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Operation
On a heating demand, the ignition control checks for a
closed limit switch and open (to prove switch is not failed
closed prior to start-up) combustion air prove switch. Once
this check is complete and conditions are correct, the ig-
nition control then allows 30 seconds for the combustion
air inducer to vent exhaust gases from the burners. When
the combustion air inducer is purging the exhaust gases,
the combustion air prove switch closes proving that the
combustion air inducer is operating before allowing the ig-
nition control to energize. When the combustion air prove
switch is closed and the delay is over, the ignition control
activates the gas valve, the spark electrode and the flame
sensing electrode. Once the gas valve is energized the
non-adjustable 40 second indoor blower delay period be-
gins. Sparking stops immediately after flame is sensed or
at the end of the 8 second trial for ignition
The control then proceeds to "steady state" mode where
all inputs are monitored to ensure the limit switch, rollout
switch and prove switch are closed as well as flame is
present. When the heat call is satisfied and the gas valve
is deenergized, a combustion air inducer post purge pe-
riod of 5 seconds begins along with a 120 second blower
off delay.
10-Power Exhaust Transformer T10 (J volt)
Transformer T10 is a field-installed 600/230V transformer
which provides power to the 208/230V power exhaust fan
in 575V applications
B-Cooling Components
All units use a cooling circuit consisting of compressor,
condenser coil and evaporator coil. See figure 5. One
drawthrough type condenser fan is used in ZGB units.
Units are equipped with belt-drive blowers which draw air
across the evaporator during unit operation.
Cooling may be supplemented by a factory- or field-in-
stalled economizer. The evaporator coil is slab type and
uses a fixed orifice refrigerant metering device. Each
evaporator is also equipped with enhanced fins and rifled
tubing. In all units each compressor is protected by a high
pressure switch (S4) on the discharge line. See figure 5.
1-Compressor B
he Clean Air Act of 1990 bans the intentional venting
of refrigerant (CFC's and HCFC's) as of July 1,
1992. Approved methods of recovery, recycling
or reclaiming must be followed. Fines and/or
incarceration may be levied for non-compliance.
Electrical shock hazard. Compressor must be
grounded. Do not operate without protective cover
over terminals. Disconnect power before removing
protective cover. Discharge capacitors before
servicing unit. Failure to follow these precautions
could cause electrical shock resulting in injury or
death.
Some scroll compressors have an internal vacuum
protector that will unload scrolls when suction
pressure goes below 20 psig. A hissing sound
will be heard when the compressor is running
unloaded. Protector will reset when low pressure
in system rises above 40 psig. DO NOT REPLACE
COMPRESSOR
All units use one scroll compressor. See "SPECIFICA-
TIONS" and "ELECTRICAL DATA" (table of contents) or
compressor nameplate for compressor specifications.
If Interlink compressor replacement is necessary, call
1-800-453-6669.
The compressor is energized by a compressor contactor.
NOTE-Refer to the wiring diagram section for specific unit
operation.
Page 27
IMPORTANT
WARNING
IMPORTANT
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