Noise with blower on heat since A/C upgrade

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Old 10-10-16, 06:06 AM
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Noise with blower on heat since A/C upgrade

I have a forced hot air system that's about 10 years old. Worked fine last year. Before this summer, I had it upgraded for central AC. The AC system worked fine for the season, but now when we put the heat on, there is a noise that sounds like the blower blade hitting something. I don't understand how the cold air can be blown through the house fine, but when the heat comes on there's this loud banging. Do the AC and heat use different blowers to push the air through the house? Is there a common screw-up that can lead to the heat blower hitting something after the system is upgraded for AC?

Thanks in advance.
 
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Old 10-10-16, 06:43 AM
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Assuming your A/C was added in the usual fashion it will be the same blower moving the air in heat or cool.

I suggest you turn off the power to the furnace/AC, remove the blower compartment access panel (usually the lower panel of the furnace) and try spinning the blower with your hand to see if it is hitting anything. Also check to see if the blower wheel moves side to side on the shaft more than a tiny bit (it shouldn't).

It's possible something was dropped into the blower area when the retrofit was done; it may just be bad timing that it is causing noise now. Could also be failing bearings on the blower or loose blower wheel.

If you have a spinning wheel humidifier that could also cause the noise, since they don't run in cool mode. If you have one, try shutting it off by setting humidity control to off.

BTW, there is usually a safety interlock that prevents the blower from running when the lower door has been removed, so don't expect to be able to run the furnace with the door off unless you temporarily defeat the safety switch just for testing.
 
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Old 10-10-16, 12:46 PM
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In addition to what Paul mentioned... try running the system on A/C and see if the noise is still there. The blower runs at different speeds for heat and A/C and that could possibly be an issue.
 
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Old 10-10-16, 07:09 PM
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Paul and Peter,

Thanks for your replies. The noise is only there with the heat, not the AC. I narrowed the noise to this blower (see attached), which I believe blows the exhaust out of my house. It's a HE heating system. It sounds like the bearings are shot, even though it worked fine last time we ran the system. Is there anyway that could have been damaged during the AC install? Are these known to "go" so suddenly, with no known warning?

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Guy
 
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Old 10-10-16, 07:51 PM
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That's called the draft inducer blower.

They just go bad. Some last several years and some last over 20.
They operate in extreme heat and the bearings eventually dry out.

I don't see how installing the A/C would have any effect on it.
 
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Old 10-10-16, 08:42 PM
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I'm pretty handy. Is this the kind of thing a DIYer can do himself?
 
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Old 10-10-16, 08:48 PM
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Sure.... post the full model number off the furnace ID tag and we'll look into it further.
 
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Old 10-11-16, 07:50 PM
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I think this is probably the numbers you want.

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Old 10-11-16, 08:42 PM
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Furnace model: TUY120R9V5W5
That inducer is part # BLW00879.

You can search using the part number. Here's one selling location.
American-Standard-inducer-3-phase-BLW00879/dp/B00CD5W1IO
 
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Old 10-13-16, 07:57 AM
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Thanks. I've seen Fasco brand blowers, which are a lot less than the Trane and Trane OEM. Is it worth the extra cost for the Trane?
 
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Old 10-13-16, 03:31 PM
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Since I replace customer equipment I try to use OEM parts.
The aftermarket part may last just as long and it may not.
 
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Old 10-22-16, 04:23 PM
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So, I order a replacement blower and the one I received is slightly different than the one currently installed. The one installed has some type of sensor built into it

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and the one I ordered does not have that sensor
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Not only that, the one I ordered does not have a hole for a sensor in the same spot; instead it has a closed plastic window.

Do I pop out the window from the new blower and remove the sensor from the installed blower to the new blower? Or, do I need to buy a new sensor for the new blower? Or, do I have the wrong blower, and have to get a blower with the sensor built in?

Thanks,
 
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