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DW and I are moving into a home shortly with knob and tube wiring. Some of the receptacles are beat and need replaced. Anything I should know or look for before I replace some of these. I believe the wiring is copper, but I will check for sure to see if it’s aluminum. The house was built in 1941 during the war. As always, thanks in advance for your advice and input.
Gary
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The first thing to look for is a prayer book.
After that, I would look for the right fuse to remove before touching it.
If you are a DIY, the next thing you'll be looking for is an electrical contractor.
Hope you don't mind the humour
*Replacing the receptalces is a good idea. But be aware that the existing wire and its insulation can be brittle. I often add a pigtail of modern wire to the old ones because 1) the old ones are often too short (by current code you need 6". 9" is better), and 2) one does not have to manhandle the old wires as much that way.When I add those pigtails, I sand the oxide off the old wire with emery cloth or plumber's sand paper till I have bright, clean copper showing. Twist the wire nut tight with pliers and gently push the old wire to the back of the box. Now you have just the new wire to work with and you can feel safer bending it all around.Note that if you don't have a ground wire nor grounded connduit, then you can't put in a grounded plug. You should install 2-prong plugs. Better yet, install a 3-prong GFCI receptacle. It is allowed, is safer, and much more useful. Downstream receptacles can then be the regular 3-prong style.I never use the 39 cent receptacles that hold 14-gauge wire with a piece of spring steel. Even more so with old wires, spend the $1.29 per receptacle to get one with decent screw terminals. -David
*Don't want to be cruel but part of the cost of the house should be to ensure that it's safe for the occupants. If you can't afford to buy this house AND upgrade the entire electrical system then you should consider not moving in.Changing the loads on unknown circuits will cause overloads and will cause fires. These old wires are normally bare and against combustionable very dry wood studs and joists.Gabe
*Gary,While knob and tube was okay in it's day it is woefully inadequate for today's needs.I'm sure the house doesn't have enough circuits, and there is no equipment grounding conductor for personal protection.It needs re-wired.
*Gary,You will get a wide range of opinion about knob and tube.It is invariably old, and has sometimes been abused. Overlamped lighting fixtures produce too much heat and can ddamage the insulation; over extented circuits and/or burying the K&T in thermal insulation can do the same.Apparently some areas of the country have problems with the insulation surviving that long, but in my area it seems to be abused wire that has those problems.It will be copper; I seriously doubt if any aluminum K&T exists in this country. (Technically, you could wire K&T style when aluminum wiring was being used, but It just wasn't done; kind of like getting a buggy whip with your Ford Taurus.)Some older copper wiring looks kind of like aluminum because the copper was plated in nickel(?) to prevent corrosion from the sulphers in the insulation.Many people would advise upgrading from K&T.IMO, if they added insulation in the attic, check closely and carefully for K&T buried in the insulation, and replace it if found.
*Don't be scared. Knob and Tube is fairly safe. But hey, what do I know, I am a carpenter, not an electrician. My house is wired with the stuff, and here is what I do, after consultation with my electrican.Knob and Tube is basically 11 guage wire, thicker than most wire in modern homes (this is good). The insulation is cloth, and if in tact is fine. The insulation is tender, and if knocked around, can fall off and be dangerous. Thankfully, most insulation will stay in fact unless it is moved around, which generally occurs only in the receptical boxes.Thankfully, the two leads are out in the open and won't heat up, and are separated by 20-12 inches in the stud cavity, so shorts are darn near impossible.When the stuff blows, it is usually in the receptical box.I usually tape up the separate leads in the box to prevent the insulation from crumbling away.I usually try to find a ground somewhere in the basement or attic (cold water pipe?) or run one from the service box and feed grounds into the recepticals.Splices can be problematic. Under our Code, any splice must be in a box, and there are no longer any clamps that fit knob and tube to place it into a box to splice. What I do is wrap both leads in several layers of tape and feed them through a Romex connector with both leads further cushioned by some scrap rubber sheathing from the Romex. Connections in the box as usual, with wire nuts.If you must splice and can not find an accessible box, then Code says you must go back and make the connection at the service box. I have never had a problem with Knob and Tube. I can't say it is a joy to work with, but if you deal with it properly, you can get by.
