User`s manual

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W1 is energized. The induced-draft motor is energized and
the burner ignition sequence begins. The indoor (evaporator)
fan motor (IFM) is energized 45 seconds after a flame is
ignited and the damper moves to the minimum position. On
units equipped for two stages of heat, when additional heat
is needed, W2 is energized and the high-fire solenoid on the
main gas valve (MGV) is energized. When the thermostat
is satisfied and W1 is deenergized, the IFM stops after a
45-second time-off delay. The economizer damper then moves
to the fully closed position. When using continuous fan, the
damper will remain in the minimum position.
H. Limit Switches
Heating limit switches (LS) close the gas valve and the Inte-
grated Gas Unit Controller (IGC) if the leaving-air tempera-
ture exceeds the maximum allowable temperature.
Normally closed LS completes a circuit to the gas valve.
Should the leaving-air temperature rise above the maximum
allowable temperature, LS opens instantly, closing the gas
valves and stopping gas flow to the burners. The inducer
motor and evaporator motor are energized to cool heat
exchanger. The combustion blower motor stops.
When the air temperature at LS drops to the low-tempera-
ture setting of the LS, the switch closes and completes the
gas valve circuit. The electric-spark ignition system cycles
and the unit returns to normal heating operation.
I. Rollout Switch
The rollout switch (RS) is a temperature-actuated automatic
reset switch which closes the main gas valve in the event of
flame rollout. The switch is located above the main burners
on the internal wind baffle. When the temperature at RS
reaches the maximum allowable temperature, the control
circuit trips, closing the gas valves and stopping gas flow to
the burners. The inducer motor and evaporator-fan motor
are energized when RS trips. Although the rollout switch has
an automatic reset, the Integrated Gas Unit Controller (IGC)
locks out the unit when a trip occurs and does not allow the
burners to ignite until the unit disconnect is reset. If the
switch cycles again, shut down the unit and call for service.
II. COOLING SECTION START-UP AND ADJUSTMENTS
A. Checking Cooling Control Operation
Start and check the unit for proper cooling control operation
as follows:
1. Place room thermostat SYSTEM switch in OFF posi-
tion. Observe that fan motor starts when FAN switch
is placed in ON position and shuts down when FAN
switch is placed in AUTO. position.
2. Place SYSTEM switch in COOL position and FAN
switch in AUTO. position. Set cooling control below
room temperature. Observe that compressor, con-
denser fan, and evaporator-fan motors start. Observe
that cooling cycle shuts down when control setting is
satisfied.
3. When using an autochangeover room thermostat,
place both SYSTEM and FAN switches in AUTO.
positions. Observe that unit operates in heating mode
when temperature control is set to ‘‘call for heating’’
(above room temperature) and operates in cooling
mode when temperature control is set to ‘‘call for cool-
ing’’ (below room temperature).
B. Checking and Adjusting Refrigerant Charge
The refrigerant system is fully charged with R-22 refriger-
ant, tested, and factory-sealed.
NOTE: Adjustment of the refrigerant charge is not required
unless the unit is suspected of not having the proper R-22
charge. This unit uses charging charts to determine proper
charge. See Refrigerant Charge section on page 33 for fur-
ther details.
C. Unit Controls
All compressors have the following internal-protection
controls:
1. High-Pressure Relief Valve — This valve (internal to
the compressor) opens when the pressure differential
between the low and high side becomes excessive and
will automatically reset when pressure returns to
normal.
2. Compressor Overload — This overload interrupts
power to the compressor when either the current or
internal temperature becomes excessive, and auto-
matically resets when the internal temperature drops
to a safe level. This overload may require up to
60 minutes (or longer) to reset; therefore, if the inter-
nal overload is suspected of being open, disconnect
the electrical power to the unit and check the circuit
through the overload with an ohmmeter or continuity
tester.
D. Compressor Rotation
On 3-phase units with scroll compressors, it is important to
be certain compressor is rotating in the proper direction. To
determine whether or not compressor is rotating in the
proper direction:
1. Connect service gages to suction and discharge pres-
sure fittings.
2. Energize the compressor.
3. The suction pressure should drop and the discharge
pressure should rise, as is normal on any start-up.
If the suction pressure does not drop and the discharge pres-
sure does not rise to normal levels:
1. Note that the evaporator fan is probably also rotating
in the wrong direction.
2. Turn off power to the unit and tag disconnect.
3. Reverse any two of the unit power leads.
4. Reapply power to the unit.
The suction and discharge pressure levels should now move
to their normal start-up levels.
NOTE: When the compressor is rotating in the wrong direc-
tion, the unit makes an elevated level of noise and does not
provide cooling.
E. Cooling Sequence of Operation
Without Economizer
When thermostat calls for cooling, terminals G and Y1 are
energized. The indoor (evaporator) fan contactor (IFC) com-
pressor contactor no. 1 (C1) and outdoor (condenser) fan con-
tactor (OFC) are energized and indoor (evaporator) fan motor
CAUTION: Complete the required procedures
given in the Pre-Start-Up section on page 20 before
starting the unit.
Do not jumper any safety devices when operating the
unit.
Do not operate the compressor when the outdoor tem-
perature is below 25 F.
Do not rapid-cycle the compressor. Allow 5 minutes
between ‘‘on’’ cycles to prevent compressor damage.