A bit of a long post but I've tried to be as specific as possible
I had a new Goodman HVAC put in Dec 2016 (model GPG1430060M41AB). For the last nine weeks the system has been cutting out when the temperatures go below 30 degrees. Once the outside temps start to warm up, it comes back on again. The diagnostic code the system has been throwing out is for the limit switch. At first my HVAC guy changed the board, made no difference. Then ordered a new motor, no difference, (although the temporary motor had a fan running all the time and the system behaved itself during that time.) Once the new motor was installed the same thing happened again. Let me give some details about the last time it went out. I turned the heat from 69 down to 65 ready for bed at about 11pm. Once the thermostat dropped and the system tried to fire up (at about 12.45am) it wouldn't come on. It tried twice more before the safety switch shut it off completely. Since I was awake I turned the thermostat off. The next morning, it was 53 inside the house and 40 outside. I turned the system back on and it came on.
Now, my HVAC guy is saying it's a problem with the ducts but that just doesn't make sense to me, especially since the HVAC was running fine for 12 months, and those ducts were running fine with the old HVAC. One pipe was a bit squished, and he said some of the returns could be better but does that explain the system turning off at 30 degrees? And also, aren't HVAC technicians supposed to check duct work before installing a new system to make sure they are compatible?
The system maintenance and parts have been covered, but the duct work is going to cost a lot. I'm just not convinced by his explanations that that is the problem.