Grandaire W4H7T User manual

Installation Instructions
NOTE: Read the entire instruction manual before starting the installation.
SAFETY CONSIDERATIONS
Improper installation, adjustment, alteration, service, maintenance, or
use can cause explosion, fire, electrical shock, or other conditions which
may cause death, personal injury, or property damage. Consult a
qualified installer, service agency, or your distributor or branch for
information or assistance. The qualified installer or agency must use
factory-authorized kits or accessories when modifying this product.
Refer to the individual instructions packaged with the kits or accessories
when installing.
Follow all safety codes. Wear safety glasses, protective clothing, and
work gloves. Use quenching cloth for brazing operations. Have fire
extinguisher available. Read these instructions thoroughly and follow all
warnings or cautions included in literature and attached to the unit.
Consult local building codes and current editions of the National
Electrical Code (NEC) NFPA 70. In Canada, refer to current editions of
the Canadian Electrical Code CSA 22.1.
Recognize safety information. This is the safety-alert symbol When
you see this symbol on the unit and in instructions or manuals, be alert to
the potential for personal injury. Understand these signal words;
DANGER, WARNING, and CAUTION. These words are used with the
safety-alert symbol. DANGER identifies the most serious hazards
which will result in severe personal injury or death. WARNING
signifies hazards which could result in personal injury or death.
CAUTION is used to identify unsafe practices which would result in
minor personal injury or product and property damage. NOTE is used to
highlight suggestions which will result in enhanced installation,
reliability, or operation.
Installation Recommendations
NOTE: In some cases noise in the living area has been traced to gas
pulsations from improper installation of equipment.
1. Locate unit away from windows, patios, decks, etc. where unit
operation sound may disturb customer.
2. Ensure that vapor and liquid tube diameters are appropriate for unit
capacity.
3. Run refrigerant tubes as directly as possible by avoiding
unnecessary turns and bends.
4. Leave some slack between structure and unit to absorb vibration.
5. When passing refrigerant tubes through the wall, seal opening with
RTV or other pliable silicon-based caulk. (See Fig. 1.)
6. Avoid direct tubing contact with water pipes, duct work, floor
joists, wall studs, floors, and walls.
7. Do not suspend refrigerant tubing from joists and studs with a rigid
wire or strap which comes in direct contact with tubing.(See Fig. 1.)
8. Ensure that tubing insulation is pliable and completely surrounds
vapor tube.
9. When necessary, use hanger straps which are 1 in. (25.4 mm) wide
and conform to shape of tubing insulation. (See Fig. 1.)
10. Isolate hanger straps from insulation by using metal sleeves bent to
conform to shape of insulation.
A07588
Fig. 1 – Piping Installation
When outdoor unit is connected to factory-approved indoor unit, outdoor
unit contains system refrigerant charge for operation with AHRI rated
indoor unit when connected by 15 ft. (4.57 m) of field-supplied or
factory accessory tubing. For proper unit operation, check refrigerant
charge using charging information located on control box cover and/or
in the Check Charge section of this instruction.
IMPORTANT: Maximum liquid-line size is 3/8-in. OD for all
residential applications including line line.
IMPORTANT: Always install the factory-supplied liquid-line filter
drier. Obtain replacement filter driers from your distributor or branch.
W4H7T
SPLIT-SYSTEM 2-STAGE HEAT PUMP
WITH R-410A REFRIGERANT
2-5 TONS
WARNING
!
ELECTRICAL SHOCK HAZARD
Failure to follow this warning could result in personal injury or death.
Before installing, modifying, or servicing system, main electrical
disconnect switch must be in the OFF position. There may be more than
1 disconnect switch. Lock out and tag switch with a suitable warning
label.
WARNING
!
EXPLOSION HAZARD
Failure to follow this warning could result in
death, serious personal injury, death, and/or
property damage.
Never use air or any gas containing oxygen for
leak testing or operating refrigerant
compressors. Never allow compressor suction
pressure to operate in a vacuum with service
valves closed. See Service Manual for
pump-down instructions.

W4H7T: Installation Instructions
Manufacturer reserves the right to change, at any time, specifications and designs without notice and without obligations.
2
Installation
Check Equipment and Job Site
IMPORTANT: All split system and packaged heat pumps must be
installed pursuant to applicable regional efficiency standards issued by
the Department of Energy.
Unpack Unit
Move to final location. Remove carton taking care not to damage unit.
Inspect Equipment
File claim with shipping company prior to installation if shipment is
damaged or incomplete. Locate unit rating plate on unit corner panel. It
contains information needed to properly install unit. Check rating plate
to be sure unit matches job specifications.
