Carrier 50HCQ12 User manual

Manufacturer reserves the right to discontinue, or change at any time, specifications or designs without notice and without incurring obligations.
Catalog No. 04-53500282-01 Printed in U.S.A. Form 50HCQ-12-03SI Pg 1 5-2020 Replaces: 50HCQ-12-02SI
Installation Instructions
CONTENTS
SAFETY CONSIDERATIONS . . . . . . . . . . . . . . . . . . . 1
MODEL NUMBER NOMENCLATURE AND
DIMENSIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Rated Indoor Airflow . . . . . . . . . . . . . . . . . . . . . . . . . . 2
REFRIGERATION SYSTEM COMPONENTS . . . . . . . 6
Reversing Valve and Check Valve Position . . . . . . . 6
Troubleshooting Refrigerant Pressure Problems and
Check Valves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Refrigerant System Pressure Access Ports . . . . . . . 7
INSTALLATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Jobsite Survey . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Step 1 — Plan for Unit Location . . . . . . . . . . . . . . . . 8
• ROOF MOUNT
Step 2 — Plan for Sequence of Unit Installation . . . 8
• CURB-MOUNTED INSTALLATION
• PAD-MOUNTED INSTALLATION
• FRAME-MOUNTED INSTALLATION
Step 3 — Inspect Unit . . . . . . . . . . . . . . . . . . . . . . . . . 8
Step 4 — Provide Unit Support . . . . . . . . . . . . . . . . . 8
• ROOF CURB MOUNT
• SLAB MOUNT (HORIZONTAL UNITS ONLY)
• ALTERNATE UNIT SUPPORT (IN LIEU OF CURB OR
SLAB MOUNT)
Step 5 — Field Fabricate Ductwork . . . . . . . . . . . . . 10
• UNITS WITH ACCESSORY ELECTRIC HEATERS
Step 6 — Rig and Place Unit . . . . . . . . . . . . . . . . . . 10
• POSITIONING ON CURB
Step 7 — Convert to Horizontal and Connect
Ductwork (when required) . . . . . . . . . . . . . . . . . . 11
Step 8 — Install Outside Air Hood . . . . . . . . . . . . . . 12
• ECONOMIZER HOOD REMOVAL AND SETUP
(FACTORY OPTION)
• TWO-POSITION DAMPER HOOD REMOVAL AND
SETUP (FACTORY OPTION)
• ECONOMIZER AND TWO-POSITION HOOD
ASSEMBLY
Step 9 — Install External Condensate Trap and Line 14
Step 10 — Make Electrical Connections . . . . . . . . . 14
• FIELD POWER SUPPLY
• ALL UNITS
• UNITS WITHOUT FACTORY-INSTALLED NON-
FUSED DISCONNECT
• UNITS WITH FACTORY-INSTALLED NON-FUSED
DISCONNECT
• CONVENIENCE OUTLETS
• FACTORY-OPTION THRU-BASE CONNECTIONS
• UNITS WITHOUT THRU-BASE CONNECTIONS
• FIELD CONTROL WIRING
• THERMOSTAT
• CENTRAL TERMINAL BOARD
• COMMERCIAL DEFROST CONTROL
• UNIT WITHOUT THRU-BASE CONNECTION KIT
• HEAT ANTICIPATOR SETTINGS
• ELECTRIC HEATERS
• CONTROL AND POWER WIRING DIAGRAMS
• ECONOMI$ER® X (FACTORY OPTION)
• SMOKE DETECTORS
• PREMIERLINK™ (FACTORY OPTION)
• RTU OPEN CONTROLLER (FACTORY OPTION)
• CONTROLLER OPTIONS
Step 11 — Adjust Factory-Installed Options . . . . . .43
• SMOKE DETECTORS
• ECONOMI$ER IV OCCUPANCY SWITCH
Step 12 — Install Accessories . . . . . . . . . . . . . . . . .43
Step 13 — Check Belt Tension . . . . . . . . . . . . . . . . .44
• BELT FORCE — DEFLECTION METHOD
• BELT TENSION METHOD
Pre-Start and Start-Up . . . . . . . . . . . . . . . . . . . . . . . .45
START-UP CHECKLIST FOR 50HCQ12 SINGLE
PACKAGE ROOFTOP
HEAT PUMP
(REMOVE AND USE FOR JOB FILE) . . . . . . . . . .47
START-UP CHECKLIST . . . . . . . . . . . . . . . . . . . . .CL-1
SAFETY CONSIDERATIONS
Improper installation, adjustment, alteration, service,
maintenance, or use can cause explosion, fire, electrical shock or
other conditions which may cause 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 and work gloves. Use
quenching cloths for brazing operations and have a fire
extinguisher available. Read these instructions thoroughly and
follow all warnings or cautions attached to the unit. Consult local
building codes and appropriate national electrical codes (in USA,
ANSI/NFPA70, National Electrical Code (NEC); in Canada, CSA
C22.1) for special requirements.
It is important to 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 the signal words DANGER, WARNING, CAUTION,
and NOTE. 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 may 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.
50HCQ12
Single Package Rooftop Heat Pump
with Puron®(R-410A) Refrigerant

2
MODEL NUMBER NOMENCLATURE AND
DIMENSIONS
See Fig. 1 for 50HCQ model number nomenclature. See Fig. 2
and 3 for unit dimensional drawings. Figure 3 shows service clear-
ance dimensions.
Rated Indoor Airflow
Table 1 lists the rated indoor airflow used for the AHRI efficiency
rating for the units covered in this document.
Table 1 — Rated Indoor Airflow
DANGER
ELECTRICAL SHOCK HAZARD
Failure to follow this warning will result in personal injury or
death.
Before performing service or maintenance operations on unit,
turn off main power switch to unit and install lock(s) and lock-
out tag(s). Ensure electrical service to rooftop unit agrees with
voltage and amperage listed on the unit rating plate. Unit may
have more than one power switch.
WARNING
UNIT OPERATION AND SAFETY HAZARD
Failure to follow this warning could cause personal injury,
death and/or equipment damage.
R-410A refrigerant systems operate at higher pressures than
standard R-22 systems. Do not use R-22 service equipment or
components on R-410A refrigerant equipment.
WARNING
PERSONAL INJURY AND ENVIRONMENTAL
HAZARD
Failure to follow this warning could cause personal injury or
death.
Relieve pressure and recover all refrigerant before system re-
pair or final unit disposal.
Wear safety glasses and gloves when handling refrigerants.
Keep torches and other ignition sources away from refriger-
ants and oils.
CAUTION
PERSONAL INJURY 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, safety glasses and gloves
when handling parts and servicing air conditioning equipment.
MODEL NUMBER RATED INDOOR AIRFLOW
(CFM)
50HCQD12 4000

