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CSRA-SVX01A-EN
Trouble Analysis
Low Ambient Start Timer (LAST) Checkout Procedure
WARNING
Hazardous Voltage!
Disconnect all electric power, including remote disconnects before
servicing. Follow proper lockout/tagout procedures to ensure the
power can not be inadvertently energized. Failure to disconnect power
before servicing could result in death or serious injury.
To determine whether or not a low ambient start timer is defective, follow
these steps.
1. Remove power from the CGA unit by opening the supply power circuit
breaker.
2. Disable both low pressure cutouts (LPCO1 and LPCO2) by disconnecting
the wires from their number 1 terminals. Tape the disconnected wires to
prevent shorting.
3. Restore power to the system, energize compressor number one and
check how long it runs before cutting out.
4. Remove power from the system and disable compressor number one.
Tape any wires removed to prevent shorting.
5. Restore power to the system, energize compressor number two and
check how long it runs before cutting out.
6. Remove power from the system and re-connect the wires removed from
the low pressure cutouts in step two. Re-connect the wires that disabled
compressor number one.
7. Restore power to the unit.
Conclusion: Compare the compressor run times verified in steps 3 and 5
with the rated duration of the low ambient start timers. (The rated duration
times are usually stamped on the timers or given in the unit literature). If the
compressor run times don't match the duration times of the low ambient start
timers, the timers are defective and must be replaced.
Preliminary Troubleshooting Inspection
If operational difficulties are encountered, be sure to perform these prelimi-
nary checks before referring to the troubleshooting charts:
[ ] Check the water temperature thermostat (WTT) to ensure that it is set
correctly, receiving control power, and "making/breaking" at the proper inter-
vals.
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