Antennas and Grounding

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I recently installed an antenna on my house. I was told it should be grounded. How do I do that?

The best place to ground an antenna is to the cold water pipe for the house within a couple of feet of where it first enters the foundation.
If your house uses a plastic water line instead of copper or metal, then you'll need to connect your ground wire to the common ground wire for the home's electrical system. This is usually a bare copper wire that you can find entering your circuit breaker panel. You can use a suitably listed clamp to attach the antenna ground to the building ground wire without the need to open the electric panel. NEVER cut the building ground wire; this must always be left in tact and unbroken.

In most cases, the best ground wire to use for an antenna is a piece of insulated #8 solid copper. This should be run in one unbroken length from the antenna's grounding terminal to the ground point you've chosen as described above. Be careful not to make sharp bends in the wire when you install it, as this may impede the flow of any fault current back to ground.

My main water line sprung a leak. The plumber wants to put in a new plastic one. My house is currently grounded to the existing metal water pipe. Is it ok to leave it grounded to this pipe, even if the pipe is disconnected from the meter?

Well, the ground wire on your water line is possibly serving more than one purpose. First of all, it is necessary to bond all metal plumbing in your house to the main electric panel. This allows the circuit breaker to trip if fault current accidentally energizes the pipe. The water bond must be installed on the pipe at the point where it enters through the foundation wall. Secondly, if your house is more than 20 years old and the water pipe entering your house is metal, then it may also serve as your primary grounding electrode. If the pipe to be replaced is an underground section, then you will need to drive an 8’ ground rod to serve as the primary grounding electrode.
If the section of pipe to be replaced is inside the house, then a bonding jumper must be installed across the non-conductive portion of the pipe. The size of this jumper is determined by the size of the electric service entering the house. For a 200 amp service, generally a piece of #4 copper, insulated or bare, will suffice.
Incidentally, there should also be a bonding jumper across your water meter, as this also is considered a break in the continuity of the pipe, even if the meter is made of metal.

I grounded my electric service to the house’s incoming copper water line. My inspector failed it. Why?

Years ago, it was acceptable to use the incoming metal water line as the grounding electrode for your house provided it had at least 10 feet contact with the earth. The Code today (2011 NEC) specifies that if your metal underground water pipe is used as a grounding electrode, then it must by supplemented by an additional electrode (such as a ground rod). You can reference this in the Code under section 250.52 and 250.53.


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