Install on a Solid, Level Mounting Pad
If conditions or local codes require the unit be attached to pad, tie down
bolts should be used and fastened through knockouts provided in unit
base pan. Refer to unit mounting pattern in Fig. 2 to determine base pan
size and knockout hole location.
For hurricane tie downs, contact distributor for details and PE
Certification (Professional Engineer), if required.
On rooftop applications, mount on level platform or frame. Place unit
above a load-bearing wall and isolate unit and tubing set from structure.
Arrange supporting members to adequately support unit and minimize
transmission of vibration to building. Consult local codes governing
rooftop applications.
Roof mounted units exposed to winds above 5 mph (8.05 km/h) may
require wind baffles. Consult the Service Manual - Residential Split
System Air Conditioners and Heat Pumps for wind baffle construction.
NOTE: Unit must be level to within ±2°(±3/8 in./ft,±9.5 mm/m.) per
compressor manufacturer specifications.
Clearance Requirements
When installing, allow sufficient space for airflow clearance, wiring,
refrigerant piping, and service. Allow 24 in. (609.6 mm) clearance to
service end of unit and 48 in. (1219.2 mm) (above unit. For proper
airflow, a 6-in. (152.4 mm) clearance on 1 side of unit and 12-in. (304.8
mm) on all remaining sides must be maintained. Maintain a distance of
24 in. (609.6 mm) between units. Position so water, snow, or ice from
roof or eaves cannot fall directly on unit.
On rooftop applications, locate unit at least 6 in. (152.4 mm) above roof
surface.
A05177
Fig. 2 – Tiedown Knockout Locations
Check Defrost Thermostat
Check defrost thermostat to ensure it is properly located and securely
attached. There is a liquid header with a distributor and feeder tube
going into outdoor coil. At the end of the one of the feeder tubes, there is
a 3/8 in. O.D. stub tube approximately 2 in. long. (See Fig. 3.) The
defrost thermostat should be located on stub tube. Note that there is only
one stub tube used with liquid header, and on most units it is the bottom
circuit.
A97517
Fig. 3 – Defrost Thermostat Location
Elevate Unit
Elevate unit per local climate and code requirements to provide
clearance above estimated snowfall level and ensure adequate drainage
of unit.
CAUTION
!
CUT HAZARD
Failure to follow this caution may result in personal injury.
Sheet metal parts may have sharp edges or burrs. Use care and wear
appropriate protective clothing and gloves when handling parts.
CAUTION
!
UNIT OPERATION HAZARD
Failure to follow this caution may result in equipment damage or
improper operation.
Locate the unit in such a way that it is stable in all circumstances
including adverse weather conditions.
UNIT BASE PAN
Dimension in.
(mm)
TIEDOWN KNOCKOUT LOCATIONS in. (mm)
ABC
35 X 35
(889 X 889) 9–1/8 (231.8) 6–9/16 (166.7) 28–7/16 (722.3)
CAUTION
!
UNIT OPERATION HAZARD
Failure to follow this caution may result in equipment damage or
improper operation.
Do not allow water and/or ice to build up in base pan.
FEEDER TUBE
DEFROST
THERMOSTAT
A97517
STUB TUBE
COIL

W4H7T: Installation Instructions
Manufacturer reserves the right to change, at any time, specifications and designs without notice and without obligations.
3
In Long-Line Applications, Install Liquid-Line
Solenoid Valve (LSV)
For refrigerant piping arrangements with equivalent lengths greater than
80 ft. (24.38 m) and/or when elevation difference between indoor and
outdoor unit is greater than ±20 ft. (±6.10 m), follow all requirements of
the Residential Piping and Long-Line Guideline. If required by
Long-Line Guideline, install LSV kit, part no. NASA001LS, specifically
designed for R-410A refrigerant heat pumps. LSV should be installed
within 2 ft. (0.61 m) of outdoor unit with flow arrow pointing toward
outdoor unit. Follow the Installation Instructions included with
accessory kit.
IMPORTANT: Flow arrow must point toward outdoor unit.
Make Piping Connections
Outdoor units may be connected to indoor section using accessory
tubing package or field-supplied refrigerant grade tubing of correct size
and condition. For tubing requirements beyond 80 ft (24.4 m),
substantial capacity and performance losses can occur. Following the
recommendations in the Residential Piping and Long Line Guideline
will reduce these losses. Refer to Table 1 for accessory requirements.
Refer to Table 2 for field tubing diameters.
There are no buried-line applications greater than 36 in. (914.4 mm)
If refrigerant tubes or indoor coil are exposed to atmosphere, they must
be evacuated to 500 microns to eliminate contamination and moisture in
the system.