3
Fig. 1 — 50HCQ12 Model Number Nomenclature (Example)
50HCQD12A1A6–0B2A0
Cooling Tons
12 - 10 ton
1
Example:
Position: 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
Sensor Options
A = None
B = RA Smoke Detector
C = SA Smoke Detector
D = RA + SA Smoke Detector
E = CO2
F = RA Smoke Detector and CO2
G = SA Smoke Detector and CO2
H = RA + SA Smoke Detector and CO2
J = Condensate Overflow Switch
K = Condensate Overflow Switch and RA Smoke Detectors
L = Condensate Overflow Switch and
RA and SA Smoke Detectors
Indoor Fan Options
1 = Standard Static Option – Belt Drive
2 = Medium Static Option – Belt Drive
C = High Static Option with High Efficiency Motor – Belt Drive
Coil Options (Outdoor – Indoor – Hail Guard)
A = Al/Cu – Al/Cu
B = Precoat Al/Cu – Al/Cu
C = E-coat Al/Cu – Al/Cu
D = E-coat Al/Cu – E-coat Al/Cu
E = Cu/Cu – Al/Cu
F = Cu/Cu – Cu/Cu
M = Al/Cu – Al/Cu – Louvered Hail Guard
N = Precoat Al/Cu – Al/Cu – Louvered Hail Guard
P = E-coat Al/Cu – Al/Cu – Louvered Hail Guard
Q = E-coat Al/Cu – E-coat Al/Cu – Louvered Hail Guard
R = Cu/Cu – Al/Cu – Louvered Hail Guard
S = Cu/Cu – Cu/Cu – Louvered Hail Guard
Voltage
1 = 575/3/60
5 = 208-230/3/60
6 = 460/3/60
Design Revision
–= Factory Design Revision
Base Unit Controls
0 = Electro-mechanical Controls can be used with W7212
EconoMi$er
®
IV (Non-Fault Detection and Diagnostic)
1 = PremierLink
TM
Controller
2 = RTU Open Multi-Protocol Controller
6 = Electro-mechanical with W7220 Economizer
controller Controls. Can be used with W7220
EconoMi$er X (with Fault Detection and Diagnostic)
Intake / Exhaust Options
A = None
B = Temperature Economizer w/ Barometric Relief
F = Enthalpy Economizer w/ Barometric Relief
K = 2-Position Damper
U = Temperature Ultra Low Leak Economizer w/
Barometric Relief
W= Enthalpy Ultra Low Leak Economizer w/
Barometric Relief
Service Options
0 = None
1 = Unpowered Convenience Outlet
2 = Powered Convenience Outlet
3 = Hinged Panels
4 = Hinged Panels and
Unpowered Convenience Outlet
5 = Hinged Panels and
Powered Convenience Outlet
Packaging Options
0 = Standard
1 = LTL
Electrical Options
A = None
C = Non-Fused Disconnect
D = Thru-The-Base Connections
F = Non-Fused Disconnect and
Thru-The-Base Connections
G = 2-Speed Indoor Fan (VFD) Controller
J = 2-Speed Indoor Fan (VFD) Controller
and Non-Fused Disconnect
K = 2-Speed Indoor Fan (VFD) Controller
and Thru-The-Base Connections
M = 2-Speed Indoor Fan (VFD) Controller
with Non-Fused Disconnect and
Thru-The-Base Connections
Refrig. Systems Options
D = Two Stage Cooling Models
Unit/Series/Model
50HCQ - Packaged Rooftop Heat Pump

4
Fig. 2 — Unit Dimensional Drawing — Size 12 Units

5
Fig. 2 — Unit Dimensional Drawing — Size 12 Units (cont)

6
Fig. 3 — Service Clearance Dimensional Drawing
REFRIGERATION SYSTEM COMPONENTS
Each heat pump refrigeration system includes a compressor, accu-
mulator, reversing valve, dual-function outdoor coil with vapor
header check valve, cooling liquid line with a filter drier and a
check valve, dual-function indoor coil with a vapor header check
valve, and heating liquid line with a check valve and a strainer.
Size 12 units have two compressor-circuits. See Fig. 4 for typical
unit piping schematic (4-row indoor coil with two compressor-cir-
cuits is shown).
Dual-function outdoor and indoor coils are designed to provide
parallel coil circuits during evaporator-function operation and con-
verging coil circuits during the condenser-function operation.
Reversing Valve and Check Valve Position
See Fig. 4 and Tables 2-4.
Troubleshooting Refrigerant Pressure Problems
and Check Valves
Refer to Fig. 4 and the Cooling Mode and Heating Mode tables
(Tables 2 and 3).
NOTE: Unit not designed to have overhead obstruction. Contact Application Engineering for guidance on any application planning overhead
obstruction or for vertical clearances.
LOCATION DIMENSION CONDITION
A
48-in. (1219 mm)
18-in. (457 mm)
18-in. (457 mm)
12-in. (305 mm)
Unit disconnect is mounted on panel
No disconnect, convenience outlet option
Recommended service clearance
Minimum clearance
B
42-in. (1067 mm)
36-in. (914 mm)
Special
Surface behind servicer is grounded (e.g., metal, masonry wall)
Surface behind servicer is electrically non-conductive (e.g., wood, fiberglass)
Check sources of flue products within 10-ft (3 m) of unit fresh air intake hood
C36-in. (914 mm)
18-in. (457 mm)
Side condensate drain is used
Minimum clearance
D
42-in. (1067 mm)
36-in. (914 mm)
Special
Surface behind servicer is grounded (e.g., metal, masonry wall, another unit)
Surface behind servicer is electrically non-conductive (e.g., wood, fiberglass)
Check for adjacent units or building fresh air intakes within 10-ft (3 m) of this unit’s flue outlet
C
D
A
B
Table 2 — Cooling Mode (Each Circuit)
COMPONENT STATUS/POSITION
Reversing Valve Energized
Check Valve A Closed
Check Valve B Open
Check Valve C Closed
Check Valve D Open
Table 3 — Heating Mode (Each Circuit)
COMPONENT STATUS/POSITION
Reversing Valve De-Energized
Check Valve A Open
Check Valve B Closed
Check Valve C Open
Check Valve D Closed
Table 4 — Defrost Mode
COMPONENT STATUS/POSITION
Defrost Thermostat Closed
Outdoor Fan(s) Off
Reversing Valve Energized
Check Valve A Closed
Check Valve B Open
Check Valve C Closed
Check Valve D Open

