Subpanel Buzzes the instant before the AC comes on?

I have a fairly new house (built Sep. 02) with a 200 amp service coming in. It is kind of long, so there is a subpanel about halfway across the basement. I was moving junk around downstairs - we call it organizing :-) - when the A/C came on. I have two AC systems (1st flr., 2nd flr.). Whichever kicked on, the second before, there would be a buzz from the subpanel the units are out of. Is this something to worry about? I went over to the main panel and heard nothing. I assume it has done this since the beginning of time, but since we ussually only "organize" in the winter I have not heard it before. Thanks for your help.
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On 4 Sep, 10:24, snipped-for-privacy@yahoo.com wrote:

Just a guess, since I can't see (or hear) your subpanel from here... You could have a loose coonection and thus you might be getting some arcing with the initial current draw.
I don't know how comfortable you are with pulling the cover, checking connections, etc. This first thing I would do is pull the cover, turn off the lights and have someone fire up the A/C. You might see the arcing if it's a loose wire or breaker. If it's internal to a breaker, then you might not see anything. The contacts and/or the thermal magnetic components may be weakened.
You also might want to inspect the busbar that the breaker plugs onto to be sure there is no discoloration or melting of the metal due to a loose connection.
Slightly OT - When I was in the service I worked on transmitters that had vacuum tubes with 15,000 volt plate voltages. It had big oil filled capacitors that could handle up to 30KV. Sometimes the transmitters would arc under normal power, but with the sheet metal panels on you couldn't see the arcs. We'd wait until after dark, remove the panels and run the power supply up to 20 - 25K trying to cause an arc. Since there wasn't a lot of room surrounding the transmitters, we were always within 8 feet or so. It's was pretty impressive (and d*mn scary) when the arc occured. The things we did for our country!
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DerbyDad03 wrote:

Hi, What equipment have you worked on? I did same thing way back in the '60s. Ditto, I think the sub panel or something is loose.
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- Hi, - What equipment have you worked on? I did same thing way back in the '60s.
- snip -
I worked on Loran-C transmitters in Germany and Alaska during the late 70's while I was in the Coast Guard.
You?
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Sounds like the breaker is on the edge of tripping during the startup of the A/C compressor motor. Mine does that, too...
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- Sounds like the breaker is on the edge of tripping during the startup - of the A/C compressor motor. Mine does that, too...
If the breaker is that close to tripping on startup, something is wrong. The tolerance between amperage of a breaker and the normal operating conditions of a circuit should not be that tight.
Note: By "normal operating conditions" I don't mean "steady state". Normal operation includes start-up conditions as well as steady state.
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Mike Granby wrote:

I agree. Circuit breakers can hum. The current produces a magnetic field which can cause parts to vibrate. When the compressor starts it draws about 6x the running current. Higher current produces more vibration.
(A sizzling sound indicates a loose connection/arc.)
-- bud--
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Ditto, it's very common

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On Sep 4, 10:24 am, snipped-for-privacy@yahoo.com wrote:

I get this same thing on my central AC. I always assumed it was the initial power draw causing the brief "buzz/vibration". Other than the sound, I've never had any problem with it. Hope this helps.
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