I have two furnaces - one for each floor. One of the furnaces that were replaced within a year keeps blowing cold air randomly. I would reset it by turning the main power switch off/on and then it would work for a while and stop working again with either a 13 or 31 code. This Payne unit seems to have a bad limit switch.

So, a furnace flue gentleman came out and inspect my piping and found something interesting. The path looks clear, but he found a "ducting" with coils that appear smaller than what should be in there. This causes hot air to accumulate and hit the limit switch after some time. Let me attach pictures here. This is a 90,000 BTU unit.

Thoughts? Bad install? Common in the field? I am not an expert so feel free to correct my terminologies or put me in my place :)


  • Feel free to buy a new coil that fits your placement, Then make sure whoever is working on it, seals it or refuse to pay, It's absorbing the amboent air but it isn't blowing out the cold air running through the coils enough cause air is blocked by the flashing and open areas. You could always reform the metal to where it's at a 45 to 35 degree angle towards the coil, and make sure it's sealed good, that might work if you don't want to buy a larger one, or a home improvement store might have a duct conversion kit that slants enough to fit that coil
    – user70085
    Nov 29 '18 at 0:09

That looks like a crappy install the coils should be sealed tight to the air handler. It can be repaired with flashing and screws or pop rivets. The reason your coils are running hot is the air is not forced through them this will have a huge affect on the efficiency and probably shorten the system life. I would get it sealed soon it can be done DIY just be carefull when drilling or screwing the flashing in place. I will usually use a bead of calking to seal the metal because air passing through a screwed flat piece of flashing without sealant can squeal quite loud, just a bead prior to screwing together makes a tight seal.

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