Product information | Carrier COBRA 48/50HJ004-014 Product data

COBRA™ Energy Recovery Units

48/50HJ004-014 with 62AQ060-300

Single-Package Rooftop Units and Field-Installed 62AQ060-300

ENERGY$RECYCLER™ Units

Application Data

CONTENTS

Page

GENERAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-10

Features/Benefits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

COBRA Curb Application . . . . . . . . . . . . . . . . . . . . . . . . 2

COBRA Iso-Exhaust Split Return Duct

Application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Field-Installed 62AQ Application . . . . . . . . . . . . . . . . 10

SYSTEM OPERATION . . . . . . . . . . . . . . . . . . . . . . . . 11-20

Cooling Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Heating Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Defrost . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Changeover Thermostats . . . . . . . . . . . . . . . . . . . . . . . 15

Fans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

COBRA and 62AQ Unit Options . . . . . . . . . . . . . . . . . 17

CONTROLS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21-28

Thermidistat™ Device. . . . . . . . . . . . . . . . . . . . . . . . . . . 21

PremierLink™ Controller . . . . . . . . . . . . . . . . . . . . . . . . 21

Gas Supply. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

WIRING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29-33

Field Power Supply. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Factory-Supplied Non-Fused Disconnect . . . . . . . 29

Field Control Wiring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

CONDENSATE PIPING . . . . . . . . . . . . . . . . . . . . . . . . . . 34

DAMPERS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

Supply-Air Dampers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

Barometric Relief Damper . . . . . . . . . . . . . . . . . . . . . . . 34

Multiple Stage Cooling Control . . . . . . . . . . . . . . . . . . 34

DESIGN EXAMPLES. . . . . . . . . . . . . . . . . . . . . . . . . . .35,36

Design Example 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

Design Example 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

SELECTION PROCEDURE WITH

PACKAGED ROOFTOP BUILDER . . . . . . . . . . . .37,38

GENERAL

Carrier’s COBRA™ energy recovery units and fieldinstalled 62AQ Energy$Recycler™ units use Carrier’s patented heat pump technology to reclaim energy from building exhaust air. This energy is then used to pre-condition ventilation air for the rooftop unit during winter and summer operation. These units are designed to satisfy higher ventilation requirements and other building codes while minimizing energy costs.

The 62AQ Energy$Recycler unit can be field-installed or factory-installed. When it is factory-installed on a 48HJ or

50HJ rooftop unit, the combined total package is designated as a COBRA unit. Factory installation of the 62AQ unit provides the benefit of reduced field-installation time, single point power connections, and the assurance of a factory test for the complete COBRA unit. The COBRA unit requires less maintenance than other energy recovery systems and can be serviced by a qualified refrigerant technician. See Fig. 1.

NOTE: The COBRA unit nameplate is located on the opposite end of the rooftop section, on the upper right-hand part of the panel due to the location of the 62AQ Energy$Recycler section.

For field-installed 62AQ applications, the 62AQ unit must be connected to the base unit in the field. The 62AQ unit attaches directly to the return air opening of the rooftop unit using hardware provided in an accessory mounting kit and support rail. Power and control wiring for the 62AQ unit are also field provided. The rooftop unit must be curb mounted in the vertical supply and return configuration only. Connection to competitive units requires field-supplied mounting arrangements and ductwork.

Additional literature available for 62AQ Energy$Recycler units or the combined COBRA units include:

• The 62AQ Energy$Recycler Product Data: applies to

COBRA and field-installed 62AQ units.

• The COBRA Energy Recovery Unit Installation, Start-

Up and Service Supplement: applies to COBRA units only.

• The 62AQ Energy$Recycler Installation, Start-Up and

Service Instructions applies to field-installed 62AQ units.

Features/Benefits —

Carrier’s COBRA and fieldinstalled 62AQ units provide all-in-one unitary offerings with energy recovery capability and total latent load control.

DOWNSIZE ROOFTOP UNIT — By pre-conditioning the outdoor air, the evaporator mixed entering air conditions can be reduced, which may allow for use of a smaller tonnage rooftop unit. Units have up to 100% outdoor air (OA) capability for compliance with industry ventilation standards.

COST EFFICIENT OPERATION — Utilizing energy from exhaust air allows for improved indoor air quality (IAQ) and enhanced rooftop unit efficiency at both peak and part load conditions.

ADDITIONAL STAGES — System flexibility allows for the energy recovery device to operate as an additional stage of heating or cooling.

EASE OF INSTALLATION — Available as a factoryinstalled option on the Weathermaster® 48/50HJ 3 to 12 1 /

2 ton rooftop product line, COBRA energy recovery units provide expanded capability to the rooftop unit’s performance. The factory-installed COBRA energy recovery unit is applicable for vertical-supply, vertical-return configuration units only.

UNIT MOUNTING — The 62AQ Energy$Recycler unit is designed to mount directly to vertically ducted rooftop units using an accessory mounting kit and support rail. No additional roof curb is required.

Book 1

Manufacturer reserves the right to discontinue, or change at any time, specifications or designs without notice and without incurring obligations.

1 Catalog No. 514-80013 Printed in U.S.A.

Form 48/50HJ,62AQ-2XA Pg 1 12-05 Replaces: 48/50HJ,62AQ-1XA

Tab 1a 1b

FACTORY INSTALLATION BENEFITS — When a 62AQ

Energy$Recycler™ unit is factory-installed on a rooftop unit, it is designated as COBRA™ unit. See Fig. 1 for COBRA configuration. Benefits of factory installation of the energy recovery section include:

• reduced field-installation time

• single point power connections

• pre-configured iso-exhaust option

• less maintenance than other energy recovery systems and serviceable by any qualified refrigeration technician

• single unit nameplate

ROOF CURB APPLICATIONS — COBRA and field-installed

62AQ units both require specific curb designs to support the additional weight of the Energy$Recycler (E$R) unit.

COBRA Curb Application —

The COBRA unit has two proven mounting options. The preferred method is to use the COBRA full-perimeter roof curb. See Fig. 2, 3A and 3B.

Two full perimeter curbs are available: part number

CRRFCURB022A00 is used with size 004-007 units, part number CRRFCURB023A00 is used with size 008-014 units.

The full perimeter curb complies with NRCA (National Roofing Contractors Association) standards.

The unit may also be mounted on a Carrier standard rooftop unit roof curb in combination with an accessory supplemental equipment support or a field-fabricated and field-installed support for the 62AQ section. The 62AQ section support is required if the Carrier standard rooftop unit roof curb is used.

See Fig. 4-7.

Ductwork attaches to the roof curb. DO NOT attach ductwork to the unit.

COBRA Iso-Exhaust, Split Return Duct Application —

A COBRA application is capable of utilizing an

“iso-exhaust” feature. Developed with indoor air quality in mind, the iso-exhaust option allows the exhaust of poor quality return air directly outside without contaminating supply air. In addition, the energy from the previously unused exhaust air is reclaimed and used to precondition the outdoor air, reducing the load on the evaporator coil and providing better comfort for occupants.

This design is ideal for applications where there is contaminated air (bathroom, photo processing, etc.) that cannot be returned to the conditioned space and, therefore, MUST be exhausted. A split-return-duct arrangement allows two separate return ducts to be attached to the roof curb: “R2,” which contains “contaminated air,” is routed into the E$R section; “R1” contains normal air that can be recirculated back to the space.

This design separates the two return airstreams so that the exhaust air and the rooftop unit return air do not mix. Thus, separate ducting is required for each stream of air, sized according to the openings of the E$R section and rooftop unit return.

The full perimeter roof curb featuring a “split-return” design is available for this application. Although the position of the

“curb splitter bracket” that separates the return air into two openings is adjustable, the COBRA “scoop” that directs the return air into the E$R section is a fixed dimension. Therefore, the “return support bracket” must be moved to appropriate dimension for the applicable scoop, and the scoop must be sealed (via provided seal-strip) to the roof curb. Additionally, the R1 and R2 field-supplied ductwork must be mated and sealed with the curb.

See Fig. 3A, 3B, 8A and 8B for additional details on

COBRA iso-exhaust dimensions.

COBRA SUPPLY FAN

NON-FUSED DISCONNECT

PREMIERLINK™

CONTROL OPTION

HIGH-STATIC FAN OPTION

STAINLESS STEEL HEAT

EXCHANGERS OPTION

EXHAUST

COBRA SUPPLY COIL

COBRA OUTDOOR

AIR (OA) DAMPER

OUTDOOR

AIR

COBRA EXHAUST COIL

COBRA EXHAUST FAN

SUPPLY

AIR

Fig. 1 — COBRA Energy Recovery Unit

RETURN

AIR

2

FULL PERIMETER

ROOF CURB

UNIT

3 to 6 Ton

7 1 /

2 to 12 1 /

2

Ton

PART NUMBER

CRRFCURB022A00

CRRFCURB023A00

WEIGHT (lb)

135

162

Fig. 2 — COBRA™ Energy Recovery Unit Mounting with Full Perimeter Unit Roof Curb

DO NOT USE THIS DRAWING TO FIELD-FABRICATE A CURB!

SIGNIFICANT PROBLEMS CAN OCCUR IF A CARRIER

APPROVED CURB IS NOT USED.

37 3/16"

DUCT OPENING SIZES

Supply = 13 7/8" x 20 1/4"

R1 = 13 5/8" x 17 3/4"

R2 = 13 5/8" x 12 5/16"

14"

R1 = Return from building to HVAC

R2 = Return from building to 62AQ

92 1/2"

2"

Deck pans

67 3/8"

3 1/4

R1

R2

Supply

2" Return support.

Only used on some applications.

Deck pans must be watertight

14"

37 3/16"

SIDE VIEW

END VIEW

Fig. 3A — COBRA Energy Recovery Unit Full-Perimeter Roof Curb — 48/50HJ004-007 with 62AQ060, 100

3

DO NOT USE THIS DRAWING TO FIELD-FABRICATE A CURB!

SIGNIFICANT PROBLEMS CAN OCCUR IF A CARRIER

APPROVED CURB IS NOT USED.

DUCT OPENING SIZES

Supply = 15 11/16" x 31 3/8"

R1 = 15 5/16" x 29 1/16"

R2 = 15 5/16" x 9" 14"

R1 = Return from building to HVAC

R2 = Return from building to 62AQ

49 15/16"

110 11/16"

2"

Deck pans

78 1/4"

3 1/4

R 1

R 2

Supply

2" Return support.

