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1-Compressors B1, B2 and B13
Compressors are supplied by various manufacturers. All units
are equipped with two independent cooling circuits except 15
ton units which are equipped with three independent cooling
circuits. Compressor electrical specifications vary by
manufacturer. Likewise, compressor capacity may vary from
first stage to second stage. In all cases, the capacity of each
compressor is added to reach the total capacity of the unit.
See unit rating plate for specific compressor capacity ratings
and electrical data.
Units with two cooling circuits:
Compressor B1 is compressor 1. It operates during all cooling
demand and is energized by contactor K1 upon receiving a
first stage demand. Compressor B2 is compressor 2. It oper
ates only during second stage cooling demand and is ener
gized by contactor K2 upon receiving a second stage de
mand.
NOTE-Refer to wiring diagram section B9 for specif
ic unit operation.
Units with three cooling circuits:
Compressor B1 is compressor 1. It operates during all cooling
demand and is energized by contactor K1 upon receiving a
first stage demand. Compressor B2 is compressor 2. It oper
ates only during first stage cooling demand and is energized
by contactor K2 upon receiving a first stage demand (after
time delay DL15 closes). Compressor B13 is compressor 3. It
is energized by contactor K14 upon receiving a second stage
demand.
Each compressor used in CHA16 units is equipped with a
selfregulating crankcase heater. Fifteen ton and smaller units
use insertion type heaters while 18.5 ton and larger units use
bellyband style heaters. All compressors are protected by in
ternal overload protection circuitry.
WARNING
Electrical shock hazard. Compressor must be
grounded. Do not operate without protective cover
over terminals. Disconnect power before removing
protective cover. Discharge capacitors before ser
vicing unit. Failure to follow these precautions could
cause electrical shock resulting in injury or death.
WARNING
Crankcase heaters must be energized for 24
hours before attempting to start compressors.
Set thermostat so there is no compressor demand
before closing disconnect switch. Attempting to
start compressors during the 24hour warmup
period could result in damaged or failed compres
sors.
2-Crankcase Heaters HR1, HR2 and HR5
CAUTION
Selfregulating crankcase heaters are connected
to line voltage at all times (not switched by unit
circuitry.)
All CHA16-1853 compressors are equipped with self-
regulating type crankcase heaters. Fifteen ton and
smaller units use insertion type heaters while 18.5 ton
and larger units use bellyband style heaters. Heater
HR1 is installed in compressor B1, heater HR2 is
installed in compressor B2 and heater HR5 is installed
in compressor B13 (if unit is equipped with three com
pressors). Crankcase heater wattage varies by com
pressor manufacturer. See unit rating plate for specific
electrical data.
3-High Pressure Limit S4, S7 and S28
The high pressure limit is a manually reset SPST N.C.
switch which opens on a pressure rise. All CHA16 units
are equipped with this limit. The switch is located in the
compressor discharge line and is wired in series with the
compressor contactor.
In three pump systems, S4 is wired in series with the first
stage compressor 1 contactor, S7 is wired in series with the
first stage compressor 2 contactor and S28 is wired in series
with the second stage compressor 3 contactor. In two pump
systems, S4 is wired in series with the first stage compressor
contactor and S7 is wired in series with the second stage
compressor contactor.
When discharge pressure rises above 410+10 psig (indi
cating a problem in the system) the switch opens and the
respective compressor is de-energized (the economizer
can continue to operate.) After the problem has been
found and corrected, the switch can be reset by pushingin
the switch button.
4-Loss of Charge Switch S24, S25 and S34
The loss of charge switch is an autoreset SPST N.C.
switch which opens on a pressure drop (almost complete
loss of charge). All CHA16 units are equipped with this
switch. The switch is located in the compressor discharge
line next to the high pressure switch and is wired in series
with the high pressure switch and compressor contactor.
In three pump systems, S24 is wired in series with first stage
(compressor #1) contactor K1, S25 is wired in series with first
stage (compressor #2) contactor K2 and S34 is wired in se
ries with the second stage (compressor #3) contactor K14. In
two pump systems, S24 is wired in series with first stage com
pressor contactor and S25 is wired in series with second
stage compressor contactor.
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