Outdoor Unit Connected to Factory Approved Indoor
Unit:
Outdoor unit contains the correct system refrigerant charge for operation
with factory approved, AHRI rated, indoor unit with highest sales
volume when connected by 15 ft (4.57 m) of field-supplied or factory
accessory tubing and factory-supplied filter drier. Check refrigerant
charge for maximum efficiency.
Service Valves
Service valves are closed and plugged from the factory. Outdoor units
are shipped with a refrigerant charge sealed in the unit. Leave the service
valves closed until all other refrigerant system work is complete or the
charge will be lost. Leave the plugs in place until line set tubing is ready
to be inserted.
Heat pumps require a piston metering device in the liquid service valve
for proper heating operation. Piston is shipped in the piston body of the
liquid service valve, temporarily held in place with a plastic cap. Do not
remove the plastic cap until line set tubing is ready to be installed.
Refer to Fig. 4 and follow these steps for piston installation:
1. Remove plastic cap holding piston in piston body of liquid service
valve.
2. Check that piston size (stamped on side of piston) matches with
number listed on unit rating plate. Return piston to piston body of
liquid service valve (either direction).
3. Find plastic bag taped to unit containing copper adapter tube, brass
nut, and plastic washer.
4. Install plastic washer in the seat inside piston body.
5. Fit brass nut onto adapter tube and install tube onto liquid service
valve. Tighten nut finger tight, then wrench additional ½ turn only
[15-ft lbs (20.3 N-m)]. Over tightening may damage the plastic
washer and service valve’s piston body.
A14235
Fig. 4 – Liquid Service Valve with Heating Piston and Adapter Tube
Table 1 – Accessory Usage
Accessory
Required for Low Ambient
Cooling Applications
(Below 55°F / 12.8°C)
Required for Long Line
Applications*
*. For tubing line sets between 80 and 200 ft. (24.38 and 60.96 m) and/or 20 ft. (6.09 m) vertical differential, refer to Residential Piping and Longline Guideline.
Required for Sea Coast
Applications
(within 2 miles/3.2 km)
Compressor Start Assist Capacitor and Relay Yes Yes No
Crankcase Heater Yes (standard) Yes (standard) No
Evaporator Freeze Thermostat Yes No No
Hard Shutoff TXV
Yes
(standard w/factory approved
indoor unit)
Yes
(standard w/factory approved
indoor unit)
Yes
(standard w/factory approved
indoor unit)
Isolation Relay Yes No No
Liquid Line Solenoid Valve No See Residential Piping
and Long Line Guideline No
Low-Ambient Pressure Switch Yes No No
Support Feet Recommended No Recommended
WARNING
!
PERSONAL INJURY AND ENVIRONMENTAL
HAZARD
Failure to follow this warning could result in personal injury or death.
Relieve pressure and recover all refrigerant before system repair or
final unit disposal.
Use all service ports and open all flow-control devices, including
solenoid valves.
Federal regulations require that you do not vent refrigerant into the
atmosphere. Recover refrigerant during system repair or final unit
disposal
CAUTION
!
UNIT DAMAGE HAZARD
Failure to follow this caution may result in equipment damage or
improper operation.
If ANY refrigerant tubing is buried, provide a 6-in (152.4 mm). vertical
rise at service valve. Refrigerant tubing lengths up to 36-in (914.4
mm). may be buried without further special consideration. Do not bury
lines longer than 36 in (914.4 mm).

W4H7T: Installation Instructions
Manufacturer reserves the right to change, at any time, specifications and designs without notice and without obligations.
4
Brazing Connections
Connect vapor tube to fitting on outdoor unit vapor service valves (see
Table 2). Connect liquid tubing to adapter tube on liquid service valve.
Use refrigerant grade tubing.
Notes:
1.Do not apply capillary tube indoor coils to these units.
2.For Tubing Set lengths between 80 and 200 ft. (24.38 and 60.96 m) horizontal or
20 ft. (6.1 m) vertical differential, refer to the Residential Piping and Longline
Guideline.
Apply heat absorbing paste or heat sink product between service valve
and joint. Wrap service valves with a heat sinking material such as a wet
cloth.
After wrapping service valve with a wet cloth, tubing set can be brazed
to service valve using either silver bearing or non–silver bearing brazing
material. Do not use soft solder (materials which melt below
800°F/427°C). Consult local code requirements.
NOTE: Some outdoor units contain a mechanical fitting at the liquid
distributor. This connection is not field serviceable and should not be
disturbed.
NOTE: For Liquid Service Valve - Braze lineset to adapter tube
BEFORE bolting adapter to valve. This helps prevent overheating and
damage to plastic washer or o-ring.
For Vapor Service Valve - remove valve core from schrader port on
Service Valve BEFORE brazing. This helps prevent overheating and
damage to valve seals (refer to Fig. 5). Replace valve core when brazing
is completed.