*Thank you all for your replies. I will look to see which receptacles need replaced the most. Gabe, in a few months I hope to relace all the wiring and upgrade to 200 amp service. David, if I put in a GFCI receptacle, all the other receptacles downstream still won't be grounded, so how is this advantageous to me?? Not trying to be a smart ass, just wondering how that helps. Thanks to all of you! Anything else I should be thinking about?? There was a 60 amp breaker box added in the laundry room for washer, dryer, furnace. Gary
*Good to hear. Have a licenced electrician do a load test on your circuits to make sure they're not already overloaded. Only takes a little time and gives great piece of mind.Gabe
*Been there, done that, never even got the darn t-shirt!I moved into a house with a nice 100 amp circut box and all the overhead lights were still knob and tube. Almost all the outlets were new romex and grounded. Seems a former owner started the upgrade then figured out, hey, I gotta cut into this lathe and plaster. That aint gonna be fun, Lets Sell! Well, I'm here, some of my skin on my knuckles is not, and it was not fun. But it is much better. It must work good tho because it ran for over 60 yrs. I've always been told, the stuff will run forever, just don't move it around alot and damage the insulation. The wire is very heavy, good for other uses. good luck
*The purpose of the ground (in a grounded appliance or tools) is to give the current an easier path than through your body. (e.g. The wire inside the computer shorts to the case. Rather than the case becoming "hot", the circuit breaker or fuse trips due to high current passing to ground.)The advantage of a GFCI is that if any current is lost (to ground, hence "ground-fault") and doesn't return on the neutral wire, it shuts down the circuits. I forget the exact numbers, but it trips for a few milliamps within a few milliseconds. Far safer than waiting for dozens of amps to trip a circuit breaker.So a GFCI doesn't "create" a ground. But it provides better safety than a grounded plug does. And since the GFCI compares hot to neutral, it doesn't need a ground to do its job.If downstream receptacles are connected to the "load" terminals of a GFCI, they are protected as well, in the same way.But you should confirm this locally as it is your local inspector who must approve of everything you do. Conceivable, he/she might insist you pull ground wire throughout the house. But GFCI's would be acceptable to most. I feel that GFCI's would give you the most safety for the money and effort invested. (Versus the huge effort of pulling ground wires.) (And versus using 2-prong receptacles because everyone will defeat those with 3-to-2 cheater adaptors in the future.) Pulling all new wires (hot, neutral and ground) is clearly the nicest solution. But also the most labor and money intensive. -David
*Gary, if the GFCI and the downstream outlets are wired correctly, they will (should?) give protection even if there is no ground. The GFCI measures the current in the hot lead against the current in the grounded (neutral or white) wire. If there is a mismatch, then the GFCI should kick off as it means the electricity is going somewhere that it shouldn't (perhaps through you). With a grounding wire on an outlet and no GFCI, if you touch the grounding wire (green or bare) and the hot wire, you will get full current going through you until the circuit breaker decides to kick off. The grounding wire (green) is basically just a backup for the grounded wire (white) in case the grounded wire is open. The GFCI should give you much less of a shock than the standard three wire outlet if you stick something in the hot side and grab a water pipe... (I hate the "grounded", "grounding" terminology, but that is what my textbook always used...)
*This is not exactly knob and tube, but it may be related. In my 1957 vintage house, I found that the electrical outlet boxes were just slightly too small to fit in GFCI outlets. Does anyone know if there is a company that makes a GFCI outlet that is slightly smaller the the Leviton GFCI? (I also tried one from Lowe's, which was the same size. Don't remember the brand name on that one.) I would prefer not having to trash the bathroom walls to replace the outlet boxes.
*CaseyR: If the boxes are the metal nail-on type with nails through the inside of the box, they are easily removed (turn off the power, remove the cable clamp, use a small prybar and hammer to knock the box back and away from the stud, allow to fall into the wall). Enlarge the hole to fit an old work plastic box and wire away. It's a little more difficult if you have cable entering top and bottom, but not impossible.Easier still, use a GFCI breaker!
*If you want an excellent source of info on K&T wiring, get David Shapiro's book "Old Electrical Wiring".If you're going to hae the whole house rewired at once, fine. If you plan to do the rewire in phases, you can test the circuits in order to prioritize then for replacement with the Ideal "Sure-test" tester. This gizmo imposes a 15 amp load on the circuit and measures voltage drop.Cliff
*There was a post sometime back from someone who had a house w/knob and tube and a previous owner had picked up grounds from nearby plumbing pipes for his receptacles.The new homeowner developed a plumbing leak,cut into a section of pipe to replace it,and when he touched both sides of the cut with wet hands was nearly electrocuted.An appliance had a partial ground in it and was sending current back on the waterline but not enough to trip the circuit breaker. When he became in series with the current,with the path across his chest,he was almost killed.As for using GFCI's for all your receptacles: Do you know why they have a test/reset button on them?Because w/everyday use they have a relatively higher failure rate.They're complicated inside and complicated things don't stand up as well.When we start new jobs and send out for temporary power boards,(all construction recept.'s have to be GFCI protected) it's unusual to have all of them working correctly and some have to be replaced.I know there are tons of GFCI 's on jobs that aren't protecting anything.I just don't find this to be an acceptable alternative for properly updating 60 year old wiring.Knob and tube systems were not designed for the loads that microwaves,dishwashers,televisions, and hair dryers place on them.If you get the house Gary just don't do any finish work in any area that has K&T or galvanized plumbing in the walls,it really does have to come out.Good luck with the new house.Barry
*CaseyR, Would it be easier to protect that circuit upstream by adding a properly grounded GFCI receptacle to the circuuit before it gets to the bathrom? Watch the loads, though. You can't put much downstream load on the things. Of course, there are also GFCI breakers but whether you could find one to fit in a 1957 panel, only an electrician or a demigod could say. I am neither.
