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If either the Loss of Charge (LOC) Switch or High Pres-
sure Switch (HPS) on either circuit opens while W1 re-
mains energized, then the compressor contactor C and
relay SVR on the corresponding circuit are de-energized;
compressor stops and liquid line solenoid is de-energized
(valve closes). Corresponding CADM initiates a TRIP
event (compressor demand sensed at CADM terminal Y
but no current is measured at T1, T2, T3 motor sensors);
CADM relay opens and RED LED is illuminated. TRIP
condition maintains lockout of compressor operation until
CADM is manually reset. Reset CADM by cycling unit
main power.
Reversing valve solenoid remains de-energized until the
next Cooling cycle is initiated.
DEFROST CYCLE
During the Heating Mode, frost and ice can develop on
the outdoor coil. Defrost sequence will clear the frost and
ice from the coil by briefly reversing the Heating se-
quence periodically.
A window to test for a need to run the Defrost cycle
opens at a fixed period after the end of the last Defrost
cycle or the previous test window closed. The window pe-
riod is determined by the configuration settings on the
DFB's DIP switches (see unit wiring diagram).
If the outdoor coil's Defrost Thermostat 2 switch (DFT2)
is closed (shorting DFB terminals DFT2 and DFT2), the
Defrost cycle will start. Output at OF is removed; outdoor
fans stop during the Defrost cycle. Output P3-6 (RVS2) is
energized; reversing valve solenoid RVS1 is energized
and reversing valve changes position, placing Circuit 2 in
a Cooling mode flow, directing hot gas into the outdoor
coil where its heat melts the frost and loosens the ice on
the coil face. If DFT1 is also closed, then output P3-7
(RVS1) is removed and RVS1 is energized and changes
position, placing Circuit 1 in cooling mode flow.
During the Defrost cycle, output EHEAT is also energized
(if not already energized by a thermostat W2 demand);
supplemental heater will be energized. During the De-
frost Cycle, LED1 on the DFB will be illuminated. The De-
frost cycle ends when DFT1 and 2 are both open (as liq-
uid temperature exiting the coil rises above DFT setpoint)
or the defrost cycle runs for 10 minutes. Output at
EHEAT is removed; supplemental heater will be de-
energized (unless thermostat has a W2 demand). Output
at OF is restored; outdoor fans start again. Outputs P3-7
(RVS1) and P3-6 (RSV2) are removed; reversing valves
return to Heating position.
Defrost cycle is fixed at a maximum 10 minute duration
limit. The period to test and initiate a Defrost cycle can be
configured for 30, 60, 90 or 120 minutes.
SUPPLEMENTAL HEAT/EMERGENCY HEAT
Supplemental heat type is determined by FHX indoor unit
options and accessories. This heat is initiated when the
indoor unit W2 terminal is energized by the thermostat.
(Or as detailed in "Defrost Cycle" on page 21.) The ther-
mostat may energizes W2 as supplemental (second
stage) heat at larger space heating demand, or when se-
lected as emergency heat mode. When the space heat-
ing demand decreases below the second stage limit, or
CHS-180-240-01SI Rev. A
emergency heat is turned off, W2 is de-energized, and
supplemental heat is turned off.
COOLING AND HEATING SHUTDOWN
Partial or complete cooling or heating functions may
shutdown caused by loss of main power, open pressure
switches, diagnostic alarms, or open internal compressor
protections. See Service section for further details.
FAN CYCLING
The CHS unit is equipped with a temperature switch that
will shut down Outdoor Fans 2 and 4 in cooling mode
when the outdoor temperature falls below 55°F (13°C) to
ensure continuous operation in both stages. The outdoor
fan will turn back on when the temperature rises above
60°F (16°C). In heating mode, the temperature switch is
bypassed through the Temperature Bypass Relay (TBR),
ensuring that all fans run at full speed. See Fig. 17 and
18 for outdoor fan labeling.
These items should be part of a routine maintenance pro-
gram, to be checked every month or two, until a specific
schedule for each can be identified for this installation:
Quarterly Inspection
(and 30 days after initial start)
INDOOR SECTION
•
•
•
•
•
Heating
•
•
•
See Tables 10 and 11 for unit specific maintenance
checklists.
Seasonal Maintenance
These items should be checked at the beginning of each
season (or more often if local conditions and usage pat-
terns dictate):
AIR CONDITIONING
•
•
•
•
•
•
•
•
Specifications subject to change without notice.
MAINTENANCE
Condenser coil cleanliness checked.
Return air filter replacement
Outdoor hood inlet filters cleaned
Fan shaft bearing locking collar tightness checked
Condensate drain checked
Power wire connections
Fuses ready
Manual-reset limit switch is closed
Condenser fan motor mounting bolts tightness
Compressor mounting bolts
Condenser fan blade positioning
Control box cleanliness and wiring condition
Wire terminal tightness
Refrigerant charge level
Evaporator coil cleaning
Evaporator blower motor amperage
21
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