On Mon, 22 Nov 2004 04:08:41 -0500, NWM
wrote:



No, your service was NOT good enough, or else you would not be having what
we call a run on condition. While it MIGHT be a simple adjustment to the fan
limit, I would be more concerned with the heat rise, and if its too high. If
it is, due to your previous techs failure to check it after cleaning the
unit, the blower will continue to cycle as it is until the burn is corrected
and the heat rise is lowered.



Ok, I had thought when you stated heat rise, you meant the heat didn't
rise up through the flue and ducts. SOunds like you mean the heat has
risen too much in the furnace , thus the second blower run when the
burner is off as a result of too much heat still inside. The first
blower run didn't force enough hot air through the ducts?

Can the heat rise be a problem of the limit switch setting? The tech
showed me that the limit was set between 100 and 150 with emergency
shut off at 210. However, I just read on the furnace that the switch
is supposed to be set at 70 and 100, unless I misread what was
labelled.

SO you are saying that the second blower run could correct itself
eventually?

Thanks again for all the helpful responses

70 and 100 is too low. 100 and 150 is apparently too high. I would
take it to 90 and 140. If that doesn't take care of the double run, I
would go to 80 and 140.

The proper setting varies from system to system. Also, its entirely
possible that the fan switch just doesn't hold its settings anymore
and needs to be replaced.

Gary R. Lloyd CMS
HVACR Troubleshooting Books/Software
http://www.techmethod.com