Only used on some applications.

Deck pans must be watertight

14"

49 15/16"

SIDE VIEW

END VIEW

Fig. 3B — COBRA™ Energy Recovery Unit Full-Perimeter Roof Curb — 48/50HJ008-014 with 62AQ200, 300

ADJUSTABLE

EQUIPMENT

SUPPORT

RUBBER

PAD

ROOF

STANDARD ROOFTOP UNIT

ROOF CURB

Fig. 4 — COBRA Energy Recovery Unit Mounting with Standard Roof Curb and Equipment Support

4

CONNECTOR

PKG. ACCY.

CRBTMPWR001A01

B C

CRBTMPWR002A01

CRBTMPWR003A01

1 ′-9 11 /

16

[551]

″ 1 ′-4″

[406]

CRBTMPWR004A01

D ALT

DRAIN

HOLE

1 3 /

4

″

[44.5]

GAS

3 /

4

″ [19]

NPT

1 /

2

″ [12.7]

NPT

3 /

4

″ [19]

NPT

POWER CONTROL

ACCESSORY

PWR

3 /

4

″ [19]

NPT

1 1 /

4

″

[31.7]

3 /

4

″ [19]

NPT

1 1 /

4

″

[31.7]

1 /

2

″

[12.7] NPT

1 /

2

″

[12.7] NPT

ROOF CURB

ACCESSORY

CRRFCURB001A01

CRRFCURB002A01

A

1

′-2″

[356]

2

′-0″

[610]

UNIT SIZE

004-007

NOTES:

1. Roof curb accessory is shipped disassembled.

2. Insulated panels.

3. Dimensions in [ ] are in millimeters.

4. Roof curb: galvanized steel.

5. Attach ductwork to curb (flanges of duct rest on curb).

6. Service clearance: 4 ft on each side.

7.

Direction of airflow.

8. Connector packages CRBTMPWR001A01 and

2A01 are for thru-the-curb type gas. Packages

CRBTMPWR003A01 and 4A01 are for thru-thebottom type gas connections.

Fig. 5 — Roof Curb Details (48/50HJ004-007 Section Only)

5

CONNECTOR

PKG. ACCY.

CRBTMPWR001A01

CRBTMPWR004A01

B C

CRBTMPWR002A01

CRBTMPWR003A01

2 ′-8 7 /

16

[827]

″ 1 ′-10 15 /

16

[583]

″

D ALT

DRAIN

HOLE

1 3 /

4

″

[44.5]

GAS

3 /

4

″ [19]

NPT

1 /

2

″ [12.7]

NPT

3 /

4

″ [19]

NPT

POWER CONTROL

ACCESSORY

PWR

3 /

4

″ [19]

NPT

1 1 /

4

″

[31.7]

3 /

4

″ [19]

NPT

1 1 /

4

″

[31.7]

1 /

2

″

[12.7] NPT

1 /

2

″

[12.7] NPT

ROOF CURB

ACCESSORY

CRRFCURB003A01

CRRFCURB004A01

A

1 ′-2″

[356]

2 ′-0″

[610]

UNIT SIZE

008-014

NOTES:

1. Roof curb accessory is shipped disassembled.

2. Insulated panels: 1-in. thick polyurethane foam,

1 3 / lb density.

4

3. Dimensions in [ ] are in millimeters.

4. Roof curb: 16-gage steel.

5. Attach ductwork to curb (flanges of duct rest on curb).

6. Service clearance 4 ft on each side.

7.

Direction of airflow.

8. Connector packages CRBTMPWR001A01 and

2A01 are for thru-the-curb gas type. Packages

CRBTMPWR003A01 and 4A01 are for thruthe-bottom type gas connections.

Fig. 6 — Roof Curb Details (48/50HJ008-014 Section Only)

6

CONDENSER-FAN

DISCHARGE AIR

EXHAUST

AIR

FRESH AIR

INLET

OUTDOOR-AIR

INLET

MOUNTING

KIT

ROOF CURB

RETURN AIR

BAFFLE

OUTDOOR AIRFLOW

FILTER

ACCESS

INDOOR AIRFLOW

SUPPLY AIR

RETURN AIR

Fig. 7 — Typical Energy$Recycler™ Installation

(Field-Installed 62AQ with Standard Unit Roof Curb Shown)

7

AA

(W)

(L)

6 2 A Q060 or 100

L O C A T I O N

1 0 .

3 i n .

1 0 .

3 i n .

A

B

(W)

(L)

6 2 A Q060 or 100

L O C A T I O N

L I P O N

S C O O P

E X T E N D S

O V E R T H I S

A R E A

S U P P L Y

LEGEND

R1 — Airflow recirculated through the 48/50HJ rooftop unit

R2 — Airflow through the

62AQ unit

62AQ SIZE

060,100

COBRA SCOOP OPENING

FOR RETURN AIR (A)

L (in.)

10.3

W (in.)

10.1

48/50HJ

SIZE

004-007

ROOFTOP RETURN-AIR

DUCT OPENING DIMENSIONS

(B)

L (ft-in.) W (ft-in.)

2-1 11 /

16

0-10 15 /

16

Fig. 8A — COBRA™ Iso-Exhaust Return Air Hood Dimensions —

48/50HJ004-007 Units with 62AQ060, 100

8

A

(W)

(L)

6 2 A Q200 or 300

L O C A T I O N

1 8 .

9 i n .

1 8 .

9 i n .

A

B

(W)

(L)

L I P O N

S C O O P

E X T E N D S

O V E R

A R E A

T H I S

6 2 A Q200 or 300

L O C A T I O N

S U P P L Y

LEGEND

R1 — Airflow recirculated through the 48/50HJ rooftop unit

R2 — Airflow through the

62AQ unit

62AQ SIZE

200, 300

COBRA SCOOP OPENING

FOR RETURN AIR (A)

L (in.) W (in.)

18.9

10.1

48/50HJ

SIZE

008

009-014

ROOFTOP RETURN-AIR

DUCT OPENING DIMENSIONS

(B)

L (ft-in.) W (ft-in.)

2-9 11 /

16

3-0 3 /

8

1-0 5 /

8

1-0 5 /

8

Fig. 8B — COBRA™ Iso-Exhaust Return Air Hood Dimensions —

48/50HJ008-014 Units with 62AQ200, 300

9

Field-Installed 62AQ Application —

A fieldinstalled 62AQ energy recovery unit cannot use a COBRA™ rooftop unit full perimeter curb. A standard curb with a mounting kit and an adjustable support are used, as shown in

Table 1 and Fig. 9 and 10.

Ductwork attaches to the roof curb; do not attach ductwork to the unit.

See the 62AQ installation instructions for details on mounting kits, support rails and installation.

Table 1 — Field-Installed 62AQ Required Equipment Support

ROOFTOP

UNIT SIZE

7 1 /

2

3-6 Ton

-12 1 /

2

Ton

62AQ UNIT

060, 100

200, 300

MOUNTING KIT

NUMBER

CRMTGKIT001A00

CRMTGKIT002A00

ADJUSTABLE EQUIPMENT SUPPORT RAIL

Part Number

CRAQSUPT001A00

Dimensions (in.)

A B C

36.9

40 8 to 14

CRAQSUPT002A00

CRAQSUPT003A00

CRAQSUPT004A00

36.9

40 14 to 24

49.7

54 8 to 14

49.7

54 14 to 24

NOTE: Pairing 3 to 6 ton rooftop units with 62AQ200 or 62AQ300 units is not a factory supported option. Contact

Application Engineer for additional information.

4”

A

ENERGY$RECYCLER™

SECTION

FLUSH MOUNTING

ROOFTOP UNIT

SECTION

C”

SCREW

SUPPORT

IN PLACE

ADJUSTABLE

EQUIPMENT

SUPPORT

(SEE FIG.10)

PAD

ROOF

UNIT ROOF

CURB

Fig. 9 — Rooftop Unit and Field-Installed 62AQ Unit

(NOT a COBRA Unit)

10” x B (SEE CHART)

PROTECTIVE

RUBBER PAD

(EPDM)

0.75” THICK

NOTE: See dimensions in Table 1.

Fig. 10 — Adjustable Equipment Support

10

SYSTEM OPERATION

The COBRA™ and field-installed 62AQ Energy$-

Recycler™ units replace the rooftop unit economizer and contain their own powered two-position outdoor air (OA) damper. See Fig. 1. Outdoor air passes through the damper, then through the upper coil and into the rooftop unit, where it mixes with return air before entering the rooftop evaporator coil. The exhaust portion of the rooftop unit return air is directed past the 62AQ Energy$Recycler (E$R) compressor, through the lower coil and then out to the atmosphere. The E$R portion of the unit is a heat pump that uses the preconditioned exhaust air as a heat source/sink. Refer to Fig. 11-17 and Tables 2A and

2B for operating information and system response.

In cooling mode the E$R upper coil acts as the evaporator.

When needed, the E$R upper coil cools and dehumidifies the outdoor air before it enters the rooftop unit. The lower coil acts as the condenser, which is cooled by building exhaust air. The net effect takes heat from the incoming outdoor air and rejects it into the exhaust air.

In heating mode, the E$R lower coil acts as the evaporator, which absorbs heat from the exhaust air before it is ejected into atmosphere. The upper coil acts as the condenser, which adds heat to the outdoor air before it enters the rooftop unit. The net effect is to remove heat from the building exhaust air and use it to warm the incoming outdoor ventilation air.

Additionally, the COBRA and field-installed 62AQ units utilize an occupied/unoccupied strategy to maximize conditioning efficiency. In general, a maximum of three stages are available for cooling: OA (if suitable for free cooling), the

62AQ Energy$Recycler unit and rooftop unit compressor 1, and the rooftop unit circuit 2. However, the 62AQ Energy$-

Recycler unit utilizes the occupied/unoccupied schedule, room temperature, humidity set points, and the OA thermostat set points to determine what is necessary to properly condition the air.

ROOFTOP UNIT

OUTSIDE AIR

ENERGY RECOVERY SECTION

EV

APORA

TO

R

MIXED AIR

EXHAUST AIR

70 F db/

67 F wb

OUTSIDE AIR

ROOF LINE

ROOM AIR

Fig. 11 — Typical Unit Airflow Diagram

SUPPLY AIR

ROOFTOP UNIT

THERMIDISTAT/

HUMIDISTAT


EV

APORA

TO

R

MIXED AIR

EXHAUST AIR

LEGEND db — Dry Bulb

RH — Relative Humidity wb — Wet Bulb

ROOF LINE

ROOM AIR

85 F db/

75 F wb

SUPPLY AIR

THERMIDISTAT/

HUMIDISTAT

NOTES:

1. If outdoor air quality is poor or outdoor air relative humidity is too high, only the rooftop unit compressor will be on during cooling. The energy recovery section will not energize when outdoor air is unsuitable.

