I performed a single heating maintenance on a 2017 zoned gas system. I checked amps, filter, electrical, cleanliness, zoning, and safeties. Before I got started, the customer mentioned that it seems like the downstairs is not heating. I investigated this concern to the best of my ability. I verified that the zoning is working properly for the upstairs and downstairs. When I was running the system with both zones on in heating, I discovered that the system is producing extremely hot air. I checked the ducts for appropriate design. I discovered that the system does not have enough return air. It currently only has approximately a 18in duct. The bypass is opening with both zones running. The unit is full of dust and debris. This is likely playing a role in the unit tripping on a thermal cut out. I advise a complete cleaning be done on the system at the least. I will get with my supervisor about a possible work around for the poor duct design.
