In 2022 I had a furnace problem where the furnace (2-stage Bryant furnace model 820TA66110V21) would shut down in the second stage before reaching the set temperature (70 degrees) when it was very cold out, apparently because the overheat safety kicked in. Service provider determined I needed better return air ducting and installed this. Later when it got cold again (2023 cold season) the furnace performed Ok but I noticed there was no second stage kicking in. Presumably the service tech left it to run as a single stage furnace. Last week I had a furnace checkup with our service provider and I mentioned this to him. He made some changes and now I'm hearing the second stage kick in. The problem is, I'm back to having the same problem I had in 2022 when it's in the teens outside. My question is whether it's possible that my furnace was performing better as a single stage furnace?
What is the manifold pressure set to for low fire and high fire and what are the corresponding temperature rise readings?
It sounds like your furnace was working fine when it ran in low fire only. Is it possible the furnace is oversized for your ductwork?
I agree with Admin. Your furnace was likely oversized. You should have left it locked into 1st stage.
Carrier and Bryant furnaces during that time had higher gas pressures and if installers never checked pressures as soon as 2nd stage kicked on furnace would trip on hi limit. I've had over 20 service calls for it and all were high pressures. Manufacturers don't know where the furnace is being installed and what altitude so pressures may be your problem