A14236
Fig. 5 – Vapor Service Valve
Clean line set tube ends with emery cloth or steel brush. Remove any grit
or debris.
Insert line set tube ends into service valve tube stubs.
Apply heat absorbing paste or heat sink product between service valve
and joint. Wrap service valves with a heat sinking material such as a wet
cloth.
Braze joints using a Sil-Fos or Phos-copper alloy.
Install Liquid Line Filter Drier Indoor
Refer to Fig. 6 and install filter drier as follows:
1. Braze 5 in. (127 mm) liquid tube to the indoor coil.
2. Wrap filter drier with damp cloth.
3. Braze filter drier to 5 in. (127 mm) long liquid tube from step 1.
4. Connect and braze liquid refrigerant tube to the filter drier.
A05227
Fig. 6 – Liquid Line Filter Drier
Refrigerant tubing and indoor coil are now ready for leak testing. This
check should include all field and factory joints.
WARNING
!
FIRE HAZARD
Failure to following this warning could result in personal injury, death
and/or property damage.
Refrigerant and oil mixture could ignite and burn as it escapes and
contacts brazing torch. Make sure the refrigerant charge is properly
removed from both the high and low sides of the system before brazing
any component or lines.
Table 2 – Refrigerant Connections and Recommended Liquid and
Vapor Tube Diameters (In.)
UNIT SIZE
LIQUID RATED VAPOR*
*. Units are rated with 25 ft. (7.6 m) of lineset. See Product Data sheet for performance
data when using different size and length linesets.
Connection
Diameter
Tube
Diameter
Connection
Diameter
Tube
Diameter
024 3/8 3/8 3/4 3/4
036 3/8 3/8 7/8 7/8
048, 060 3/8 3/8 7/8 1-1/8
CAUTION
!
UNIT DAMAGE HAZARD
Failure to follow this caution may result in equipment damage or
improper operation.
Service valves must be wrapped in a heat–sinking material such as a
wet cloth while brazing.
CAUTION
!
BURN HAZARD
Failure to follow this Caution may result in personal injury.
Components will be HOT after brazing. Wear appropriate personal
protective equipment and allow to cool before handling parts and
equipment
CAUTION
!
UNIT DAMAGE HAZARD
Failure to follow this caution may result in equipment damage or
improper operation.
1. Installation of filter drier in liquid line is required.
2. Filter drier must be wrapped in a heat-sinking material such as a
wet cloth while brazing.

W4H7T: Installation Instructions
Manufacturer reserves the right to change, at any time, specifications and designs without notice and without obligations.
5
Evacuate Refrigerant Tubing and Indoor Coil
Refrigerant tubes and indoor coil should be evacuated using the
recommended deep vacuum method of 500 microns. The alternate triple
evacuation method may be used (see triple evacuation procedure in
service manual). Always break a vacuum with dry nitrogen.
Deep Vacuum Method
The deep vacuum method requires a vacuum pump capable of pulling a
vacuum of 500 microns and a vacuum gage capable of accurately
measuring this vacuum depth. The deep vacuum method is the most
positive way of assuring a system is free of air and liquid water. A tight
dry system will hold a vacuum of 1000 microns after approximately 7
minutes. See Fig. 7.
A95424
Fig. 7 – Deep Vacuum Graph
Final Tubing Check
IMPORTANT: Check to be certain factory tubing on both indoor and
outdoor unit has not shifted during shipment. Ensure tubes are not
rubbing against each other or any sheet metal. Pay close attention to
feeder tubes, makings sure wire ties on feeder tubes are secure and tight.
Be sure field wiring complies with local and national fire, safety, and
electrical codes, and voltage to system is within limits shown on unit
rating plate. Contact local power company for correction of improper
voltage. See unit rating plate for recommended circuit protection device.
NOTE: Operation of unit on improper line voltage constitutes abuse and
could affect unit reliability. See unit rating plate. Do not install unit in
system where voltage may fluctuate above or below permissible limits.
Make Electrical Connections
NOTE: Use copper wire only between disconnect switch and unit.
NOTE: Install branch circuit disconnect of adequate size per NEC to
handle unit starting current. Locate disconnect within sight from and
readily accessible from unit, per Section 440-14 of NEC.
Route Ground and Power Wires
Remove access panel to gain access to unit wiring. Extend wires from
disconnect through power wiring hole provided and into unit control
box.
Connect Ground and Power Wires
Connect ground wire to ground connection in control box for safety.
Connect power wiring to contactor as shown in Fig. 8.
A94025
Fig. 8 – Line Connections
Connect Control Wiring
Route 24v control wires through control wiring grommet and connect
leads to control wiring. See Thermostat Installation Instructions for
wiring specific unit combinations. (See Fig. 9 and Fig. 10.)