2. Space temperature unoccupied set point = 84 F

Space temperature = 85 F

Space relative humidity set point = 65% RH

Space relative humidity = 63% RH

Fig. 12 — Typical Unoccupied Cooling Operation (Unsuitable Outdoor Air)

11

Cooling Mode —

The cooling changeover thermostat located on the hood of COBRA™ and 62AQ energy recovery units determines when the energy recovery unit goes into economizer mode. When the outdoor temperature is below the cooling set point, the unit will be in economizer mode.

In the unoccupied mode, fans are normally set for AUTO operation, causing the fans to cycle on only as needed for heating or cooling. If the light commercial Thermidistat™ device is set for “AUTO” fan, the rooftop unit fan will be off except when cooling or humidity control is required. The energy recovery unit fans will be off except when unit is running in the economizer mode. If the light commercial Thermidistat device is set to “ON” for fan, the energy recovery unit and rooftop unit fans will run continuously. If outdoor air is below the outdoor air thermostat set point, the compressors are locked off and the unit operates in economizer mode when cooling is required. If outdoor air is unsuitable due to humidity or quality, the energy recovery unit turns off and only the rooftop unit compressor runs when cooling is required.

NOTE: The energy recovery unit does not run and dampers are closed when the outdoor air is unsuitable for cooling and the mode is unoccupied. If outdoor air is suitable, first stage cooling is energy recovery unit in economizer mode and all compressors are off. Second stage cooling adds the energy recovery unit compressor and rooftop unit compressor no. 1.

In occupied mode, when the energy recovery unit compressor runs in cooling mode, it is extracting heat from the incoming outdoor air and rejecting heat to the exhaust air. The energy recovery unit and rooftop unit fans run continuously. On a first stage call, all compressors will be off if the outdoor air is suitable for free cooling. Otherwise, the energy recovery unit compressor and rooftop unit compressor no. 1 will run whenever there is a first stage demand for cooling. For units with a 2-stage rooftop unit, the energy recovery unit compressor and the rooftop unit compressor no. 1 and 2 will run whenever there is a demand for cooling on a second stage call.

Units with a single stage rooftop unit are not factory configured for a second stage call. If there is a demand for humidity control but not cooling, only the energy recovery unit

67 F db/

57 F wb

OUTSIDE AIR


EV

APORA

TO

R

MIXED AIR compressor will run. If there is a field-installed CO

2 sensor and the levels are below that sensor set point, then the unit will operate in the unoccupied mode sequence (the energy recovery unit dampers will be closed and rooftop unit operation maintains space conditions only).

Heating Mode —

The heating changeover thermostat located on the energy recovery unit hood determines the stage

1 to stage 2 switchover point in heating mode.

In unoccupied mode, the energy recovery unit is off and all compressors are locked off. First stage heat is rooftop unit heat at 50%. Second stage heat is rooftop unit heat at 100%.

In unoccupied mode, when the energy recovery unit compressor runs in heat mode, it is extracting heat from the exhaust air and rejecting heat to the incoming outdoor air; it is returning energy to the building that would, otherwise, be “thrown away.” The energy recovery unit and rooftop unit fans run continuously. The rooftop unit compressors are always off. On a first stage call, the energy recovery unit compressor is on in heat mode. Rooftop unit heat is off if the outdoor air is above the set point. Rooftop unit heat is on at 50% if the outdoor air is below the set point. On a second stage call, the energy recovery unit compressor is on in heat mode. Rooftop unit heat is on a

50% if the outdoor air is above the set point. Rooftop unit heat is on at 100% if the outdoor air is below the set point.

Defrost —

If the temperature of the 62AQ section condenser (exhaust air) coil drops below 28 F at the defrost thermostat (DFT) and the defrost timer is at the end of a timed period (adjustable to 30, 50 or 90 minutes), then the reversing valve solenoid (RVS) is energized and the condenser fan contactors are deenergized. This switches the position of the reversing valve and shuts off the 62AQ section condenser

(exhaust air) fan. The unit continues to defrost until the coil temperature measured at the DFT reaches 65 F or the defrost cycle completes a 10-minute cycle. At the end of the defrost cycle the RVS deenergizes and the exhaust fan motor energizes to put the unit in heating mode. If the space thermostat is satisfied during a defrost cycle, then the 62AQ section will continue in the Defrost mode until the defrost cycle is complete.

ROOFTOP UNIT

EXHAUST AIR


RH — Relative Humidity wb — Wet Bulb

ROOF LINE

ROOM AIR

85 F db/

72 F wb

SUPPLY AIR

THERMIDISTAT/

HUMIDISTAT

NOTES:

1. First stage — Unit is in economizer mode.

2. Second stage — Both energy recovery section and rooftop unit section compressors are not running.

3. Space temperature unoccupied set point = 84 F




Fig. 13 — Typical Unoccupied Cooling Operation (Suitable Outdoor Air)

12

95 F db/

78 F wb

OUTSIDE AIR


EV

APORA

TO

R

EXHAUST AIR

MIXED AIR

ROOFTOP UNIT


RH — Relative Humidity wb — Wet Bulb

ROOF LINE

ROOM AIR

78 F db/

69 F wb

SUPPLY AIR

THERMIDISTAT/

HUMIDISTAT

NOTES:

1. Space temperature occupied set points

Stage 1 = 75 F

Stage 2 = 76.5 F




2. Stage 1 Cooling = Energy Recovery section compressor ON, Rooftop Unit section compressor no. 1 ON.

Stage 2 Cooling = Energy Recovery section compressor ON, Rooftop Unit section compressors no. 1 and 2 ON. (2-Stage Rooftop units only)

Fig. 14 — Typical Occupied Cooling Operation (Space Temperature and Humidity Above Set Points)

ROOFTOP UNIT

95 F db/

78 F wb

OUTSIDE AIR


EV

APORA

TO

R

MIXED AIR

EXHAUST AIR



ROOF LINE

ROOM AIR

78 F db/

75 F wb

SUPPLY AIR

THERMIDISTAT/

HUMIDISTAT

NOTES:


Stage 1 = 75 F

Stage 2 = 76.5 F




2. Stage 1 Cooling = Energy Recovery section compressor ON, Rooftop Unit section compressor no. 1 ON.

Stage 2 Cooling = Energy Recovery section compressor ON, Rooftop Unit section compressors no. 1 and

2 ON. (2-Stage Rooftop units only)

Fig. 15 — Typical Occupied Cooling Operation

(Space Temperature Above Set Point and Space Humidity Below Set Point)

13

85 F db/

75 F wb

OUTSIDE AIR


EV

APORA

TO

R

EXHAUST AIR

MIXED AIR

ROOFTOP UNIT



ROOF LINE

ROOM AIR SUPPLY AIR

74 F db/

65 F wb

THERMIDISTAT/

HUMIDISTAT

NOTES:


Stage 1 = 75 F

Stage 2 = 76.5 F




2. Energy recovery section will energize compressors to provide humidity relief. Rooftop unit compressors will not energize.


(Space Temperature Below Set Point and Space Humidity Above Set Point)

ROOFTOP UNIT

95 F db/

78 F wb

OUTSIDE AIR


EV

APORA

TO

R

EXHAUST AIR

MIXED AIR


IAQ — Indoor-Air Quality


ROOF LINE

ROOM AIR

72 F db/

60 F wb

SUPPLY AIR

THERMIDISTAT/

HUMIDISTAT

NOTES:


Stage 1 = 75 F

Stage 2 = 76.5 F




2. Unit will not bring on compressors. Energy recovery and rooftop supply fans will run to provide outdoor air to satisfy IAQ ventilation demand.


(Space Temperature and Humidity Below Set Points)

14

Table 2A — COBRA™ Energy Recovery Unit Sequence of Operation — Unoccupied

COOLING

Indoor Temperature Above Y2*

Humidity Low & OAT Low

Humidity Low & OAT High

Humidity High & OAT Low

Humidity High & OAT High

Indoor Temperature Between Y1 & Y2*





Indoor Temperature Below Y1

Humidity Low

Humidity High

NOTE: OAT < 55 F all compression off

HEATING

Indoor Temperature Above W1

Indoor Temperature Between W1 & W2

Indoor Temperature Below W2

LEGEND

E$R — Energy$Recycler™ Unit

OAT — Outdoor Air Temperature

RTU — Rooftop Unit

E$R Compressor

On

Off

Off

Off

Off

Off

Off

Off

Off

Off

E$R Compressor

Off

Off

Off

UNOCCUPIED

E$R Fans RTU Compressor 1

On (cyc.)

Off

Off

Off

On (cyc.)

Off

Off

Off

Off

Off

On

On

On

On

Off

On

On

On

Off

On

E$R Fans

Off

Off

Off

RTU Compressor 2*

Off

On

On

On

Off

Off

On

On

Off

On

RTU Fans

On (cyc.)

On (cyc.)

On (cyc.)

On (cyc.)

On (cyc.)

On (cyc.)

On (cyc.)

On (cyc.)

Off

On (cyc.)

RTU Heat

Off

Off

Off

Off

Off

Off

Off

Off

Off

Off

RTU Compressor 1

Off

Off

Off

RTU Compressor 2*

Off

Off

Off

RTU Fans

Off

On (cyc.)

On (cyc.)

RTU

Heat†

Off

On, 50%

On, 100%

*Second stage for Y2 call applicable on rooftop units with 2 circuits only.

†50% rooftop unit heat only applicable with 2-stage electric or gas heating units.