7
Fig. 4 — Typical Unit Piping Schematic
Fig. 5 — CoreMax1Access Port Assembly
Refrigerant System Pressure Access Ports
There are two access ports in each circuit - on the suction tube and
the discharge tube near the compressor. These are brass fittings
with black plastic caps. The hose connection fittings are standard
1/4-inch SAE male flare couplings.
The brass fittings are two-piece High Flow valves, with a recep-
tacle base brazed to the tubing and an integral spring-closed
check valve core screwed into the base. See Fig. 5. This check
valve is permanently assembled into this core body and cannot
be serviced separately. Replace the entire core body if necessary.
Service tools are available from RCD that allow the replacement
of the check valve core without having to recover the entire sys-
tem refrigerant charge. Apply compressor refrigerant oil to the
check valve core’s bottom O-ring. Install the fitting body and
torque to 96 10 in-lbs (10.9 1 Nm). Do not exceed 106 in-lbs
(11.9 Nm) when tightening.
INSTALLATION
Jobsite Survey
Complete the following checks before installation.
1. Consult local building codes and the NEC (National Elec-
trical Code) ANSI/NFPA 70 for special installation
requirements.
2. Determine unit location (from project plans) or select unit
location.
3. Check for possible overhead obstructions which may
interfere with unit lifting or rigging.
COMPRESSOR
ACCUMULATOR
HPS
COMPRESSOR
ACCUMULATOR
HPS
Filter
Drier 2B
1B
LPS/LOC
Acutrol DFT 1
Cooling Liquid Lines
DFT 2
2A
1A
1D
2D
Outdoor Coil
Indoor Coil
Comp 2
Comp 1
2C
1C Strainer
Heating Mode Liquid Lines
Acutrol
Reversing
Valve
Reversing
Valve
1. CoreMax is a registered trademark of Fastent, Inc.
5/8” HEX 0.47
30°
0.596
1/2-20 UNF RH
1/2” HEX
45°
WASHER
O-RING
7/16-20 UNF RH
DEPRESSOR PER AHRI 720
+.01/-.035
FROM FACE OF BODY
This surface provides a metal to metal seal when
torqued into the seat. Appropriate handling is
required to not scratch or dent the surface.
SEAT CORE
(Part No. EC39EZ067)

8
Step 1 — Plan for Unit Location
Select a location for the unit and its support system (curb or other)
that provides for the minimum clearances required for safety (in-
cluding clearance to combustible surfaces), unit performance and
service access below, around and above unit as specified in unit
drawings. See Fig. 3.
NOTE: Consider also the effect of adjacent units.
Unit may be installed directly on wood flooring or on Class A, B,
or C roof-covering material when roof curb is used.
Do not install unit in an indoor location. Do not locate air inlets
near exhaust vents or other sources of contaminated air.
Although unit is weatherproof, avoid locations that permit water
from higher level runoff and overhangs to fall onto unit.
Select a unit mounting system that provides adequate height to al-
low installation of condensate trap per requirements. Refer to Step
9 — Install External Condensate Trap and Line on page 14 for re-
quired trap dimensions.
ROOF MOUNT
Check building codes for weight distribution requirements. Unit
operating weight is shown in Table 5.
Table 5 — Operating Weights
Step 2 — Plan for Sequence of Unit Installation
The support method used for this unit will dictate different se-
quences for the steps of unit installation. For example, on curb-
mounted units, some accessories must be installed on the unit be-
fore the unit is placed on the curb. Review the following for rec-
ommended sequences for installation steps:
CURB-MOUNTED INSTALLATION
1. Install curb.
2. Install field-fabricated ductwork inside curb.
3. Install accessory thru-base service connection package
(affects curb and unit) (refer to accessory installation
instructions for details).
4. Prepare bottom condensate drain connection to suit
planned condensate line routing (refer to Step 10 — Install
External Condensate Trap and Line on page 14 for
details).
5. Rig and place unit.
6. Install outdoor air hood.
7. Install condensate line trap and piping.
8. Make electrical connections.
9. Install other accessories.
PAD-MOUNTED INSTALLATION
1. Prepare pad and unit supports.
2. Check and tighten the bottom condensate drain connection
plug.
3. Rig and place unit.
4. Convert unit to side duct connection arrangement.
5. Install field-fabricated ductwork at unit duct openings.
6. Install outdoor air hood.
7. Install condensate line trap and piping.
8. Make electrical connections.
9. Install other accessories.
FRAME-MOUNTED INSTALLATION
Frame-mounted applications generally follow the sequence for a
curb installation. Adapt the sequence as required to suit specific
installation plan.
Step 3 — Inspect Unit
Inspect unit for transportation damage. File any claim with trans-
portation agency.
Confirm before installation of unit that voltage, amperage and cir-
cuit protection requirements listed on unit data plate agree with
power supply provided.
On units with hinged panel option, check to be sure all latches are
snug and in closed position.
Locate the carton containing the outside air hood parts. Do
not remove carton until unit has been rigged and located in final
position.
Step 4 — Provide Unit Support
ROOF CURB MOUNT
Accessory roof curb details and dimensions are shown in Fig. 6.
Assemble and install accessory roof curb in accordance with in-
structions shipped with the curb.
Curb should be level. This is necessary for unit drain to function
properly. Unit leveling tolerances are shown in Fig. 7. Refer to
Accessory Roof Curb Installation Instructions for additional infor-
mation as required.
Install insulation, cant strips, roofing felt, and counter flashing as
shown. Ductwork must be attached to curb and not to the unit. The
accessory thru-the-base power connection package must be in-
stalled before the unit is set on the roof curb.
If electric and control wiring is to be routed through the basepan,
attach the accessory thru-the-base service connections to the base-
pan in accordance with the accessory installation instructions.
NOTE: The gasketing of the unit to the roof curb is critical for a
watertight seal. Install gasket supplied with the roof curb as shown
in Fig. 6. Improperly applied gasket can also result in air leaks and
poor unit performance.
SLAB MOUNT (HORIZONTAL UNITS ONLY)
Provide a level concrete slab that extends a minimum of 6 in.
(150 mm) beyond unit cabinet. Install a gravel apron in front of
condenser coil air inlet to prevent grass and foliage from obstruct-
ing airflow.
NOTE: Horizontal units may be installed on a roof curb if
required.
ALTERNATE UNIT SUPPORT (IN LIEU OF CURB OR
SLAB MOUNT)
A non-combustible sleeper rail can be used in the unit curb sup-
port area. If sleeper rails cannot be used, support the long sides of
the unit with a minimum of 3 equally spaced 4-in. x 4-in. (102 mm
x 102 mm) pads on each side.
50HCQ12D
COMPONENT UNIT LB (KG)
Base Unit 1390 (632)
Economizer
Vertical 100 (45)
Horizontal 115 (52)
Powered Outlet 32 (15)
Curb
14 in. (356 mm) 180 (82)
24 in. (610 mm) 235 (107)

