Aprilaire Steam Humidifier FAQ`s

Aprilaire Steam Humidifier FAQ’s
General
Question: What is an Aprilaire Steam Humidifier?
Answer: An Aprilaire Steam Humidifier is a self-contained device that takes tap water
and boils it, using electric immersion heaters, to create steam. The steam flows through
a steam hose and is injected into a moving airstream by way of a distribution tube. The
steam flows out of the distribution tube into the duct work through a series of small
‘tubelets’ which create an even, drip-free transfer of steam into the moving airstream.
Question: What is the difference between Models 1150, 1160, and
1180?
Answer: The Aprilaire Steam Humidifier Model 1150 is a 12 lbs/hr capacity unit which
uses an ‘on/off’ Automatic Steam Humidifier Control. The Model 1160 is a 24 lbs/hr
capacity unit which uses a ‘modulating’ Automatic Steam Humidifier Control. The
Model 1180 is a 48 lbs/hr capacity unit which uses a ‘modulating’ Automatic Steam
Humidifier Control. In addition to the higher capacity, the modulating control of the
Model 1160 and 1180 allows for more flexibility in controlling indoor relative humidity.
Installation
Question: Are there types of water that the steam units should not be
connected to?
Answer: Yes. The units should not be connected to deionized water (DI) or reverse
osmosis (RO) systems. Both DI & RO water lack the conductivity required to enable
the water level probe control to properly function and allow the humidifier to operate.
In addition, DI water can have a corrosive effect on the non-stainless steel components
in the system, leading them to pre-mature failure.
Question: How much hard piping can you use with the 10 ft. steam
hose to extend the distance from the humidifier to the steam
distribution tube?
Answer: The issue is really about how much of a loss in steam capacity is acceptable
because the shorter the distance from the steam humidifier to the distribution tube, the
less steam loss there will be due to condensation. This is true whether using steam hose
alone or in combination with hard copper tubing.
The 1 ½ in. diameter steam hose supplied with Aprilaire Steam Humidifier Models 1150
and 1160 limits the loss to 0.15 lbs/hr for every foot of hose. When using non-insulated
copper tubing of the same diameter, the loss is 0.11 lbs/hr for every foot of tubing.
When using copper tubing with fiberglass insulation, the condensation loss drops to
0.02 lbs/hr for every foot of tubing.
The 2 in. diameter steam hose supplied with Aprilaire Steam Humidifier Model 1180
limits the loss to 0.20 lbs/hr for every foot of hose. When using non-insulated copper
tubing of the same diameter, the loss is 0.14 lbs/hr for every foot of tubing. When using
copper tubing with fiberglass insulation, the condensation loss drops to 0.025 lbs/hr for
every foot of tubing.
Here’s an example: a Model 1150 is installed with a 10 ft run of steam hose along with
an additional 15 ft run of insulated copper tubing. The nominal capacity of the 1150 is
12 lbs/hr.
Steam loss in the hose:
Steam loss in copper tubing:
10 (ft) x 0.15 (lbs/hr/ft) =
15 (ft) x 0.02 (lbs/hr/ft) =
Net steam delivered to duct:
1.5 lbs/hr
0.3 lbs/hr
10.2 lbs/hr
The example above is based on 80°F ambient air temperature and 2” fiberglass insulation.
All manufacturers of steam humidifiers (such as Nortec, Carnes, Pure, Armstrong,
Neptronic, and Dristeem) who use a hose and tube type system rate the output of the
humidifier and the actual output is slightly less depending upon the length and type of
hose or pipe used.
Question: Do the steam hose and distribution have to be sloped back
towards the humidifier?
Answer: The steam hose and/or tubing must have a minimum pitch of 2”/ft from the
distribution tube back to the humidifier to allow for condensation within the tube to fall
back into the steam chamber. If the application configuration does not allow for this, a
drip tee, P-trap, and drain must be installed at the steam distribution tube & hose
connection point. Refer to the ‘Installation, Operation, and Maintenance Manual’ for
more detailed information.
