McQuay seasoncon ALP-067A, Installation And Maintenance Data

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NOTE: Line is only hot when the unit thermostat calls for compressor to run.
Compressor Lockout - Optional
Compressor lockout consists of a solid state time delay wired in
series with the compressor contactor(
Its purpose is to prevent
rapid compressor cycling when cooling demands are erratic.
The cir-
cuit illustrated above is for the lead compressor in each refriger-
and circuit. The circuit for the second compressor(s) performs the
same function but is wired differently (see unit wiring diagram).
When the unit thermostat no longer calls for cooling and the com-
pressor contactor have opened,
the lockout time delay breaks open
the circuit preventing compressore re-start.
The circuit remains open for a period of 5 minutes so that if the
unit thermostat should call for cooling before the delay period has
expired, the compressor will not re-start.
After 5 minutes, the
time delay will close its contacts to complete the circuit and be
ready for start up. The time delay opens its contacts whenever pow-
er to terminal 4 is interrupted and resets closed automatically af-
ter the time delay period.
To check the control,
the compressor(s) must be running initially.
Move the pumpdown switch (PSl or PS2) to the "man. pumpdown" posi-
tion. Immediately after the compressor(s) have stopped running,
move the pumpdown switch back to the "auto. pumpdown" position.
The
lead compressor should not re-start for 5 minutes.
The second com-
pressor in the refrigerant circuit should start approximately 20
seconds after the lead compressor,
high enough to require it.
provided that the cooling load is
the same way.
Each refrigerant circuit can be checked
LINE
(SEE NOTE)
LOCKOUT
TIME DELAY
TO UNIT THERMOSTAT
NOTE: Hot whenever freeze control and high
pressure control permit safe operation.
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