Use No. 18 AWG color-coded, insulated (35°C minimum) wire. If
thermostat is located more than 100 ft (30.5 m) from unit, as measured
along the control voltage wires, use No. 16 AWG color-coded wire to
avoid excessive voltage drop.
All wiring must be NEC Class 2 and must be separated from incoming
power leads.
Use furnace transformer, fan coil transformer, or accessory transformer
for control power, 24v/40va minimum.
NOTE: Use of available 24v accessories may exceed the minimum 40va
power requirement. Determine total transformer loading and increase
the transformer capacity or split the load with an accessory transformer
as required.
CAUTION
!
UNIT DAMAGE HAZARD
Failure to follow this caution may result in equipment damage or
improper operation.
Never use the system compressor as a vacuum pump.
WARNING
!
ELECTRICAL SHOCK HAZARD
Failure to follow this warning could result in personal injury or death.
Do not supply power to unit with compressor terminal box cover
removed.
500
MINUTES
01234 567
1000
1500
LEAK IN
SYSTEM
VACUUM TIGHT
TOO WET
TIGHT
DRY SYSTEM
2000
MICRONS
2500
3000
3500
4000
4500
5000
WARNING
!
ELECTRICAL SHOCK HAZARD
Failure to follow this warning could result in personal injury or death.
The unit cabinet must have an uninterrupted or unbroken ground to
minimize personal injury if an electrical fault should occur. The ground
may consist of electrical wire or metal conduit when installed in
accordance with existing electrical codes.

W4H7T: Installation Instructions
Manufacturer reserves the right to change, at any time, specifications and designs without notice and without obligations.
6
A12258
Fig. 9 – Thermidistat Wiring with Fan Coil
and 2-Stage Heat Pump
A12259
Fig. 10 – Thermidistat with Variable Speed Furnace
and 2--Stage Heat Pump
A09306
Final Wiring Check
IMPORTANT: Check factory wiring and field wire connections to
ensure terminations are secured properly. Check wire routing to ensure
wires are not in contact with tubing, sheet metal, etc.
Compressor Crankcase Heater
All sizes are equipped with a crankcase heater. Furnish power to heater a
minimum of 24 hours before starting unit. To furnish power to heater
only, set thermostat to OFF and close electrical disconnect to outdoor
unit.
A crankcase heater is required if refrigerant tubing is longer than 80 ft.
(24.4 m), or when outdoor unit is 20 ft. (6.1 m) below the indoor unit.
Refer to the Residential Piping and Long Line Guideline.
Install Electrical Accessories
Refer to the individual instructions packaged with kits or accessories
when installing.
Airflow Selections (ECM Furnaces)
The ECM Furnaces provide blower operation to match the capacities of
the compressor during high and low stage cooling operation. Tap
selections on the furnace control board enable the installing technician to
select the proper airflows for each stage of cooling. Below is a brief
summary of the furnace airflow configurations
1. The Y2 call for high stage cooling energizes the “Cool” tap on the
control board. The grey wire from cool tap is connected to tap 5 on
the motor. Refer to the furnace Product Data to find the
corresponding airflow. If the airflow setting for high cooling needs
to be switched from tap 5 to a different tap, jumper a connection
from the cool tap to the desired tap so that the Y2 signal is
communicated via the cool tap to the desired speed tap.
2. The Y1 call for low stage cooling energizes the “Fan” tap on the
control board. The red wire from the fan tap is connected to tap 1 on
the motor. Refer to the furnace Product Data to find the
corresponding airflow. If the airflow setting for low cooling needs
to be switched from tap 1 to a different tap, jumper a connection
from the Fan tap to the desired tap so that the Y1 signal is
communicated via the Fan tap to the desired speed tap. The Y1
setting will also govern the continuous fan airflow for the furnace.
Refer to the literature for the furnace for further details.
Airflow Selection for Variable Speed Furnaces
(non-communicating)
The variable speed furnaces provide blower operation to match the
capacities of the compressor during high and low stage cooling
operation. The furnace control board allows the installing technician to
select the proper airflows for each stage of cooling. Below is a summary
of required adjustments. See furnace installation instructions for more
details:
1. Turn SW1-5 ON for 400 CFM/ton airflow or OFF for 350 CFM/ton
airflow. Factory default is OFF.
2. The A/C DIP switch setting determines airflow during high stage
cooling operation. Select the A/C DIP switch setting corresponding
to the available airflow shown in the furnace Installation
Instructions that most closely matches the required airflow shown
in the air conditioning Product Data for HIGH speed.