Question: Is connecting the humidifier to 208 volt verses the
recommended 240 volt electrical connection acceptable?
Answer: Yes. Operating the Models 1150 and 1160 at 208 VAC, single-phase versus
240 VAC, single-phase will have no negative impact on the life of any part of the
humidifier and will not affect the product warranty. The Model 1180 will also work
with 208 VAC triple-phase, versus 240 VAC
However, the capacity of the units will be less at the lower voltage. See below:
240 VAC
Electrical Capacity
Data
208 VAC
Electrical Capacity
Data
1150
240/1/60
12 lbs/hr
208/1/60
9 lbs/hr
1160
1180
240/1/60
240/3/60
24 lbs/hr
48 lbs/hr
208/1/60
208/3/60
18 lbs/hr
36 lbs/hr
Model
Question: What are the recommended minimum and maximum
distances for installing the steam tube from HVAC equipment
components such as the coil, filter, or blower?
Answer: In order to prevent hot steam from condensing onto surfaces in the duct work
such as coils, filters, blowers, elbows, or dampers, the steam distribution tube must not
be installed immediately upstream of any such obstructions. In virtually all
applications, 36” of clear, obstruction-free duct (return or supply) should be sufficient
distance to allow for full absorption of the steam into the airstream. The ideal
installation would be to install the distribution tube immediately downstream of the
HVAC equipment in a long (>36”) and obstruction-free section of the duct. Factors that
can reduce the actual distance required include: lower outdoor air requirements
(higher return air temperature), higher airflow velocity, and lower humidity load. If
your project does not allow for the recommended 36” of free and clear unobstructed
duct run, Refer to the ‘Installation, Operation, and Maintenance Manual’ for more
detailed information, including a procedure for calculating actual absorption distance
for a given set of conditions.
Question: Can flex duct be used in conjunction with Aprilaire Steam
Humidifiers?
Answer: In order to support the weight of the steam distribution tube and steam
hose, the distribution tube must be installed in a solid section of the ductwork or
plenum, allowing for minimum required absorption distance as described above.
However, if absorption distance requirements have been met, there is no reason
flex duct could not be used in either the supply or return branches.
Question: What are the minimum airflow requirements for Aprilaire
Steam humidifiers?
Answer: In reality, this question applies to all applications. The minimum airflow
relates to a bigger issue, duct saturation which can be the result of low air velocity in the
ductwork. Once 90% RH is exceeded in the duct, the air starts to become saturated,
(meaning that it cannot hold any more moisture) and it will start to condense on the duct
work. This is especially critical in low CFM and low outside air applications, typical of
residential variable speed equipment. When the humidifier calls the blower, at first it is
typical of the variable speed furnace to run at a very low speed, as low as 200 CFM. The
ductwork is sized for the maximum air delivery of the furnace system, and therefore when
it is runs at a low speed, the velocity may be as low as 100 FPM. At these very low
velocities, steam may actually be able to flow against the airflow, creating saturation in the
duct.
The solution to this problem is to maintain a minimum of 300 FPM velocity in the duct and
install the high humidity limit switch as a precaution.
The key here is to size the ductwork accordingly, or if the ductwork is existing, increase the
airflow. Please see the formula and example below for calculating air velocity:
CFM=DUCT AREA (in SQ FT) X VELOCITY (in Feet Per Minute, FPM)
Example:
If the job has a 400 CFM air flow and the duct is 20"x12"( 20X12/144=1.67 sq. ft.) , the
velocity is 239 FPM. (400 CFM/ 1.67 sq. ft. in the duct = 239 FPM). By increasing the air
flow to 500 CFM, we can deliver a velocity of 300 FPM. If we needed to stay at 400 CFM,
we would need to modify the duct system to approximately 16"x12" (1.33 sq.ft.) to deliver
300 FPM. (400 CFM/300 FPM= 1.33 Sq ft). The problem with modifying the duct system
for the low airflow is that the system would not perform properly at higher speeds as the
velocity would be too high, creating excess noise, and the pressure will increase and may
result in lower air flows than are acceptable. In most applications, it’s recommended the
installing contractor simply increase the airflow to accommodate the humidifier.
