When is it time to rewire an older house?

alabamanicoleJuly 30, 2010

Several months ago I purchased a home built in 1962. The H.I. identified a few minor problems (which were corrected). So far I have replaced and upgraded the breaker panel to 200 amp service, external wiring placed in conduit and an earth ground added. The bathrooms, kitchen, garage and utility are on grounded GFCI circuits, much of which was rewired ~10 years ago. The basement has also been wired with grounded wire.

Existing wire is cloth-covered copper with no ground wire except on the new circuits, which are plastic covered copper.

So far so good. I need to add a couple of grounded circuits. As of now my attic has NO insulation at all, so I want to finish any wiring upgrades before I bury it in insulation. I have an electrician coming out to add those circuits and inspect all the existing wiring, but I'm trying to prime my BS detector in case the electrician smells (another) fat paycheck. Lots of old threads in this forum have helped a lot! (And yes, I would get a 2nd opinion anyway.)

But surfing the web has not been very helpful; one site said a house needed to be rewired every 20 years. (Guess what they were selling?)

I have no immediate reason to believe the wiring is inherently unsafe, and construction quality and the materials originally used on the house are very high. Barring the electrician finding any portions of the wiring which are deteriorated or damaged, is there a rule of thumb when the home will likely need to have the wiring replaced? If I knew, for example, that the wiring would likely need to be replaced in 5 years, I might do it now before insulating, or it might affect my choice of insulation type.

Perhaps I can't find a rule of thumb because there isn't one -- but just knowing that for sure would be a help.

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kudzu9

In my opinion, if you aren't having problems, there is nothing deteriorated or damaged, and the wiring is adequate for the demands placed on it there is no reason to do some wholesale replacement. I owned a house similar to yours (built in 1952), and over time I did remodels and upgraded as I went along. I never found any of the older 14-2 wiring in a deteriorated condition, or connections that had deteriorated. But I did replace it as the opportunity presented itself since I wanted to go to grounded wiring and also add some GFCIs. I ultimately ended up with every circuit replaced and upgraded. However, neurotic as I am, I never felt like there was any urgency in replacing the wiring.

If you were in a house where you had discovered some poor or incorrectly done wiring, I would have a different view, but it sounds like you have a decent quality house and you should do what is really needed. I've never heard of a rule of thumb about frequency of replacement, because there really isn't one. I have friends who are living in houses that are 80 years old with the original knob and tube wiring. It's been inspected and it's just fine.

    Bookmark   July 30, 2010 at 12:25PM
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normel

Having done many, many rewires of houses built prior to 1970, I have found the biggest problems are in the wiring to lights. It was typical to use small boxes with power fed to the light then to the receptacles, resulting in overfilled boxes. Use of too high a wattage light bulbs led to dry and brittle insulation... try replacing a light fixture and all of a sudden you have several inches of bare wire. My advice would be to rewire all the lights now while there is no insulation to deal with and before you start to have problems.

    Bookmark   July 30, 2010 at 12:44PM
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alabamanicole

Thank you for the feedback. I don't want to spend the money to rewire if it's not necessary. My alarm clock doesn't NEED a ground. :)

I will have the electrician check the ceiling fixtures while he is up there checking everything out. In the parts of the house that haven't been renovated (i.e. the bedrooms and living room) I believe the ceiling fixtures are original. Of course they still sell those same square, glass, semi-flush fixures, so I could be wrong!

    Bookmark   July 30, 2010 at 1:18PM
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brickeyee

"My alarm clock doesn't NEED a ground. ":

This.

The general use circuits in a house rarely have grounded equipment plugged in to them anyway (lights, clocks, etc.).

Making sure you have polarized receptacles (larger blade for the neutral side) is more useful, and can be done without changing any permanent wiring in the wall.

Just replace the receptacle with a polarized receptacle (making sure to put the hot and neutral on the correct screws).

1982 Nm cable should have plastic insulation on the wires (older stuff can be rubber) and unless overheated by a light fixture should be fine.

Newer fixtures can cause problems with the temperature rating of the old insulation (old was 60C, new is 90C).

It is often enclosed fixtures that require the 90C insulation, while more open ones will be fine with 60C insulation.
You need to watch what fixtures you purchase.

It is simple to add another box in an attic to feed the fixture box with 90C wire from a from or so away.
Without an attic it is harder since a junction box cannot be hidden above a finished ceiling (access from the attic is fine).

