SS-APG008H-EN
13
Controls
The TTA/TWA unit is available with either Symbio™ 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.