Unit Operation
Question: How much water is in the steam chamber each unit?
Answer: The operating capacity of the steam chamber in the Model 1150 is 1.4 gallons
of water, the operating capacity of the Model 1160 is 2.0 gallons, and the operating
capacity of the Model 1180 is 3.7 gallons.
Question: How long does it take the units to fill the steam chamber
and bring the water to boil?
Answer: Starting from an empty steam chamber, it takes just under 10 minutes for the
units to fill the tank with water and bring the water to boil. If the tank is full but the
water is cold because there has not been a call for humidity for some time, it will take
between 6 and 7 ½ minutes for the water to come to a boil.
Question: What are the lengths of time between drain intervals based
on varying water conditions?
Answer: When the Steam Humidifier is installed, a ‘water type’ dip-switch setting is
configured by the installer according to the water being supplied to the unit. The Steam
Humidifier will initiate auto drain cycles of the steam chamber at different times based
on this water type setting.
For ‘Normal’ water (hardness greater than 4 but less than 10 grains/gallon) the
humidifier will attempt to initiate the auto drain sequence after 36 hours of heater
operation. If there is a humidity demand at that time it will not drain. Instead it will
wait until the 72nd hour of heater run time. At that point the auto drain sequence
will override a humidity demand signal and the unit will drain. The cycle is then
repeated.
For ‘Hard’ water (hardness greater than or equal to 10 grains/gallon) the
humidifier will attempt to initiate the auto drain sequence after 24 hours of heater
operation. If there is a humidity demand at that time it will not drain. Instead it will
wait until the 36th hour of heater run time. At that point the auto drain sequence
will override a humidity demand signal and the unit will drain. The cycle is then
repeated.
For ‘Soft’ or ‘Softened’ water (hardness less than or equal to 4 grains/gallon) the
humidifier will attempt to initiate the auto drain sequence after 160 hours of heater
operation. If there is a humidity demand at that time it will not drain. Instead it will
wait until 240 hours of heater run time. At that point the auto drain sequence will
override a humidity demand signal and the unit will drain. The cycle is then
repeated.
The settings above are based on laboratory and field tests of standard units and may
not be applicable for every application. Also, not all water softeners work equally; as a
result, it may be beneficial to increase the auto drain frequency by configuring the
water type setting for hard water even if using Softened water.
Question: What are the power requirements for each unit?
Answer: The Model 1150 uses one 4 kW heater, the Model 1160 uses two 4 kW heaters
for 8 kW total, and the Model 1180 uses three 5.33 kW heaters for 16 kW total. The
current draw at 240 VAC is 16.7 Amps for the Model 1150, 33.3 Amps for the Model
1160, and the current draw for the Model 1180 at 240/3/60 is 38.5 Amps. The Model
1150 requires a 25 Amp (minimum) circuit breaker, the Models 1160 and 1180 requires
a 50 Amp (minimum) circuit breaker.
Question: What is the operating weight of the units?
Answer: The operating weight for a Model 1150 with a full steam chamber is 67 lbs.
The Model 1160 operating weight is 74 lbs, and the Model 1180 operating weight is 116
lbs.
Question: There was a pungent smell coming from the steam hose the
first time the unit was started up. Is this normal?
Answer: Yes. When the rubber in the steam hose is heated up the first time, a strong
odor may be present for about 15-30 minutes. This will only occur during the initial
period of operation.
Automatic Steam Humidifier Control Operation
Can the Automatic Steam Humidifier Control be used to control more
than 1 Aprilaire Steam humidifier?
Answer: No, the Automatic Steam Humidifier Control is designed to be powered
from one humidifier and then send a command signal back to that one humidifier.
Connecting a control to more than one unit could cause unpredictable operation.
Question: If used in conjunction with the Aprilaire Model 8570
thermostat, will the humidity level be displayed?