9
Fig. 6 — Roof Curb Details
REV
-
50TM500827

10
Fig. 7 — Unit Leveling Tolerances
Step 5 — Field Fabricate Ductwork
Cabinet return-air static pressure (a negative condition) shall not
exceed 0.35 in. wg (87 Pa) with economizer or 0.45 in. wg
(112 Pa) without economizer.
For vertical ducted applications, secure all ducts to roof curb and
building structure. Do not connect ductwork to unit.
Insulate and weatherproof all external ductwork, joints, and roof
openings with counter flashing and mastic in accordance with ap-
plicable codes.
Ducts passing through unconditioned spaces must be insulated
and covered with a vapor barrier.
If a plenum return is used on a vertical unit, the return should be
ducted through the roof deck to comply with applicable fire codes.
UNITS WITH ACCESSORY ELECTRIC HEATERS
All installations require a minimum clearance to combustible sur-
faces of 1 in. (25 mm) from duct for first 12 in. (305 mm) away
from unit.
Step 6 — Rig and Place Unit
Keep unit upright and do not drop. Spreader bars are required.
Rollers may be used to move unit across a roof. When the unit is
ready to be rigged and no longer will be lifted by a fork truck, the
wood protector under the basepan must be removed. Remove 4
screws from each base rail. Wood protector will drop to the
ground. See instructions on the unit base rails. Level by using unit
frame as a reference. See Table 5 and Fig. 8 for additional infor-
mation.
Lifting holes are provided in base rails as shown in Fig. 8. Refer to
rigging instructions on unit.
Before setting the unit onto the curb, recheck gasketing on curb.
Rigging materials under new unit (cardboard or wood) must be re-
moved PRIOR to placing the unit on the roof curb.
A
B
C
MAXIMUM ALLOWABLE
DIFFERENCE IN. (MM)
A-B B-C A-C
0.5 (13) 1.0 (25) 1.0 (25)
CAUTION
PROPERTY DAMAGE HAZARD
Failure to follow this caution may result in damage to roofing
materials.
Membrane roofs can be cut by sharp sheet metal edges. Be
careful when placing any sheet metal parts on such roof.
CAUTION
UNIT DAMAGE HAZARD
Failure to follow this caution may result in equipment damage.
All panels must be in place when rigging. Unit is not designed
for handling by fork truck when packaging is removed.

11
Fig. 8 — Rigging Details
POSITIONING ON CURB
For full perimeter curbs CRRFCURB072A00 and 073A00, the
clearance between the roof curb and the front and rear base rails
should be 1/4 in. (6.4 mm). The clearance between the curb and the
end base rails should be 1/2 in. (13 mm). For retrofit applications
with curbs CRRFCURB003A01 and 4A01, the unit should be po-
sition as shown in Fig. 9. Maintain the 15 1/2 in. (394 mm) and
8 5/8 in. (220 mm) clearances and allow the 22 5/16 in. (567 mm)
dimension to float if necessary.
Fig. 9 — Retrofit Installation Dimensions
If the alternative condensate drain location through the bottom of
the unit is used in conjunction with a retrofit curb, the hole in the
curb must be moved 12 1/2 in. (320 mm) towards the end of the
unit.
Although unit is weatherproof, guard against water from higher
level runoff and overhangs.
Remove all shipping materials and top skid. Remove extra center
post from the condenser end of the unit so that the condenser end
of the unit matches Fig. 21-23. Recycle or dispose of all shipping
materials.
Step 7 — Convert to Horizontal and Connect
Ductwork (when required)
Unit is shipped in the vertical duct configuration. Unit without fac-
tory-installed economizer or return-air smoke detector option may
be field-converted to horizontal ducted configuration using acces-
sory CRDUCTCV001A00. To convert to horizontal configura-
tion, remove screws from side duct opening covers (see Fig. 10)
and remove covers. Discard the supply duct cover. Install accesso-
ry CRDUCTCV001A00 to cover the vertical supply duct opening.
Use the return duct cover removed from the unit end panel to cov-
er the vertical return duct opening. Use the screws to install the
covers on vertical duct openings with the insulation-side down.
The panels must be inserted into the notches on the basepan to
properly seal. The notches are covered by the tape used to secure
the insulation to the basepan and are not easily seen. See Fig. 11
for position of the notches in the basepan. Seals around duct open-
ings must be tight. Secure with screws as shown in Fig. 12. Cover
seams with foil duct tape.
Field-supplied flanges should be attached to horizontal duct open-
ings and all ductwork should be secured to the flanges. Insulate
and weatherproof all external ductwork, joints, and roof or build-
ing openings with counter flashing and mastic in accordance with
applicable codes.
Do not cover or obscure visibility to the unit’s informative data
plate when insulating horizontal ductwork.
Fig. 10 — Horizontal Conversion Panels
NOTES:
1. SPREADER BARS REQUIRED — Top damage will occur if spreader bars are not used.
2. Dimensions in ( ) are in millimeters.
3. Hook rigging shackles through holes in base rail, as shown in detail “A.” Holes in base rails are centered around the unit center of
gravity. Use wooden top to prevent rigging straps from damaging unit.
UNIT MAX WEIGHT DIMENSIONS
ABC
lb kg in. mm in. mm in. mm
50HCQD12 2075 943 116.0 2945 58.5 1485 59.5 1510
DETAIL “A”
SEE DETAIL “A”
(914 - 1371)
36” - 54”
“B”
“A”
“C”
PLACE ALL GASKET IN PLACE BEFORE PLACING
UNIT ON ROOF CURB.
DUCT END
REMOVABLE HORIZONTAL
SUPPLY DUCT OPENING COVER
REMOVABLE HORIZONTAL
RETURN DUCT OPENING COVER