Table 2B — COBRA Energy Recovery Unit Sequence of Operation — Occupied

E$R Compressor

OCCUPIED

E$R Fans RTU Compressor 1 RTU Compressor 2* RTU Fans COOLING

Indoor Temperature Above Y2*





Indoor Temperature Between Y1 & Y2*






Humidity Low

Humidity High


HEATING



OAT >Set Pt (30 F)

OAT <Set Pt (30 F)




LEGEND

E$R — Energy$Recycler Unit

OAT — Outdoor Air Temperature


On

On

On

On

Off

On

On

On

Off

On

E$R Compressor

Off

On

On

On

On

On

On

On

On

On

On

On

On

On

On

E$R Fans

On

On

On

On

On

On

On

On

On

Off

On

On

On

Off

Off

Off

On

On

On

Off

Off

On

On

Off

Off

On

On

On

On

On

On

On

On

On

On

RTU Heat

Off

Off

Off

Off

Off

Off

Off

Off

Off

Off


Off

Off

Off


Off

Off

Off

RTU Fans

On

On

On

RTU Heat

Off

Off

On, 50%

Off

Off

Off

Off

On

On

On, 50%

On, 100%

*Second stage for Y2 call applicable on rooftop units with 2 circuits only.

†50% rooftop unit heat only applicable with 2-stage electric or gas heating units.

Changeover Thermostats —

Changeover thermostats are used to adjust the changeover set points for heating and cooling. The thermostats must be relocated from the shipping location to the operating location in the supply outdoor air hood. See Fig. 18 for shipping arrangement.

COOLING — The cooling outdoor air changeover thermostat set point determines when the energy recovery unit goes into economizer mode (energy recovery compressor OFF, energy recovery supply fan ON). It is adjustable from 45 F to 75 F, will

“make” as the temperature falls and will reset at 4º F differential above the set point.

For example, if the cooling changeover thermostat is set for

72 F, the unit is in unoccupied or occupied mode, the outdoorair temperature is 70 F, there is low space relative humidity, and the unit cooling set point (Y1) is 75 F, then the first stage of cooling is the 62AQ Energy$Recycler section economizer. The second stage of cooling is the 62AQ Energy$Recycler section and the rooftop unit compressor no. 1. The rooftop unit no. 2 compressor is locked out below 55 F.

HEATING CHANGEOVER

THERMOSTAT (RED LABEL)

COOLING CHANGEOVER

THERMOSTAT

Fig. 18 — Changeover Thermostat

Shipping Location

15

HEATING — The heating outdoor air changeover thermostat determines the heating stage 1 to heating stage 2 switchover point. During heating, the rooftop unit supply fan and energy recovery unit supply fan are both always on. It is adjustable from 5 F to 50 F, will “make” as the temperature falls and will reset at 4º F differential above the set point.

As an example, if the switchover set point is 30 F and the outdoor ambient temperature is above 30 F, then the first stage of heating is the energy recovery unit. The second stage of heating is the energy recovery unit and the first stage of heating for the rooftop unit.

If the switchover set point is 30 F and the outdoor ambient temperature is below 30 F, then the first stage of heating is the

62AQ Energy$Recycler™ unit and the first stage of heating for the rooftop unit. The second stage of heating is the 62AQ

Energy$Recycler unit and the second stage of heating for the rooftop unit.

NOTES:

1. On rooftop units with only single stage heat, set the heating changeover thermostat as low as possible for 2-stage heat capability.

2. On units produced prior to December 2004, the labels for the Heating thermostats may require replacement. The correct label is shown in Fig. 19. See Service Managers

Bulletin (SMB) 04-0044 for obtaining a current outdoor air thermostat for heating label.

Fans —

There are two fans in the Energy$Recycler (E$R) portion of the COBRA™ energy recovery unit or fieldinstalled 62AQ unit: the supply fan and exhaust fan. For applicable fan curves, see the 62AQ Energy$Recycler Installation,

Start-Up and Service Instructions or the 62AQ

Energy$Recycler Product Data manual.

MAX

50 ˚

MIN

0 ˚ 10 ˚

20 ˚

40 ˚ 30 ˚ o OUTDOOR AIR THERMOSTAT

MOUNTING

1. MOUNT HEATING OUTDOOR AIR

THERMOSTAT (RED LABEL) WITH

2. SET DESIRED OUTDOOR AIR

TEMPERATURE BELOW WHICH

THE SECOND STAGE HEAT OF

THE MAIN UNIT IS ALLOWED

TO BE ENERGIZED.

Fig. 19 — Outdoor-Air Thermostat Heating Label

If the desired fan speed is not specified during the job selection, the proper settings for the E$R supply fan and damper and exhaust fan and damper must be determined using the applicable fan tables, the desired outdoor air cfm and return static pressure. See applicable Supply Air Fan Kit Accessory Installation

Instructions for additional details on altering fan speeds.

16

COBRA™ and 62AQ Unit Options

HUMIDI-MIZER™ OPTION (Units after October 2004) —

Units equipped with the Humidi-MiZer dehumidification option are capable of increased humidity control by utilizing a common subcooling/reheat dehumidification coil. This unique and innovative design provides the capability of the rooftop unit to operate in both a subcooling mode and a hot gas reheat

(HGRH) mode. A 48/50HJ rooftop unit equipped with the

Humidi-MiZer system can be used with or without a 62AQ

Energy$Recycler™ unit. See Fig. 20 for the HGRH mode of operation. See the Humidi-MiZer Application Data manual for additional details.

The incorporation of the Humidi-MiZer adaptive dehumidification system on a COBRA unit or a rooftop unit with a field-installed 62AQ unit adds significant flexibility to the overall system. The response of the Humidi-MiZer system to varying space conditions is extremely dynamic. The 48/50HJ rooftop unit equipped with the Humidi-MiZer system, with or without a COBRA energy recovery unit, will respond based on the temperature and humidity requirements as sensed in the space. Either a Carrier Thermidistat™ device (combined temperature and humidity sensing capability) or separate thermostat and humidistat can be used with the Humidi-MiZer system. Tables 3A and 3B outline the sequence of operation for

COBRA/62AQ energy recovery units equipped with the

Humidi-MiZer dehumidification option.

Unoccupied mode with Humidi-MiZer (Table 3A) — In the unoccupied mode, the Energy$Recycler (E$R) unit is off and all compressors are locked off. First stage heat is rooftop unit heat at 50%. Second stage heat is rooftop unit heat at 100%.

Occupied Mode with Humidi-MiZer (Table 3B) — In the occupied mode, when the E$R compressor runs in heat mode, it extracts heat from the exhaust air and rejects heat to the incoming outdoor air, returning energy to the building that otherwise would be wasted. The E$R and rooftop unit fans run continuously. Rooftop unit compressors are always off.

On a first stage call, the E$R compressor is on in heat mode.

If the outdoor air is above the set point, rooftop unit heat is off.

Rooftop unit heat is on at 50% if the outdoor air is below the set point. On a second stage call, the E$R compressor is on in heat mode. Rooftop unit heat is on at 50% if the outdoor air is above the set point. Rooftop unit heat is on at 100% if the outdoor air is below the set point.

NOTE: If there is a thermostat call from the space for heating, all dehumidification (both subcooling mode and hot gas reheat mode) will not operate.

Discharge

Line

Compressor

(Crankcase

Heater)

HGSV

(Hot Gas

Solenoid Valve) Condenser

Coil

Evaporator

Coil

Subcooling / Reheat

Dehumidification

Coil r

Outdoor Ai

Liq uid

Lin e

Suction Line

CCH

(Crankcase

Heater)

LPS

(Low Pressure

Switch)

(Equalizer

Line)

(Bulb)

Indoo r Air

TXV

(Thermostatic

Expansion

Valve)

Fig. 20 — Humidi-MiZer Dehumidification Option Schematic

(Hot Gas Reheat Mode of Operation)

LLSV

(Liquid Line

Solenoid Valve)

17

Table 3A — Humidi-MiZer™ Adaptive Dehumidification System Rooftop with COBRA™ Energy Recovery Unit

Sequence of Operation — Unoccupied

UNOCCUPIED

E$R Fans RTU Compressor 1 RTU Compressor 2 RTU Fans RTU Heat COOLING

Indoor Temperature Above Y2





Indoor Temperature Between Y1 & Y2






Humidity Low

Humidity High


HEATING




LEGEND

E$R — Energy$Recycler™ Unit

HGRH — Hot Gas Reheat

OAT — Outdoor Air Temperature

E$R Compressor

On

Off

Off

Off

Off

Off

Off

Off

Off

Off

E$R Compressor

Off

Off

Off


SC — Subcooling

On (cyc.)

Off

Off

Off

On (cyc.)

Off

Off

Off

Off

Off

E$R Fans

Off

Off

Off

On without SC

On without SC

On with SC

On with SC

Off

On without SC

On with SC

On with SC

Off

On with HGRH


Off

Off

Off

Off

On without SC

On with SC

On with SC

Off

Off

On with HGRH

On with HGRH

Off

On with HGRH


Off

Off

Off

On (cyc.)

On (cyc.)

On (cyc.)

On (cyc.)

On (cyc.)

On (cyc.)

On (cyc.)

On (cyc.)

Off

On (cyc.)

RTU Fans

Off

On (cyc.)

On (cyc.)

Off

Off

Off

Off

Off

Off

Off

Off

Off

Off

RTU Heat

Off

On, 50%

On, 100%

Table 3B — Humidi-MiZer Adaptive Dehumidification System Rooftop with COBRA Energy Recovery Unit

Sequence of Operation — Occupied

OCCUPIED

E$R Fans RTU Compressor 1 RTU Compressor 2 RTU Fans RTU Heat COOLING

Indoor Temperature Above Y2





Indoor Temperature Between Y1 & Y2






Humidity Low

Humidity High


HEATING








LEGEND

E$R — Energy$Recycler Unit

HGRH — Hot Gas Reheat

OAT — Outdoor Air Temperature

E$R Compressor

On

On

On

On

Off

On

On

On

Off

On

E$R Compressor

Off

On

On

On

On


SC — Subcooling

On

On

On

On

On

On

On

On

On

On

E$R Fans

On

On

On

On

On

On without SC

On without SC

On with SC

On with SC

Off

On without SC

On with SC

On with SC

Off

On with HGRH


Off

Off

Off

Off

Off

Off

On without SC

On with SC

On with SC

Off

Off

On with HGRH

On with HGRH

Off

On with HGRH


Off

Off

Off

Off

Off

On

On

On

On

On

On

On

On

On

On

RTU Fans

On

On

On

On

On

Off

Off

Off

Off

Off

Off

Off

Off

Off

Off

RTU Heat

Off

Off

On, 50%

On, 50%

On, 100%

MOISTUREMI$ER™ OPTION (Units prior to October

2004) — Units equipped with the MoistureMi$er dehumidification option have an up to 40% increase in latent capacity in hot, humid climates. The MoistureMi$er dehumidification option increases humidity control and comfort in the occupied space by automatically lowering the evaporator coil temperature down to optimum dehumidification levels while simultaneously reheating the leaving air to prevent overcooling. The

MoistureMi$er capabilities have been incorporated into the

Humidi-MiZer system; the MoistureMi$er is no longer an available option for units produced after October 2004.

