Controls - Trane TTA Series Application Manual

Controls

The TTA/TWA unit is available with either ReliaTel™ or thermostat control. 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 crank
case heater has warmed up.
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-APG008-EN