12
Fig. 11 — Location of Notches
Fig. 12 — Horizontal Duct Panels In Place
Step 8 — Install Outside Air Hood
ECONOMIZER HOOD REMOVAL AND SETUP
(FACTORY OPTION)
The hood is shipped in knock-down form and located in the return
air compartment. It is attached to the economizer using two plastic
tie-wraps.
1. To gain access to the hood, remove the filter access panel.
(See Fig. 13.)
2. Locate and cut the (2) plastic tie-wraps, being careful not
to damage any wiring. (See Fig. 14.)
3. Carefully lift the hood assembly through the filter access
opening and assemble per the steps outlined in Econo-
mizer and Two-Position Hood Assembly on page 13.
Fig. 13 — Typical Access Panel Locations
Fig. 14 — Economizer Wiring
TWO-POSITION DAMPER HOOD REMOVAL AND
SETUP (FACTORY OPTION)
The hood is shipped in knock-down form and assembled to a met-
al support tray using plastic stretch wrap. Located in the return air
compartment, the assembly’s metal tray is attached to the basepan
and also attached to the damper using two plastic tie-wraps.
1. To gain access to the hood, remove the filter access panel.
(See Fig. 13.)
2. Locate the (2) screws holding the metal tray to the basepan
and remove. In order to remove the screws, it may be nec-
essary to remove the panel underneath the two-position
damper. Locate and cut the (2) plastic tie-wraps securing
the assembly to the damper. (See Fig. 15.) Be careful not
to damage any wiring or cut tie-wraps securing any
wiring.
3. Carefully lift the hood assembly (with metal tray) through
the filter access opening and assemble per the steps out-
lined in Economizer and Two-Position Hood Assembly on
page 13.
4. If removed, reattach the panel under the damper.
BASEPAN
NOTCHES NOTCHES
SCREWS
DUCT COVERS
SHEET METAL
FACE UP
BASEPAN
FILTER ACCESS PANEL
INDOOR COIL ACCESS PANEL
ECONOMIZER
CUT PLASTIC TIES
(2) PLACES
REMOVE
HOOD PARTS

13
Fig. 15 — Damper Assembly
ECONOMIZER AND TWO-POSITION HOOD
ASSEMBLY
NOTE: If the power exhaust accessory is to be installed on the
unit, the hood shipped with the unit will not be used and must be
discarded. Save the aluminum filter for use in the power exhaust
hood assembly.
1. The indoor coil access panel will be used as the top of the
hood. Remove the screws along the sides and bottom of
the indoor coil access panel. See Fig. 16.
Fig. 16 — Indoor Coil Access Panel Relocation
2. Swing out indoor coil access panel and insert the hood
sides under the panel (hood top). Be careful not to lift the
panel too far as it might fall out. Use the screws provided
to attach the hood sides to the hood top. Use screws pro-
vided to attach the hood sides to the unit. See Fig. 17.
Fig. 17 — Economizer Hood Construction
3. Remove the shipping tape holding the economizer baro-
metric relief damper in place (economizer only).
4. Insert the hood divider between the hood sides. See
Fig. 17 and 18. Secure hood divider with 3 screws on each
hood side. The hood divider is also used as the bottom fil-
ter rack for the aluminum filter.
5. Attach the post that separates the filters with the screws
provided.
6. Open the filter clips which are located underneath the
hood top. Insert the aluminum filter into the bottom filter
rack (hood divider). Push the filter into position past the
open filter clips. Close the filter clips to lock the filter into
place. See Fig. 18.
7. Install the two rain deflectors on the edge of the hood top
as shown in Fig. 17.
8. Caulk the ends of the joint between the unit top panel and
the hood top.
9. Replace the filter access panel.
Fig. 18 — Economizer Filter Installation
HOOD PARTS
PLASTIC TIE WRAP
QTY (2)
SCREWS FOR METAL TRAY
QTY (2)
TOP
PANEL
INDOOR
COIL
ACCESS
PANEL
INDOOR
COIL
ACCESS
PANEL
CAULK
HERE
TOP
PANEL
RAIN DEFLECTORS
TOP
PANEL
INDOOR COIL
ACCESS PANEL
SCREW
HOOD DIVIDER
LEFT
HOOD
SIDE
DIVIDER
BAROMETRIC
RELIEF
CLEANABLE
ALUMINUM
FILTER
FILTER
HOOD
FILTER
CLIP
OUTSIDE
AIR

14
Step 9 — Install External Condensate Trap and
Line
The unit has one 3/4-in. condensate drain connection on the end of
the condensate pan and an alternate connection on the bottom. See
Fig. 19. Unit airflow configuration does not determine which
drain connection to use. Either drain connection can be used with
vertical or horizontal applications.
When using the standard side drain connection, ensure that the red
plug in the alternate bottom connection is tight. Do this before set-
ting the unit in place. The red drain pan plug can be tightened with
a 1/2-in. square socket drive extension.
To use the alternate bottom drain connection, remove the red
drain plug from the bottom connection (use a 1/2-in. square sock-
et drive extension) and install it in the side drain connection.
The piping for the condensate drain and external trap can be com-
pleted after the unit is in place. See Fig. 20.
Fig. 19 — Condensate Drain Pan (Side View)
Fig. 20 — Condensate Drain Pan Piping Details
All units must have an external trap for condensate drainage. In-
stall a trap at least 4 in. (102 mm) deep and protect against
freeze-up. If drain line is installed downstream from the external
trap, pitch the line away from the unit at 1 in. per 10 ft (25 mm
per 3 m) of run. Do not use a pipe size smaller than the unit con-
nection (3/4in.).
Step 10 — Make Electrical Connections
NOTE: Check all factory and field electrical connections for tight-
ness. Field-supplied wiring shall conform with the limitations of
minimum 63°F (33°C) rise.
FIELD POWER SUPPLY
For those units without through-the-curb power, conduit must be
used to route the main power from the condenser end of the unit to
either the factory option disconnect, the bottom of the control box
or the single point box accessory. One inch conduit is provided be-
hind the access panel located under the control box. For those
units that require conduit larger than 1 inch, it must be field sup-
plied. Figures 21-23 show the various wire routings.
If the field disconnect is larger than 100A, it must be attached to
the unit using accessory CRDISBKT001A00 (see Fig. 24). Follow
the instructions provided with this accessory. For smaller field dis-
connects, be sure to use 1/2-in. screws to mount the disconnect di-
rectly to the end panel, following the instructions on the Field Dis-
connect Warning label (see Fig. 25). In either case, set the discon-
nect vertical location on the unit so that a 90 degree fitting can be
used to connect the conduit to the disconnect.
Fig. 21 — Conduit into Factory Option Disconnect
DRAIN
(FACTORY-INSTALLED)
PLUG
CONDENSATE PAN (SIDE VIEW)
STANDARD
SIDE DRAIN
ALTERNATE
BOTTOM DRAIN
NOTE: Trap should be deep enough to offset maximum unit static
difference. A 4-in. (102 mm) trap is recommended.
MINIMUM PITCH
1˝ (25 mm) PER
10´ (3 m) OF LINE
BASE RAIL
OPEN
VENT
TO ROOF
DRAIN
DRAIN PLUG
ROOF
CURB
SEE NOTE
3˝ (76 mm)
MIN
WARNING
ELECTRIC SHOCK HAZARD
Failure to follow this warning could result in personal injury or
death.
Unit cabinet must have an uninterrupted, unbroken electrical
ground to minimize the possibility of personal injury if an
electrical fault should occur. This ground may consist of elec-
trical wire connected to unit ground lug in control compart-
ment, or conduit approved for electrical ground when installed
in accordance with NEC; ANSI/NFPA 70, latest edition (in
Canada, Canadian Electrical Code CSA [Canadian Standards
Association] C22.1), and local electrical codes.

