
3 (from Step 4)
Cable power output:
6450 W (from Step 4)
Load current:
13.4 A (from Table 2) x 1.732 = 23.2 A
23.2 A
29.0 A
x 1.25 ) =
Load current (A)
Minimum circuit breaker rating (A)
6450 W
Cable (W)
x
3
Number of cables
THERMAL Building SOLUTIONS
) / 1000
EN-RaychemMISurfaceSnowMelting-DG-H57045
=
30 A
Circuit breaker rating (A)
=
12/15
19.4 kW
Transformer load (kW)
41 / 43
Surface snow melting – MI Mineral insulated Heating Cable System
Step  Select the control system and power distribution Control Systems
See Table 6 Control Systems.
Thermostats, controllers and
accessories
Description
T ECW-GF
Electronic thermostat with 25-ft sensor
____________
T ECW-GF-DP
Remote display panel for ECW-GF
____________
T ETI PD Pro
Automatic snow and ice melting controller
____________
T ETI GF-Pro
Automatic snow and ice melting controller
____________
T MI-GROUND-KIT
Grounding kit for nonmetallic enclosures
____________
T APS-3C
Automatic snow melting controller
____________
T APS-4C
Automatic snow melting controller
____________
T SC-40C
Satellite contactor
____________
T CIT-1
Overhead snow sensor
____________
T SIT-6E
Pavement-mounted sensor
____________
T RCU-3
Remote control unit for APS-3C
____________
T RCU-4
Remote control unit for APS-4C
____________
T ACS-UIT2
ACS-30 user interface terminal
____________
T ACS-PCM2-5
ACS-30 power control panel
____________
T ProtoNode-LER
Multi-protocol gateway
____________
T ProtoNode-RER
Multi-protocol gateway
____________
T RTD3CS
Resistance temperature device for Raychem ACS-30
____________
T RTD10CS
Resistance temperature device for Raychem ACS-30
____________
T RTD200
Resistance temperature device for Raychem ACS-30
____________
T RTD50CS
Resistance temperature device for Raychem ACS-30
____________
Quantity
Power Distribution and Control Panels
See Table 7 Power Distribution.
Power distribution and control
panels
Description
Quantity
T SMPG1
Single-phase power distribution panel
____________
T SMPG3
Three-phase power distribution panel
____________
Contactors
Description
Quantity
T E104
Three-pole, 100 A per pole contactor
____________
T E304
Three-pole, 40 A per pole contactor
____________
Example: Surface Snow Melting System
0 APS-4C
Automatic snow melting controller
0 SIT-6E
Pavement-mounted sensor
1
1
Step  Select the accessories See Table 8 Accessories.
Accessories
Description
Quantity
T HARD-SPACER-GALV-25MM-25M
T HARD-SPACER-SS-25MM-25M
T SMCS
T D1297TERM4
Galvanized steel prepunched strapping
____________
____________
____________
____________
Stainless steel prepunched strapping
Snow melt caution sign
Cast aluminum junction box
Example: Surface Snow Melting System
0
Junction box
(contractor supplied)
0 HARD-SPACER-GALV-25MM-25M1 Prepunched strapping
3
0 SMCS
2
Snow melt caution sign
1 Only required for two-pour slab construction
Step  Complete the Bill of Materials
Use the information recorded in this worksheet to complete the Bill of Materials.
42 / 43
EN-RaychemMISurfaceSnowMelting-DG-H57045
12/15
THERMAL Building SOLUTIONS
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thermal.info@pentair.com
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change specifications without prior notice.
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THERMAL Building SOLUTIONS
EN-RaychemMISurfaceSnowMelting-DG-H57045
12/15
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