Product data

25
LEGEND
Operating sequence — 50TFQ004-012 and
50HJQ004-012
Cooling, units without economizer — When thermo-
stat calls for cooling, terminals G and Y1 are energized.
The indoor-fan contactor (IFC), reversing valve solenoid
(RVS1) and compressor contactor no. 1 (C1) are energized
and indoor-fan motor, compressor no. 1, and outdoor fans
start. The outdoor-fan motor(s) run continuously while unit
is cooling. On 50TFQ008-012 units, if the thermostat
calls for a second stage of cooling by energizing Y2, com-
pressor contactor no. 2 (C2) and reversing valve solenoid
(RVS2) are energized and compressor no. 2 starts.
Heating, units without economizer (50TFQ004-
007 and 50HJQ004-007) — Set system switch at
AUTO. or HEAT position. Set thermostat at desired
temperature.
When the thermostat calls for heat, the IFC, outdoor-fan
contactor (OFC), and compressor contactor are energized.
The RVS is deenergized and switches position, and the in-
door fan, outdoor fan, and compressor are energized.
If the thermostat calls for a second stage of heat, the
heater contactor (HC) is energized and starts the electric
heaters.
When the space temperature approaches the heating
temperature set point, heating stages cycle off. The revers-
ing valve solenoid is reenergized.
Heating, units without economizer (50TFQ008-
012 and 50HJQ008,012) — Upon a request for heat-
ing from the space thermostat, terminal W1 will be ener-
gized with 24 v. The IFC, outdoor-fan contactor (OFC),
C1, and C2 will be energized. The reversing valves switch
position and the indoor fan, outdoor fan, compressor
no. 1, and compressor no. 2 are energized.
If the space temperature continues to fall while W1 is en-
ergized, W2 will be energized with 24 v, and the heater
contactor(s) (HC) will be energized, which will energize the
electric heater(s).
When the space thermostat is satisfied, W2 will be deen-
ergized first, and the electric heater(s) will be deenergized.
Upon a further rise in space temperature, W1 will be
deenergized, and the reversing valve solenoids (RVS1 and
RVS2) will be energized.
Cooling, units with Durablade economizer — When
the outdoor-air temperature is above the outdoor-air ther-
mostat (OAT) setting and the room thermostat calls for
cooling, compressor contactor no. 1 is energized to start
compressor no. 1 and the outdoor-fan motor(s). RVS1 (re-
versing valve solenoid) is energized. The indoor-fan motor
is energized and the economizer damper moves to the
minimum position. Upon a further call for cooling, com-
pressor contactor no. 2 will be energized (50TFQ008-012
and 50HJQ008,012), starting compressor no. 2. RVS2 is
energized. After the thermostat is satisfied, the damper
moves to the fully closed position.
When the outdoor-air temperature is below the OAT set-
ting and the thermostat calls for cooling, the economizer
dampers move to the minimum position. If the supply-air
temperature is above 57 F, the damper continues to open
until it reaches the fully open position or until the supply-
air temperature drops below 52 F.
When the supply-air temperature falls to between 57 F
and 52 F, the damper will remain at an intermediate open
position. If the supply-air temperature falls below 52 F, the
damper will modulate closed until it reaches the minimum
position or until the supply-air temperature is above 52 F.
When the thermostat is satisfied, the damper will move to
the fully closed position.
If the outdoor air alone cannot satisfy the cooling re-
quirements of the conditioned space, economizer cooling
is integrated with mechanical cooling, providing second-
stage cooling. Compressor no. 1 and the outdoor fan will
be energized and the position of the economizer damper
will be determined by the supply-air temperature. Com-
pressor no. 2 (50TFQ008-012 and 50HJQ008,012) is
locked out.
When the second stage of cooling is satisfied, the com-
pressor, RVS2, and outdoor-fan motor(s) will be deener-
gized. The damper position will be determined by the
supply-air temperature.
When the first stage of cooling is satisfied, the damper
will move to fully closed position.
AHA — Adjustable Heat Anticipator
CB — Circuit Breaker
CC — Cooling Compensator
CLO — Compressor Lockout
DM — Damper Motor
EAS — Economizer Actuator
Auxiliary Switch
EMC — Economizer Motor Contactor
FU — Fuse
IFC — Indoor-Fan Contactor
IFCB — Indoor-Fan Circuit Breaker
IFR — Indoor-Fan Relay
L—Light
MAT — Mixed-Air Thermostat
OAT — Outdoor-Air Thermostat
PL — Plug Assembly
SR — Solenoid Relay
TB — Te rm ina l B lock
TC — Thermostat Cooling
TH — Thermostat Heating
TRAN — Transformer
Terminal (Marked)
Terminal (Unmarked)
Terminal Block
Splice
Factory Wiring
Field Wiring
Option/Accessory Wiring
To Indicate Common Potential
Only, Not To Represent Wiring