I finally got my ac guy to do my house. Downstairs unit is 3 ton condenser and airhandler inside. Just had it wired-no problem. Upstairs unit (1 1/2 ton) condenser with air handler. The air handler has a constant hum to it, kind of like a transformer humming. The ac guy said that it was ok, and it was exactly that- the transformer. Does that make sense? Why doese’nt the downstairs unit make the same noise. And yes, i do realize they are different sizes. All in all, I love having ac, I’m just curious about the “hum”.
thanks
Chris
Easton, MA
Replies
Different transformers make more or less hum. More the design than the size. Also it is not uncommon for lamination and mounting straps to become loose and for them to make more noise.
But I suspect that the big difference is what and how they are mounted. The sheet metal on the upstairs unit is probably acting as a big sounding board.
Moving or remounting the transformer might help.
A stiffer portion of a sheet metal enclosure might help. A little vibration at the center of a large unsupported sheet can act like an amplifier.
A small transformer can often be remounted using double-stick tape available at most hardwares. Larger transformers can go on commercial heavy-duty foam tape available at commercial body shop supply houses or some hardware stores. On clean surfaces it is amazing what this stuff will hold. I hear the heavy duty version is used to hold on truck shells on Mack trucks.
If necessary you can add screws to hold but any direct attachments will transmit the vibrations. Even using bolts an oversized holes so they don't touch, a couple of nuts and bolts, a couple fender washers and some rubber gasket material on both sides of the sheet metal can isolate vibration. Don't compress the rubber too much tightening the bolts. Lockite helps prevent the bolts from backing out.
Once hung a large transformer off pieces of radial tire tread. These worked to keep the vibration from transmitting to the bar joists.
Let us know how this shakes out.
Bill and 4Lorn are right on.
In addition, the fact that a transformer makes noise (as evidenced by loose laminations, etc as previously mentioned) means that it is likely to fail in a few years as the vibrations help to wear thru the insulation on the wire. etc.
A noisy 60 Hz transformer = a very poor quality transformer or a 'lemon' transformer. Get your HVAC guy to replace it under warranty, even a replacement of the same brand is likely to be much better. If same noise when replaced, insist (or DIY) on replacement with another brand of transformer.
Edit PS/to Chris-- can you tell us the brand you have ??- I usually use Rheem, and have not had that problem, nor even with Goodman. Edfit 2 - a hum, very small, barly audible with your ear right against it, in your size xfmr due to magnetostriction of the iron core is normal and is basic physics. DW arranged shipment of multi megawatt GE transformers when she worked for them a few years back. When we toured Glen canyon Dam in the 80's, she wanted to see one of the transformers she had once done the shipping arrangements for (50 ton + transformers, etc). We walked up to a 20 ft wide by 30 ft high transfomer that had an audible hum to it, but not objectionalbly loud, say about 65 dB. She said, " that's why the engineers called them BIG HUMMERS" !
Edited 6/8/2004 12:24 am ET by JUNKHOUND
Edited 6/8/2004 12:35 am ET by JUNKHOUND
Hey dude!
Thanks for the tip. I believe I have a Goodman air handler. Are they any good. I'm going to mention the transformer thing to my electrician.
thanks again
chris
Easton, MA