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Author Topic: !970 [Maybe 1950s?] House. No Grounds.  (Read 8496 times)

Kevin Maxwell

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Re: !970 [Maybe 1950s?] House. No Grounds.
« Reply #20 on: August 03, 2018, 01:12:38 PM »

50’s and later puts you into a confluence of wiring types.  If you’re lucky it’s flexible metal conduit (FMC).  Also commonly called BX.  You may also have early MC which may have a very thin “ground” wire.  You could also have early type NM (commonly called romex).

FMC is the best because you can just repull circuits.  My ‘30s vintage house is all FMC and that’s made replacing wire easy.  Pull out all but one wire then tie on the new wires to the one old one and pull them in.  USE STRANDED WIRE!!!!!!!!!  I pull in a dedicated ground bonding wire because FMC isn’t an acceptable ground path. 

If you have early MC then you can get a ground path through the jacket but it’s not a good path.  Same as with the FMC.  What can happen is there can be enough resistance in the jacket to cause it to heat up and start a fire before a breaker trips.  Rare but possible.  That’s why a legit ground bonding wire is required.

Both MC and NM without proper grounds require opening walls and/or fishing new cable to get proper grounds.

Good luck!

My house was built in 1942 and has the BX wiring to a lot of places. I hesitate to try and change any outlets because the coating on the wire flakes off if you touch it. I was thinking of trying to pull new wire thru it, the type that comes in one wire per roll in separate colors. It is much thinner with a higher current capacity then wire like that used to be. I think it is called THHN. I didn’t realize that I might be able to pull only one wire of the old out and use the other to pull the new thru the BX. I have asked other people (electricians) about the idea of pulling new wire thru the BX and they said it couldn’t be done. Is there a reason not to just pull out the old with a pull line tied to the end as you pull it out? I was thinking along the lines of then pulling something thru to sweep the BX out of any coating that may have flaked off. Do you use pig snot on the new wire to pull it thru? I am tempted to pull 14gauge thru to most of the outlets.

If I move and sell this house it will be torn down and have a monstrosity built in its place. That is what is happening to all of the houses on my street. So anything I do is just for now for me. I have run new wiring to somethings in the house as they were needed. My service is probably only 60amps per phase. I could probably pop the main fuse (yes fuse) If I turned on everything in the house all at the same time. 
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Stephen Swaffer

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Re: !970 [Maybe 1950s?] House. No Grounds.
« Reply #21 on: August 03, 2018, 06:12:06 PM »

Pulling THHN through BX won't satisfy any knowledgable inspector.  Personally, I wouldn't try it-but then I am usually working for other people and have to be concerned about liability so listed/code coompliant is a major concern  Practically speaking, I'm not sure it would even work very well.  Often when pulling wire through FMC (flexible metal conduit) as it is intended you have to stretch the FMC out straight if it there is any significant length and/or you are approaching the allowable fill capacity.

BX is less likely to have shared neutrals than knob & tube.  I could be tempted to change out the panel and use AFCI breakers-knowing they'll trip if any arcing occurs.  I've mentioned this before, but I'm no longer OK with the old edison fuses being in a home.  The fuses are fine-but I've seen too many boxes with the fiber insulators disintegrating-once that happens you don't need a penny to bypass a bad (or good!) fuse.

As for the 200 amp service-if you have an electric dryer and either an electric stove or a hot water heater and central air, a 1650 sq ft house requires a 200 amp service to meet code.  You might save $75-100 by downsizing to a 100 amp-hardly worth it.
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Dennis Wiggins

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Re: !970 [Maybe 1950s?] House. No Grounds.
« Reply #22 on: August 03, 2018, 06:38:29 PM »

Check YouTube... I think you'll find your answer.

And that answer is?

-Dennis

FWIW: Tease - make fun of or attempt to provoke (a person or animal) in a playful way. 

This is serious stuff we're talking about.

-D
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brian maddox

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Re: !970 [Maybe 1950s?] House. No Grounds.
« Reply #23 on: August 03, 2018, 07:54:02 PM »

.....

As for the 200 amp service-if you have an electric dryer and either an electric stove or a hot water heater and central air, a 1650 sq ft house requires a 200 amp service to meet code.  You might save $75-100 by downsizing to a 100 amp-hardly worth it.


As someone who regularly used to spec 100 Amp 3-phase service for a few stick speakers, i can assure you it never occurred to me to DOWNsize my electrical service.  :)
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Stephen Swaffer

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Re: !970 [Maybe 1950s?] House. No Grounds.
« Reply #24 on: August 03, 2018, 10:27:26 PM »

Obviously not after the fact-but if I am installing a panel in a home like they did there is almost zero arguement to do a 100 instead of a 200.
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Erik Jerde

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Re: !970 [Maybe 1950s?] House. No Grounds.
« Reply #25 on: August 03, 2018, 11:44:41 PM »

My house was built in 1942 and has the BX wiring to a lot of places. I hesitate to try and change any outlets because the coating on the wire flakes off if you touch it. I was thinking of trying to pull new wire thru it, the type that comes in one wire per roll in separate colors. It is much thinner with a higher current capacity then wire like that used to be. I think it is called THHN. I didn’t realize that I might be able to pull only one wire of the old out and use the other to pull the new thru the BX. I have asked other people (electricians) about the idea of pulling new wire thru the BX and they said it couldn’t be done. Is there a reason not to just pull out the old with a pull line tied to the end as you pull it out? I was thinking along the lines of then pulling something thru to sweep the BX out of any coating that may have flaked off. Do you use pig snot on the new wire to pull it thru? I am tempted to pull 14gauge thru to most of the outlets.