15
Fig. 22 — Conduit into Control Box
Fig. 23 — Conduit into Single Point Box
Fig. 24 — Mounting Position for Field Disconnects
(over 100A)
Fig. 25 — Mounting Position for Field Disconnects
(up to 100A)
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 control transformer must be rewired
by moving the black wire with the 1/4-in. female spade connector
from the 230-v connection and moving it to the 200-v 1/4-in. male
terminal on the primary side of the transformer. Refer to unit label
diagram for additional information.
Field power wires are connected to the unit at line-side pressure
lugs at the main terminal block (TB1) or at factory-installed option
non-fused disconnect switch. (See Fig. 27). Max wire size is #2
AWG (copper only). See Fig. 26.
Fig. 26 — Power Wiring Connections
Units Without Disconnect Option
Units With Disconnect Option
2
4
6
1
3
5
L1
L2
L3
Optional
Disconnect
Switch
Disconnect factory test leads; discard.
Factory
Wiring
11 12 13
L1 L2 L3
TB1
208/230-3-60
460-3-60
575-3-60
Disconnect
per
NEC

16
NOTE: TEST LEADS — Unit may be equipped with short test
leads (pigtails) on the field line connection points on contactor C
or optional disconnect switch. These leads are for factory-run test
purposes only; remove and discard before connecting field power
wires to unit connection points. Make field power connections di-
rectly to line connection pressure lugs only.
Fig. 27 — Disconnect Switch and Unit
ALL UNITS
All field wiring must comply with NEC and all local codes.
Size wire based on MCA (Minimum Circuit Amps) on the unit in-
formative plate. See Fig. 26 and the unit label diagram for power
wiring connections to the unit power terminal blocks and equip-
ment ground. Maximum wire size is #2/0 AWG AWG (copper on-
ly) per pole.
Provide a ground fault and short circuit over-current protection de-
vice (fuse or breaker) per NEC Article 440 (or local codes). Refer
to unit informative data plate for MOCP (Maximum Over-Current
Protection) device size.
Voltage to compressor terminals during operation must be within
voltage range indicated on unit nameplate. On 3-phase units, volt-
ages between phases must be balanced within 2% and the current
within 10%. Use the formula shown in the following example to
determine the percent of voltage imbalance.
Example: Supply voltage is 230-3-60
AB = 224 v
BC = 231 v
AC = 226 v
Determine maximum deviation from average voltage.
(AB) 227-224 = 3 v
(BC) 231-227 = 4 v
(AC) 227-226 = 1 v
Maximum deviation is 4 v.
Determine percent of voltage imbalance.
This amount of phase imbalance is satisfactory as it is below the
maximum allowable 2%.
Operation on improper line voltage or excessive phase imbalance
constitutes abuse and may cause damage to electrical components.
Such operation would invalidate any applicable Carrier warranty.
NOTE: Check all factory and field electrical connections for tight-
ness.
UNITS WITHOUT FACTORY-INSTALLED NON-FUSED
DISCONNECT
When installing units, provide a disconnect switch per NEC (Na-
tional Electrical Code) of adequate size. Disconnect sizing data is
provided on the unit informative plate. Locate on unit cabinet or
within sight of the unit per national or local codes. Do not cover
unit informative plate if mounting the disconnect on the unit cabi-
net.
UNITS WITH FACTORY-INSTALLED NON-FUSED
DISCONNECT
The factory-installed optional disconnect switch is located in a
weatherproof enclosure located under the main control box. The
manual switch handle is accessible through an opening in the ac-
cess panel. Discard the factory test leads (see Fig. 28). The factory
disconnect is 80A disconnect.
Fig. 28 — Location of Non-Fused Disconnect
Enclosure
To field install the NFD shaft and handle (Fig. 29):
1. Remove the unit front panel (see Fig. 2).
2. Remove (3) hex screws on the NFD enclosure - (2) on the
face of the cover and (1) on the bottom.
3. Remove the front cover of the NFD enclosure.
4. Make sure the NFD shipped from the factory is at OFF
position (the arrow on the black handle knob is at OFF).
5. Insert the shaft with the cross pin on the top of the shaft in
the horizontal position.
WARNING
FIRE HAZARD
Failure to follow this warning could result in personal injury,
death, or property damage.
Do not connect aluminum wire between disconnect switch and
unit. Use only copper wire.
Average Voltage = (224 + 231 + 226) =681 = 227
3 3
% Voltage Imbalance = 100 x 4= 1.78%
227
COPPER
WIRE ONLY
ELECTRIC
DISCONNECT
SWITCH
ALUMINUM
WIRE
ABC
MOTOR
IMPORTANT: If the supply voltage phase imbalance is more
than 2%, contact your local electric utility company immedi-
ately.

