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B-Cooling Components
Units use independent cooling circuits consisting of sepa
rate compressors, outdoor coils and indoor coil (with 2 sep
arate stages). See figure 7. Units are equipped with two
draw-through type condenser fans. All units are equipped
with belt‐drive blowers which draw air across the indoor coil
during unit operation.
Cooling may be supplemented by a factory‐ or field‐
installed economizer. The indoor coils are slab type and are
stacked. Each indoor coil uses a thermostatic expansion
valve as the primary expansion device. Each indoor coil is
also equipped with enhanced fins and rifled tubing. In all
units each compressor is protected by a freezestat (on
each indoor coil) and a high pressure switch (S4, S7). Low
ambient switches (S11, S84) are available as an option for
additional compressor protection.
1-Compressors B1 and B2
Units use two scroll compressors. All compressors are
equipped with independent cooling circuits. Compressor
capacity may vary from stage to stage. In all cases, the ca
pacity of each compressor is added to reach the total ca
pacity of the unit. See “SPECIFICATIONS” and “ELEC
TRICAL DATA” (table of contents) or compressor
nameplate for compressor specifications.
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.
Each compressor is energized by a corresponding com
pressor contactor.
NOTE-Refer to the wiring diagram section for specific unit
operation.
If Interlink compressor replacement is necessary, call
1-800-453-6669.
IMPORTANT
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 un
loaded. Protector will reset when low pressure in
system rises above 40 psig. DO NOT REPLACE
COMPRESSOR.
2-Thermal Protectors S5, S8
Some compressors have thermal protectors located on top
of the compressor. The protectors open at 248
°
F + 9
°
F
(120
°
C + 5
°
C) and close at 169
°
F + 18
°
F (76
°
C + 10
°
C).
3-High Pressure Switches S4 and S7
The high pressure switches is a manual reset SPST N.C.
switch which opens on a pressure rise. The switch is lo
cated in the compressor discharge line and is wired in se
ries with the compressor contactor coil.
S4 (first circuit) and S7 (second circuit) are wired in series with
the respective compressor contactor coils.
When discharge pressure rises to 640 ± 10 psig (4412 ±
69 kPa) (indicating a problem in the system) the switch
opens and the respective compressor is de-energized
(the economizer can continue to operate).
4-Low Ambient Switches S11 & S84
(optional)
The low ambient switch is an auto‐reset SPST N.O. pres
sure switch which allows for mechanical cooling operation
at low outdoor temperatures. In all models a switch is lo
cated in each liquid line prior to the indoor coil section.
S11 and S84 wired in parallel are wired in series with out
door fan relay K10.
When liquid pressure rises to 450 ± 10 psig (3102 ± 69
kPa), the switch closes and the condenser fans are ener
gized. When liquid pressure on both refrigerant circuit
drops to 240 ± 10 psig (1655 ± 69 kPa), the switch opens
and the condenser fans are de-energized. This intermittent
fan operation results in higher evaporating temperature al
lowing the system to operate without icing the indoor coil
and losing capacity.
5-Reversing Valve L1 and L2
A refrigerant reversing valve with a 24 volt solenoid coil is
used to reverse refrigerant flow during unit operation. The
reversing valve is connected in the vapor line of the refriger
ant circuit. The reversing valve coil is energized during
cooling demand and during defrost.
Reversing valve L1 and L2 are controlled by the defrost
control board CMC1 in response to cooling demand or
by defrost.