3. The CF DIP switch setting determines airflow during low stage
cooling operation. Select the CF DIP switch setting corresponding
to the available airflow shown in the furnace installation
instructions that most closely matches the required airflow shown
in the air conditioning Product Data for LOW speed. If a higher or
lower continuous fan speed is desired, the continuous fan speed can
be changed using the fan switch on the thermostat. Refer to the
furnace Installation Instructions for details of how to use this
feature.

W4H7T: Installation Instructions
Manufacturer reserves the right to change, at any time, specifications and designs without notice and without obligations.
7
Airflow Selection for FV4C Fan Coils
(non-communicating)
The FV4C provides high- and low-stage blower operation to match the
capacities of the compressor at high- and low-stage.
To select recommended airflow, refer to the FV4C Installation
Instructions. The FV4C utilizes an Easy Select control board that allows
the installing technician to select proper airflows. This fan coil has an
adjustable blower-off delay factory set at 90 sec. for high- and low-stage
blower operation.
Start-Up
Follow these steps to properly start up system:
1. After system is evacuated, fully open liquid and vapor service
valves.
2. Unit is shipped with valve stem(s) front seated (closed) and caps
installed. Replace stem caps after system is opened to refrigerant
flow (back seated). Replace caps finger-tight and tighten with
wrench an additional 1/12 turn.
3. Close electrical disconnects to energize system.
4. Set room thermostat at desired temperature. Be sure set point is
below indoor ambient temperature.
5. Set room thermostat to HEAT or COOL and fan control to ON or
AUTO mode, as desired. Operate unit for 15 minutes. Check
system refrigerant charge.
Sequence of Operation
NOTE: Defrost control board is equipped with 5 minute lockout timer
that is initiated upon any interruption of power.
Turn on power to indoor and outdoor units. Transformer is energized.
These models utilize a 2-stage indoor thermostat. With a call for first
(low) stage cooling or heating, the outdoor fan and low-stage
compressor are energized. If low-stage cannot satisfy cooling or heating
demand, high-stage is energized by the second (high) stage of the indoor
thermostat. After the second stage is satisfied, the unit returns to
low-stage operation until second stage is required again. When both,
first and second stage cooling or heating are satisfied, the compressor
will shut off.
Cooling
With first stage cooling, Y1 and O are powered on; and with second
stage cooling, Y2, Y1 and O are powered on. The O energizes the
reversing valve, switching it to cooling position. The Y1 signal sends
low voltage through the safeties and energizes the T1 terminal on the
circuit board. If the compressor has been off for 5 minutes, or power has
not been cycled for 5 minutes, the OF2 relay and T2 terminal will
energize. This will close the contactor and start the outdoor fan motor
and compressor. When the cycle is complete, Y1 is turned off, stopping
the compressor and outdoor fan. The 5 minute time guard begins
counting. Compressor will not come on until this delay expires. In the
event of a power interruption, the time guard will not allow another
cycle for 5 minutes.
Heating
With first stage heating, Y1 is powered on; with second stage heating,
Y2 and Y1 are powered on. The Y1 signal sends low voltage through
the safeties and energizes the T1 terminal on the circuit board. If the
compressor has been off for 5 minutes or power has not been cycled for
5 minutes, the OF2 relay and T2 terminal will energize. This will close
the contactor and start the outdoor fan motor and compressor.
When the cycle is complete, Y1 is turned off, stopping the compressor
and outdoor fan. The 5 minute time guard begins counting. Compressor
will not come on until this delay expires. In the event of a power
interruption, the time guard will not allow another cycle for 5 minutes.
Compressor Operation
The basic scroll design has been modified with the addition of an
internal unloading mechanism that opens a by-pass port in the first
compression pocket, effectively reducing the displacement of the scroll.
The opening and closing of the by-pass port is controlled by an internal
electrically operated solenoid. The modulated scroll uses a single step of
unloading to go from full capacity to approximately 67% capacity.
A single speed, high efficiency motor continues to run while the scroll
modulates between the two capacity steps. Modulation is achieved by
venting a portion of the gas in the first suction pocket back to the low
side of the compressor, thereby reducing the effective displacement of
the compressor.
Full capacity is achieved by blocking these vents, thus increasing the
displacement to 100%. A DC solenoid in the compressor controlled by a
rectified 24 volt AC signal in the external solenoid plug moves the slider
ring that covers and uncovers these vents.
The vent covers are arranged in such a manner that the compressor
operates at approximately 67% capacity when the solenoid is not
energized and 100% capacity when the solenoid is energized. The
loading and unloading of the two step scroll is done ”on the fly” without
shutting off the motor between steps.
NOTE: 67% compressor capacity translates to approximately 75%
cooling or heating capacity at the indoor coil.
