Old Building Wire Testing

[rp9ball]

We have a customer who is concerned with the existing building wire. It is the cloth wrap wire installed in the old black steel conduit.
The customer would like us to test the integrity of this wire. Is that possible with this type of wire?

Is it worth the cost, since we would have to remove and reinstall all light fixtures (Some of which are original) and devices? It would be a nightmare to trace all these conduits as they are buried in the concrete floors and walls. Might as well replace the wire at that point - IMO.

This is a 3 story historical building, so that limits the install of new conduit and wire.

Just looking for any input or ideas.

Thanks

 

[user 100]

We have a customer who is concerned with the existing building wire. It is the cloth wrap wire installed in the old black steel conduit.
The customer would like us to test the integrity of this wire. Is that possible with this type of wire?

Is it worth the cost, since we would have to remove and reinstall all light fixtures (Some of which are original) and devices? It would be a nightmare to trace all these conduits as they are buried in the concrete floors and walls. Might as well replace the wire at that point - IMO.

This is a 3 story historical building, so that limits the install of new conduit and wire.

Just looking for any input or ideas.

Thanks

Oh sure it can be megged, but would it really be of benefit? That is the question.

Another big thing to consider here is this: is the system adequate as is? Most of the old legacy devices and fixtures prolly need replacing anyway.

Is this conduit old rigid or was it gas pipe that was repurposed? If the former, might just be better to go ahead and pull new wire if you can and forget the test. Not to sure about the legality of reusing the old gas pipe, though new wires run thru it would be safer than whats there now- getting around the 90's on that would be a major pitb.

 

[hbiss]

Likely you have type RH conductors maybe pulled through the old gas piping used for the original gas lights. If you remove a few devices and see that the conductors are in good shape I don't see any reason for concern. If you do find that you have to replace wiring, you should be able to pull it through the existing conduit.

I suppose if you do want to test the only way is to megger and, as you said, that would mean removing devices.

-Hal

 

[rp9ball]

It is not gas piping - unless they used the same pipe for electrical and gas back in the day.

It was built in 1927.

I'm thinking it will be harder to remove the old wire than pull in the new wire.

 

[petersonra]

I don't know what standard you would use to determine if the wire is any good if you did an insulation test. Does anyone publish such a standard?

I would want to get some dispensation from the building department on leaving the old black pipe in place. They might go along with it on the grounds that it is an historical relic and shouldn't be changed out. or they might make you replace it and put in conduit or EMT that you will then have to paint to make it look like the old stuff.

You might also be able to remove the old wiring and use the old pipe as a sleeve for some kind of cable. I would want to run that by the building dept too.

I think you will find that the old fixtures might have issues as well. These days there are guys who can repair and refurbish them and I think even UL list them.

 

[just the cowboy]

I would not megger them.

I would not megger them.

I would not want to take a chance of the 500v from the megger punching thru the insulation that is working now. Check like someone said a few spots, it is probably rubber under the cloth and even though the cloth may be soft or crumbly, the rubber may be fine.

 

[Fulthrotl]

I would not want to take a chance of the 500v from the megger punching thru the insulation that is working now. Check like someone said a few spots, it is probably rubber under the cloth and even though the cloth may be soft or crumbly, the rubber may be fine.

i'd megger it at 125 volts.

you aren't going to help something fail, and you will get
a pretty good idea how the insulation is.

lamps out of the lampholders, and the occasional odd thing
like a doorbell transformer, and you can test everything
without pulling it apart.

leave the switches closed so you test the switchlegs, and
you should be able to megger the whole thing at once.

 

[Jraef]

I would take the position that if you have no reason to believe something is wrong, it's better to leave it undisturbed and use it. That old type R wire was fairly tough long lasting stuff with rubber insulation, the cloth braid was just there to keep the rubber from "grabbing" the conduit as it was pulled. After that, it actually served no purpose, so fraying of the cloth is meaningless. Kind of like the nylon jacket on THHN now.

I ripped out some from my house in Seattle that was built in 1906 without electricity, but was wired some time in the 20s with Type R (RH was introduced in the 30s as the "High Heat" version, because R was 60C, RH was 75C). Most of it was in the ceilings on K&T, I never had any trouble with it. But when I added to the house, they wouldn't let me connect to it and it would have been too complicated to leave both systems in place.

Cool article on early building wire history can be seen here. I had heard most of this from the old timer I worked with on my house, but it's all pretty much the same info.
http://www.edisontechcenter.org/OnWireInsulation.html

 

[infinity]

Just my opinion but wiring installed in 1927 has exceeded it's useful life expectancy and should be removed, especially for rubber insulated conductors.

 

[ptonsparky]

My experience with that type of wire has been that it is dried and crumbles at each outlet box. The wire may be acceptable once it enters the raceway but that does you little good.

Are there bushings on the ends of the raceway?

 

[rlundsrud]

I agree with Tom on this. If you try to pull down a fixture the insulation may crumble away. It is all or none, either replace all of it or don't touch it. FYI, you shouldn't have any issues pulling out the old stuff.

 

[drcampbell]

... you shouldn't have any issues pulling out the old stuff.

Sometimes the cotton cover absorbs moisture and the inside of the conduit rusts. The cotton and the rust then become a monolithic matrix material that adheres the wire to the conduit.

 

[ptonsparky]

Sometimes the cotton cover absorbs moisture and the inside of the conduit rusts. The cotton and the rust then become a monolithic matrix material that adheres the wire to the conduit.

= pull harder

 

[GoldDigger]

= pull harder

Pull out the copper and leave the insulation?
Not much room to pull new wire then.

Sent from my XT1585 using Tapatalk

 

[drcampbell]

pull harder

Tried that. The wire broke before the rust let go. And since Roto-Rooter doesn't make a bit that small, I ended up replacing the conduit.
I kept a section of that pipe for show & tell, but it's lost now.

 

[rp9ball]

My experience with that type of wire has been that it is dried and crumbles at each outlet box. The wire may be acceptable once it enters the raceway but that does you little good.

Are there bushings on the ends of the raceway?

Yes, metal bushings on most of the conduits.

 

[Sahib]

Any symptoms such as frequent tripping breaker, blowing fuse, dimming lights, charring smell or shock there? A IR scan conducted? Why not refer to NFPA 70B for further guidance?

 

[growler]

Just my opinion but wiring installed in 1927 has exceeded it's useful life expectancy and should be removed, especially for rubber insulated conductors.

My experience with that type of wire has been that it is dried and crumbles at each outlet box. The wire may be acceptable once it enters the raceway but that does you little good.

If they are doing any sort of remodel or rehab on the building it's a good idea to replace wiring that's as old as this.

It's not just the wiring that needs replaced in many old buidings, the plumbing and heating systems are often just as bad.