I just installed a add-on wood/coal furnace that works really good... The problem that iI am having is that the gas furnace that I added on to has too much air pressure... I need to step the fan down but I do not know how to do that... It is a newer furnace... It is a Concord 90 plus model number CG90UA125D20D-1... I have know idea where I put the darn installation manual I have been lookig for it for weeks.

The problem you are going to face is that the furnace manufacturer requires a minimum of air flow across the heat exchanger in that new furnace. If you just start lowering the blower speed it could damage the furnace and no warranty will cover this damage. Try to find another solution first then if the blower speed needs to be lowered still contact a HVAC company so they can check to make sure the correct heat rise and flow requirements are met so no damage to your new furnace happens.

Yes I know... I just need to slow it down because it is over powering the blower on the wood furnace... The gas furnace is not hooked to a fuel line...

Just look at the wiring diagram on the back of the blower door. It has the motor wiring on it.

If your wood burner has a blower, why are you using the central system blower at all? If the central blower is overpowering the wood blower, most likely you will not be able to slow the central blower enough to remedy this problem.

It is a add- on wood furnace... The blower on the wood furnace is only to get the heat to the plenum of the gas furnace... The blower on the gas furnace forces the hot air through the house.In the installation manual for the wood furnace it did say that I might have to step the blower speed to med. To low speed...

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Originally Posted by hvac1000

Just look at the wiring diagram on the back of the blower door. It has the motor wiring on it.

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Thank you very much!

I was able to slow down the speed on the Concord furnace... Now we are getting the heat through out the house that we needed... Thank you very much!

Good deal.

Heat uses low speed already, Cooling is the high speed, unless you have medium speed on heat now there is no way to slow the fan down.