View Full Version : Grounding questions: Gas, plumbing, appliances
08-13-2009, 03:27 PM
After plumbers replaced galvanized with PEX + copper piping in two parts of our house, I noticed that the ground wires for the gas line/water heater and washing machine didn't seem to "go anywhere." I have read the thread "Where to ground after installing pex," but still have questions:
1. Please define the terms "bonded" and "grounded."
2. The water heater HW line is linked to the gas line with heavy copper wire. Is this still correct? If not, what needs to be done to correct the situation?
3. The washing machine stubs aren't grounded, so far as I can tell. The above-mentioned thread states that they are supposed to be separately grounded. What is the proper procedure for doing so?
4. What is the purpose of the "ground line" that is attached to the washing machine and a screw in the power outlet? This outlet is on old wiring and, so far as I can tell, is not grounded.
Thanks for any clarification.
In its simplest terms, the original galvanized piping was a continuous metal path from all the faucets and fixtures to the earth outside the house. When they replaced some of it with PEX, they broke the paths. You would either have to install "bridges" connecting both sides of the piping around the PEX, or provide an alternate means of reaching a ground. The gas line is "bonded" to the water lines to protect it in the case of a short circuit or lightning strike. That path also has to be continuous to an "earth/ground" point. In this area, even when the piping is copper, but the water line to the building is PVC, the electric panel has to be labled "Non metallic service line", and a mechanical grounding path established independent of the plumbing system.
08-14-2009, 08:15 AM
If you have ever replaced a plug on a cord, you may have noticed that it is easy with stranded wire for one wire to "stick out". Hard to get all those little wires to stay under the screw!
And this can happen with any sort of appliance. A "stray wire" can stick out and touch a piece of metal on the case of the appliance.
Or with age, the insulation on wires can become brittle and fall off. Then you get the live wire touching the metal case of the appliance!
And there can be other malfunctions which cause the metal case of an appliance to become energized.
Anyway you touch the metal case of the appliance and you can be electrocuted. That is unless it is grounded. So for safety in a malfunction situation, appliances with metal cases have these grounded via the 3rd prong on the electric cord or via a ground wire.
Then you have appliances which connect to metal pipes. Furnace to metal gas pipe, washer to metal water pipes, water heater to hot and cold water pipes, etc.
One of these appliances could have a malfunction which energizes the metal case of the appliance AND the metal pipes attached to the appliance!
So it is possible to have an appliance malfunction, then you go into the bathroom to turn on the water faucet, then get electrocuted by the faucet! (via the metal pipe which connects to a malfunctioning appliance.)
So for this reason, it is a good idea to have all metal pipes grounded (bonded). Then if there is a malfunction, instead of the metal pipe becoming energized, typically a breaker would trip. You and your family are safe (the main idea behind electrical rules and codes).
So a safety thing basically to ground/bond all metal pipes in a house.
08-14-2009, 11:41 AM
Bonding means that two conducting items are electrically connected together at approx. zero ohms. For example, in a main panel, both the ground bar and the neutral bar are BONDED to the panel. The ground bar is GROUNDED by being connected to a wire connected to a ground rod, etc.