We had a problem with our Geo Unit not putting out enough heat to keep the house at 70 degrees last night (Low outside temp in the vicinity of -0 F with 35-45 mph winds). The inside temperature went down to 67 F and then hovered there with the unit running all night.
It is a three stage unit (2 compressor stages and the 3rd stage is auxiliary electric resistance). It appeared to me that only the first stage was running so I took some plenum and loop in-out temperature readings and called the heating company about it. Since the loop in and out temperatures were only 3.4 degrees apart and the heat plenum temperature was 82.4 degrees they too thought only the first stage was running.
Their tech came out and determined that the thermostat was setup for a 2 stage system not 3 stage. So, we have been running on the first stage through the cooling season and (until today) the heating season with no apparent problems.
It was an easy programming change and we are now loaded for whatever nature hangs on us.
I turned the circuit breaker off on the 3rd stage since I really prefer to pay the electric company as little as possible.
Tonight we are headed to -15 F with some wind so the 2nd stage will get to finally do its job. The Tech and I concur that we may never need the third stage unless something extreme occurs, like -30 F and 50mph winds. I am fine with that. Service call charge $0.00. I am fine with that too.