INDOOR AIR QUALITY AND CO

2

CO

2

SENSORS — If a space sensor is desired, a field-installed 25% outdoor-air damper must be used for proper Demand Control Ventilation (DCV) operation. If not, the 62AQ Energy$Recycler Unit outdoor-air dampers will remain shut unless the space CO above the CO

2 set point.

2 levels are

The 25% outdoor-air damper should be placed in the normal location on the base rooftop unit. See Fig. 21. This damper will allow additional outdoor air to be brought in if the CO

2 level is high, independent of 62AQ unit operation. In the occupied mode, the 62AQ will usually bring in enough fresh air to maintain CO

2 levels below the set point. If not, the 25% outdoor-air damper will open to allow additional fresh air to be brought in. See Fig. 22 and 23 for control wiring. The recommended CO

2 sensor is a 33ZCSENC02 and the recommended

25% outdoor-air damper is a CRTWOPOS001A01 or a

CRTWOPOS002A01 (dependent on rooftop unit size). See

33ZCSENC02 or 25% outdoor-air damper installation instructions for additional information.

ENERGY EFFICIENCY RATIO (EER) — The Air Conditioning and Refrigeration Institute (ARI) rates rooftop units with specific external static pressure per net capacity rating with no outdoor air. The 62AQ Energy$Recycler unit uses outdoor air that is pre-conditioned by the return air. Therefore, no

ARI rating is available for COBRA™ and field-installed 62AQ units since there is no standard for these types of units.

18

ECONOMIZER USAGE — The energy recycler portion of a

COBRA unit or a field-installed 62AQ energy recovery unit contains an integral economizer with barometric relief for

“free” cooling when conditions are right. Therefore, an additional economizer is not needed and cannot be mounted on a rooftop unit equipped with the 62AQ Energy$Recycler™ feature.

AIRFLOW CONSIDERATIONS — A rooftop unit equipped with a 62AQ Energy$Recycler section is potentially capable of allowing up to 100% OA. This application depends specifically on the air conditions and the amount of airflow desired. Table 4 shows typical OA expectations for a COBRA or field-installed

62AQ Energy$Recycler unit. For exact capabilities on specific

COBRA applications, refer to the Packaged Rooftop Builder

(PRB) selection software. Field-installed 62AQ applications on similar rooftop models as COBRA units will have similar OA capabilities. See Table 5 for factory supported rooftop and

62AQ unit combinations.

When sizing the E$R unit, it is also important to select the correct ratio of outdoor air to exhaust air. When using the electronic selection software, the program will not allow unacceptable ratios. In general, the exhaust airflow determines the energy capacity available to condition the incoming outside air. Typically, the exhaust air cfm must be at least 50% the value of the OA cfm to satisfactorily precondition the OA.

Conversely, the OA flow must be great enough to properly transfer energy from the OA coil.

Therefore, a minimum OA flow exists; the exhaust air flow cannot be greater than the incoming OA flow. Additionally, allowing the exhaust airflow to be greater than the incoming outdoor airflow could result in space pressurization problems.

See Table 5 for minimum and maximum airflow parameters.

Table 5 — Factory Supported Rooftop Unit with

62AQ Unit Combination and Allowable Airflows

48/50HJ

UNIT SIZE

004-007

008-014

62AQ

MODEL

(E$R)

060

100

060*

100*

200

300

OUTDOOR AIR

CFM RANGE

(Min-Max)

300 600

500 - 1000

300 600

500 - 1000

1000 - 2000

1800 - 3000

LEGEND

E$R — Energy$Recycler Unit

OA — Outdoor Air

EXHAUST

CFM RANGE

(Min-Max)

300 - 100% of OA Value




1000 - 100% of OA Value

1800 - 100% of OA Value

*This unit combination is available only when the 62AQ is field-installed as an accessory.

Table 4 — Typical COBRA™ Unit Outdoor Air Usage

48/50HJ

UNIT

SIZE

004

005

006

007

008

009

012

014

NOM.

TONS

3

4

5

6

7 1 /

2

9 1 /

2

10

12 1 /

2

LEGEND

OA — Outdoor Air

RETURN

AIR AT

325 Cfm/Ton

(Total Cfm)

975

1300

1625

1950

2438

2763

3250

4063

OUTDOOR

AIR

(Cfm)

1000

1000

1000

1000

3000

3000

3000

3000

%

OA

103

77

62

51

123

109

92

74

RETURN

AIR AT

350 Cfm/Ton

(Total Cfm)

1050

1400

1750

2100

2625

2975

3500

4375

NOTE: Shading indicates outdoor-air usage capabilities of at least 100%.

OUTDOOR

AIR

(Cfm)

1000

1000

1000

1000

3000

3000

3000

3000

%

OA

114

101

86

69

95

71

57

48

RETURN

AIR AT

375 Cfm/Ton

(Total Cfm)

1125

1500

1875

2250

2813

3188

3750

4688

OUTDOOR

AIR

(Cfm)

1000

1000

1000

1000

3000

3000

3000

3000

%

OA

107

94

80

64

89

67

53

44

RETURN

AIR AT

325 Cfm/Ton

(Total Cfm)

1200

1600

2000

2400

3000

3400

4000

5000

OUTDOOR

AIR

(Cfm)

1000

1000

1000

1000

3000

3000

3000

3000

%

OA

100

88

75

60

83

63

50

42

Optional 25% OA Damper

ENERGY$RECYCLER™

SECTION

OPTIONAL

HUMIDI-MIZER COIL

EVAPORATOR

ROOFTOP UNIT (RTU)

COMPRESSOR 2

OUTSIDE

AIR

EXHAUST

AIR

COILS

COMPRESSOR MIXED AIR

HEAT

ROOF LINE

RA1 RA2

RETURN AIR SUPPLY AIR

COMPRESSOR 1

THERMIDISTAT™/

HUMIDSTAT

Fig. 21 — 25% Outdoor Air Damper Location

19

3

2

1

5

4

8

7

6

33ZCSENCO2

R1

24v Power

NO

(Alarm Relay

Contact)

1

R1

3

24v Power 4

R1

6

62AQ CONNECTION

BOARD

GRA

HM

OC

GRA

YEL

YEL

VIO

W2

T STAT

W1

WHT

WHT

R

C

Y1

Y2

G

W1

W2

OC

DEHUM

Commercial

Thermidistat

COM

6 7 10 8 2 3 4 1 5 9 11 12

CRTWOPOS001A01 or CRTWOPOS002A02

TWO POSITION DAMPER PLUG

LEGEND

Field-Provided Wires

NOTES:

1. R1 is a 2-pole, normally open relay (recommended relay: HN61KK040).

2. The space CO

2 level and set point can be read and changed locally.

Fig. 22 — CO

2

Sensor Wiring with Electro-Mechanical Controls

7

8

5

6

3

4

1

2

TB-2

(base unit control box)

SIG COM

4-20 mA

3

2

5

4

1

8

7

6

33ZCSENCO2

R1

24v Power

NO

(Alarm

Relay

Contact)

1

R1

3

24v Power 4

R1

6

HM

OC

W2

T STAT

W1

GRA

GRA

YEL

YEL

VIO

WHT

WHT

COM

6 7 10 8 2 3 4 1 5 9 11 12

CRTWOPOS001A01 or CRTWOPOS002A02

TWO POSITION DAMPER PLUG

LEGEND

Field-Provided Wires

NOTES:

1. R1 is a 2-pole, normally open relay (recommended relay: HN61KK040).

2. The space CO

2 level can be read on the Carrier Comfort Network®; set point must be changed locally.

Fig. 23 — CO

2

Sensor Wiring with PremierLink™ Direct Digital Control (DDC)

20

CONTROLS

There are three required inputs to properly control

COBRA™ or field-installed 62AQ units: temperature, humidity and an occupied/unoccupied schedule. The four recommended control combinations are:

• Thermidistat™ and electro-mechanical controls (Fig. 24)

• digital thermostat, humidistat and electro-mechanical controls (Fig. 25)

• humidistat, space temperature sensor and PremierLink™ controls (Fig. 26)

• Thermidistat and PremierLink controls (Fig. 27)

The most widely used combinations are the light commercial Thermidistat or PremierLink with thermostat and humidistat.

If the unit is equipped with the Humidi-MiZer™ or

MoistureMi$er™ option, these systems also require a humidity input. Non-E$R units require this humidity input to be wired into terminals in the rooftop unit. However, this is not necessary for a COBRA or field-installed 62AQ E$R unit. The E$R wiring accepts the sensed space humidity input and sends the appropriate signal to the rooftop unit. See Fig. 24-27.

NOTE: The humidity sensor device used with a COBRA or field-installed 62AQ unit with or without a Humidi-MiZer or

MoistureMi$er dehumidification option must be a contact closure type device such as a humidistat or a light commercial

Thermidistat device.

Thermidistat Device —

The light commercial Thermidistat device is a 7-day programmable, wall-mounted, low voltage field-installed control. It combines temperature and humidity control in a single unit and provides separate set points for heating and cooling. The control adds a dehumidification control function with separate set points for up to

2 occupied and unoccupied periods per day.

Different heating and cooling set points and times are programmable for up to 4 periods per day, 7 days per week. In case of a power loss, an internal memory stores programs and settings for unlimited time, and the clock continues to run for at least 8 hours. Batteries are not used. The light commercial

Thermidistat device (or Humidistat and temperature sensor) provides direct control of the energy recovery section, rooftop unit fans, and rooftop unit compressor in response to the programmed time schedules and temperature settings. The dehumidification output signal controls the energy recovery compressor to cool and dehumidify the supply air.

The light commercial Thermidistat device provides many operational control features which include a time guard timer, staging timer, minimum on-time, set point adjustment, equipment run indicators, dehumidification output and set point adjustment, auto changeover, power checks, error codes and smart recovery.

For additional information on the light commercial

Thermidistat device, refer to the light commercial Thermidistat device installation instructions.

