buzz in switch box

I noticed this morning when the central air comes on, there is a buzz sound in the main switch box. We have circuit breakers. It is just a quick buzz when the unit clicks on. Is this a normal thing?

 

Could possibly be a breaker that is slightly loose (not fully seated). It is probably not loose enough to be noticeable normally, only when the A/C kicks on and demands a large rush of current. If you have push-in type breaker, which most of all residentials are, then you could try to push slightly on the breaker when the A/C starts and see if this helps. Might have worked itself loose over the years.

 

Thanks for your quick reply. I will try what you suggested, but I am thinking this might could cause a fire?

 

I suppose it's remotely possible, but remember that the breaker panel is a fully enclosed metallic box, and not for nothing. Heat and potential arcing are contained in this fire resistant package. And there is no readily combustible material in there to actually produce a flame. Insulation on modern wiring is rated anywhere from 60 to 90 degrees centigrade (140 - 194 degrees F), and will stink up the joint long before it catches fire. Plus, loose breakers ordinarily produce relatively low heat. If heat is being produced by this breaker, which isn't highly likely, you should be able to feel it with your hand. But go ahead and try what hotarc suggested and let us know what you find.

Juice