*Gary, I don't know about where you are, but our code will not allow us to put new style recepticles on an ungrounded system. When we have customers that insist on the newer styles we fill the ground slot with colored silicon to match the plug, that way nobody assumes they are using a grounded system.cheersbake
*Unfortuntely the existing panel is Federal Pacific, which I need to replace as soon as I find the time to get through the permit bureaucracy. I thought about doing the upstream thing, but the wiring is kinda weird. They didn't use wire nuts. The wiring is "daisy chained" using 14-2 cable which they stripped the outer sheath way back and they then stripped a one inch section about three inches back and twisted this with the end of the next leg of the daisy chain. This splice was then soldered and covered with vinyl electrical tape. The end of the one lead was left with about two inches of insulation and then the last half inch was stripped and inserted into a backwired three wire outlet (which I have replaced with two wire outlets).I thus couldn't figure out which was upstream and which was downstream without cutting some wires which would then necessitate opening up the wall and adding a junction box because one of the wires would then be too short... For the bathroom itself, I could have installed GFCIs because they stripped about an inch of insulation in the middle of the wire and then looped it around the screw on the outlet - the part hooked on the screw was part of the continuous wire. This would have given me enough wire to backwire a GFCI. As soon as I get things sorted out, I will be renting the house out, so I don't know how much I will be able to do myself under Calif. code until I move back in.
*Gary,First my disclaimer - I am not an electrician, nor do I play one on TV. I did work with a good electrician once that checked my old knob and tube wiring and recommended that we put in a new meter base and new service entrance with a 150 amp outside panel under the new meter base. We ran new wire to all of the heavy-load appliances (range, water heater, central heat and air unit, etc.) and had a 60 amp breaker with new wire running into the knob and tube panel. The K & T then became a sub-panel, powering only light circuits and the outlets. We even put the bathroom wall outlet on a new circuit, for sake of the 1600 watt hair dryer.This was 15 years ago, and all is well.Good luck. Greg.
*Thanks to all for the advice. I will have an electrician in within two weeks for estimates. I know this is a tough question to ask here, but what would be the approximate cost to rewire the whole house1) 3 story tall brick colonial2) living room3) dining room4) kitchen5) laundry room6) 3 bedrooms7) 1 and a half baths8) approx 1600 sq ft. totalnew panel, receptacles switches, etc. Any guesses???Gary
*No idea about the rewire....but....lots of K @ T around these parts...and even more hidden in attics feeding the 2nd floor ceiling lights......and I've been working around it for years. So...my 2 cents....added together with input from my electrician....who deals with it daily. Knob and Tube in good shape is perfectly safe. Assuming.....the biggie here....that it is fused correctly. Have the electrician check that first. If fused right.......it's fine.....as long as it's not messed with. You can even splice to romex around here. In a box. Me....I'd do the quick safety check.....K and T in bad shape.....jerry-rigged...and overloaded....is as much a fire trap as the older type construction is was used in......no fire blocking.....and that's how it got such a bad name. If deemed safe....I'd still plan on upgrading the service.....but you might not have to rush right into it. Jeff
*On the subject of rewiring, I was wondering if it made sense to place sub panels at different locations in the the house to 'feed' specific areas. Wouldn't that be easier than restringing several wires directly from the main panel?steve
*> I was wondering if it made sense to place sub panels at different locations Yes, especially with a 3 story house, it's nice to let each floor be served by a panel on that floor, so you don't have to run up and down stairs when you trip a breaker.-- J.S.
*I owned a house built in 1926 with K+t wiring to the ceiling fixtures and a pre curser to romex going to the outlets etc. Had no clue as to how to work on the wiring but found an old wiring book called "Practical Electricity and House Wiring " by Richter published in 1950. Had great illustrations on how to install, splice and run circuits in K+T. Good luck. NG