? on type of wire

[SmithBuilt]

What type of wire would have been used in the 1950's to 60's in a church/commercial building? It has a cloth cover but I cannot read the print. It's in a long conduit run and I would rather not pull it out. I really just need to be sure it is 75 deg. wire.

Was the wire back then all rated at 75 degree? Was any 90 degree?

 

[beanland]

Rubber with Cotton

Rubber with Cotton

That will be rubber insulation with cotton braid. Makes it RHW or RHH. Given the age, I would assume 75C rating. The old rubber does not melt if overheated so is considered thermoset but will char and become brittle with age.

 

[infinity]

It could be RW which only had a 60 degree rating.

 

[Dennis Alwon]

What type of wire would have been used in the 1950's to 60's in a church/commercial building? It has a cloth cover but I cannot read the print. It's in a long conduit run and I would rather not pull it out. I really just need to be sure it is 75 deg. wire.

Was the wire back then all rated at 75 degree? Was any 90 degree?

If you do not know for sure, you would need to use the 60C column. If the panels are old then the lugs are probably only rated 60C.

 

[haskindm]

See 110.14(C). Wires smaller than 1/0 should be used at 60 degree ampacity regrdless of the insulation being rated higher. You don't say what size wire you are examining, but you will probably need to assume it is at 60 degrees. If you can't read the labelling, how do you know what size it is?

 

[SmithBuilt]

RW? I've never seen any.

lugs are probably only rated 60C

That's probably true. The breaker is square d 992 series. I will check.

how do you know what size it is?

I used micrometers and determined it was exactly 102 thousands of an inch diameter. Or 10ga.

Just kidding. It just looks like #10.

In light of the fact the breaker is probably 60C I will have to ride back to the job site and look again. Something I should have looked at the first time.

Thanks for the help.

 

[Michael15956]

Guys,

This tread prompted this question.

If installing a new light fixture on the said wiring or any wiring rated 60C or 75C and the light fixture requires 90C wiring. Is there any other option then rewiring the whole circuit?

Michael

 

[infinity]

Guys,

This tread prompted this question.

If installing a new light fixture on the said wiring or any wiring rated 60C or 75C and the light fixture requires 90C wiring. Is there any other option then rewiring the whole circuit?

Michael

Yes, install the old cable in a junction box and splice on a piece of 90 degree cable to feed the new fixture.

 

[Dennis Alwon]

See 110.14(C). Wires smaller than 1/0 should be used at 60 degree ampacity regrdless of the insulation being rated higher.

I disagree with this statement. If the wire insulation and terminals are rated for higher temp. then you can use the 75C rating on wires smaller than 1/0. Read all of art 110.14 esp. (C)(a)(3)

 

[Michael15956]

Yes, install the old cable in a junction box and splice on a piece of 90 degree cable to feed the new fixture.

Thanks Trevor,

There's no problem splicing the 90C wire to the 75C wire at the j-box?

At the light fixture connection where 90C wire is required, is the reason because of heat build-up from the light?

 

[infinity]

Thanks Trevor,

There's no problem splicing the 90C wire to the 75C wire at the j-box?

At the light fixture connection where 90C wire is required, is the reason because of heat build-up from the light?

Yes, the heat generated by a light fixture can deteriorate lower temperature wire over time. This is especially true for old rubber conductors.

 

[haskindm]

I disagree with this statement. If the wire insulation and terminals are rated for higher temp. then you can use the 75C rating on wires smaller than 1/0. Read all of art 110.14 esp. (C)(a)(3)

Dennis,
You are of course correct. I assumed the rest was a given. IF all the terminations are rated 75 degree and the wire is rated 75 or 90 degree then the 75 degree column may be used. When there is any doubt as to the rating of ALL terminations the 60 degree column must be used.

 

[Michael15956]

Dennis,
You are of course correct. I assumed the rest was a given. IF all the terminations are rated 75 degree and the wire is rated 75 or 90 degree then the 75 degree column may be used. When there is any doubt as to the rating of ALL terminations the 60 degree column must be used.

