Electrical Wiring in the Home/Buzzing noise


I recently moved into a brand new house.  One of the first things I noticed when I plugged in my plasma tv, was a loud hum from the TV that was not present in my previous home.  I assumed there may have been some damage during shipping.  However, I purchased a brand new microwave for my kitchen and plugged it into an outlet in the kitchen and it had a very noticeable buzz.  I unplugged it and plugged it into the GFCI outlet on the other side of the kitchen and it works fine, no buzzing/humming.  What can possibly be causing my electrical appliances to buzz on some outlets and not others?

There may be several reasons.

When you transferred to another outlet that didn't cause buzzing, it may have been on a different circuit on the other leg of the transformer. Most residential service is provided from single phase transformers with a center-tapped secondary to provide 120/240.

Breaker panels are laid out like the following:
+ means a connection
| means bypass

A  1 ---+--|--- 2
B  3 ---|--+--- 4
A  5 ---+--|--- 6
B  7 ---|--+--- 8
A  9 ---+--|---10
B 11 ------+---12

When you connect to circuit breakers 1, 2, 5, 6, 9, 10 you are connecting to one end of the 240 volt secondary winding from the transformer. When you connect to circuit breakers 3, 4, 7, 8, 11, 12 you are connecting to the other end of the 240 volt secondary winding from the transformer.
If you connect between breakers 1 and 3 [or 4, 7, 8, 11, 12], you get 240 volts because you are accessing both ends of the secondary transformer winding.
If you connect between 1 and 2 [or 5, 6, 9, 10] you get zero voltage because you are connecting both wires to the same end of the transformer winding.
If you connect between any one breaker and the grounded center point of the winding, you get 120 volts.

There may be a problem anywhere in the wiring on the side of the service you are connecting to, including that connected to another breaker, so if circuit 1 causes buzzing, so might circuit 2, 5 or 6, because the buzz comes from the circuits and equipment powered from that end of the transformer winding as well as the commonly shared wiring for those circuits including half of the transformer winding.

Grounding problems in equipment and audio wiring can cause buzzing in harmonic frequencies based on 60 hertz [cycles].

Also, some types of electronic power supplies are known to cause buzzing in audio circuits, and you have already provided evidence that you have PLENTY of electronic equipment.
You may be able to make the buzzing stop by turning off other circuits than the one your microwave and TV are connected to. Maybe you can isolate the source of the problem that way.

There was one person who discovered their doorbell button was shorted and the chime solenoid was continually energized, but that of course, didn't make his TV hum.

Love to hear what you find.

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Electrical Wiring in the Home

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Robert Wilber


Licensed Philadelphia electrician serving Delaware, Chester, Montgomery and Philadelphia County in Pennsylvania. I install and repair residential, commercial and industrial wiring and lighting. Troubleshooting and repair of problems that stump other people is my favorite. I am willing to help people figure out why things don`t work. I understand motor controls, transformers and machine wiring. I do not teach basics to novices or do free design work.


Experience in the area I have 44 years experience in residential, commercial and industrial electrical construction and repair, 480 volts and below. This is not to be confused with one week repeated two thousand times.

44 years experience in residential, commercial and industrial electrical construction and repair

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