17
6. Measure the tip of the shaft to the top surface of the
pointer to be 3.75 to 3.88 in. (95 to 99 mm) for 80A and
100A NFD and 3.43 to 3.56 in. (87 to 90 mm) for 200A
NFD.
7. Tighten the locking screw to secure the shaft to the NFD.
8. Turn the handle to the OFF position with red arrow point-
ing at OFF.
9. Install the handle on to the painted cover horizontally with
the red arrow pointing to the left.
10. Secure the handle to the painted cover with (2) screws and
lock washers supplied.
11. Engaging the shaft into the handle socket, re-install (3)
hex screws on the NFD enclosure.
12. Re-install the unit front panel.
Fig. 29 — Handle and Shaft Assembly for NFD
CONVENIENCE OUTLETS
Two types of convenience outlets are offered on 50HCQ
models: non-powered and unit-powered. Both types provide a
125-volt GFCI (ground-fault circuit interrupter) duplex re-
ceptacle rated at 15A behind a hinged waterproof access cov-
er, located on the end panel of the unit. See Fig. 30.
A 20 amp non-powered convenience outlet is available as a
field-installed accessory.
Non-Powered Convenience Outlet
This type requires the field installation of a general-purpose 125v
15A circuit powered from a source elsewhere in the building. Ob-
serve national and local codes when selecting wire size, fuse or
breaker requirements, and disconnect switch size and location.
Route 125v power supply conductors into the bottom of the utility
box containing the duplex receptacle.
Fig. 30 — Convenience Outlet Location
Unit-Powered Convenience Outlet
A unit-mounted transformer is factory-installed to step down the
main power supply voltage to the unit to 115-v at the duplex re-
ceptacle. This option also includes a manual switch with fuse, lo-
cated in a utility box and mounted on a bracket behind the conve-
nience outlet; access is through the unit’s control box access panel.
See Fig. 30.
The primary leads to the convenience outlet transformer are not
factory-connected. Selection of primary power source is a custom-
er-option. If local codes permit, the transformer primary leads can
be connected at the line-side terminals on the unit-mounted non-
fused disconnect switch; this will provide service power to the unit
when the unit disconnect switch is open. Other connection meth-
ods will result in the convenience outlet circuit being de-energized
when the unit disconnect switch is open. See Fig. 31. On a unit
without a unit-mounted disconnect, connect the source leads to the
main terminal block (TB1).
If the convenience outlet transformer is connected to the line side
of a field disconnect, the conduit provided with the unit must be
used to protect the wire as they are routed from the transformer to
the field disconnect. The end of the conduit with the straight con-
nector attaches to the field disconnect. The other end does not
need to connect to the transformer; however, the conduit must be
routed so that all wiring is either in the conduit or behind the ac-
cess panel.
If the convenience outlet transformer is connected to the line side
of the factory disconnect option, route the wires through the web
bushing located on the bottom of the disconnect box. For the load
side wiring to the factory option disconnect, route the wires
through the hole on the right side of the disconnect. Be sure to cre-
ate a drip loop at least 6 inches long.
WARNING
ELECTRICAL OPERATION HAZARD
Failure to follow this warning could result in personal injury or
death.
Units with convenience outlet circuits may use multiple dis-
connects. Check convenience outlet for power status before
opening unit for service. Locate its disconnect switch, if appro-
priate, and open it. Lock-out and tag-out this switch, if neces-
sary.
CONVENIENCE
OUTLET
GFCI
PWD-CO
FUSE
SWITCH
PWD-CO
TRANSFORMER
DISCONNECT
ACCESS PANEL

18
Fig. 31 — Powered Convenience Outlet Wiring
Duty Cycle
The unit-powered convenience outlet has a duty cycle limitation.
The transformer is intended to provide power on an intermittent
basis for service tools, lamps, etc; it is not intended to provide 15-
amps loading for continuous duty loads (such as electric heaters
for overnight use). Observe a 50% limit on circuit loading above 8
amps. (i.e., limit loads exceeding 8-amps to 30 minutes of opera-
tion every hour).
Test the GFCI receptacle by pressing the TEST button on the face
of the receptacle to trip and open the receptacle. Check for proper
grounding wires and power line phasing if the GFCI receptacle
does not trip as required. Press the RESET button to clear the
tripped condition.
Fuse On Power Type
The factory fuse is a Bussman “Fusetron”1 T-15, non-renewable
screw-in (Edison base) type plug fuse.
Installing Weatherproof Cover
A weatherproof while-in-use cover for the factory-installed conve-
nience outlets is now required by UL standards. This cover cannot
be factory-mounted due its depth; it must be installed at unit instal-
lation. For shipment, the convenience outlet is covered with a
blank cover plate.
The weatherproof cover kit is shipped in the unit’s control box.
The kit includes the hinged cover, a backing plate and gasket.
DISCONNECT ALL POWER TO UNIT AND CONVE-
NIENCE OUTLET.
Remove the blank cover plate at the convenience outlet; discard
the blank cover.
Loosen the two screws at the GFCI duplex outlet, until approxi-
mately 1/2-in. (13 mm) under screw heads are exposed. Press the
gasket over the screw heads. Slip the backing plate over the screw
heads at the keyhole slots and align with the gasket; tighten the
two screws until snug (do not over-tighten).
Mount the weatherproof cover to the backing plate as shown in
Fig. 32. Remove two slot fillers in the bottom of the cover to per-
mit service tool cords to exit the cover. Check for full closing and
latching.
Fig. 32 — Weatherproof Cover Installation
FACTORY-OPTION THRU-BASE CONNECTIONS
This service connection kit consists of a 1/2-in. electrical bulkhead
connector and a 1 1/2-in. electrical bulkhead connector, all factory-
installed to the basepan cover plate. Remove the cover plate from
the shipping bracket and attach to basepan with 8 screws provided.
The 1/2-in. bulkhead connector enables the low-voltage control
wires to pass through the basepan. The 1 1/2-in. electrical bulkhead
connector allows the high-voltage power wires to pass through the
basepan. See Fig. 33.
Check tightness of connector lock nuts before connecting electri-
cal conduits.
Field-supplied and field-installed liquidtight conduit connectors
and conduit may be attached to the connectors on the basepan.
Pull correctly rated high voltage and low voltage wires through
appropriate conduits. Connect the power conduit to the internal
disconnect (if unit is so equipped) or to the external disconnect
(through unit side panel). Remove one of the two knockouts locat-
ed on the bottom left side of the unit control box. Use this hole for
the control conduit.
1. Bussman and Fusetron are trademarks of Cooper Technologies
Company.
WARNING
ELECTRICAL OPERATION HAZARD
Failure to follow this warning could result in personal injury or
death.
Using unit-mounted convenience outlets: Units with unit-
mounted convenience outlet circuits will often require that two
disconnects be opened to de-energize all power to the unit.
Treat all units as electrically energized until the convenience
outlet power is also checked and de-energization is confirmed.
Observe National Electrical Code Article 210, Branch Cir-
cuits, for use of convenience outlets.
UNIT
VOLTAGE
CONNECT
AS
PRIMARY
CONNECTIONS
TRANSFORMER
TERMINALS
208, 230 240 L1: RED + YEL
L2: BLU + GRA
H1 + H3
H2 + H4
460 480
L1: RED
Splice BLU + YEL
L2: GRA
H1
H2 + H3
H4
575 600 L1: RED
L2: GRA
H1
H2
TOP
TOP
TOP
WET LOCATIONS
WET LOCATIONS
COVER - WHILE-IN-USE
WEATHERPROOF
BASEPLATE FOR
GFCI RECEPTACLE
GASKET
GFCI RECEPTACLE
NOT INCLUDED

