OM WGS-5
WGS 130A to 190A
17
Low Ambient Start Logic
Low pressure operation at start (due to low ambient air temperature)is allowed for every
start regardless of the condenser saturated temperature at start or condenser configuration
( water-cooled or remote condenser). This is called Start Logic. START Logic is active for
a time period determined by the unit Startup Timer setpoint. This was called the Low OAT
Start Timer in previous software versions.
The Low OAT Restart Failure logic, which applies ONLY to units configured for remote
condenser, still allows for three start attempts. If the condenser saturated temperature at
start is less than 70
F, another start attempt is allowed until failure of the third attempt,
which will generate an alarm.
Remote Condenser EXV Operation
For units configured for remote condensers, there is pre-open logic that allows the electronic
expansion valve to open prior to starting the compressor. This allows the expansion valve
to be in a better position for control at start-up. The factory mounted liquid line solenoid
remains closed until the compressor starts. On units configured for remote condensers, if
the evaporator pressure is greater than the condenser pressure at start, the pre-open logic is
bypassed. NOTE: Pre-open logic also exists for units configured as packaged water cooled
condensers.
Electronic expansion valve post-open logic has been added to help prevent hydraulic lock
between the liquid line solenoid and the electronic expansion valve when a circuit cycles
off. After the compressor performs a pump down and cycles off, the electronic expansion
valve will re-open for 30 seconds and then return to its closed position.
Summary of Contents for WGS130AA: WGS140AW
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