how to increase a furnace fan speed

aumanpj

I put it all back together so that I could turn on the power to do as you say, and now it won't work. I get a low buzzing noise, some clicks and strange slinking noises. ugh... what have I done? I should have left this thing alone. Any idea what's going wrong?

aumanpj

the vibration, slinking and clicking must be coming from the AC. I turned the AC circuit breaker off and now all I get is a buzzing from the furnace.

Any input from anyone would be greatly appreciated here.

aumanpj

look at the first photo in post 10. see the red wire with a prong on the end of it... it's just loosely laying about. might it have slipped out of the back of the transformer without my knowing it and now that's what's causing my problem?

beenthere

Yes. It is probably one of the wires that needs to be in the relay.
Should be able to look at the relay and see which slot it came out of.

The pic in post 9 is too dark for me to tell.

tobybul

I realize this is an older thread but I have a related question. I have a Bryant HE furnace circa 1997 with a 3 ton ac. I would like to increase my fan speed also. I know that the fan is already tapped to the highest speed. Ideally, I need about a 20% increase in cfm to have better air flow in the 2 farthest rooms. My thought is to replace the fan motor with a slightly higher rpm.

I don't think it will adversely affect the discharge air temps of the unit in both heating and cooling.

Have you done anything close to this? Thanks

beenthere

Before getting a higher RPM and higher HP motor. Remove the blower panel, hold the safety switch in, and have someone see if the air low increases to those rooms.

tobybul

Not having opened the blower panel before, are you saying there is some sort of "safety switch" inside it? Does holding it down bypass fan speed controls?

beenthere

Holding it down only bypasses it. Its just a switch that is there to help prevent someone from getting shocked/electrocuted by touching a wire in the blower compartment.

tobybul

ok, so am confused now. What am I trying to do then by holding it down?

Evstarr

I think the goal is to see if you get more air with the door open since you'll be bypassing the filter and returns while it's open.
You have to hold the switch with your finger because the door won't be there to hold it closed.
If the switch isn't closed the blower won't work.

beenthere

Its a way to see if you have enough return air. With the panel off and the switch held in. The blower is pulling in as much air as it can. If the air flow to those 2 rooms increases, then your short on return. And adding a return may be all you need to do. If the air flow doesn't increase, then your supply duct is too small. And putting in a higher speed, higher HP motor will make your duct system loud, and give you more air flow to all supplies, not just those 2 rooms.

tobybul

Oh Ok. I guess I was not following that. Now that I understand I will say that the issue is not the return. In any system, there will always be an issue with return duct - and supply duct - static pressure. I agree that there maybe some cfm gained by removing the cause of return static but it won't be significant for what I am trying to attain.

When the system was installed in 97, I set up my return filtering with 2 16x25's so its a V shape. Plus I use pleated filters. This slows down the velocity of the air at the filters allowing for less static pressure and better filtering.

As to increased air flow to all registers, they can be balanced with the dampers. And yes, noise may become a factor but I don't think it will be noticeable with a 20% increase.

beenthere

The V shape increases return static. Have you ever actually measured your static pressure?

tobybul

Not if the filter compartment is larger. Plus, more filter surface area reduces static pressure.

beenthere

I take that to mean you have never measured the static.