PremierLink Controller —

The PremierLink digital controller, is a Direct Digital Control (DDC) box that mounts in the rooftop unit under the main unit control box. It is designed to be connected to the Carrier Comfort Network® (CCN) system, where all the input and output points and control screens can be monitored for servicing and troubleshooting purposes. However, the PremierLink can also be connected and operated via a thermostat. For details and additional information, refer to the Retrofit PremierLink Installation Instructions and Application Data.

The PremierLink controller is available factory-installed or as a field retrofit accessory. The PremierLink controller is designed to allow users the access and ability to change factory defined settings, thus expanding the function of the standard rooftop unit control. However, the PremierLink controller does not have an incorporated visual interface. It requires a

CCN accessory such as a Navigator™ device, System Pilot or personal computer equipped with Carrier’s Proprietary

ComfortWORKS® or ServiceTool software.

The PremierLink controller does not support humidity control. A separate field-supplied humidity device that supports contact closure must be used. However, remote humidity sensing and control on a CCN ystem is possible using a PremierLink controller, a 3V™ universal controller and a 3V compatible humidity sensor. In this configuration, the universal controller provides 24 vdc power to the humidity sensor and accepts a 4 to 20 mA humidity signal from the humidity sensor.

The universal controller provides an output relay contact that is connected to the HM terminal in the 62AQ section’s control box. The humidity sensor output does not connect directly to the COBRA unit. The universal controller is used to configure the humidity sensor’s set point; when the sensed humidity level is reached, the controller sends a signal to the HM terminal.

The universal controller is also connected to the CCN bus wiring, therefore the humidity set point and sensed humidity value is displayed on the network. One universal controller can be used for up to eight (8) different COBRA units.

The PremierLink controller has two modes of sensor input:

Temperature mode or Sensor mode. In Temperature mode, the

PremierLink controller accepts input from a Carrier approved space thermostat. Input connections for this mode use terminal strip TB3 as shown in Fig. 28-30. Terminal strip TB3 connects to the J4 contacts on the PremierLink module. When the

PremierLink controller is factory-installed, it is completely wired, except for the field-installed sensors. Currently, the only sensor that is included from the factory is the supply air temperature sensor. The following field installed sensors are required for PremierLink controller operation:

• space temperature — in sensor mode a space temperature sensor (SPT) is required, or for thermostat mode a thermostat is required, for all applications.

• outdoor-air temperature sensor (OAT) — required for all applications.

• supply-air temperature sensor (SAT) — required for all applications (included when PremierLink controller is factory- installed).

• indoor-air quality sensor (IAQ) — required for demand control ventilation.

• outdoor-air quality sensor (OAQ) — required for demand control ventilation.

21

BASE UNIT

CONNECTION

BOARD

R

Y1

Y2

W1

W2

G

C

X

CONTROL BOX

CONTROL

BOX

CONNECTION

BOARD

HM

OC

W2

T STAT

W1

W2

UNIT

W1

HM

HM

THERMOSTAT

CONNECTION

BOARD

R

C

Y1

Y2

G

W1

W2

OC

DEHUM

LIGHT COMMERCIAL THERMIDISTAT

Fig. 24 — Control Wiring with Thermidistat™ and Electro-Mechanical Controls

22

BASE UNIT

CONNECTION

BOARD

W2

G

C

X

R

Y1

Y2

W1

CONTROL BOX

CONTROL

BOX

CONNECTION

BOARD

HM

OC

W2

T STAT

W1

W2

UNIT

W1

HM

HM

HUMIDISTAT

HM

R

GRA

RED

OPEN HOLE

FOR WIRES

O/W 2

Y1/W 2

R

G

Y/Y 2

W/W1

C

B

L

DO NOT

USE

SI

S2

MOUNTING HOLES

Fig. 25 — Control Wiring with Digital Thermostat, Humidistat and Electro-Mechanical Controls

23

BLU

BRN

BLK

TB2

3

4

1

2

7

8

5

6

TB1

R

Y1

Y2

W1

W2

G

C

X

CONTROL BOX

PREMIERLINK

CONTROLS

ROOFTOP UNIT

SECTION

CONTROL

BOX

HM

OC

W2

T STAT

W1

W2

UNIT

W1

HM

HM

HUMIDISTAT

HM

R

GRA

R1

RED

1 2 3 4 5 6 RED(+)

WHT(GND)

BLK(-)

SW1

SEN SET

BLK

(T56)

BRN (GND)

BLU (SPT)

CCN COM

SENSOR WIRING

JUMPER

TERMINALS

AS SHOWN

Cool Warm

SPACE TEMPERATURE SENSOR

(33ZCT56SPT)

Fig. 26 — Control Wiring with Humidistat, Space Temperature Sensor, and PremierLink™ Controls

24

7

8

5

6

1

2

3

4

TB1

R

Y1

Y2

W1

W2

G

C

X

CONTROL BOX

PREMIERLINK

CONTROLS

CONTROL

BOX

HM

OC

W2

T STAT

W1

W2

UNIT

W1

HM

HM

THERMOSTAT

CONNECTION

BOARD *

C

G

R

Y1

Y2

W1

W2

OC

DEHUM

LIGHT COMMERICAL THERMIDISTAT

NOTE: Thermidistat connection terminal arrangement for schematic purposes only.

Fig. 27 — Control Wiring with Thermidistat™ and PremierLink™ Controls

25

26

27

GAS VALVE

CONNECTION

GAS

REGULATOR

(FIELD

SUPPLIED)

MANUAL

SHUTOFF

(FIELD

SUPPLIED)

GAS

PIPING

Fig. 32 — Thru-the-Bottom Gas Connections

TERMINAL

BLOCK

Fig. 30 — Field Wiring Connections

(Terminal Block in Energy Recovery Section)

Gas Supply —

The gas supply for 48HJ gas heat units can be run through the curb or through the bottom of the unit.

See Fig. 31 and 32. When installing the gas supply through the curb, the gas piping will exit through the side of the roof curb. The thru-the-curb accessory service connections (part numbers CRBTMPWR001A01 and CRBTMPWR02A01) are required. A field-supplied regulator is installed outside the unit and the piping is connected to the unit gas valve.

When installing gas supply through the bottom of the unit, the gas piping is routed through a knockout in the unit basepan and then connected to the unit gas valve. The thru-the-bottom accessory service connections (part numbers CRBTMPWR003A01 and CRBTMPWR004A01) are required. See Fig. 33 and 34.

EMBOSSMENT BRASS FITTING

SUPPORT

BRACKET

Fig. 33 — Internal Gas Piping with Thru-the-Bottom

Connection (3 to 6 ton Models Shown)

GAS VALVE

CONNECTION

GAS

REGULATOR

(FIELD

SUPPLIED)

MANUAL

SHUTOFF

(FIELD

SUPPLIED)

GAS

PIPING

Fig. 31 — Thru-the-Curb Gas Connections

UNION

LOUVERED

PANEL

DRIP LEG

MANUAL

SHUT OFF

Fig. 34 — External Gas Piping with Thru-the-Bottom

Connection (3 to 6 Ton Models Shown)

28

WIRING

For a COBRA™ unit, all interconnecting wiring between the rooftop unit section and the energy recovery section is factory-supplied and factory-wired. Wiring from power supply to unit is field-supplied. See the COBRA installation manual or the 62AQ Energy$Recycler™ Installation Manual for applicable unit wiring diagrams.

For routing of electrical wires through the base of the unit, via thru-the-bottom service connections (part numbers

CRBTMPWR001A01, 002A01, 003A01, and 004A01) see applicable installation instructions. See Fig. 35. See Fig. 36 for factory-supplied wiring routing in unit. These connections must be installed prior to setting the unit on the roof curb.

DO NOT install wire or gas connections through the base of the unit without proper watertight connectors.

Field Power Supply

COBRA UNITS — All units except 208/230-v units are factory wired for the voltage shown on the nameplate. If the 208/

230-v unit is to be connected to a 208-v power supply, the transformer must be rewired by moving the black wire with the

1 /

4

-in. female space connector from the 230-volt connection and moving to the 200-volt side of the transformer.

1 /

4

-in. male terminal on the primary

Refer to unit label diagram for additional information.

Pigtails are provided for field wire connections. Use factorysupplied splices or UL (Underwriters’ Laboratories) approved copper/aluminum connector. See Fig. 35-38 for COBRA power wiring information.

NFD

COBRA™ UNIT

When installing units, provide a disconnect per the NEC

(National Electrical Code). All field wiring must comply with

NEC and local requirements.

FIELD-INSTALLED 62AQ UNITS — Field-installed 62AQ units are labeled with a separate nameplate from the rooftop unit. Both units must be provided with a disconnect; unlike a

COBRA unit, the 62AQ unit cannot be powered with a single rooftop disconnect. However, Fig. 39 and 40 show two available methods of providing power wiring for field-installed

62AQ units. Note that Method A requires use of the “combined power” information, as seen on a typical electronic performance selection. Fig. 35, 36, 39 and 40 for field-installed

62AQ power wiring.

See the installation manual for 62AQ units for additional information.

When installing units, provide a disconnect per the NEC

(National Electrical Code). All field wiring must comply with

NEC and local requirements.

Factory-Supplied Non-Fused Disconnect —

The factory-supplied disconnect is capable of handling disconnect amps up to 80 A for the Weathermaster® COBRA unit. For disconnect amps greater than 80 A, a field-supplied disconnect is required.

Field Control Wiring —

A COBRA or field-installed

62AQ unit requires 3 inputs for proper control of the unit: temperature, humidity and an occupied/unoccupied schedule.

Table 1 shows the recommended sensor configurations.

See Fig. 30 and 41 for terminal block locations. See

Fig. 24-27 for control wiring information. See Fig. 42 for CCN

(Carrier Comfort Network®) wiring information.

NFD

COBRA UNIT

NFD

COBRA UNIT

NFD

COBRA UNIT

MAIN POWER SUPPLY

(FUSES OR HACR BKRS)

POWER

WIRING

LEGEND

NFD — Non-Fused Disconnect

NOTE: If disconnect amps exceed 80 amps, a field-supplied disconnect is required.

