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  1. #1
    Join Date
    Sep 2008
    Posts
    1

    Default "Updated Electrical"

    We're considering buying a 1935 English Tudor style house in Los Angeles. The current owner says she updated the electrical. In the basement, I can still see cloth wiring connected to a working light. I know she updated the electrical panel to 220, and the old knob & tube panel is cleaned out.

    What are the possible scenarios we could see with an "updated" electrical system, and what is the likelihood that we would have to lay out some major cash to bring the house up to today's standards?

    Also, is it reasonably safe to have cloth wiring and new electrical subsiding together on the same system?

    Thanks!

  2. #2
    Join Date
    Jan 2008
    Location
    Lakeland ,MN
    Posts
    356

    Default Re: "Updated Electrical"

    Quote Originally Posted by CalGirl View Post
    We're considering buying a 1935 English Tudor style house in Los Angeles. The current owner says she updated the electrical. In the basement, I can still see cloth wiring connected to a working light. I know she updated the electrical panel to 220, and the old knob & tube panel is cleaned out.

    What are the possible scenarios we could see with an "updated" electrical system, and what is the likelihood that we would have to lay out some major cash to bring the house up to today's standards?

    Also, is it reasonably safe to have cloth wiring and new electrical subsiding together on the same system?

    Thanks!
    She might have had the service updated (panel only). In most areas of the country you are required to replace all the knob and Tube wiring that is open in the basement when you put a new service in. But when it is with in a covered wall it is not required unless you are openning up the wall. So I would doubt all the wiring has been replaced. I suggest hiring a Licsensed electrical contractor to look the house over. He will also give you a good idea of cost. Money well spent and a piece of mind that your home is safe. good luck I hope it all works out
    Harry

  3. #3
    Join Date
    Jun 2007
    Location
    Fayette County, Ohio
    Posts
    5,774

    Default Re: "Updated Electrical"

    One thing that should be pointed out is that not all "cloth" covered wiring is Knob and Tube. That wiring may have been of a later vintage but before "plastic" coated and may have been in good enough condition that it didn't need to be replace. To be sure have an electrical inspection done.
    Jack
    Be sure you live your life, because you are a long time dead.-Scottish Proverb

  4. #4
    Join Date
    May 2008
    Location
    Pacific Northwet
    Posts
    1,565

    Default Re: "Updated Electrical"

    There was a transitional period where NM cable used thermoplastic insulation on the individual conductors -- just like it does today -- and a cloth braid outer jacket. Some of this NM cable even had a ground conductor. If the insulation on the wires is not rubber, and it has a ground conductor, it probably is just fine to leave it there. Anything else doesn't meet modern standards.

    The main difference as I understand it is that the insulation on modern NM "Romex" is fire retardent.

  5. #5
    Join Date
    Jan 2008
    Posts
    731

    Default Re: "Updated Electrical"

    Quote Originally Posted by Fencepost View Post
    There was a transitional period where NM cable used thermoplastic insulation on the individual conductors -- just like it does today -- and a cloth braid outer jacket. Some of this NM cable even had a ground conductor. If the insulation on the wires is not rubber, and it has a ground conductor, it probably is just fine to leave it there. Anything else doesn't meet modern standards.

    The main difference as I understand it is that the insulation on modern NM "Romex" is fire retardent.
    really?? never heard of older NM having thermoplastic insulation on the wires and cloth, not (tw) rubber and cloth or thermoplastic and paper? I know older BX had rubber insulated wires with braided cloth and paper but had never heard of a thermoplastic wire insulation under cloth in NM.

    what can you expect? brittle rubber insulation under the loam (woven cloth jackets). since you have an upgraded circuit breaker panel and hopefully no more fused neutrals going in to it suggest arc fault protection either cbs or condulets to arc fault then back to your k&t. other things to expect are old outlet boxes not deep enough for fill clearance to hold modern gfci devices or larger switches like electronic dimmer switches and fixture boxes too shallow and not supported by structure so that mounting a modern light fixture or fan to it wouldnt be safe (could fall down on you and take the ceiling and plaster along with it). other things to find are splices not in boxes and ground jumpers from boxes to the plumbing all over the place. you might also find other generations of wiring patched in like older bx, greenfield, and various generations of non-metalic cable. missing loaming between last knobs and into boxes, and cracked tubes and knobs - if they are cracked they dont work properly to isolate the wiring from the framing. there is special braided tape not thermoplastic that you use to tape so it doesn't get a heat build up.

    other things to find are insulation and other things to close to the K&T system and repair work not maintaining the distance between the hot and neutrals and not being loamed when they are closer.

    getting your own electrician familiar with K&T to inspect and check out/test the set up would be a good idea.

  6. #6
    Join Date
    Jun 2007
    Location
    Shamokin, Pa.
    Posts
    645

    Default Re: "Updated Electrical"

    Quote Originally Posted by Fencepost View Post
    There was a transitional period where NM cable used thermoplastic insulation on the individual conductors -- just like it does today -- and a cloth braid outer jacket. Some of this NM cable even had a ground conductor. If the insulation on the wires is not rubber, and it has a ground conductor, it probably is just fine to leave it there. Anything else doesn't meet modern standards.

    The main difference as I understand it is that the insulation on modern NM "Romex" is fire retardent.
    I agree with that.
    I've seen that type of Romex. I call it cloth Romex for lack of a better term.
    Romex "B" the standard of today. has a better heat rating than the original Romex.
    I'll have to "google" the specs though.

  7. #7
    Join Date
    Aug 2007
    Location
    Denver, CO
    Posts
    666

    Default Re: "Updated Electrical"

    I doubt that K&T was being used much in 1935. Although I would also guess that a gounding conductor was used with a non- metallic cable at that time.

    My biggest concern would be all ceiling or wall mounted lighting fixtures with lamps in close proximity to the electrical junction boxes in the ceiling or walls. Heat generated by the lamps could degrade the conductor insulation of conductors both with-in the junction boxes and wiring extending outside of the boxes.

    Nothing to panic about but maybe worth a check and see.

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