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CONTROLS
OPERATING SEQUENCE — SIZE 036-073 UNITS
Cooling, Units Without Economizer —
When the thermostat
calls for cooling, terminals G and Y1 are energized. The indoor
(evaporator) fan contactor (IFC), and compressor contactor
no. 1 (C1) are energized and the indoor (evaporator) fan motor
(IFM), compressor no. 1, and condenser fan start. The outdoor
(condenser) fan motor (OFM) runs continuously while unit is
cooling.
Cooling, Units With EconoMi$er —
When the outdoor-air
temperature (OAT) is above the ECON SP set point and the
room thermostat calls for Stage 1 cooling (R to G + Y1), the
indoor (evaporator) fan motor (IFM) is energized and the
EconoMi$er damper modulates to minimum position. The com-
pressor contactor is energized to start the compressor and out-
door (condenser) fan motor (OFM). After the thermostat is
satisfied, the damper modulates to the fully closed position
when the IFM is deenergized.
When the OAT is below the ECON SP setting and the room
thermostat calls for Stage 1 cooling (R to G + Y1), the
EconoMi$er modulates to the minimum position when the IFM
is energized. The EconoMi$er provides Stage 1 of cooling by
modulating the return and outdoor air dampers to maintain a
55 F supply air set point. If the supply-air temperature (SAT) is
greater than 57 F, the EconoMi$er modulates open, allowing a
greater amount of outdoor air to enter the unit. If the SAT drops
below 53 F, the outdoor air damper modulates closed to reduce
the amount of outdoor air. When the SAT is between 53 and
57 F, the EconoMi$er maintains its position.
If outdoor air alone cannot satisfy the cooling requirements of
the conditioned space, and the OAT is above the MECH CLG
LOCKOUT set point, the EconoMi$er integrates free cooling
with mechanical cooling. This is accomplished by the strategies
below.
NOTE:
Compressor has a 2-minute Minimum On, Minimum Off,
and Interstage delay timer.
1. If Y1 is energized, and the room thermostat calls for Y2
(2-stage thermostat), the compressor and OFM are ener-
gized. The position of the EconoMi$er damper is main-
tained at its current value.
2. If Y1 is energized for more than 20 minutes, and Y2 is not
energized (whether or not a 2-stage thermostat is used),
the compressor and OFM are energized. The position of the
EconoMi$er damper is maintained at its current value.
3. If Y1 is energized, and the compressor is already energized
(see Step 2) and the room thermostat calls for Y2, the com-
pressor continues to operate.
4. If the compressor is energized and the thermostat is satis-
fied, the compressor, the OFM, and IFM are deenergized
and the EconoMi$er modulates closed.
When the OAT is below the MECH CLG LOCKOUT set point,
the compressors remain off.
Heating, Units Without Economizer —
Upon a call for heating
through W1, indoor (evaporator) fan contactor (IFC) and heater
contactor no. 1 (HC1) are energized. On units equipped for
2 stages of heat, when additional heat is needed, heater con-
tactor no. 2 is energized through W2.
Heating, Units With Economizer —
When the room tempera-
ture calls for heat through terminal W1, the indoor (evaporator)
fan contactor (IFC) and heater contactor no. 1 (HC1) are ener-
gized. On units equipped for 2 stages of heat, when additional
heat is needed, heater contactor no. 2 is energized through W2.
The economizer damper moves to the minimum position. When
the thermostat is satisfied, the damper moves to the fully closed
position.
OPERATING SEQUENCE — SIZE 090-150 UNITS
Cooling, Units Without Economizer —
When the thermostat
calls for cooling, terminals G and Y1 are energized. The indoor
(evaporator) fan contactor (IFC), compressor contactor no. 1
(C1) and outdoor fan contactor (OFC) are energized and the
indoor (evaporator) fan motor (IFM), compressor no. 1, and con-
denser fans start. The outdoor (condenser) fan motors (OFM)
run continuously while unit is cooling. If the thermostat calls for
a second stage of cooling by energizing Y2, compressor con-
tactor no. 2 (C2) is energized and compressor no. 2 starts.
Cooling, Units With EconoMi$er —
When the outdoor-air
temperature (OAT) is above the ECON SP set point and the
room thermostat calls for Stage 1 cooling (R to G + Y1), the
indoor (evaporator) fan motor (IFM) is energized and the
EconoMi$er damper modulates to minimum position. The com-
pressor contactor is energized to start the compressor and out-
door (condenser) fan motor (OFM). After the thermostat is
satisfied, the damper modulates to the fully closed position
when the IFM is deenergized.
When the OAT is below the ECON SP setting and the room
thermostat calls for Stage 1 cooling (R to G + Y1), the
EconoMi$er modulates to the minimum position when the IFM
is energized. The EconoMi$er provides Stage 1 of cooling by
modulating the return and outdoor air dampers to maintain a
55 F supply air set point. If the supply-air temperature (SAT) is
greater than 57 F, the EconoMi$er modulates open, allowing a
greater amount of outdoor air to enter the unit. If the SAT drops
below 53 F, the outdoor air damper modulates closed to reduce
the amount of outdoor air. When the SAT is between 53 and
57 F, the EconoMi$er maintains its position.
If outdoor air alone cannot satisfy the cooling requirements of
the conditioned space, and the OAT is above the MECH CLG
LOCKOUT set point, the EconoMi$er integrates free cooling
with mechanical cooling. This is accomplished by the strategies
below.
NOTE:
Compressor has a two-minute Minimum On, Minimum
Off, and Interstage delay timer.
1. If Y1 is energized, and the room thermostat calls for Y2
(2-stage thermostat), compressor no. 1 and OFM are ener-
gized. The position of the EconoMi$er damper is main-
tained at its current value.
2. If Y1 is energized for more than 20 minutes, and Y2 is not
energized (whether or not a 2-stage thermostat is used),
compressor no. 1 and OFM are energized. The position of
the EconoMi$er damper is maintained at its current value.
3. If Y1 is energized, and compressor no. 1 is already ener-
gized (see Step 2) and the room thermostat calls for Y2, the
compressor continues to operate. If Y2 remains energized
for more than 20 minutes, compressor no. 2 is energized.
NOTE:
Compressor no. 2 cannot be energized unless there is a
signal for Y2 from the space thermostat.
4. If compressor no. 2 is energized, and the Y2 signal from the
thermostat is satisfied, compressors 1 and 2 are deener-
gized. Reasserting Y2 will start compressor no. 1 and (after
a 20-minute interstage delay) compressor no. 2.
5. If compressor no. 1 is energized and the thermostat is satis-
fied, compressor no. 1, the OFM, and IFM are deenergized
and the EconoMi$er modulates closed.
When the OAT is below the MECH CLG LOCKOUT set point,
the compressors remain off.