Heat Pumps are inefficient below 30 and most do basically nothing by 15. With supplemental heating working it should keep going. Is it a coil heater? Seems like it's not really working if you have it and it's failing at 28.
That is MOSTLY true. There are a range of heat pumps available now, that work beyond temps where they used to work. Mine works consistently well down to 15F. Mitsubishi has one that works to -15F, but I only think it's available in ductless mini-split form.
I had a breaker die in my air handler. Had to move around the heat strips to the functional breaker. I wasn't able to find these things anywhere locally - I had to use a site, called simplybreakers (
Simply Breakers - Buy Circuit Breakers Online ), which has... every breaker known to man, at good prices.
I have 4 heat strips, one of which is entirely missing the 10ga wire to it. I wonder if it was intentionally never connected. With my setup, I had 2x heat strips hooked up to the dead breaker, 1 on the functional breaker, plus the control wires. I turned everything off, and moved one heat strip off the dead breaker to the functional one, so I'm running at 2/4 heat strips currently.
I woke up Saturday morning (last week) and it was mid 50s inside.. sucked, but not the worst possible thing. The wood stove did OK, but could only manage getting things up to low 60s on that side of the house, since it's moving the cold indoor air through the baffles and ejecting it up top. Now that I have 2/4 heat strips working, it keeps the house mid 60s.
I haven't received the new breaker yet, but when I get it I'll try hooking up all 4 and see how it works then. The unplugged heat strip was hopefully left unwired for cost savings, rather than something else. It's impossible to find a schematic for my air handler, even though it's dated 2014... TEM3, not TEM4 Trane, 5 ton model. Even the Bluon app doesn't have anything listed for TEM3. Son of a bitch. The condenser outside is from 2019, so hopefully that lasts a long time.