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Paul T. 12-06-2008 08:08 AM

Ruud furnace problem
 
I have a Ruud furnace and have been having some issues with it's cycle.
It will start and build heat in the burners than the fan will come on for about 1 min. than the fan will shut down and the burns will stay lite.
It continually repeat this cycle until the house is warm.
I know this can't be efficient or good for the furnace. We have replaced the sensor with the thermostate in the unit that kicks the fan on and it still does the same thing. I was told it was the amount of cold air coming into the unit that was causing this so I added a heat duct to the cold air return immediatly out side of the plenium , didn't change it. My repairman has cleaned the burners and it worked for about 24 hrs than it started again.
Help I am just a builder and not a furnace repair man but with the economy here in Michigan being very slow I can't afford to replace the whole furnace but hope to repair it.
HELP!!!
Thanks in advance.

lrfllc 12-06-2008 02:59 PM

Try checking the air flow through the furnace. Does it have a clean filter? If it has an ac coil check to make sure its not clogged. Will have to remove it to look under it. You may be able to pull it out enough to look at it. Remove the heating run you put on the cold air side! Make sure all return air duct/grills are clean and open! I think your problem is you don't have enough air going across the heat exchanger. One last thing make sure the heat exchanger areaa directly above the burnners is clean and clear.

Reagrd, Larry pickeringtonHVAC.com

Paul T. 12-06-2008 04:51 PM

Larry,
It has a new air filter. No to the a/c unit . I will check the heat exchanger, I have not done that yet. The warm air duct that I put in goes directly into the cold air right before the air filter. If that is a problem it is an easy fix. We have a old farm house with little to no insulation and the cold air returns do get very cold inbetween normal cycles. That is why I figured the themo switch in the burner area was cooling so fast.
Thanks.
Paul T.

beenthere 12-06-2008 11:47 PM

Was the blower motor changed within the past year.
Did the tech check your manifold pressure.

Paul T. 12-07-2008 04:15 AM

No to the motor change. Yes to the pressure.

beenthere 12-07-2008 04:22 AM

Hmmm.

In the past, when it didn't cycle on and off.
Was the air coming out of the registers hot, or just warm.

Is this natural gas, or propane.
What was the manifold pressure.

Did he just clean the burners, or did he also pull the orfices, and clean them too.
Most don't clean the orfices.

Can you look and see if more rust has fallen onto your burners.

Paul T. 12-07-2008 04:37 AM

Quote:

Originally Posted by beenthere (Post 195007)
Hmmm.

In the past, when it didn't cycle on and off.
Was the air coming out of the registers hot, or just warm.

Is this natural gas, or propane.
What was the manifold pressure.

Did he just clean the burners, or did he also pull the orfices, and clean them too.
Most don't clean the orfices.

Can you look and see if more rust has fallen onto your burners.

Air comes out hot. Propane. I think he cleaned all I was not home when he did it. Pressure was 10 on the water column. No there is no rust on the burners.

beenthere 12-07-2008 05:23 AM

Some years back, when I was a service manager for a company.
I had a tech call and say he was having troubles.
I told him to pull and clean teh burners and orfices.
Later he calls back and says he done, but it still isn't working right.

I went out to the call.
Check minifold pressure and then pulled teh orfices.
He looked supprized. After I cleaned them, it worked as good as new.

Most techs don't pull orfices.

So don't think he did just because he pulled the burners, if he didn't list it as part of his labor description.

10" isn't always right for propane.
It could be set to 10.5 to 11". And still be within factory tolorence.

donimbimbo 12-07-2008 06:25 AM

I had a forced air system for 18 years at our previous house. After one service call the same thing happened. Our furnace was oil fired. Turns out the low limit fan control got changed (nowbody knew why). Dropping this down to 100 or so fixed the problem.


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