Hey all. Hoping someone can help me a tad and offer some input. I’m pretty handy and have been digging in to this issue a little more. We had been fleeced by our previous HVAC folks. And by fleeced, I mean, assumed they’re competent.
I’ll try to be brief.
We have 3 zones. Heat pump, and 2 stage gas furnace (propane) - brains is a NCM-300 panel from EWC. Pretty basic setup. There’s also a barometric damper between supply/return but it’s only like 2’ from where it leaves the furnace and 2’ before it returns.
I noticed some short cycling recently and was like, crap, forgot to clean this out in September. So I cleaned the A coil, blower, replaced filters - all good! Or so I thought..
When running for an extended period of time (big temp rise called for on thermostat for example) after 5-8 minutes after 2nd stage gas furnace kicks in, high limit trips and shuts off.
I turned all heat to emergency mode to only use the gas furnace, same exact behavior.
I have some questions while I’m trying to find a reputable and competent with zoned system HVAC company...
With a heat pump and 2 stage gas furnace. Where does the logic exist that determines when 2nd stage gas comes on? Wondering if that was “tweak-able” there is a w2 staging timer on the control board; but I’m not sure if that’s time that heat pump runs before kicking over to gas?
Is the barometric damper garbage? Should I be looking at a “modulating bypass damper?”
Efficient or possible to disable 2nd stage gas completely if first stage can keep up without running 24/7?
Ultimately I surmise I’m either not moving enough air across the heat exchanger, furnace is oversized, or something else I’m not thinking of... we’ve been in the house a few years and it’s very possible it’s been doing this the whole time and we’ve only recently known about it.
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