Controls - Trane BCHC Application Manual

Controls

ReliaTel™ or thermostat control may be available on some model (4) TTA/TWA units. It is important
to understand that if the staging of compressors is turned over to a third party, the compressor
protection, provided through system stability, is also turned over to the third party. Simply stated,
this means that when a compressor turns on, it shouldn't turn off until the expansion valve comes
under control. And, once the compressor turns off, it should be allowed to stay off until the
crankcase heater has warmed up, or if the system doesn't have a crankcase heater, until the
compressor sump stabilizes.
System stability must be programmed in the third-party system control. To accomplish this, the
system controls must incorporate a 5-minute-on, a 5-minute-off, and a 5-minute-interstage
differential on each compressor stage.
10 SS-APG010C-EN