Questions after a home rewire
Hey all, long time lurker, first time poster here!
I have a couple of questions regarding a rewire job my wife and I had done on our new (old) home.
The house was built just after WWII and a home inspection found that it had a mish-mash of wiring. Some new Romex for places like the kitchen (good!), some aluminum (uh-oh), and some much older copper with no ground. The panel was a 100 amp service IIRC and was maxed out.
We paid to have a "complete" rewire done. I specifically stated a few major things we had to have corrected to the electrician doing the job.
1. Upgrade to a new 200 amp service.
2. All aluminum MUST GO.
3. Ground all of the outlets
4. Various other minor things like new circuits and outlets and such.
The service panel was upgraded to 200A, and to my knowledge all the aluminum is gone. None enters the main panel and every outlet, switch or junction I've worked on or checked is copper.
Now that I've explained that, I can finally ask my questions:
One thing that concerns me is my home's grounding. The electrician installed a new grounding rod and grounded the new box to it. However, the old system was grounded to the cold water pipes as many old homes were, and for some reason or other he left this ground wire in place.
This concerns me for obvious reasons, but I'm not touching it without talking to an expert. To make matters even more hairy, I'm not certain that this is even a valid ground anymore since a previous owner interrupted the pipes in different locations with PVC fittings. I've visually traced the pipe from where the grounding wire is attached to them (near the breaker panel) to where the pipes actually enter my home from the street, and it's not a continuous metal path the whole way - PVC fittings interrupt it.
Should I leave this connected? It is probably still acting as a ground through some convoluted path in my plumbing, but can the difference in potential between the pipes and the new rod cause issues?
The second thing I'm curious about is all of the outlets that were supposed to be grounded. I used one of those simple plug-in outlet testers which lights up to tell you of any problems and it reads that all the outlets are grounded and wired properly.
However, I opened one recently to replace a damaged outlet and found NO ground wire and old two wire copper still coming into the junction box. All of the other outlets that already existed (not the new ones he installed) are the same. No ground wire, nothing connected to the grounding screw, but the outlet still reads grounded on the little tester.
Is it possible he grounded the metal work boxes themselves? If he did so, should the outlets themselves be pigtailed to the box, or are the mounting screws sufficient? I actually don't think he did this since I've checked carefully and see no evidence they fished anything new to any of these outlets. I have a sneaky suspicion this guy "cheated" somehow to make the old outlets appear grounded to a simple tester.
I need to test these mystery outlets with my multimeter.
Correct me if this is wrong:
If they are properly grounded I should read 120V from hot to neutral, 120v from hot to ground, and 0V from neutral to ground, correct? If not, what's the proper way to test?
Thanks for any advice guys. Sorry my post is so long winded, but I wanted to make sure I gave enough info for you to help.
Did you have a local electrical inspector to check the job? Where I am, we can't get a new meter hooked up without the inspector's sticker on the meter base.
I don't know how he would have grounded the boxes but yes, they do need to be pigtailed with green wire to the green screw. You can purchase the pigtales with a screw already in one end to be screwed into the back of the box.
Our inspectors also require grounding to the metal pipes, along with the ground rod. Your metal pipe could be made continous by clamping short wires (the same size as your ground rod has on it) across the plastic fittings. I advocate any mechanical ground that is available; in addition to the ground rod. Your electrician may be in for some liability, depending on your local codes. It sounds like he has set up an unsafe system there.
Thanks for the reply Glenn!
It was my understanding that the project was inspected, but I haven't checked for the inspection sticker. I'll do so tonight when I return home. Even if it's there, it's possible it may only apply to the new service connection and breaker panel, not the entire house re-wire.
The reason I'm not sure if it was inspected is because the way this was job arranged was a bit unorthodox. When we closed on the house, we had no choice but to leave town the day after we signed due to my wife's job. While we were gone our realtor gave the electrician access to the house to do the job and checked in on him and his crew while the work was preceeding. The last of the job was being finished up the day we got back and checked in. Up until this recent discovery, I had no cause to complain about the work or service. The electrician even came back by the house once or twice just based on one or two simple questions I had regarding certain minor issues which he probably could have just answered over the phone.
As far as pigtailing, I don't think there's any sort of ground connect to the outlet receptacles. They're metal boxes (all the old ones I've checked so far anyway), but it's not BX cable and there's no grounding wire, so pigtailing to the box won't do anything will it?
BTW, how on earth do you think he rigged them this way? :confused:
As for grounding the disjointed sections of the pipe, I'll get that done ASAP. What size of grounding wire should I use? As I mentioned our service is now 200 amps. The copper grounding wire on the main box looks pretty substantial - I'm guessing 4 or 6 guage. Is there a standard size I should purchase?
Also, is there any danger in having the cold water pipes serve as a ground? In other words, could the plumbing in my house become energized in some way?
I'm all for caffeine and other good ways to wake up in the morning, but I'll pass on a high voltage shower! :eek:
Thanks again for the advice!
There is no way to be electricuted in your shower due to a ground wire attached anywhere on your plumbing.. Short of a lightning strike:)
If the water in your shower is sufficient conductor to carry electricity, then it would also be sufficient to bridge the plastic pipe sections all the way back to the water main at the street.
Code requires your plumbing to be grounded.
Pigtails to the box will do nothing if the box is not grounded.
Thanks Square, just making sure. I recall reading a story a long while back about an apprentice plumber being electrocuted when cutting out old cast iron, and it stuck with me.
Just to be sure before I begin another project - the only proper way to ground these outlets is to run new grounded Romex to them that is properly grounded at the main panel, correct? In other words I'm not missing some trick of the trade?
Thanks again for all the advice guys!
Go to your meter base outside. If it is a new, 200amp one there should be a sticker on it. I hope they didn't use the old existing 100amp meter base with a 200amp panel.
If the common wire is used as a ground it can fool a plug-in electrical tester; however, when there is power being used in that outlet, the common (white) wire becomes a current-carrying wire. This could be a dangerous situation.
In some cases inspectors will allow existing work to stand, thus you still have a 2 wire system. If, by some freak circumstance, the boxes are actually grounded a ground wire (green) should be connected to the outlet's green screw and there is one or more holes in the box to screw the other end into.
The plumber was most likely shocked by his power tool, not the wiring being grounded to the drain (cast iron) pipe. The plumber became the ground, since electricity takes the easiest route. I think #4 bare copper wire will work for the jumpers over the plastic fittings.
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