1940 residential wiring condition

[powerplay]

I was asked if wiring in an 1940 home was worth saving while the drywall had been removed. I think the blue sheathed copper wires in metal boxes were original and it and it appeared to be in excellent condition. A megger could help shed light on the condition, but could it also damage old insulation? ..also wonder how long the old wiring is supposed to last. It is due to change, but curious if no renovation was being done, how long would this old wiring be good for?

 

[electricguy61]

It likely doesn't have a correctly sized grounding conductor, which would make it unusable for connection to anything.

I believe it should be replaced.

 

[infinity]

I agree, if the walls are open the old junk should go.

 

[Sierrasparky]

The older wiring will not be rated for 90 deg C at a fixure outlet required by todays lighting fixtures. This could be a problem when you change the fixures.

If the walls are open replace what you can at least the switch legs. Certainly add more circuits. Panel upgrade too.

I know the while you are doing this syndrome can get expensive though.

 

[gndrod]

1940 wiring

1940 wiring

Hard to believe a 1940 house, in most cases, does not have K &T especially in attics. NEC 394.12(5) does not permit K & T in hollow walls, ceilings and attic extensions that have loose, foamed or blown-in insulation that envelops conductors.

 

[powerplay]

I was informed it was an 1943 house and there was no insulation in the walls...maybe replaced with blue cable? When did copper romex/loomex start being used?

 

[K8MHZ]

I was informed it was an 1943 house and there was no insulation in the walls...maybe replaced with blue cable? When did copper romex/loomex start being used?

My house is circa 1942. Asphalt covered NMS makes up the vast majority of the wiring. There are some short K&T runs in the basement and detached garage. (now disconnected). There is no plastic sheathed NM except that which has been recently installed.

I don't think plastic sheathed cable was available in 1943.

 

[stevebea]

A megger could help shed light on the condition, but could it also damage old insulation?

A very good question.... I would like to hear some forum members opinion on this subject.

 

[iwire]

I agree, if the walls are open the old junk should go.

I agree, now is the time.

 

[K8MHZ]

I agree, now is the time.

So does the City of Muskegon Inspection Department.

If the walls are opened, all wiring has to be brought up to current code and any wiring that is unsafe, damaged or in bad repair must be removed and replaced. That means any cable or wiring type with no EGC must go.

 

[powerplay]

this blue sheathed cable has a copper bond in it... apparently not 90 degree rated insulation ?

 

[kwired]

So does the City of Muskegon Inspection Department.

If the walls are opened, all wiring has to be brought up to current code and any wiring that is unsafe, damaged or in bad repair must be removed and replaced. That means any cable or wiring type with no EGC must go.

Does that apply to all wiring in the wall? What about cables that just pass through like some home runs or switch legs and only part of the circuit is exposed by opening the wall in question?

 

[K8MHZ]

Does that apply to all wiring in the wall? What about cables that just pass through like some home runs or switch legs and only part of the circuit is exposed by opening the wall in question?

I'm not sure. I have only done entire re-mods. That is a good question, though.

 

[al hildenbrand]

this blue sheathed cable has a copper bond in it... apparently not 90 degree rated insulation ?

Can you post a picture(s)? This doesn't sound like anything I've run into.

 

[al hildenbrand]

When did copper romex/loomex start being used?

Nonmetallic Cable, as a wiring method, predates your 1943 house by over two decades.

So does the City of Muskegon Inspection Department.

If the walls are opened, all wiring has to be brought up to current code and any wiring that is unsafe, damaged or in bad repair must be removed and replaced. That means any cable or wiring type with no EGC must go.

Unless this is actually written in the local ordinance, what would prevent one from adding the EGC?

Does that apply to all wiring in the wall? What about cables that just pass through like some home runs or switch legs and only part of the circuit is exposed by opening the wall in question?

I'm not sure. I have only done entire re-mods. That is a good question, though.

Every once in awhile I'll get involved with someone who is trying to use everything that is already there, and only add what is missing to bring the job into compliance with the current Code. Almost always, the desire to reuse the old wiring comes from a misguided attempt to control cost.

It's the little things, about the Code, that tend to make the reuse of the old wiring impractical. I'd say the most common sticking point is box volume calculation. Most of the 1940s wiring I've seen uses a lot of steel wall cases that are 3" x 2" x 2?" and they are defined in Table 314.16(A) as having only 12.5 cubic inches.

To pay me to rebuild a wall case, to reuse the old cable, is more expensive than to have a demo guy remove everything and let me install all new.

But sometimes the old method used 4" x 4" x 1?" with plasterrings, sometimes the method is flexible metal conduit or another raceway type. These tend to be more practical to reuse, but not always.

 

[K8MHZ]

Unless this is actually written in the local ordinance, what would prevent one from adding the EGC?

I was told by our local inspector that Michigan now requires everyone to be on the same set of rules, specifically the 08 NEC and the 09 MRC.

So, if there is any deviation from the NEC, it will be in the MRC. Localities aren't supposed to be able to make up their own rules any more.

Even if it was legal just to pull an EGC, you would have to find someone else to do it. That's not my style of work.

If the questions arise on partial re-mods, it's simple. Just get the AHJ there before you start for a plan approval.

When we start pulling a single wire EGC so we don't have to replace old existing wiring, all we will be doing is racing to the bottom.

 

[al hildenbrand]

That's not my style of work. . .

When we start pulling a single wire EGC so we don't have to replace old existing wiring, all we will be doing is racing to the bottom.

So this is your preference. OK.

Still, there is nothing in the NEC to prevent extending the EGC to an ungrounded outlet by a single wire.

I look at it another way. When the old two wire ungrounded method is installed to the Code of it's time, is not "unsafe", is not "damaged", is not "in bad repair", then adding the single wire EGC makes this "Code" installation safer (again, allowing that the current box volume calculation works).

 

[mivey]

It's the little things, about the Code, that tend to make the reuse of the old wiring impractical. I'd say the most common sticking point is box volume calculation. Most of the 1940s wiring I've seen uses a lot of steel wall cases that are 3" x 2" x 2?" and they are defined in Table 314.16(A) as having only 12.5 cubic inches.

To pay me to rebuild a wall case, to reuse the old cable, is more expensive than to have a demo guy remove everything and let me install all new.

But sometimes the old method used 4" x 4" x 1?" with plasterrings, sometimes the method is flexible metal conduit or another raceway type. These tend to be more practical to reuse, but not always.

That's what I have found. Not to mention the existing wire is almost always too short.

The old stuff is often more trouble to work around than it is worth. If it is open, replace it and save yourself a bunch of trouble.