Computers and other electronics often need grounds (and surge protection equipment also needs a ground) but you can add them as needed to just those locations.

    Bookmark   July 30, 2010 at 5:43PM
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abbey_cny

The problem with the wiring to lights that Normel mentioned is exactly what I found in my older (1950) house. Two of the ceiling fixtures were enclosed fixtures, and both failed shortly after I moved in. When new light bulbs didn't fix the problem, I called in an electrician who explained what happened pretty much as Normel did. I had the wiring to the fixtures replaced, and replaced both fixtures with open type fixtures. No problems since.

    Bookmark   July 30, 2010 at 7:49PM
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scottys

Normel, so right you are. It was 3 years after I bought my house that I had enough money to gut the circa 1953 kitchen and start over...The flying saucer looking kitchen fixture was flush with the ceiling and covered with thick glass. Inside there were 4 sockets each containing a 60 watt bulb which I continued to use when replacements were needed. Well during the remodel, when the fixture was removed, the wires literally disintergrated when they were touched both inside the fixture and inside the ceiling box.
Now that the remodel is complete I chose a semi-flush schoolhouse type of light that will not overheat the wires inside the ceiling, which of course were all replaced.

    Bookmark   July 31, 2010 at 9:23AM
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inox

You might find this previous thread helpful:

Here is a link that might be useful: Minimum 90°C Supply Conductors

    Bookmark   July 31, 2010 at 9:32AM
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alabamanicole

"Making sure you have polarized receptacles (larger blade for the neutral side) is more useful, and can be done without changing any permanent wiring in the wall. "

That's already done.

The 3 outlets I am adding are for the office (computer), the home theater PC, and a GFCI circuit for the fish tank (which is currently being annoying in the kitchen.) Otherwise I really can't think of any other places it's necessary to have a grounded outlet.

"1982 Nm cable should have plastic insulation on the wires (older stuff can be rubber) and unless overheated by a light fixture should be fine."

The house was cabled in 1962. The cable is copper and looks like it is wrapped in cloth; the insulation is probably rubber.

Now the 60c vs. 90c thing is confusing. *NO* UL listed fixtures are sold now which are rated for 60c. If I understand my research correctly, that means no fixtures in the house can be safely replaced without at least partially rewiring those lines? I have a lot of fixtures I want to replace, but not right now.

Also, do I now need to worry about the flush-mount schoolhouse fixtures they installed in the kitchen? Not only are they enclosed, but it gets super hot here in Alabama up in that attic.

"It is simple to add another box in an attic to feed the fixture box with 90C wire from a from or so away. "

But I still guess it'll be $100 each. That adds up in a hurry.

    Bookmark   July 31, 2010 at 6:02PM
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inox

The NEMA workaround described in the pdf to which I linked suggests replacing NM cable with NM-B cable for at least 18 inches from the center of the light fixture. The problem is not that the newer lights draw so much more current, but that the heat they put out eventually cooks the insulation on the wiring closest to the fixture, and in time, the insulation could simply come off, and lead to arcing, which in turn, could start a fire.

Here is a link that might be useful: Use of Type NM-B Cable for Wiring of Residential Lighting Fixtures

    Bookmark   August 1, 2010 at 12:04PM
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brickeyee

"The house was cabled in 1962. The cable is copper and looks like it is wrapped in cloth; the insulation is probably rubber."

PVC plastic started right after WWII, still cloth covered.

If you look at the insulation under the cloth over braid (used to mark wire color) you may see slightly rough rubber or smoother PVC plastic.

Coloring plastic was being developed and the testing labs had to be convinced the coloring did not affect the properties of the PVC.

If they tested one color they would only list that color PVC.

There are 60 C UL listed fixtures out there, just not at the big box stores.

You need to hunt for them.

    Bookmark   August 1, 2010 at 2:45PM
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alabamanicole

inox - I understand the work-around. I also understand how atrociously expensive it will be to have every ceiling box in the attic done. At that point, it might be worth rewiring those cable runs.

brickeye - I will keep looking online. All I have is big box here for lighting fixtures. Even if they have 60c fixtures that are UL listed, the guys in the orange aprons sure wouldn't know. Possibly the restoration companies have them if I find myself willing to pay their prices.

Thanks all; I think I have enough info calibrate my BS meter for when the electrician presents me with his findings.

    Bookmark   August 1, 2010 at 4:23PM
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