The compressor will always start unloaded and stay unloaded for five
seconds even when the thermostat is calling for high stage capacity.
Quiet Shift-2
Quiet shift- 2 is a field selectable defrost mode (factory set to OFF),
which will reduce the occasional noise that could be heard at the start of
defrost cycle and restarting of heating cycle. It is selected by placing DIP
switch 3 on defrost board in the ON position. When Quiet Shift- 2
switch is placed in ON position, and defrost is initiated, the following
sequence of operation will occur: The compressor will be de- energized
for approximately 1 minute, then the reversing valve will be energized.
A few seconds later, the compressor will be re- energized and the normal
defrost cycle starts.
Once defrost termination conditions have been met, the following
sequence will occur: The compressor will be de- energized for
approximately 1 minute, then the reversing valve will be de- energized.
A few seconds later, the compressor will be re- energized and the normal
heating cycle starts.
CAUTION
!
PERSONAL INJURY HAZARD
Failure to follow this caution may result in personal
injury.
Wear safety glasses, protective clothing, and gloves when handling
refrigerant and observe the following:
• Front seating service valves are equipped with Schrader valves.
CAUTION
!
ENVIRONMENTAL HAZARD
Failure to follow this caution may result in environmental damage.
Federal regulations require that you do not vent refrigerant to the
atmosphere. Recover during system repair or final unit disposal.
CAUTION
!
UNIT OPERATION AND SAFETY HAZARD
Failure to follow this caution may result in personal injury, equipment
damage or improper operation.
• Do not overcharge system with refrigerant.
• Do not operate unit in a vacuum or at negative pressure.
• Do not disable low pressure switch in scroll compressor applications.
• Compressor dome temperatures may be hot.

W4H7T: Installation Instructions
Manufacturer reserves the right to change, at any time, specifications and designs without notice and without obligations.
8
Defrost
The defrost control is a time/temperature control which has field
selectable settings of 30, 60, 90, or 120 minutes, factory set to 60
minutes. These settings represent the initial time period that must pass
after closure of the defrost thermostat before the defrost sequence
begins, after which the defrost period varies with defrost length. If Quiet
Shift 2 is enabled, the variable defrost intervals will be disabled to
provide options where using a specific setting is desired. In this case the
30, 60, 90, or 120 minutes setting will not change unless the dipswitch is
changed and power is cycled.
The defrost thermostat senses coil temperature throughout the heating
cycle. When the coil temperature reaches the defrost thermostat setting
of approximately 32°F (0°C), it will close, which energizes the DFT
terminal and begins the defrost timing sequence. When the DFT has
been energized for the selected time, the defrost cycle begins. Defrost
cycle is terminated when defrost thermostat opens, or automatically after
10 minutes.
Defrost Speedup
To initiate a forced defrost, speedup pins (J1) must be shorted with a flat
head screwdriver for 5 seconds and RELEASED. If the defrost
thermostat is open, a short defrost cycle will be observed (actual length
depends on Quiet Shift- 2 switch position). When Quiet Shift- 2 is off,
only a short 30 second defrost cycle is observed. With Quiet Shift- 2 ON,
the speedup sequence is approximately 3 minutes; 1 minute compressor
off period followed by 30 seconds of defrost with compressor operation.
When returning to heating mode, the compressor will turn off for an
additional 1 minute.
If the defrost thermostat is closed, a complete defrost cycle is initiated. If
the Quiet Shift- 2 switch is turned on, the compressor will be turned off
for two 1 minute intervals as explained previously.
A05378
Fig. 11 – Defrost Control
Check Charge
NOTE: CHARGE IN HIGH STAGE ONLY.
Factory charge amount and desired subcooling are shown on unit rating
plate. Charging method is shown on information plate inside unit. To
properly check or adjust charge, conditions must be favorable for
subcooling charging. Favorable conditions exist when the outdoor
temperature is between 70°F and 100°F (21.11°C and 37.78°C), and the
indoor temperature is between 70°F and 80°F (21.11°C and 26.67°C).
Follow the procedure below:
Unit is factory charged for 15ft (4.57 m) of lineset. Adjust charge by
adding or removing 0.6 oz/ft (.018 kg/m) of 3/8 liquid line above or
below 15ft (4.57 m) respectively.
For standard refrigerant line lengths (80 ft/24.38 m or less), allow system
to operate in cooling mode at least 15 minutes. If conditions are
favorable, check system charge by subcooling method. If any adjustment
is necessary, adjust charge slowly and allow system to operate for 15
minutes to stabilize before declaring a properly charged system.
If the indoor temperature is above 80°F (26.67°C), and the outdoor
temperature is in the favorable range, adjust system charge by weight
based on line length and allow the indoor temperature to drop to 80°F
(26.67°C) before attempting to check system charge by subcooling
method as described above.
