Bad Grounding for Telephone, TV, and Power
Dear Mr. Electrician: My neighbor was blown out of her chair when lightning hit her TV. How can I prevent that from happening to me?
Answer: Basically everything needs to be properly grounded and bonded in such a manner as to provide a good direct path for lightning to flow to the earth. The photos below depict an actual job of mine correcting the grounding for a 1940’s single family detached house. Article 250 in the concerns grounding and bonding. Some relevant sections are: 250.8, 250.52, 250.90, 250.94, 250.104. Also read article 800.100 on grounding communication circuits and 820.100 which concerns the grounding of cable TV systems. National Electrical Code
This is how I found the TV and telephone lines grounded. It turns out that this pipe was not connected to anything. It was in the ground only a few inches and contained a piece of cut electrical cable, the remains of which is protruding from the pipe. Needless to say, this would not be adequate protection if lightning were to strike.
This was the existing ground connection for the cable TV service to the house. I installed a new #10 copper wire and clamped it to the grounding electrode conductor which was connected to the water pipe inside of the house.
Here is the newer telephone demarcation box with a ground connection that is not very good.
The arrow indicates the existing grounding terminal on the original telephone demarcation point. It was still active with it now being fed from the new outside telephone demarcation box. The existing ground wire was attached to a water pipe at a sink in the back of the basement instead of the water main near the water meter.
Inside of the main electrical panel. The arrow points to the grounding electrode conductor.
A close shot of the grounding electrode conductor as it enters the main electrical panel.
Here is a close shot of the neutral and ground terminal bar inside of the main electrical panel for the entire house. The arrows point to the grounding electrode conductor and the terminal screw where it is connected.
This is the old water main with the old grounding electrode conductor still attached. The old water main is not connected to any interior metal piping.
What I found for the existing grounding electrode connection to the new main water pipe. Note the rusted ground clamp.
The new connecting the grounding electrode conductor to the water main just after it enters the basement. water pipe ground clamp
This photo depicts the water meter and the bonding jumper connection points on each side of the meter. You can also see the old water main.
I cleaned the water pipe with to get it ready for the new water pipe ground clamp emery cloth
The same pipe section as above, but with a new water pipe ground clamp and wire attached.
This is how a water meter should be jumped with a ground bonding jumper. #6 copper wire is sufficient, but I used #4 in the picture. The purpose of the water meter bonding jumper is to maintain grounding continuity on the water pipes.
The cable TV demarcation point is now properly grounded to protect from lightning strikes. The new #10 green, copper, ground bonding conductor was brought into the house via a new drilled hole.
The new #10 green, copper, ground bonding conductor is connected to the ground terminal screw inside of the main telephone demarcation box for the house. I installed the new wire through the existing phone wire tube to avoid another hole in the wall.
I clamped the TV and telephone ground bond wires to the grounding electrode conductor that is connected to the water main pipe at one end and to the main electrical panel at the other end. As an alternative, I could have installed an as required in article 250.94 of the National Electrical Code. All of the ground wires would then just terminate together there. Intersystem Bonding Termination
In addition to the other bonding and grounding, I also bonded all of the interior metal piping which includes the cold water pipe to the hot water pipe and the gas pipe as required in article 250.104 (A) and (B) of the . If this house contained a hot water baseboard heating system with metal pipes, those would have to be bonded to the cold water pipe as well. It is very convenient to bond all three pipes at the water heater and they are accessible for the inspector to see. Please note that some areas of the country may not permit the gas pipe to be bonded. You should check with your local building department. National Electrical Code
Here’s a close shot of the same water heater bond. Each pipe was cleaned with emery cloth before the ground clamps were attached.
For more information on steps that can be taken to improve lightning protection, please read
. NFPA 780
For another article by me on the topic of grounding,