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airheatman, HVAC Technician
Category: HVAC
Satisfied Customers: 8373
Experience:  Furnace, A/C and heat pump specialist.
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I have a Carrier Performance 96 Furnace with A/C Coil. It

Customer Question

I have a Carrier Performance 96 Furnace with A/C Coil. It was installed several years ago (4-5) and has worked perfectly ever since.
However, at the end of last years heating season I noticed a buzzing noise coming from the vicinity of the furnace. It is at a lower frequency that 60Hz so I don't think it is directly related to AC power. It is load enough to be easily heard in the furnace room, but not alarmingly so. It is also sporadic and did not happen at all of the summer.
I would think it is something rattling, but it doesn't sound like any rattle I have ever heard before. It is more like the sound a clutch on a power drill makes when it slips but not as sharp. Any ideas?
Submitted: 1 year ago.
Category: HVAC
Expert:  BillyHvac replied 1 year ago.


There is only one component that make sound whether the unit is in operation or not.

This is the transformer in the furnace that takes 120v and creates 24v for the control circuit. It is a very common issue with control transformers. It can be remedied by replacing the transformer...or mounting on a rubber washer or other vibration eliminating pad.

If you have any other questions please let me know.


Customer: replied 1 year ago.
I told you in the question that it was not a 60Hz hum. It is not even sinusoidal and does not sound like an electrical hum. Also, it only occurs when the first is heating, not when it is of or cooling. Please read my question again, and if you have no idea what the answer is, please just say so and spare us both some time and aggravation.
Having you say that you have no idea would tell me that it is probably not specifically related to the furnace, but perhaps to the piping or the way the furnace was installed. That would be worth $16 dollars. Telling me that it is a transformer because it buzzes whether the furnace is running or not isn't.
I do appreciate that you are trying to help, but so far you haven't.
Expert:  BillyHvac replied 1 year ago.

I can tell you like precision, and I appreciate that. But in your quest for an exact answer and the resulting have not supplied critical info. All you said was in the vicinity of the furnace. That in itself is vague as to location.

Is it during operation?

Is it during down time?

thus my answer which is the ONLY load all the time is 99% true. A transformer resonation is not just the coil vibration or as you say 60 hz...the metal wall, mounts etc dictate the noise which covers the spectrum.

Now...if you came to me with:

The FURNACE is making a noise on START UP...or DURING operation, we can dig further. But with terms like vicinity, no mention of operation or not...I am sure you can see the answer would be difficult.

Plus I think someone else maybe better suited for this question. I will opt out and see if someone can deliver better information on the scenario you have given.

I apologize for your aggravation...After being a Licensed Contractor in 2 states and hired by manufacturers for training their techs I am accustomed to a different reception.

I wish you the best and will opt out so the others can help you. Or if you wish, I will forward to customer service so that the entire amount of $16.00 is refunded.

Customer: replied 1 year ago.
I am sorry that I let my aggravation come out in my response. I had been struggling with the website to figure out to ask for more information. On the other I did supply more information than you suggest: the problem only occurs when the furnace is heating implies not when turned off or when it is cooling. In any case, this is clearly not something you have run into in working on other furnaces and suggests a problem specific to the installation. I don't doubt that you know your trade and so you have given me an answer of sorts and I won't fight over the $16. Thanks again for your time.Tim
Expert:  BillyHvac replied 1 year ago.


Expert:  airheatman replied 1 year ago.

Can you attach a short video clip of the furnace making the noise you are referring to? One of the most common issues and what I suspect is an issue with the gas valve . Could be pressure to valve fluxuating or diaphragm in valve going bad.