Electric Forced Air Furnace

I agree but it’s fun to guess.

Me too, I saw a RT compressor burn up one time because it had been running the wrong direction since installation.

I bet you’re on the right track there David

Just curious what are you calling a RT compressor and how do you tell if it is running backwards

what is the size of the return in question? how did you conclude air is blowing in and not out? placeing your hand to it can make it feel one way when it is realy doing something else. place a tissue paper to it for a real test. was it suppose to be a supply and someone put return grill on instead.turn the heat up and do you get hot air out the return grill? are their any other supplys in this room?

I should have typed “RTU”
Roof Top Unit, electric A/C - Nat. gas heat.-230 volt 3 ph.

By the refrigerant operating pressures and compressor amp draw.

The tech didn’t read the installations and did the install during the heating season.

The compressor didn’t last very long once the stat called for cooling.

A three phase reciprocating compressor can not run backward no such thing was it a scroll compressor.

Yes, I believe that one had a two-stage Copeland scroll compressor as I recall.

You can also tell by the sound of the compressor as well as the low head pressure, high back pressure and low amp draw.

A scroll can not run backwards.

It may even lock up.

No high temp at the compressor discharge.

So are you two saying no compressor can run in the wrong direction?

I’ve reversed the rotation on many 10 horse 3 phase compressors in refer cars back when I worked refrigeration on the rail road.

Anyway, what ever this one was it definitely did run backwards.

Recips can run any direction as long as the oil pump works backwards (if it has one). OPSC will shut down the compressor in 60 sec. if the pump doesnt pump that way.

I do not like to run older compressors backwards even if you can because they were broken in and worn out in that direction.

I only reverse phase to unstick a locked compressor.