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aumanpj 08-02-2010 10:10 PM

how to increase a furnace fan speed
 
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I have an Ultra 2 gas fired high efficiency furnace with AC. I want to increase the fan speed. I have been reading online and am not sure what I must do. Attached is a photo of my fan limit control. Is this what I use to increase the fan speed? If so, how should I change it?

I read this: http://www.doityourself.com/stry/adj...nace-fan-speed but I do not see any jumpers they refer to.

Basically, I am a new home owner having lived in my new home since April of last year. I was quite impressed by the air flow of our new home and how quickly the home could change temperature. Last August we had a new control panel put in and I think the technician may have changed the settings. The unit just isn't blowing like I remember it.

I'd appreciate any input you could provide. Thank you.

beenthere 08-02-2010 10:31 PM

The fan limit doesn't control fan speed. There should be another relay. probably in the blower compartment. With the blower motor wires connected to it.

Look in there, and post a pic of it if you can.

aumanpj 08-03-2010 07:42 AM

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Is this the blower compartment?

aumanpj 08-03-2010 07:44 AM

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Here are some other shots of the furnace.

beenthere 08-03-2010 07:55 AM

Yes. that was the blower compartment.

But. Your furnace is older then I thought. So the control for the fan speed, is in the burner compartment.

On the right hand side. The 4X4 box with the transformer and relay(known as a fan relay center) is where the blower's wires are connected for the cooling and heating speed.

Black is high, blue med, and red is low. One of them should be connected to the relays normally closed contacts so the fan limit can run the blower in heating speed. And another connected tot eh normally open contact of the relay for cooling speed. Its possible that the tech connected med(blowers blue wire) for cooling. if so, connect the black wire instead.

aumanpj 08-03-2010 08:24 AM

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I think this photo depicts the wire setup on the box near the transformer you are pointing me to. Is that right? How do the wires look? Can you see the adjustment needed?

aumanpj 08-03-2010 08:28 AM

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here are the only other 4x4 boxes that I see; although, I doubt they are where you're pointing me to. I do not see near them the transformer. Isn't the transformer the copper wire covered device?

beenthere 08-03-2010 10:59 AM

The first pic with the wires, is the box I'm talking about. But the line voltage wires that need to be checked/changed. Are in the box.
Need to turn the power off and open it up.

aumanpj 08-03-2010 12:31 PM

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here is the back of the face plate.

aumanpj 08-03-2010 12:33 PM

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Here are two photos of the inside of the box. I don't see any jumpers. Hmmm... now what?

beenthere 08-03-2010 03:21 PM

Follow the wires from the blower motor. What colors are connected where?

Looks loke the black(high speed) is wired nutted off.

aumanpj 08-03-2010 03:28 PM

the red wire is capped off.

the blue one goes into a nut with two black wires - one of which goes into the switch on the other side of the furnace wall, the other goes into a plug labelled coil 1 at the back of the transformer.

the black one goes into a nut with another block one that enters into coil 4 at the back of the same transformer.

the white one goes directly into the switch

beenthere 08-03-2010 04:27 PM

Did the blower move more or less air in heating mode last winter?

You may have traced them back wrong. The black, red and blue should not all be connected. Only 2 of them.

aumanpj 08-03-2010 05:33 PM

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This was our first winter in the house and so I have no basis by which to say how the heat compared.

See image for detail of wires. The only other wires in the mix are black and orange. They, however, travel to the blower door. They operate the door trip which turns the fan off when opened.

beenthere 08-03-2010 06:03 PM

Ok. With the power on. Carefully turn the dial of the fan limit unit the blower comes on. Listen to it.

Then let the dial go, so the blower shuts off. Then have someone turn the fan switch on the thermostat to on. Listen to the blower. Which seemed to blower more? if by the dial. Switch the blue and black wires. If by the fan switch on the thermostat. Then the tech may have used a lower horse power motor.


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