If the indoor temperature is below 70°F (21.11°C), or the outdoor
temperature is not in the favorable range, adjust charge for line set length
above or below 15ft (4.57 m) only. Charge level should then be
appropriate for the system to achieve rated capacity. The charge level
could then be checked at another time when the both indoor and outdoor
temperatures are in a more favorable range.
NOTE: If line length is beyond 80 ft (24.38 m) or greater than 20 ft
(6.10 m) vertical separation, See Long Line Guideline for special
charging requirements.
Heating Check Chart Procedure
To check system operation during heating cycle, refer to the Heating
Check Chart on outdoor unit. This chart indicates whether a correct
relationship exists between system operating pressure and air
temperature entering indoor and outdoor units. If pressure and
temperature do not match on chart, system refrigerant charge may not be
correct. Do not use chart to adjust refrigerant charge.
Verify units for proper switching between low & high
stages
Check the suction pressures at the service valves. Suction pressure
should be reduced by 3-10% when switching from low to high capacity.
Compressor current should increase 20-45% when switching from low
to high stage. The compressor solenoid when energized in high stage,
should measure 24vac at leads inside control box.
When the compressor is operating in low stage the 24v DC compressor
solenoid coil is de-energized. When the compressor is operating in high
stage, the 24v DC solenoid coil is energized. The solenoid plug harness
that is connected to the compressor HAS an internal rectifier that
converts the 24v AC signal to 24v DC. DO NOT INSTALL A PLUG
WITHOUT AN INTERNAL RECTIFIER.

W4H7T: Installation Instructions
Manufacturer reserves the right to change, at any time, specifications and designs without notice and without obligations.
9
Unloader Test Procedure
The unloader is the compressor internal mechanism, controlled by the
DC solenoid, that modulates between high and low stage. If it is
suspected that the unloader is not working, the following methods may
be used to verify operation.
1. Operate the system and measure compressor amperage. Cycle the
unloader on and off at 30 second plus intervals at the thermostat
(from low to high stage and back to low stage). Wait 5 seconds
after staging to high before taking a reading. The compressor
amperage should go up or down at least 20 percent.
2. If the expected result is not achieved, remove the solenoid plug
from the compressor and with the unit running and the thermostat
calling for high stage, test the voltage output at the plug with a DC
voltmeter. The reading should be 24 volts DC.
3. If the correct DC voltage is at the control circuit molded plug,
measure the compressor unloader coil resistance. The resistance
should be approximately 1640 milliohms. If the coil resistance is
infinite or is grounded, the compressor must be replaced.
Final Checks
IMPORTANT: Before leaving job, be sure to do the following:
1. Ensure that all wiring is routed away from tubing and sheet metal
edges to prevent rub-through or wire pinching.
2. Ensure that all wiring and tubing is secure in unit before adding
panels and covers. Securely fasten all panels and covers.
3. Tighten service valve stem caps to 1/12-turn past finger tight.
4. Leave Owner’s Manual with owner. Explain system operation and
periodic maintenance requirements outlined in manual.
5. Fill out Dealer Installation Checklist and place in customer file.
Troubleshooting
If the compressor fails to operate with a cooling call, the table below
(Resistance table) can be used to verify if there is any damage to the
compressor windings causing system malfunction.
Major Components
2-Stage Compressor
The 2-stage compressor contains motor windings that provide 2-pole
(3500 RPM) operation.
Compressor Internal Relief
The compressor is protected by an internal pressure relief (IPR) which
relieves discharge gas into compressor shell when differential between
suction and discharge pressures exceeds and 550 - 625 psi. The
compressor is also protected by an internal overload attached to motor
windings.
Compressor Control Contactor
The contactor has a 24 volt coil and is controlled by Y1 input from the
thermostat
Low Pressure Switch
Low pressure switch is provided in line with the Y1 signal to the
contactor for protection.
Care and Maintenance
For continuing high performance and to minimize possible equipment
failure, periodic maintenance must be performed on this equipment.
Frequency of maintenance may vary depending upon geographic areas,
such as coastal applications. See Users Manual for information.
Table 3 – Winding Resistance
Winding
Winding resistance at 70°F +/- 20°F
(21.11°C +/- 11.11°C)
Unit Size
024 036 048 060
Start (S-C) 1.652 1.587 1.299 1.203
Run (R-C) 1.065 0.751 0.477 0.383
®

© 2022 Carrier. All rights reserved.
A Carrier Company
Edition Date: 03/22 Catalog No: W4H7T-01SI
Replaces:New
W4H7T: Installation Instructions
Manufacturer reserves the right to change, at any time, specifications and designs without notice and without obligations.
10