Trane RTWA 70-125 TON - Manual (Page 37)

RLC-SVD03A-EN 37
Compressor Capacity
NOTE: Enabling the “Compressor Test” only affects which compressor will
be cycled on next and is not an override mode. The chiller will continue to
operate normally (not withstanding circuit lockout) and will stage
compressors on and off, as well as attempt to modulate running compressors
to maintain chilled water setpoint. Be aware that during manual control of the
load/unload solenoids, as explained in item 6, below, other compressors may
stage and/or attempt to modulate and thus will affect the leaving chilled water
temperature. However, all diagnostics are still active. No specific action, other
than reconnecting the solenoid valves to their respective outputs on the
MCSP, is required to return the Chiller to normal operation.
5. Allow the compressor to start and monitor compressor currents either in
the Compressor Report display (maximum phase % RLA) or with a
clamp-on type ammeter.
Load
1. Once the compressor has started, allow the Unload Solenoid Valve to
remain energized for approximately 30 seconds, then open the Unload
toggle switch to de-energize the valve. Verify that at least one condenser
fan is on before continuing with the checkout, as low differential refriger-
ant pressures will preclude proper Slide Valve operation. Record the cylin-
der cavity pressure and the compressor currents.
2. Manually close and open the Load toggle switch, to energize the Load
Solenoid, in 4 or 5 short “pulses”. Each load pulse should be approxi-
mately one second in duration, with approximately 10 seconds between
pulses.
NOTE: Loading the compressor faster than this rate could cause control
instability and possible diagnostics. Leave the toggle switch open, i.e., valve
de-energized.
3. If the %RLA or the current and pressure increases,' then the Load Sole-
noid and Slide Valve are operating properly.
4. If the %RLA or current does not increase, read the pressure at the cylin-
der cavity; Pressure increases, to approximately condenser pressure
(condenser pressure read via the CLD) without an increase in % RLA
(unless already fully loaded), indicate the Slide Valve is bound.
5. If cylinder cavity pressure does not increase, check the coil of the Load
Solenoid.
6. If the coil checks out, then one of two problems exist. Either the Load
Solenoid Valve is malfunctioning or the Unload Valve is stuck open.
NOTE: Refer to the flow chart shown in Figure 5 .