19
Fig. 33 — Thru-Base Connection Fittings
UNITS WITHOUT THRU-BASE CONNECTIONS
1. Install power wiring conduit through side panel openings.
Install conduit between disconnect and control box.
2. Install power lines to terminal connections as shown in
Fig. 26.
FIELD CONTROL WIRING
The 50HCQ unit requires an external temperature control de-
vice. This device can be a thermostat (field-supplied) or a Pre-
mierLink™ controller (available as factory-installed option or as
field-installed accessory, for use on a Carrier Comfort Network®
or as a stand-alone control) or the RTU Open Controller for
Building Management Systems using non-CCN protocols (RTU
Open is available as a factory-installed option only).
THERMOSTAT
Select a Carrier-approved accessory 2-stage Cooling/Heating ther-
mostat. The 50HCQ models do not require a thermostat with an O
function to control the reversing valve operation. If using an elec-
tronic thermostat, configure it for “non-heat pump” operation. In-
stall the accessory thermostat according to installation instructions
included with the accessory.
Locate the thermostat accessory on a solid wall in the conditioned
space to sense average temperature in accordance with the ther-
mostat installation instructions.
If the thermostat contains a logic circuit requiring 24-v power,
use a thermostat cable or equivalent single leads of different col-
ors with minimum of seven leads. If the thermostat does not re-
quire a 24-v source (no “C” connection required), use a thermo-
stat cable or equivalent with minimum of six leads. See Fig. 34.
Check the thermostat installation instructions for additional fea-
tures which might require additional conductors in the cable.
For wire runs up to 50 ft. (15 m), use no. 18 AWG (American
Wire Gage) insulated wire [35°C (95°F) minimum]. For 50 to
75 ft. (15 to 23 m), use no. 16 AWG insulated wire [35°C (95°F)
minimum]. For over 75 ft. (23 m), use no. 14 AWG insulated wire
[35°C (95°F) minimum]. Wire sizes larger than no. 18 AWG can-
not be directly connected to the thermostat and will require a junc-
tion box and splice at the thermostat.
Fig. 34 — Typical Low-Voltage Control Connections
CENTRAL TERMINAL BOARD
The Central Terminal Board (CTB) is a pass through connection
point. The CTB provides the capability to add factory-installed
options and field-installed accessories to the units by cutting
jumper wires without having to change or reroute wires through
the structure of the unit. The CTB does not provide any micropro-
cessor control; it is simply a basic multifunction wiring terminal
configuration.
COMMERCIAL DEFROST CONTROL
The Commercial Defrost Control Board (DFB) coordinates ther-
mostat demands for supply fan control, 1 or 2 stage cooling, 2
stage heating, emergency heating and defrost control with unit op-
erating sequences. The DFB also provides an indoor fan off delay
feature (user selectable). See Fig. 35 for board arrangement.
The DFB is located in the 50HCQ unit’s main control box (see
Fig. 2 and 36). All connections are factory-made through harness-
es to the unit’s CTB, to IFC (belt-drive motor) or to ECM (direct-
drive motor), reversing valve solenoids and to defrost thermostats.
Refer to Table 6 for details of DFB Inputs and Outputs.
LOW VOLTAGE
CONDUIT
CONNECTOR
HIGH VOLTAGE
CONDUIT
CONNECTOR
X
C
G
W2
R
C
W2
G
W1
O/B/Y2 Y2
W1
R
Y1 Y1
Typical
Thermostat
Connections
T
H
E
R
M
O
S
T
A
T
(Note 1)
(Note 2)
1. Typical multi-function marking. Follow manufacturer’s configuration
instructions to select Y2. Do not configure for O output.
2. W2 connection not required on units without electric heating.
Field Wiring
Central
Terminal
Board
NOTES:

20
Fig. 35 — Defrost Control Board Arrangement
Reversing valve control
The DFB has two outputs for unit reversing valve control. Opera-
tion of the reversing valves is based on internal logic; this applica-
tion does not use an “O” or “B” signal to determine reversing
valve position. Reversing valves are energized during the cooling
stages and the defrost cycle and de-energized during heating cy-
cles. Once energized at the start of a cooling stage, the reversing
valve will remain energized until the next heating cycle demand is
received. Once de-energized at the start of a Heating cycle, the re-
versing valves will remain de-energized until the next cooling
stage is initiated.
Compressor control
The DFB receives inputs indicating Stage 1 Cooling, Stage 2
Cooling and Stage 1 Heating from the space thermostat or unit
control system (PremierLink™ controller or RTU Open control-
ler); it generates commands to start compressors with or without
reversing valve operation to produce Stage 1 Cooling (one com-
pressor runs), Stage 2 Cooling (both compressors run) or Stage 1
Heating (both compressors run).
Auxiliary (Electric) Heat control
The 50HCQ unit can be equipped with one or two auxiliary elec-
tric heaters, to provide a second stage of heating. The DFB will
energize this Heating System for a Stage 2 Heating Command
(heaters operate concurrently with compressor(s) in the Stage 1
Heating cycle), for an Emergency Heating sequence (compressors
are off and only the electric heaters are energized) and also during
the Defrost cycle (to eliminate a “cold blow” condition in the
space).
Fig. 36 — Defrost Control Board Location
DIP
SWITCHES
SPEED-UP
JUMPERS