Fig. 35 — Typical Field Wiring Power Connections

29

MOTORIZED OUTDOOR AIR DAMPER

ENERGY

RECOVERY

SECTION

ROOFTOP

UNIT

SECTION

CONTROL

BOX

UNIT

CONTROL

BOX DISCONNECT

UNIT

WIRING

FACTORY-MOUNTED

STEP DOWN

TRANSFORMER

(460-V 004-007 ONLY)

Fig. 36 — Factory Wire Routing for COBRA™ Energy Recovery Unit

POWER WIRING OPTIONS FOR FIELD INSTALLED 62AQ ENERGY RECYCLER

(NOT Applicable to COBRA Units)

Disconnect sized per 62QA

MOCP and

Disconnect ratings

Wire sized per 62AQ Amp rating

(62AQ MCA)

Disconnect sized per combined MOCP and

Disconnect ratings

62 AQ

Field-

Ins talled

48/50HJ Rooftop Unit

Wire sized to handle combined

Amp load (Combined RTU with

62AQ MCA)

NOTE: Single power feed to rooftop unit and branch feed to 62AQ unit.

LEGEND

MCA — Minimum Circuit Amps

MOCP — Maximum Overcurrent Protection

RTU — Rooftop Unit

Fig. 37 — Method A: Field-Installed 62AQ Combined Power Wiring Connections

Disconnect sized 62AQ MOCP and

Disconnected ratings

Wire sized per 62AQ

Amp rating

(62AQ MCA)

Disconnect sized per

RTU MOCP and

Disconnect ratings 62 AQ

Field-

Ins talled

48/50HJ Rooftop Unit

Wire sized per RTU Amp load

(RTU MCA)

LEGEND

MCA — Minimum Circuit Amps

MOCP — Maximum Overcurrent Protection

RTU — Rooftop Unit

NOTE: Dual power feed to both rooftop and 62AQ units.

Fig. 38 — Method B: Field-Installed 62AQ With Separate Power Wiring

30

RACEWAY LOW VOLTAGE

CONNECTIONS

INTEGRATED GAS UNIT

CONTROLLER (IGC)

FIELD-SUPPLIED

DISCONNECT

(IF REQUIRED)

PREIMERLINK™

CONTROL

(OPTIONAL)

CONDUIT WITH

WATERTIGHT

CONNECTIONS

(FIELD-SUPPLIED)

OPTIONAL

INTERNAL

DISCONNECT

(80 AMP MAX)

ROOF CURB

POWER

SUPPLY

POWER WIRING

Fig. 39 — Power Wiring Routing with Thru-the-Bottom Accessory (COBRA™ and 62AQ Units)

RACEWAY LOW VOLTAGE

CONNECTIONS

INTEGRATED GAS UNIT

CONTROLLER (IGC)

FIELD-SUPPLIED

DISCONNECT

(IF REQUIRED)

PREIMERLINK™

CONTROL

(OPTIONAL)

WIRING KNOCKOUT

CONDUIT

ROOF

CONDUIT

OPTIONAL IINTERNAL

DISCONNECT

(80 AMP MAX)

ROOF CURB

POWER

SUPPLY

POWER WIRING

Fig. 40 — Power Wiring Routing from Outside of Unit (COBRA and 62AQ Units)

31

PREMIERLINK™ TERMINAL

BLOCK

(TB2) (TB3)

CONTROL WIRING

TERMINAL BLOCK

(TB1)

DISCONNECT

POWER WIRING

Fig. 41 — Field Wiring Connections (Terminal Blocks in Rooftop Unit Section)

32

COBRA™ ENERGY RECOVERY

UNIT CONTROL

BOX

TB3

1

2

3

4

RED

WHT

BLK

7

8

5

6

3 WIRE COM BUS

COBRA ENERGY RECOVERY

UNIT CONTROL

BOX

TB3

1

2

3

4

RED

WHT

BLK

7

8

5

6

3 WIRE COM BUS

COBRA ENERGY RECOVERY

UNIT CONTROL

BOX

TB3

1

2

3

4

RED

WHT

BLK

7

8

5

6

3 WIRE COM BUS

Cool Warm

T-58

DIGITAL

DISPLAY

SENSOR

Cool Warm

T-58

DIGITAL

DISPLAY

SENSOR

Cool Warm

T-58

DIGITAL

DISPLAY

SENSOR

CCN

ASCII

OUTPUT/INPUT

READ/WRITE

Carrier

COMFORT

NETWORK

TEMPORARY OR PERMANENT ACCESS

RS-232

RS-232

MODEL TO

RS-

485

R

S

-4

85

RS232, RS485 ADAPTER PC

BUILDING MECHANICAL ROOM

LID2B

3 RD

PARTY*

CONTROL

PLATFORM

*Example: METASYS, Allerton, ALC, Landis Stafa.

DATA LINK

READ/WRITE

Fig. 42 — CCN Bus Wiring

OR

33

CONDENSATE PIPING

Condensate piping from the COBRA™ energy recovery unit exits at the Energy$Recycler™ unit, near the bottom left corner of the exhaust air outlet. Condensate from the rooftop unit is piped to the Energy$Recycler condensate pan, so only one field-installed condensate line is required.

The bottom drain on the rooftop unit cannot be used as a condensate drain on a COBRA unit. An external P trap at least

4 in. deep is required, and must be protected against freeze-up in cold climates. Do not use pipe smaller than ¾ in. See Fig. 43.

Additionally, ensure that condensate drain from the rooftop section and the condensate drain hose from the drain pan is not crimped or sagging or water will not flow through the tubing.

DAMPERS

The outdoor-air dampers of the energy recovery section are fully adjustable. See Fig. 44.

Supply-Air Dampers —

The supply-air damper is a motorized, two-position (open/closed), spring-return type damper. There are 3 adjustable outdoor air intake stops to fix the amount of outdoor air intake in economizer mode. The factory set position is 45 degrees. The supply air fan motor is a

3-speed motor that is factory set for medium speed.

Barometric Relief Damper —

The barometric relief damper is located in the exhaust fan section. The exhaust air fan motor is a 3-speed motor that is factory set for medium speed. The damper limiter can be set for 30, 45, or 60 degrees open (90 degrees open is not required) based on cfm and fan speed.

Multiple Stage Cooling Control —

Stage 1 is free cooling by opening the supply-air dampers and bringing in

CONDENSATE DRAIN

FROM ROOFTOP

SECTION cool outside air. Stage 2 is efficient cooling with the energy recovery section as outdoor temperatures rise. Stage 3 is cooling operation of the rooftop unit during peak outdoor conditions.

SUPPLY

AIR DAMPER

TWO-POSITION

OUTDOOR AIR DAMPER

STOPS (ADJUSTABLE)

BAROMETRIC RELIEF DAMPER

(IN EXHAUST HOOD)

Fig. 44 — Outdoor-Air Dampers

CONDENSATE DRAIN FROM

ENERGY RECOVERY SUPPLY

(EVAPORATOR) COIL

ENERGY RECOVERY EXHAUST

(CONDENSER) COIL

ENERGY RECOVERY

SECTION DRAIN PAN

Fig. 43 — Condensate Drain Location

34

CONDENSATE

DRAIN

OUTLET

FROM UNIT

DESIGN EXAMPLES

Design Example 1 —

Carrier’s COBRA™ energy recovery unit pre-conditions ventilation air by recovering energy from the building exhaust air during both summer and winter operation. Additionally, the COBRA energy recovery unit will benefit the application by potentially allowing higher amounts of outdoor air to be utilized. This section outlines two brief design examples to illustrate the flexibility and dehumidification capacity of a COBRA energy recovery unit or

Weathermaster® 48/50HJ rooftop unit with the field-installed

62AQ Energy$Recycler™ section and how this system would perform.

Consider a school classroom in Houston, Texas with the following design characteristics:

• Total classroom area = 1,500 sq ft

• Total classroom volume = 15,000 cu ft

The design occupancy for this classroom is 30 students or roughly 10 people per 500 sq ft. Based on this occupancy, in accordance with ASHRAE (American Society of Heating,

Refrigeration, and Air Conditioning Engineers) 62, the design ventilation rate would be 15 cfm/person or 450 cfm total for this classroom.

To evaluate the full and part load rooftop performance, design requirements for the classroom will be evaluated at three conditions to assess annual full and part load operation to include:

1. Peak dry bulb (outdoor)

2. Peak dew point (outdoor)

3. Extremely high humidity (outdoor)

For each condition, the necessary rooftop performance will be calculated to evaluate the capacity requirements and associated required supply-air temperature from the unit to maintain space comfort conditions. The following formulas will be used:

OA Sensible Load = 1.08 x cfm oa

OA Latent Load = 0.7 x cfm oa x (T x (W oa oa

– T

– W sp sp

)

)

Where:

Cfm oa

= outdoor airflow in cu ft/min

T oa

T sp

W oa

W sp

= temperature of outdoor air in degrees of Fahrenheit

= temperature of space in degrees of Fahrenheit

= grains of water per pound of dry air of outdoor air

= grains of water per pound of dry air of space

NOTE: The W oa and W sp values of outdoor air can be obtained using the psychrometric chart.

For Houston, the outdoor peak dry bulb (db) and coincident mean wet bulb (mwb) 1% conditions are 94 F db and 77 F (per the ASHRAE Fundamentals Handbook). The design room conditions are 75 F (space temperature) db and 62.5 F wet bulb

(wb) (or roughly 50% relative humidity). At these conditions, the calculated indoor sensible (wall, roof, solar, windows, etc.) and latent (people) room loads for the classroom are

33,000 Btuh and 6,150 Btuh. The total room load is 33,000 +

6,150 = 39,150 Btuh.

For design purposes, there will be roughly 6.5 air changes per hour for the classroom. Therefore, the constant volume supply air from the rooftop unit would be (15,000 cu ft x 6.5)/

60 = approximately 1,600 cfm. For this design supply airflow rate, the mixed air conditions entering the standard evaporator coil is 80.3 F db/66.7 F wb. See Table 6 for summary of peak db temperature conditions. In addition the calculated outdoor air loads are:

OA (sensible) = 1.08 x 450 x (94 – 75) = 9,276 Btuh

OA (latent) = 0.7 x 450 x (111 – 72) = 11,934 Btuh

The total capacity required of the rooftop unit including all sensible and latent room and outdoor loads is:

33,000 + 6,150 + 9,276 + 11,934 = 60,360 Btuh

35

Including total sensible capacity:

33,000 + 9,276 = 42,776

Total latent capacity:

6,150 + 11,934 = 18,084

Select the 48/50HJ006 5-ton rooftop unit based on the total outdoor air and room load requirements.

