Carrier 50TFQ004 Product Data page 66

Controls (cont)
3. If Y1 is energized, and the compressor is already
energized (see Step 2) and the room thermostat calls
for Y2, the compressor continues to operate.
4. If compressor is energized and the thermostat is satis-
fied, the compressor, the OFM, and IFM are deener-
gized and the EconoMi$er modulates closed.
When the OAT is below the MECH CLG LOCKOUT set
point, the compressors remain off.
Cooling, units with EconoMi$er (50TFQ008-014)
— 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-fan motor (IFM)
is energized and the EconoMi$er damper modulates to
minimum position. The compressor contactor is energized
to start the compressor and outdoor-fan motor (OFM) and
RVS1 (reversing valve solenoid). After the thermostat is
satisfied, the damper modulates to the fully closed position
when the IFM is deenergized.
When the OAT is below the ECON SP setting and the
room thermostat calls for Stage 1 cooling (R to G + Y1),
the EconoMi$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 out-
door air. When the SAT is between 53 and 57 F, the
EconoMi$er maintains its position.
If outdoor-air alone cannot satisfy the cooling require-
ments of the conditioned space, and the OAT is above the
MECH CLG LOCKOUT set point, the EconoMi$er inte-
grates free cooling with mechanical cooling. This is accom-
plished by the strategies below.
66
NOTE: Compressors have a 2-minute Minimum On, Mini-
mum 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 energized. The EconoMi$er damper is main-
tained at its current position.
2. If Y1 is energized for more than 20 minutes, and Y2
is not energized (whether or not a 2-stage thermostat
is used), compressor no. 1 and OFM are energized.
The EconoMi$er damper is maintained at its current
position.
3. If Y1 is energized, and compressor no. 1 is already
energized (see Step 2) and the room thermostat calls
for Y2, compressor no. 1 continues to operate. If Y2
remains energized for more than 20 minutes, com-
pressor 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, compressor no. 1
and 2 are deenergized. Reasserting Y2 will start com-
pressor no. 1 and (after a 20-minute interstage delay)
compressor 2.
5. If compressor no. 1 is energized and the thermostat is
satisfied, compressor no. 1, the OFM, and IFM are
deenergized and the EconoMi$er modulates closed.
Heating, units with economizer — Upon a call for
heat through W1, the IFC energizes to start the evaporator
fan and the economizer damper blade opens to the mini-
mum position. If the accessory two-position damper is
used, the outdoor-air damper opens to the minimum posi-
tion whenever the evaporator fan runs. If unit is equipped
with 2 stages of heat, when additional heat is needed a call
is made through W2.
As space temperature approaches the heating tempera-
ture set point, heating stages cycle off. Economizer or two-
position damper returns to fully closed position.