too much power? - http://www.hvacmechanic.com/ Forums
Original message
| chris henley
 |  "too much power?"
, posted Wed 15 Oct 12:52  
I installed a 92% Frigidaire high efficiency furnace for a friend. It keeps shutting down, i believe, because of insufficient duct sizes or it's just too strong (100,000 BTU's output for 2100 sq' old home). Seems it's overheating cuz the air isn't moving enough.
If i cut new return air and blow vents and the furnace works, is it a good solution? Any other suggestions?
Vancouver Property Services
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Replies:
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| Freon
| "Re(1):too much power?" , posted Fri 17 Oct 13:19
Calculate the potential air flow rate (cubic feet/min) based on the size of the exosting ducts. This is a very simple calculation. For a 100,000BTU furnace I would expect you need the duct system (supply AND return) to support close to 2,000 cfm.
Using a thermometer, take the air temperature as the air leaves the furnace before it shuts down. Subbtract the house air temp(average). That difference is the temperture rise and you want to compare it to what's listed on the furnace data tag near the controls. It is possible the furnace is overheating and it's possible there may be a faulty high temp sensor. Only the data will tell you for sure.
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