Specifications

4
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$er integrates free
cooling with mechanical cooling. This is accomplished by the
strategies below.
NOTE: Compressors have a 2-minute Minimum On,
Minimum Off, and Interstage delay timer.
1. If Y1 is energized, and the room thermostat calls for Y2
(2-stage thermostat), compressor no. 1, RVS1 and OFM
are energized. The EconoMi$er damper is maintained 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, RVS1 and OFM are energized.
The EconoMi$er damper is maintained at its current
position.
3. If Y1 is energized, and compressor no. 1 is already
energized (see Step 2) and the room thermostat calls for
Y2, compressor no. 1 continues to operate. If Y2 remains
energized for more than 20 minutes, compressor no. 2
and RVS2 are energized.
NOTE: Compressor no. 2 cannot be energized unless
there is a signal for Y2 from the space thermostat.
4. If compressor no. 2 is energized, and the Y2 signal from
the thermostat is satisfied, compressor no. 1 and 2, RVS1,
RVS2 and ODF are deenergized. Reasserting Y2 will
start compressor no. 1 and (after a 20-minute interstage
delay) compressor 2.
5. If compressor no. 1 is energized and the thermostat is sat-
isfied, compressor no. 1, the OFM, RVS1 and IFM are
deenergized and the EconoMi$er modulates closed.
HEATING, UNITS WITH ECONOMIZER INCLUDING
DURABLADE, ECONOMI$ER (Johnson) OR ECONO-
MI$ER2 (Sizes 004-007) — 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
economizer damper blade opens to minimum position. The
RVS is deenergized and switches position, and the indoor 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 tem-
perature set point, heating stages cycle off. The reversing valve
solenoid is reenergized.
HEATING, UNITS WITH ECONOMIZER INCLUDING
DURABLADE, ECONOMI$ER (Johnson) OR ECONO-
MI$ER2 (Sizes 008,012) — Upon a request for heating from
the space thermostat, terminal W1 will be energized 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. The economizer damper blade opens to minimum
position.
If the space temperature continues to fall while W1 is
energized, 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 deener-
gized 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.
DEFROST (Sizes 004-007) — As frost builds up on the out-
door coil, the coil temperature drops below 28 F. When this
outdoor-coil temperature drop is sensed by the defrost thermo-
stat (DFT) and the defrost timer is at the end of a timed period
(adjustable at 30, 50, or 90 minutes), the unit operates in a
defrost cycle controlled by the defrost timer and thermostat.
During this cycle, the reversing valve solenoid (RVS) is
energized and the outdoor fan shuts off. The electric heaters (if
installed) will be energized.
The unit continues to defrost until the coil temperature as
measured by DFT reaches 65 F, or the duration of defrost cycle
completes a 10-minute period.
At the end of the defrost cycle, the electric heaters (if
installed) and the reversing valve will be deenergized, and the
outdoor-fan motor will be energized. The unit will now operate
in the Heating mode.
If the thermostat is satisfied during a defrost cycle, the unit
will continue in the Defrost mode until the time or temperature
constraints are satisfied.
DEFROST (Sizes 008,012) — When the temperature of the
outdoor coil drops below 28 F as sensed by the defrost thermo-
stat (DFT2) and the defrost timer is at the end of a timed period
(adjustable at 30, 50, or 90 minutes), reversing valve solenoids
(RVS1 and RVS2) are energized and the OFC is deenergized.
This switches the position of the reversing valves and shuts
off the outdoor fan. The electric heaters (if installed) will be
energized.
The unit continues to defrost until the coil temperature as
measured by DFT2 reaches 65 F, or the duration of defrost
cycle completes a 10-minute period.
During the Defrost mode, if circuit 1 defrosts first, RVS1
will oscillate between Heating and Cooling modes until the
Defrost mode is complete.
At the end of the defrost cycle, the electric heaters (if
installed) will be deenergized; the reversing valves switch and
the outdoor-fan motor will be energized. The unit will now
operate in the Heating mode.
If the space thermostat is satisfied during a defrost cycle, the
unit will continue in the Defrost mode until the time or temper-
ature constraints are satisfied.