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I am in the process of slowly updating the wiring in my house. The service panel is new as of 1995 and the wiring is a mix of updates, all the original knob & tube is gone (well i did find one 5 foot run from a junction box to a receptacle that I replaced)
I found a couple of two prong outlets that had +- 15 year old 3-wire cable going to them but the ground was simply tied off. I added three-prong receptacles and connected the ground and it tested okay using my multi-meter.
Two other easily accessible outlets have older insulated two-wire cable going to them. There is no ground wire and it is not armored cable. The cable is in really quite good condition and I wouldn't see a need to replace it if it weren't for the lack of ground.
At least one of the outlets is less than five feet from a copper water pipe in the basement. I am extremely tempted to run a ground from the receptacle to this pipe and be done with it, leaving the old two-wire cable in place.
Will it work? yes the outlet will work.
Will it work as a ground? Kind of.
You will probably get a "grounded" signal from your tester, but unless the water pipe is also connected to the electrical panel, AND the water pipe is metal everywhere, you will not be truly grounded.
The ground wire from the outlet should really run all the way back to the panel and attach to the ground bus bar inside the panel. The ground bus bar in turn should be grounded to the earth. The most common way to do that is with a ground rod pounded into the ground near the panel.
Water pipes used to be used for the ground system in years past, however when plastic pipe is used, you will lose the ground.
At least one of the outlets is less than five feet from a copper water pipe in the basement. I am extremely tempted to run a ground from the receptacle to this pipe and be done with it, leaving the old two-wire cable in place.
Is this against code? Would it work?
Is this contrary to the building codes? Yes and you can view the International Residential Code (IRC) for free here Free Resources. The section referencing what you are thinking of is Section E3508, Grounding Electrode System, and specifically E3508.1.1, Metal underground water pipe.
As noted by Barking Spider if there is not a complete metallic path to ground then the Equipment Grounding Conductor (EGC, third prong) will not be properly grounded. It would only take one insulated union (connector) in the path to isolate the outlets' EGC from ground.
Even if there is a straight path to ground there are three other factors used to make the requirement in E3508.1.1. One is to prevent any future repairs or modifications to the plumbing system to inadvertently cause an isolated EGC. If the run is long enough, and/or there are resistive connections along the path (i.e. a corroded or fouled connector or badly brazed joint), then the path to ground could potentially become a much higher resistance than another unintended path. If an equipment failure occurred that energized the metal water piping it could potentially take a different path to ground and cause injury along the way.
Would it work? Maybe but it would not be the safe method to add an EGC to outlets.
thanks for the replies and the code citation in particular. does it seem silly to run merely a ground wire back to the panel? i suppose i might as well replace the whole wire with new romex. fortunately much of the electrical in the house is updated and i have a good ground back at the panel, at least i assume i do. a lot of the updating was done around 1995 by a certified electrician. i don't see any evidence that they grounded to the adjacent water piping but i will double check for a ground bar.
something i did notice is that at least two circuits are joined to a fuse inside the panel, not in external junction boxes. meaning i have two independent wires running into the main panel but on a single breaker. is this a problem?
sorry if i'm using some of the wrong terms, but hopefully that all made sense.
this is my first forray into household electric. i rewired a camper and have done a lot of cat-5 wiring in houses and businesses, but that is it. so far, electric seems pretty straightforward. i just have to remember the consequences of not being meticulous and respectful towards the power i'm dealing with.
something i did notice is that at least two circuits are joined to a fuse inside the panel, not in external junction boxes. meaning i have two independent wires running into the main panel but on a single breaker. is this a problem?
Not sure if there is a code problem with this, but I have seen it before and it worked fine in my house.
One option is to get one of those double breakers and put one of the two wires on each side. THe double breakers are two thin breakers banded together and made to fit in a single slot. Thus, a single 15 amp breaker is repalced by a double 15 amp breaker providing two breaker circuits in a single slot.
I had an older house where we had to use several of these to accomodate the number of sperately protected circuits that we needed. They are expensive compared to regular breakers, but the wiring was inspected and approved after we put them in.
Two circuits on one breaker or fuse is not a problem, IF:
1. The two HOT wires are not both connected under the same screw on the fuse or breaker. (NOTE: there are some Square D breakers that do allow for two conductors).
and
2. The number of the fixtures on the two circuits do not exceed the limit of the overcurrent device (fuse or breaker).
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