McQuay SEASONCON ALP-037A, Руководство пользователя, Страница: 41 / 43

LOW AMBIENT START (OPTIONAL)
Low ambient start
is
available on all units as an option with
FANTROL and included automatically with optional
SPEEDTROL or DAMPERTROL. It consists of a solid state
normally closed time delay wired in series with a relay.
These are both wired in parallel to the liquid line solenoid
valve so that when the solenoid valve is energized by the
unit thermostat, the low ambient start relay is also ener-
gized through the time delay. The relay has contacts that
essentially short-circuit the low pressure control and allow
the compressor to start with the low pressure control open.
After about 2-3/4 minutes, the time delay will open and
de-energize the r-clay. If the system has not built up enough
evaporator pressure to close the low pressure control, the
compressor will stop. The time delay can be reset to its
original normally closed position by moving the pumpdown
switch(es) o r P S 2 t o t h e “ m a n u a l p u m p d o w n ”
position. Moving the pumpdown switch back to the “auto.
pumpdown” position will again energize the relay for
another attempt at start-up. If the system has built up
enough evaporator pressure, the compressor will continue
to run.
To check the control, turn off all power to the unit and
remove the wire(s) leading to the terminals of the low pres-
sure control(s) LPI and LP2. Remove the compressor fuses
and jumper across terminals “L” and “M” of the freeze
control(s) and oil pressure safety control(s). Energize the
control circuit by turning on the control circuit disconnect
or main power disconnect (depending on the installation)
and the control stop switch
Sl .
The compressor contactors
should pull in instantly.
NOTE:
Line is only hot when the unit thermostat calls for compressor to run.
COMPRESSOR LOCKOUT (OPTIONAL, ALP-037A THRU 078B)
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 circuit illustrated above is
for the lead compressor in each refrigerant circuit. T h e
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 compressor contactor have opened, the lockout time
delay breaks open the circuit preventing compressor
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
restart. 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 power to
terminal 4 is interrupted and resets closed automatically
after the time delay period.
To check the control, the compressor(s) must be running
initially. Move the pumpdown switch PSI or PS2 to the
“manual pumpdown” position. 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
compressor in the refrigerant circuit should start approxi-
mately 20 seconds after the lead compressor, provided that
the cooling load is high enough to require it. Each refrig-
erant circuit can be checked the same way.
LINE
(SEE NO-I
LOCKOUT
TIME DELAY
TO UNIT THERMOSTAT
N O T E : Hot whenever freeze control and high
pressure control permit safe operation
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