We are remodeling a 1920"s house that has had various electrical updates previous to our ownership. At the moment we are preparing the house for a electrical overhaul by a licensed electrician. Before doing this we want to educate ourselves. There are a mixture of 3 prong and 2 prong outlets. Testing the 3 prong outlets indicate many have an "open ground". What is an open ground and how do you fix it? Does it need to be fixed?
As Sven says this means that there is no ground connected to that receptacle.
I was recently at a house where I touched the metal faceplate of an outlet while plugging something in and happened to be leaning on the radiator. I got quite a shock. In this instance the remodel clips on the outlet box were touching the outlet screws on one side which made it an accident waiting to happen. There was a ground wire in the box but it was "open" (not connected) somewhere before it got to that outlet. If the ground was connected the breaker would've tripped and someone would know that there was a problem there.
BTW, this circuit also extended into the Kitchen (lighting circuit) which made the light switch next to the sink also "live", so it could've been real bad.
Re: What is an "open ground"#17951 12/04/0206:00 PM12/04/0206:00 PM
Depending on what the electrical updates were. 1920s homes were wired with knob and tube. No ground present, at the time they felt this to be safe, and it really wasn't a bad system because the neutral and hot conductors were separated. However, updating could be a problem if what you say is 3 prong outlets with no ground. Sounds like the person just replaced an old outlet without replacing the wiring. If it were my house, I would start by replacing the fuse box to circuit breaker with new service entrance cable, meter socket,and a new grounding system. 2nd I would run new lines to all the major appliances, like the refridge, counter outlets in kitchen, washer, dryer, heating system. After that I would replace wiring to easy acess places like the 1st fl receptacles, acssesed from cellar, after that I would try to replace lighting if not to much wall ripping is involved. Then proceed to the 2nd fl, using the attic for acess to walls and lights. Could be an expensive propostion, But if you replace the service and all major appliances with new wiring, you may be taking a big load of the system depending how it was wired. Then you can start replacing the rest of the wiring as your able to. Hope this helps a little.
[This message has been edited by Wirenuttt (edited 12-04-2002).]
Re: What is an "open ground"#17952 12/04/0206:58 PM12/04/0206:58 PM
remarked; A panel from the 60's might be good if it's the old bull dog type, pushmatic took over the line in the 70's. These panels are bolt in stlye circuit breakers which hold a high A.I.C. (amps interupting capacity) which means it has a high resistance to arc faults through transmission lines. If it's a F.P.E. (Federal pacific electric) it's junk, not sure if the trash man would even take it. This fpe type had a real bad problem with the style of the breaker fitting into the panel, they would loosen up, I've seen plenty of them where the cover actually held the breakers in place. This is a fire waiting to happen, because of resistance. Loose connections make resistance, resistance leads to heat, and if the load(appliance for instance)is drawing a lot of power this could lead to an electrical fire. KNob and tube is the first electrical installation introduced to the public. It's an open insulated conducter, not sheilded like the wiring methods of today, which is attached with ceramic that nails directlly to a joist. The tubes are ceramic sleeves that when penetrating through a wood member creates a sheild. The old timers will tell you it was the best method created because the hot and neutral were separated by several inches, as to not allow shorts. About the CIrcuit breaker panel: what size main do you have? IS it a 60 amp or a 100 amp main breaker. If it's a 60, it should be updated for that reason alone. Most homes over 1500 sq. ft. with gas appliances have 200 amp services. An electrician can do a demand load calculation for you to establish what you need to have by the code book.
Re: What is an "open ground"#17955 12/05/0207:45 AM12/05/0207:45 AM
Wirenutt...we will definitly check the circuit breaker panel for the information you have given us and how many amps the breaker is. Unfortunately we do not live in the house yet. It is about 2 hours away and we intend to go there Dec 13-15. So can we get back with you? In the meantime we have removed all the plaster, sheetrock from most of the walls on the first floor and gone around both floors putting notes on the walls and ceiling on what is needed...new plug, upgrade existing plug, move this plug, switch, overhead light, etc. The upstairs will have exposed walls but the downstairs won't. Now we think we are ready for the next step which is putting together a request for bids. Do you have any advice on this? Is there a preferred method for writing a bid? Is there anything else we can do to prepare for a electricians visit to the house? We appreciate your help.
Re: What is an "open ground"#17957 12/06/0211:42 PM12/06/0211:42 PM
Just my curiousity, but isn't the reason they replace the knob and tube wiring because of inductive heating?
Doing it right does mean using the tree analogy. But if you have to live with it while the work is done, it is possible to use a GFCI to work with a 3 prong plug as long as the receptacle is labeled "No Equipment Ground". It's safer than just leaving a 3 hole receptacle with an open ground. NEC 210-7(d)(3).