Answer: Yes. If the serial output (I+, I-) from the Automatic Steam Humidifier Control
is connected to the corresponding terminals on the Aprilaire 8570 thermostat, the
thermostat will display the indoor relative humidity. In addition, it will display the
outdoor temperature, assuming the outdoor temperature sensor is connected to the
Humidifier Control. Note that the indoor humidity will only be displayed on the 8570
when the blower is running.
Question: Can the Aprilaire Model 8570 thermostat be used in
conjunction with the ‘blower control by the humidifier’ feature of the
humidifier?
Answer: No. The humidifier cannot turn on the blower to satisfy a demand for
humidity when the serial outputs from the Automatic Steam Humidifier Control are
connected to the Model 8570 thermostat. In this application, the 8570 thermostat will
only allow the humidifier to operate during heating calls or thermostat-controlled fan
calls.
Question: Can the Model 8870 Communicating Thermostat be used
to control Aprilaire Steam Humidifiers?
Answer: The Model 8870 can be used with the Model 1150 because requires a 0 VDC
and 10 VDC ‘on/off’ signal and Model 8870 can provide a 0 VDC dry contact. The
Model 1160 and 1180 require a 0-10 VDC or 4-20 mA ‘modulating’ signal. The 8870
thermostat does not provide such output.
Question: What is ‘on/off’ versus ‘modulation’ control in the
Automatic Steam Humidifier Control?
Answer: With the on/off control used in the Model 1150, the Control tells the Steam
Humidifier to either be ‘full on’ or ‘off’ – nothing in between. This is fine for many
applications. With the modulating control used in the Model 1160 and 1180, the output
of the Control, and hence the Steam Humidifier, is a proportion of maximum output
based on how far the measured RH is from the setpoint RH. The output of the Steam
Humidifier is varied by turning the heaters on and off at a rate that changes as the
measured RH approaches the setpoint RH. It is a method for ‘throttling’ the Steam
Humidifier with the end result being a more precise control of indoor RH.
Question: On the left hand side of the Automatic Steam Humidifier
Control – under the wiring access door – there is a potentiometer
knob. What does this do? And what is the importance of the
proportional control band?
Answer: For the Model 1150 On/Off Control, the potentiometer is not active. The
potentiometer is functional only when the Control is used with a Model 1160 and 1180,
which is when the control is configured for modulation. This potentiometer is designed
to allow for flexibility in operation as far as the response time to meet humidification
requirements. There are 4 positions: 6, 9, 12 (factory setting), and 15. These numbers
refer to the ‘proportional control band,’ and the lower the number, the faster the
response time to meet the humidification need as the control modulates. The larger the
number, the longer the time it will take to respond to the humidity requirement. The
main difference is that at a lower number setting, the humidifier responds quickly but
the result can be more on/off cycles than desired as it reaches set point. This means it’s
possible to hear the contactor clicking on and off rapidly as the humidity level reaches
set point. By increasing to a higher number on the potentiometer, the rapid cycling is
reduced, and as a result the control responds slower to meet the humidity need.
Question: What is the humidity operating range of the Automatic
Steam Humidifier Control?
Answer: 15% to 55% RH.
Question: When installed in the automatic mode, does the Automatic
Steam Humidifier Control turn off when the outdoor temperature is
above a certain temperature?
Answer: Yes. When the Automatic Steam Humidifier Control is installed in the
automatic mode, the humidifier will not operate if the outdoor temperature is above
60°F.
Can the unit be operated based on a “signal by others” if there is
a building automation system present in the building?
Answer: Yes. The unit is capable of operating on a 0-10 vdc or 4-20 mA signal as
provided by others. Please refer to the unit configuration portion of the Installation
and Safety manual for humidifier set-up.
Maintenance
Question: What kind and frequency of maintenance is required for
these units?
Answer: Yearly cleaning of the steam chamber, drain piping, and water level probe is
all that is typically required. The use of naturally-occurring soft water, or water treated
by an ion exchange softener, may extend the required maintenance interval.