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Phil
Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 8702
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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I have a Lennox Surelight Elite furnace model G26Q4/5-125-5.

Customer Question

I have a Lennox Surelight Elite furnace model G26Q4/5-125-5. Sometimes when it first starts, there is a humming noise. I have changed the inducer motor, fan motor and capacitor. After the changes the humming was not quite as bad but it is still there intermittently.
I have had two different repairmen out to look at it. The last one told me to call him when it did it. Well he is 40 miles away and it was a ridiculous thing to say particularly since right now it is an intermittent problem. I need suggestions on what it could
be and what I could have them check next.
Submitted: 1 year ago.
Category: HVAC
Expert:  Phil replied 1 year ago.

Hello,

Tell me how loud the hum is. A good way to gauge that is for you to tell me how far away from the furnace can get and still hear the humming.

I also need to know if it is a steady even humm when its humming, or if it changes tone a lot.

How long does the humm continue after it first starts.

We can go from there.

Customer: replied 1 year ago.
Furnace is downstairs. I can hear it upstairs even with the door closed to downstairs. The tone of the hum doesn't change.
I'd say it hums for 2-3 minutes approx. I'll try to time it next time. I've been trying to get down there and take a video with my phone when it starts but haven't been able to catch it yet.
Expert:  Phil replied 1 year ago.

Thanks, ***** ***** working with it, and patience will eventually reveal whats going on. Your experience with it will be the key, combined with your removing the service panels on the furnace and feeling around for the source of the vibration. (be careful not to stick your fingers in the blower wheel or any of the 120 volt wire connections at the fan motor or on the printed circuit board).

You will have to hold the furnace blower door switch closed when doing that, or tape it down.

Let me know what you can discover or the next day or two or week etc.

We can go from there without a time limit.

Customer: replied 1 year ago.
It doesn't do it when the air conditioner is on. Only heat and it seems to be worse first thing in the am when the furnace starts to heat the house from 65 to daytime temperature. Would the main circuit board cause the inducer fan to hum if something wasn't sending the right signal? All fans are brand new.
Expert:  Phil replied 1 year ago.

The if the inducer fan runs sometimes, then a bad circuit board would not cause it to hum when its not running.

The 24 volt transformer however hums 24/7 to a very faint degree.

If I were there I could find the humm in less than 30 seconds, you can do it too... you feel around with your fingers that way you can track down the vibration connected with the humm... I would be careful not top poke my fingers into any red hot, or moving fan blades or high voltage electrical wires.

If you appreciate my input so far, locate the "rate your expert" link, and rate my work positively... we can go from there.

Lacking that I can spend days with a customer at my own expense,without any compensation. Rating does not increase your charges or close the question and it allows you unlimited follow up which it looks like you might need in this case.

Expert:  Phil replied 1 year ago.

A humming 24volt transformer can vibrate the furnace cabinet and cause a slightly loose cabinet door to vibrate and noise.. try feeling around for what makes the humm stop.

If you appreciate my input so far, locate the "rat eyour expert" link, and rate my work positively... we can go from there.

Lacking that I can spend days with a customer at my own expense,without any compensation. Rating does not increase your charges or close the question and it allows you unlimited follow up.

Customer: replied 1 year ago.
ok I'll try. I sat down there by it for 2 hours yesterday and it never hummed once. Then this morning........it hummed again.
I ran down but it stopped before I got to it. It's driving me crazy lol but I will keep trying to catch it and get back to you. Please be patient. I've had two different repairmen here and neither one fixed it. They just kept replacing fans but it still does it.
Expert:  Phil replied 1 year ago.

This will take patience,

If you appreciate my input so far, locate the "rate your expert" link, and rate my work positively... we can go from there.

Lacking that I can spend days with a customer at my own expense,without any compensation. Rating does not increase your charges or close the question and it allows you unlimited follow up.