Have an issue w/ a 7.5 Trane RTU that smoked it's 24 volt transformer. Replaced transformer w/ one that has a circuit breaker. Tripped out as soon as power is applied. Traced back to wire # 172A connected to the Reliatel board, disconnected that wire, and the transformer does not trip. At least I have some air movement now and perhaps some electric heat. This wire 172A goes thru pressure switches before it gets to the board, but they seem to be OK. Any ideas or help would greatly be appreciated.