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Buzzing noise - heatpump resistance mode


CheckItOut
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This was a five-year old Trane that made a loud buzzing noise at the evap box when run in resistance heat mode. Sounded like one of those little hand-held engravers and was loud enough that I could easily hear it from the main floor with attic door closed (unit was in the attic). I'm writing it up for further eval but just curious if anyone knows...

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Last time I had that happen on an electric furnace, I found that there was a transformer screwed to the wall of the controller tray and it was loose. Every time the heat came on, that transformer fibrated just like the tool engraver I used to have - which wasn't much more than a tranformer mounted on a piece of carbide. I took a nut driver, snugged up the two sheetmetal screws holding the transformer in place and the buzz ceased immediately.

Five seconds to fix it - it would have taken five minutes to write it up.

ONE TEAM - ONE FIGHT!!!

Mike

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I think what you are hearing is the collective and random gasping for breath of the thousands of hamsters running on their little treadmills to provide the power for the heating elements.

Or maybe they have a bug zapper installed inline.

But those are both just WAG and most likely completely erroneous.

Seriously, I've never heard anything like that. Maybe some sort of a contact issue?

I'm sure someone with a real answer will let us know.

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Originally posted by CheckItOut

This was a five-year old Trane that made a loud buzzing noise at the evap box when run in resistance heat mode. Sounded like one of those little hand-held engravers and was loud enough that I could easily hear it from the main floor with attic door closed (unit was in the attic). I'm writing it up for further eval but just curious if anyone knows...

Noisy transformer or solenoid?

- Jim Katen, Oregon

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Originally posted by CheckItOut

This was a five-year old Trane that made a loud buzzing noise at the evap box when run in resistance heat mode. Sounded like one of those little hand-held engravers and was loud enough that I could easily hear it from the main floor with attic door closed (unit was in the attic). I'm writing it up for further eval but just curious if anyone knows...

The noise is coming from a contactor that energizes the strip heat.

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Originally posted by Terence McCann

Originally posted by CheckItOut

This was a five-year old Trane that made a loud buzzing noise at the evap box when run in resistance heat mode. Sounded like one of those little hand-held engravers and was loud enough that I could easily hear it from the main floor with attic door closed (unit was in the attic). I'm writing it up for further eval but just curious if anyone knows...

The noise is coming from a contactor that energizes the strip heat.

So, good thing, bad thing? Is it likely to get worse and fail or could it go on forever without issues - except for the noise, that is?

OT - OF!!!

M.

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Originally posted by hausdok

Originally posted by Terence McCann

Originally posted by CheckItOut

This was a five-year old Trane that made a loud buzzing noise at the evap box when run in resistance heat mode. Sounded like one of those little hand-held engravers and was loud enough that I could easily hear it from the main floor with attic door closed (unit was in the attic). I'm writing it up for further eval but just curious if anyone knows...

The noise is coming from a contactor that energizes the strip heat.

So, good thing, bad thing? Is it likely to get worse and fail or could it go on forever without issues - except for the noise, that is?

OT - OF!!!

M.

Bad thing. If a contactor is buzzing or chattering it's time for replacement. When contactors start to do this there is a good possibility that the contacts aren't making good contact. Then it's like a loose electrical connection, volts drop and amperage goes up.

A small hum from a contactor typically isn't bad but if it's making enough noise to draw your attention, then it's time for replacement.

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Originally posted by CheckItOut

This was a five-year old Trane that made a loud buzzing noise at the evap box when run in resistance heat mode. Sounded like one of those little hand-held engravers and was loud enough that I could easily hear it from the main floor with attic door closed (unit was in the attic). I'm writing it up for further eval but just curious if anyone knows...

Are we talking indoor evaporator (cooling mode)

or the outdoor evaporator (heating mode)?

I suspect we are talking about the indoor coil which would technically be the condenser coil for heating purposes.

I come across this in my own reports and finally just quit specifying the "evaporator or condenser" and just used "indoor or outdoor" just to keep from looking foolish when the tech comes out to fix something on my report.

I agree it is likely a solenoid or transformer that should be checked out.

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Electric heat banks are usually timed on by sequencers which are bimetal snap discs and usually very quiet except for a quiet snap when turning off or on.

I would be inclined to belive it is the motor contactor or transformer, but why only in resistance heat mode? Best left to the HVAC guys to determine the problem, as long as yoiu noted it.

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Originally posted by newguy

Electric heat banks are usually timed on by sequencers which are bimetal snap discs and usually very quiet except for a quiet snap when turning off or on.

I would be inclined to belive it is the motor contactor or transformer, but why only in resistance heat mode? Best left to the HVAC guys to determine the problem, as long as yoiu noted it.

You're thinking of a hi-limit protection device that will open the circuit in case of a lack of air flow/over temp etc. When you pull in a bank of electric strip heat you do it with a contactor.

That answers the question of why only in the resistance heat mode.

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  • 2 weeks later...

No I meant sequencers, i am trying to figure out how to load a picture. Here is a brief discription.

The terminals at the base are the 24 volt ac. control inputs.

Caution: some Lennox Furnaces have sequencers with 240 volt inputs.

The specs on the top of the unit indicate the the first stage is "first on last off" and the second stage is "last on and first off" Some setups the sequencer also controls the blower fan in the unit.

Units with more elements will have additional sequencers that are "last on" first off".

Then I found this

Different manufacturers use different devices, some use contactors, while others will use relays or sequencers. Some use a combination of contactors and sequencers to activate a second stage heat bank.

Which leads us to a noisy relay or contactor.

Image Insert:

2008121421475_sequenceside.jpg

15.86 KB

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A Trane heatpump actually and it only happened when the temps dropped so low that the heating elements came on. I don't know whether Trane units have sequencers or not but I seem to recall that the last Lennox heatpump I looked at did.

It looks like he's probably got a pretty good handle on what's caused the noise. If they ever find out I hope he comes back and tells everyone whether any of us was right.

ONE TEAM - ONE FIGHT!!!

Mike

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