Variable Speed Head Pressure Control; Table 14.4: Variable Speed Heat Pressure Control - Addison RC/FC Series Installation Operation & Maintenance

Table 14.4: Variable Speed Head Pressure Control
Problem
No Fan Operation
Fan Stops When
Pressure Reached
The High End Of The
Operating Range
No Fan Modulation
(On-Off Operation)
Fan Starts At
Full Speed
Erratic Fan Operation
Erratic Pressure
Control
Regulator Leakage
Regulator Hunting
(Chattering) With
Large Fluctuations
In Controlled Pressures
Probable Cause
No 24V control voltage
No input pressure to control
Bad fan motor
Pressure transducer problem
Control is not wired correctly
Control is not wired correctly
Control is not wired correctly
Control is not wired correctly
Dirty or blocked condensing unit coil
Defective regulator
Dirt causing regulator to bind
Power source to hot gas solenoid or
operation of the solenoid is intermittent
Dirt in regulator causing seat to remain open Clean regulator Install strainer
Worn or eroded seating surface on regulator
Regulator is oversized
Regulator and liquid injection thermovalve
have control interaction
Regulator and cylinder unloaders have
control interaction
RC/FC Series Installation, Operation, and Maintenance Manual
Check for 24 VAC at control
Check alignment of capillary fitting
Schrader valve depressor must depress
Schrader valve enough to allow pressure
into capillary
Disconnect power, when P266 is used,
place a jumper from L1 to M1 and connect
power, if fan does not start, motor is bad
and should be replaced
Disconnect 6 pin connector from right side
of control, place a jumper wire between
third pin from the top and bottom pin on
the control (not the cable) If fan goes to
full speed, check for input pressure If it
has been determined there is adequate
pressure, the transducer is bad and the
control must be replaced
See wiring diagrams
See wiring diagrams
See wiring diagrams
See wiring diagrams
Clean condensing unit coil
Replace defective part
Disassemble regulator and clean internal
parts Install strainer
Determine if problem is caused by supply
voltage, solenoid or excessive MOPD, make
changes necessary to correct problem
Replace defective part
Contact Addison for correctly
sized regulator
Increase superheat setting, dampen bulb
response by repositioning
Increase differential between the controls
by lowering the regulator's setpoint
Solution
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