Is ductwork size insufficient for furnace? - http://www.hvacmechanic.com/ Forums
Original message
| snigadnol
 |  "Is ductwork size insufficient for furnace?"
, posted Mon 10 Nov 00:40:  
When I moved into my home 5 years ago, we had the old furnace replaced. For the first year, everything ran fine. However, over the last 4 years, the furnace limit switch has repeatedly tripped due to excessive heat in the exchanger, and this has gotten worse every year. I've had the furnace tuned up, blower cleaned, A-coil inspected, and all those have turned up nothing to cause this to happen. I recently had all the ducts cleaned. I have installed the cheapest, thinnest filters available to allow as much air as possible to pass thru, but still is not enough. My repairman is pretty sure its insufficient ductwork sizing to feed the furnace. My returns are ducted thru the crawlspace, and my supplies are ducted thru the attic.
My questions are:
1. What's a rough idea of how expensive reworking my ductwork system would be? My house is 1800 sqft w/ crawlspace.
2. Could I just add more supplies and returns to my existing system to get a similar result?
3. Are there any alternatives I might try short of doing #1 and #2.
Any help would be greatly appreciated. Thanks.
[this message was edited by snigadnol on Mon 10 Nov 00:48] |
| Replies:
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| Jojo98
| "Re(1):Is ductwork size insufficient for furna" , posted Mon 10 Nov 13:20
If you have an undersized duct, you can tell by the air filter be sucked into the return quite forcefully; if it is a supply issue, then there should be a whistle noise coming from the registers. Disconnect the return at the furnance. If the furnance does not trip on high limit then you have a return issue. If it does and there isn't a whistle noise coming from the registers, call a different service company.
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| | snigadnol
| "Re(2):Is ductwork size insufficient for furna" , posted Mon 10 Nov 19:38
Just to see what would happen, I ran the furnace w/o a filter, and then I ran w/ the filter in place, but left the compartment open so room air cold also be pulled into the blower/exchanger. In both cases, the limit did not trip. Does that make it a return problem?
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| snigadnol
| "Re(1):Is ductwork size insufficient for furna" , posted Mon 10 Nov 00:43:
[this message was edited by snigadnol on Mon 10 Nov 19:50] |
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