short cycle furnace - http://www.hvacmechanic.com/ Forums

Original message

LarPJ

165.247.252.129

"short cycle furnace" , posted Tue 4 Nov 21:54

This is my first winter in this house. When we had it inspected, we discovered that the furnace short-cycles. The owners had the flame sensor cleaned, the blower speed changed and the gas pressure checked. It apeared to be working ok. That was last Spring. Now I am noticing that it is short cycling again (sometimes five seconds on and 20 seconds off.) This summer we had several occassions where ice formed around the A-coil and would not allow air to pass though. Of course, this always happened on the hottest days when it was running quite a bit. I don't recall any short-cycling, though. It has always seemed to me that there wasn't enough air being circulated through the house - very little air movement at the registers and the intakes. My father had an almost-new, three-speed blower motor that I put in to replace the original motor in case the old one was the reason I wasn't moving enough air, but that didn't work. So, what is causing my furnace to short-cycle? Does the blower speed need to be faster or is there some sensor that needs to be replaced? Thanks for any and all help!

Replies:

Xenos
Webmaster

64.230.161.32

"Re(1):short cycle furnace" , posted Wed 5 Nov 19:13

The A/C freezing and the furnace overheating ( or sounds to be) are virtually the same problem. I would suspect that the evaporator is dirty or plugged. Or at least something is restricting the air flow.

Xenos.

The best way to escape a problem is to solve it.