Table 6 — Peak Dry Bulb Temperature Summary

TEMPERATURE SUMMARY

Outside-Air Temperature

Space Temperature

Entering-Air Temperature

DRY BULB

94 F

75 F

80.3 F

WET BULB

77 F

62.5 F

66.7 F

Now that the desired supply air quantity is known, it is possible to estimate the required supply-air temperature and performance for the rooftop unit to maintain the desired indoor conditions. At peak conditions, the SHR (the sensible to total heat rise in the room) and associated supply air temperature requirement is:

SHR (Peak Dry Bulb) = 33,000/39,150 = 0.84

33,000 Btuh = 1.08 x 1,600 cfm x (75 F – T)

Supply Air Temperature = 56 F

A supply-air temperature of 56 F is required for the sensible to total (SHR) heat ratio of 0.84 in the room. A supply-air temperature of 56 F is required to absorb the proportions of sensible and latent room load (per the SHR), so that space conditions are maintained at 75 F. Table 7 outlines a comparison of classroom requirements vs. actual rooftop performance to summarize the required classroom conditioning and the associated rooftop capacity under peak dry bulb conditions.

Table 7 — Peak Dry Bulb Operation Summary,

Normal Design Cooling Mode

48/50HJ006

Total Capacity

Outdoor Sensible

Outdoor Latent

Sensible Capacity

Latent Capacity

Room Sensible

Room Latent

Supply Air

SHR

CLASSROOM

REQUIREMENTS

(Computer Simulation)

60,360 Btuh

9,276 Btuh

11,934 Btuh

—

—

33,000 Btuh

6,150 Btuh

56 F

0.84

LEGEND

DB — Dry Bulb

ECAT — Carrier Electronic Catalog Program

SHR — Sensible Heat Ratio

WB — Wet Bulb

NOTES:

1. Data provided in terms of gross capacities.

2. Peak Dry Bulb Condition = 94 F DB/77 F WB.

ROOFTOP

PERFORMANCE

(ECAT)

61,113 Btuh

—

—

42,930 Btuh

18,183 Btuh

33,718 Btuh

6,249 Btuh

55.8 F

0.84

Table 7 provides a breakdown of all the room load information and rooftop performance. To determine the available capacity that the rooftop unit has for room sensible and latent conditioning, the outdoor loads were subtracted from the total loads. For example, to evaluate the sensible capacity available for room conditioning, the outdoor sensible load of 9,276 Btuh was subtracted from the total rooftop sensible capacity of

42,930 Btuh. This yields a sensible capacity of 33,718 Btuh, which closely matches the classroom sensible requirement of

33,000 Btuh. The same calculation can be made to evaluate latent capacity requirements as shown in Table 7. Overall, under the peak dry bulb condition, the rooftop unit is sized appropriately to handle both the outdoor ventilation loads and room loads.

A COBRA™ energy recovery unit makes it possible to:

• Select a smaller 4-ton 48/50HJ rooftop to operate with the same total airflow to satisfy the same conditions.

• Pre-condition the same or larger quantities of outdoor air, depending on the application and climate.

• Provide an additional stage of capacity for both cooling and heating mode for enhanced part load performance.

In the previous example the following design changes would be made to accommodate more people. The occupancy would be increased from 30 to 35 people, increasing the required ventilation to 525 cfm (35 x 15 cfm/person).

A COBRA energy recovery unit is sized to accommodate and pre-treat the outdoor air to the rooftop unit. The COBRA unit brings in 600 cfm of outdoor air and pretreats it. Using the peak dry bulb information from the example (94 F db/

77 wb F), the pre-treated outdoor air is mixed with the portion of the return air that is not used for energy recovery, resulting in a 75 F db/63 F wb mixed air condition entering the rooftop evaporator coil.

The outdoor and total equipment capacity requirements are as follows:

OA (sensible) = 1.08 x 570 x (94 – 75) = 10,882 Btuh

OA (latent) = 0.7 x 570 x (111 – 72) = 13,923 Btuh

Notice that these outdoor air loads are higher than was previously calculated in the example using 30 people. See

Table 8 for peak db with COBRA unit temperature summary.

In addition, the indoor latent load will increase as follows:

35 x 205 Btuh/person = 7,175 Btuh

Table 8 — Peak Dry Bulb with COBRA Unit,

Temperature Summary


Outside-Air Temperature

Space Temperature

Entering-Air Temperature

DRY BULB WET BULB

94 F

75 F

75 F

77 F

62.5 F

63 F

The total capacity required of the rooftop unit including all sensible and latent room and outdoor loads is:

33,000 + 7,175 + 10,882 + 13,923 = 64,980 Btuh.

Table 9 outlines the performance of the 4-ton 48/50HJ005 unit in combination with a COBRA energy recovery unit.

Overall, the combined unit capacities and supply-air temperature closely match the conditions for the room loads to maintain space conditions. In addition, the combined system is able to condition more outdoor air. Since the energy recovery unit consists of a heat pump that can operate as the first stage of heating or cooling, additional system flexibility is provided utilizing a smaller size rooftop unit.

Additionally, use of the Humidi-MiZer™ adaptive dehumidification system with the COBRA or field-installed 62AQ unit will significantly affect the capacity and performance of the unit. For a design example in this application, reference

Carrier’s electronic software or the Humidi-MiZer Application

Data manual.

Table 9 — Peak Dry Bulb Operation Summary,

48/50HJ005 with COBRA™ Energy Recovery Unit

48/50HJ005

Total Capacity

Outdoor Sensible

Outdoor Latent

Sensible Capacity

Latent Capacity

Room Sensible

Room Latent

Supply Air

SHR

CLASSROOM

REQUIREMENTS

(Computer Simulation)

64,980 Btuh

10,882 Btuh

13,923 Btuh

—

—

33,000 Btuh

7,175 Btuh

56 F

0.84

COBRA UNIT

PERFORMANCE

(ECAT)

62,920 Btuh

—

—

40,380 Btuh

22,540 Btuh

29,498 Btuh

8,617 Btuh

58.3 F

0.77

LEGEND

DB — Dry Bulb

ECAT — Carrier’s Electronic Catalog Program

SHR — Sensible Heat Ratio

WB — Wet Bulb

NOTES:

1. Data provided in terms of gross capacities.

2. Outdoor Peak Dry Bulb Condition = 94 F DB/77 F WB.

Design Example 2 —

Carrier’s COBRA energy recovery unit preconditions the outdoor air, resulting in the ability of the combined rooftop unit and 62AQ Energy$Recycler section to condition larger latent loads. However if the latent requirements are large enough, the Humidi-MiZer dehumidification system may also be required to properly control the space humidity.

Consider an application where the COBRA unit is designed to operate in a region and/or application where a low sensible/ high latent load exists. In this example, a COBRA unit consisting of a 10-ton 48HJ012 rooftop with a 62AQ200 unit is used to supply 4000 cfm to the space, with the following conditions:

AIRFLOW SUMMARY

Total Supply Air

Outdoor Air (RA1)

Recirculation Air (RA2)

AIRFLOW (Cfm)

4000

2000

1400

Table 10 — Dry Bulb with COBRA Unit

Temperature Summary


DRY

BULB

75 F Outside-Air Temperature

Space Temperature Set Point

COBRA Supply-Air Temperature

75 F

Return-Air Temperature 75 F

Evaporator Entering-Air Temperature 74 F

54 F

WET

BULB

73 F

64 F

66 F

66 F

52 F

% RH

90

55

63

65

87

The given COBRA supply air temperatures indicate that the supply air humidity level is over 90%. Therefore, another device is necessary to control humidity levels in this application. By using a Humidi-MiZer dehumidification system, the latent capacity can be significantly increased and the sensible capacity decreased. In this situation, the Humidi-MiZer system will operate in the hot gas reheat mode (HGRH) and will result in leaving air conditions of 72 F db/60 F wb with 50% humidity.

36

SELECTION PROCEDURE WITH

PACKAGED ROOFTOP BUILDER

The selection procedure with Packaged Rooftop Builder

(PRB) works like a normal selection procedure, except that ratings for the rooftop section, 62AQ Energy$Recycler™ section, and the combined COBRA™ energy recovery unit ratings are all shown. See Fig. 45 and 46.

First, select the desired COBRA unit and applicable options in the Factory Options tab. To select the field-installed 62AQ only, go to the Accessories tab. Note that the COBRA option is only applicable for 3 to 12 1 /

2 selections. All other 3 to 12 1 /

2 tion only.

ton 48HJ and 50HJ unit ton models are for field installa-

Next, select the applicable operating requirements for the

Energy$Recycler section (62AQ) in the Design Criteria tab.

Finally, click on the Performance tab. The performance output screen will be shown with the pre-treated (energy recovery unit) airflow data included on the screen. The rooftop unit performance data, energy recovery unit performance data, and the combined COBRA energy recovery unit performance data are all shown on the same page. The rooftop unit electrical data, 62AQ Energy$Recycler unit electrical data, and the combined COBRA energy recovery unit electrical data are also shown on the page.

Fig. 45 — Electronic Selection Program — COBRA Design Criteria

37

Fig. 46 — Electronic Selection Program — Performance Summary

38

Copyright 2005 Carrier Corporation

Book 1

Manufacturer reserves the right to discontinue, or change at any time, specifications or designs without notice and without incurring obligations.

1 Catalog No. 514-80013 Printed in U.S.A.

Form 48/50HJ,62AQ-2XA Pg 40 12-05 Replaces: 48/50HJ,62AQ-1XA

Tab 1a 1b

Product information | Carrier COBRA 48/50HJ004-014 Product data

COBRA™ Energy Recovery Units

48/50HJ004-014 with 62AQ060-300

Single-Package Rooftop Units and Field-Installed 62AQ060-300

ENERGY$RECYCLER™ Units

Application Data

CONTENTS

GENERAL

Features/Benefits —

COBRA Curb Application —

COBRA Iso-Exhaust, Split Return Duct Application —

Field-Installed 62AQ Application —

SYSTEM OPERATION

Cooling Mode —

Heating Mode —

Defrost —

Changeover Thermostats —

Fans —

COBRA™ and 62AQ Unit Options

Optional 25% OA Damper

CONTROLS

Thermidistat Device —

PremierLink Controller —

Gas Supply —

WIRING

Field Power Supply

Factory-Supplied Non-Fused Disconnect —

Field Control Wiring —

CONDENSATE PIPING

DAMPERS

Supply-Air Dampers —

Barometric Relief Damper —

Multiple Stage Cooling Control —

DESIGN EXAMPLES

Design Example 1 —

Design Example 2 —

SELECTION PROCEDURE WITH

PACKAGED ROOFTOP BUILDER

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