grounding a mailbox - isn't it already grounded?

Question

I live right next to some suspended power lines. My mailbox is very close to them, and anytime I touch the mailbox, I get a mild shock. It seems to me I need to do something to ground the mailbox but...it's already on a post going into the ground. Why isn't the electrical charge transferring to the ground? Is there anything I can do? (I can't move the mailbox -- any place I can put it, it will get the charge. Also the type of mailbox I need to use is decreed by the HOA.)

Based on comments and responses so far (1/20/15) it seems like the consensus on the information I provided initially is that the mailbox is well-grounded, and the shock I feel is actually a charge leaving my body that I already had. Based on this, I tested with the mailbox some more, assuming that if this was the case I would only feel the shock once and not on repeated touches. What I found was that I am only shocked if I touch the mailbox door (which, you know, is kind of required to use it) and that I feel the shock even on repeated touches. I'm thinking perhaps the door and the box are made of different materials, and the door is building up a charge that the box and post are not conducting to the ground. Any new ideas based on this additional information?

And hence the charge is discharged via the grounded mailbox. — Ignacio Vazquez-Abrams, Jan 10 '15 at 17:25
Hey @sparky, the OP stated right already "type of mailbox I need to use is decreed by the HOA". — Michael Karas, Jan 10 '15 at 18:32
Get one or make one out of wood, that looks like the one decreed by HOA. Better yet consider moving away from those power lines. — sparky Al, Jan 10 '15 at 18:44
Hi, I'm a well-grounded mailbox situated next to a house that is under some power lines. Everyday, the owner of the house touches me when checking mail and gives me a shock. The human wears shoes with elastomeric soles. How can I get the human grounded so that I don't receive a shock? Or should I lift my own ground? — Kaz, Jan 20 '15 at 23:10
@Kaz this comment is helpful how? Did you post it before the new information was added to the question? — user3006472, Jan 22 '15 at 15:26

Michael Karas · Answer 1 · 2015-01-10T18:14:50.460

In all likelihood the mail box is already a real good ground as pointed out in the comments. Your body is accumulating the charge as you are in the presence of the power line but wearing shoes that insulate you from the ground. When you touch the mail box the accumulated charge on your body is transferring to ground through the mail box.

There are several things you could try to work around this situation:

You could look into purchasing a static discharge strap and / or heel strap for your shoes. These are available for use in factories and service depots where people handle electronics equipment that is sensitive to accumulated static charge. If you had this type of strap inside your shoe where it was touching your foot or slightly damp sock and then extending to the heel clip where it touches the ground this would discharge you as you walk along the ground toward the mail box.
You could look at attaching a resistor to the mail box and then to a metal plate that was insulated from the mail box. A resistor of say 1Mohm could be used. Then each time you go to the mail box you would touch the metal plate first. This would help to discharge your body before you touch the mail box. The resistor would slow down how fast the charge on your body dissipates and eliminate the shock sensation.

A final comment.

Some people are more sensitive to this type of situation than others. There are even folks that believe that living in the near vicinity of a high tension power line is unhealthful. You may want to investigate and learn more about this subject. It may help you to fully access the situation and determine if folks in your household are adversely affected by the high tension power lines.

grounding a mailbox - isn't it already grounded?

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