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| Joined: | Wed Aug 16th, 2006 |
| Location: | Michigan USA |
| Posts: | 1186 |
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Fault code 31 indicates "pressure switch failed to close" which is exactly what it should be given the pressure switch hose was cracked (not typical by the way on a 4 year old furnace) -
As for inadequate return air, it has absolutely nothing to do with the combustion process. Combustion air is brought in through the pvc pipe into a sealed combustion chamber then exhausted through another pvc pipe.
However inadequate return air will cause a furnace to cycle on the hi limit control(causes stress on the heat exchanger). Your furnace is rated for 40-70F temperature rise, meaning if the return(room air) temp is 70F then the supply air can be as high as 140F (recommended rise is 55F). Take a temperature measurement a few feet downstream from the supply pleneum and subtract the room air temp. Allow the furnace to come up to temp for 5 minutes or so before taking the reading.
On new equipment start-up this would have been a required set-up check. Keep us posted...
Last edited on Fri Nov 3rd, 2006 05:35 pm by hvacdrd
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