If I move and sell this house it will be torn down and have a monstrosity built in its place. That is what is happening to all of the houses on my street. So anything I do is just for now for me. I have run new wiring to somethings in the house as they were needed. My service is probably only 60amps per phase. I could probably pop the main fuse (yes fuse) If I turned on everything in the house all at the same time.

I mis-wrote above when I said BX and FMC were the same.  BX is actually a mfgr name for MC.  I do hear FMC called BX a lot.  I try to avoid using BX or romex as these aren’t actual NEC designations.

So, if you have actual BX you can’t pull in new conductors.  If you have FMC you can.  There’s a significant size difference between them.  1/2” FMC can handle 9 12ga 90deg THHN conductors for 4 20A circuits and ground bond while being code compliant.  It can be a bitch to pull depending on how the FMC was run but it can be done.  A single 15A ckt would be cake.

I have replaced nearly all the wiring in my home because the insulation was failing in the outlet and switch boxes.  It was good as new in the conduit.  A couple locations actually had visable scorching on the backs of the switch plates.

If you have FMC and pull in new wire stranded is much easier to work with as I said above.  It’s also worth it to buy switches and outlets that you can land stranded directly to.  The standard cheapo ones you get for under a buck at the home center would need spade lugs crimped on to work.  Ground wires pretty much always need spade lugs or a pigtail.
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Bob Leonard

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Re: !970 [Maybe 1950s?] House. No Grounds.
« Reply #26 on: August 05, 2018, 11:49:14 PM »


BX is a common name for armored cable. Romex is a common name for vinyl cable.

When I bought my more than 100 year old house I had a combination of knob and tube, rubberized crap #14, and BX. There were no grounds, or so I first thought.

The service was 30amp w/ fuses and the run from the weather head to the box had been replaced with aluminum. I was denied a VA loan for $25K and the house was about a week away from being condemned. I had to replace the electrical, move to city sewage, replace all of the DWV and every inch of pipe run in this house.

There was no question in my mind that the electrical would be the first project tackled. I enlisted a close friend who was/is a master licensed electrician in 3 states, and followed his lead.

The first thing we did was run 1.5 inch EMT from on end of the house to the other with 4 11/16" boxes every 10 feet. Inside that 1.5" EMT we ran 24ea. #12 runs of THNN leaving a 2' service loop at each box. From the box we used romex to each outlet, and every outlet or switch was replaced.

Once that phase was completed (1 day) we took the next weekend to move to a new service. We installed a 200 amp box 30 20 amp breakers, 200 amp main breaker and copper cable to a new meter trough and out to a new weather head.

We took the next weekend and replaced every run and every outlet in the house including new runs for the electric stove, boiler, new kitchen circuit, bathroom, etc.

The electric company came in that Monday and ran a new main line then put in the new meter and I got the first full nights sleep in over a month. Fire scare me.

Since then there have been a lot of changes to this old house. Many circuits have been moved, many new circuits run, old circuits removed. But, everything comes from or is removed from that first run of circuits inside the 1.5" EMT using #12 romex to the circuit, or larger as needed. That's the way I would approach the problem at hand.

Also be aware that most BX will have a ground cable. For an interim step  you could provide a ground to the box if metal and change the outlet which will self ground to the box.

Replace everything and you'll sleep much better at night.
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Erik Jerde

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Re: !970 [Maybe 1950s?] House. No Grounds.
« Reply #27 on: August 06, 2018, 12:50:09 AM »

The first thing we did was run 1.5 inch EMT from on end of the house to the other with 4 11/16" boxes every 10 feet. Inside that 1.5" EMT we ran 24ea. #12 runs of THNN leaving a 2' service loop at each box. From the box we used romex to each outlet, and every outlet or switch was replaced.

24 runs of 12ga THHN in the same pipe would require a derating to 45% capacity per NEC.  I hope you’ve got all those circuits protected at 15A not 20A.  The most 12ga THHN current carrying conductors you can put in a single pipe and still run 20A OCPD is 9.
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Bob Leonard

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Re: !970 [Maybe 1950s?] House. No Grounds.
« Reply #28 on: August 06, 2018, 07:03:27 AM »

Not 40 years ago.
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John Roberts {JR}

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Re: !970 [Maybe 1950s?] House. No Grounds.
« Reply #29 on: August 06, 2018, 10:03:45 AM »

Not 40 years ago.
The physics wasn't different 40 years ago, just our understanding and rules.

15A fuses/breakers can cover most domestic branches. When in doubt do what's right.

JR

PS: Another old guy who remembers when mortgages were hard to get.  ::)
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Re: !970 [Maybe 1950s?] House. No Grounds.
« Reply #29 on: August 06, 2018, 10:03:45 AM »


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