I agree but now have this question. Does this also apply to NM Cable? 334.80 limits the ampacity to 60C. The conductors' insulation inside the jacket are rated at 90C.

 

[Dennis Alwon]

I agree but now have this question. Does this also apply to NM Cable? 334.80 limits the ampacity to 60C. The conductors' insulation inside the jacket are rated at 90C.

Michael is is quite simple really. If you use nm cable the temp. rating is 60C regardless of the fact that 90C is inside. The 90C column can be used for NM cable for derating purposes but it can never be used higher than 60C.

Let's say you have 4 nm cables 12/2 inside a 2" PVC pipe being used as a sleeve and the pipe is 10' long. Table 310.15(B)(2)(a) derates the wires to 70% but 12/2NM can be used at the 90C (art. 334.80) #12 at 90C is good for 30 amps -- take 70% and you still are good at 21 amps so you can still use a 20 amp breaker on the circuit.

 

[Michael15956]

Dennis,

Thanks, I understand your post.

What I don't understand is section 110.14(C)(1)(a)(3), "Conductors with higher temp. ratings if the equip. is listed and ID for use with such conductors."

Originally Posted by haskindm
Dennis,
You are of course correct. I assumed the rest was a given. IF all the terminations are rated 75 degree and the wire is rated 75 or 90 degree then the 75 degree column may be used. When there is any doubt as to the rating of ALL terminations the 60 degree column must be used.

Section 110.14(C)(1)(a)(3) seems to be in conflict with 334.80?

Hope you can understand where my confusion is.

Michael

 

[Dennis Alwon]

Dennis,

What I don't understand is section 110.14(C)(1)(a)(3), "Conductors with higher temp. ratings if the equip. is listed and ID for use with such conductors."

Section 110.14(C)(1)(a)(3) seems to be in conflict with 334.80?

Hope you can understand where my confusion is.

Michael

I see your confusion but art. 334.80 will override 110.14(C)(1)(a)(3). Art. 110.14 is talking about conductors rated at higher temp. but since NM cable is limited to 60C then this section will not apply. If you were to run thhn wire in conduit and the terminals were rated 75C then you could use the 75C column to determine the ampacity of the wire.

I am not sure why NM is limited to 60C but 334.80 says it is, so we cannot use the 75C column.

Think of it like this--- no restriction--- thhn (90C) wire -- we use the 75C column if our terminals are rated 75C. No problem. Now the code puts a restriction on our install because we used NM cable. NM cable (60C) now the thhn wire inside the jacket is no longer rated 90C so we cannot use the higher temp. rating except for derating.

Hope this helps.

 

[Michael15956]

Thanks again Dennis,

But, not letting you run just yet!:smile:

I though that only NEC Chapters 5,6,7 can modify Chapters 1-4?

334.112 mandates 90C conductor from 310.13. So THHN could be placed inside the NM jacket by the manufacture. So, a person could remove the outer jacket of NM-B and place the conductors in conduit to run them at the 75C or 90C column?

 

[Dennis Alwon]

I though that only NEC Chapters 5,6,7 can modify Chapters 1-4?

Chapters 5,6,7 can modify chapter 1-4 but sometimes section in the first 4 chapters put different restrictions on certain events. I also don't necessarily view art. 334.80 as overriding art 110.14. It simply says that NM cable is not rated 75C. Not any different than the NEC stating that TW insulation is rated 60C thus it cannot be used at the 75C rating either.

334.112 mandates 90C conductor from 310.13. So THHN could be placed inside the NM jacket by the manufacture. So, a person could remove the outer jacket of NM-B and place the conductors in conduit to run them at the 75C or 90C column?

Yes and no-- technically you could do that but you can also be turned down for it because the wire in NM cable is not marked. How would an inspector know if the wire was truely thhn? Also it would cost more to do it that way. I am sure it is done and I know I have read somewhere at this forum that certain jurisdiction do allow NM cable to be stripped and used in carflex as the feed from the disco to an a/c unit. But it is not really legal but it is safe.


Sorry but past my bedtime-- I'll check in in the morning. Later