User Guide

FORM 145.15-IOM7 (412)
24 JOHNSON CONTROLS
described above), the microprocessor control board
will continue to monitor the low-pressure limit switch
for any openings. If the low-pressure switch opens for
greater than 5 seconds, the microprocessor control
board will de-energize the compressor, initiate the
ASCD, and stop the fan.
If the call for cooling is still present at the conclusion
of the ASCD, the microprocessor control will re-
energize the compressor.
Should a low-pressure switch fault three (3) times
within one (1) hour of operation, the microprocessor
control board will lock-out the compressor and flash a
fault code indicating a low-pressure lock-out.
Condensate Overflow Switch
A Condensate Overflow fault occurs when the
Condensate Overflow switch opens for more than two
line cycles. The compressor is shutdown regardless
of Minimum Run Time, ASCD is initiated, and alarm is
tripped. The fan continues operating in its current
state. Compressor will re-energize once the
Condensate Overflow switch closes, and ASCD has
been satisfied and a call for cooling is still present.
The microprocessor control board logs the first
incident per compressor request. If the compressor
request is removed, the fault occurrence counter is
reset to zero. Should the Condensate Overflow
switch open three within two hours of run time, the
microprocessor control board will lock-out the
compressor, turn off the fan and flash a fault code
indicating a Condensate Overflow lock-out.
SAFETY CONTROLS
The microprocessor control monitors the following
inputs:
1. A High-Pressure Switch on each compressor
circuit to protect against excessive discharge
pressures.
2. A Low-Pressure Switch on each compressor
circuit to protect against loss of refrigerant charge.
3. A Condensate Overflow Switch to protect against
condensate overflow.
Compressor Protection
In addition to the external pressure switches, the
compressor also has inherent (internal) protection. If
there is an abnormal temperature rise in a
compressor, the internal protection will immediately
shut down the compressor. The microprocessor
control incorporates features to minimize compressor
wear and damage. An anti-short cycle delay (ASCD)
is utilized to prevent short cycling of the compressor.
Additionally, a minimum run time is imposed any time
a compressor is energized. The ASCD is initiated on
unit start-up and on any compressor reset or lockout.
Microprocessor Control Unit Flash Codes
Various flash codes are utilized by the microprocessor
control to aid in troubleshooting. Flash codes are
distinguished by the short on and off cycle used
(approximately 200ms on and 200ms off). To show
normal operation, the control boards flash a 1 second
on, 1 second off “heart beat” during normal operation.
This is to verify that the microprocessor is functioning
correctly. Do not confuse this with an error flash code.
To avoid confusion the 1-flash, fault code is not used.