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Joined: Mar 2001
Posts: 9
T
TRS Offline OP
Junior Member
Hi all,
Though I've been reading everything for a while this is my first post. Let me start by saying that this an excellent forum, full of very useful information.

While I am that dreaded DYI'er, I'm also very conservative, try to learn as much as I can before beginning a job, and always have my work checked over by a professional.

That said, the answers to some of my questions have been difficult to find.

For example, what is the temperature rating of Romex? Is it suitable for use with halogen fixtures (box attached to directly to can) that require wiring rated to 90 deg. C? If so, can nonmetallic clamps be used on the box housing?

Another minor concern I've had is with the use of 20+ cubic inch single-gang boxes in 2X4 partition walls. The deep box brings the wires entering the box very close to the finish surface on the other side of the wall. Is this of any concern?

Your help is greatly appreciated.

-TRS

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Joined: Oct 2000
Posts: 5,392
S
Member
Hi TRS
let me take a stab at this;

300-4(d) states "installed and supported so that the nearest outside surface of the cable or raceway is not less than 1 1/4" from the nearest edge of the framing member."

so i guess as long as you use the outside entries into your deeper boxes, you are NEC compliant.

temperature rating as applied to those cieling mounted halogens seems to be something i have not grasped as yet.

i have a customer who has had me install two so far, cooked the 90deg new NM both times.

obviously i am overlooking something

perhaps others will comment..

[Linked Image]

Joined: Mar 2001
Posts: 9
T
TRS Offline OP
Junior Member
I've since re-posted this question on a more appropriate (DYIer)forum. At the time I posted here I did not realize that this was exclusively a pro's forum. Sorry for the intrusion.

Best Regards,

-TRS

Joined: Mar 2001
Posts: 9
T
TRS Offline OP
Junior Member
Sparky, no sooner had I posted by exit from this forum and you had replied. Thanks for taking the time. As long as the thread's alive and there seems to be some interest in the issue, I'll be interested to read any other responses regarding the temp issue. On the DIY forum, the general opinion seems to be that NM and NM-B or recent manufacture (i.e. last 10 years at least) is rated to 90 deg. C. In that regard, it's interesting that you're having the problem with heat.

Thanks again,
-TRS

Joined: Oct 2000
Posts: 5,392
S
Member
TRS;
you are not intruding at all. we all come here to learn. i see by your profile you are a scientist? you should visit the theory section, help keep us in line....

[Linked Image]

Joined: Oct 2000
Posts: 2,722
Broom Pusher and
Member
TRS,

Welcome to the group!

First off, there are no stupid questions that could be asked [posted] in this forum, so feel free to ask anything at all - even if it's non-electrical related. This applies to anyone reading / surfing the group.

As to the temperature ratings of the NM Cable [Romex], I'm almost completely positive that all NM Cable made since like 1995, or sooner, is rated for 90 degrees C. Max.
If this is incorrect, someone please reply to this message and correct it!

I very rarely use NM Cable, but have checked it out occasionly at Home Centers [Like the "Big Orange Box" - coining another person's nickname for The Home Depot]. The conductors inside appeared to have THHN insulation, plus the NM jacket appeared to be similar to the jackets of 90 degree C. rated cable that I used in the past.
I would verify the max. temp. by either checking the box it was in, or with the Manufacturer.

Now for the non-metallic connectors;
They will [or should] have a temp. rating labeled on them. The few I have dealt with in the past seemed to have a labeled max. temp. rating of 90 Degrees C., so verify this with a listed rating.

As to the deep boxes, your concern to the closeness of the cables in the back is valid, but not normally addressed as to the attachment to a stud would be. In other words, the typical restrictions of spacing cables is applied to where it lands on the stud, or other framing member, in relationship to it possibly being hit by a nail from drywall installation, lath installation or sheer panel installation.

I am sure that another person in this group can address this better and correct me where I am wrong, but I think there isn't any thing in the NEC restricting this part. Someone more apt to Residential work, or some of the Inspectors in the group, could verify this.
It's not that you couldn't try to do something to reduce the potential hazard - by all means please do!! Just because the NEC doesn't require something, or has little requirements for something does not mean that one couldn't try to make things a little more secure.
The NEC is first of all, the minimum requirements that are to be considered. The local codes [AHJ - Authority Having Jurisdiction], if more restrictive than the NEC, will need to be satisfied for full compliance. So Once again, the most famous catch phrase of these forums is used once again - "Verify This With The AHJ".
Secondly, the NEC is not a design manual or instruction booklet, it is just a set of agreed upon safety guidelines that are used to establish minimum safe installation requirements.
This simply means that you don't use the NEC to Engineer or Design a project's systems, but the installation it's self needs to be done within it's minimum requirements. Exceeding the minimums is quite fine, where as not meeting the minimums is a "no-no" [Linked Image]
This once again might be incorrectly worded, so feel free anyone, to correct me.

Sounds like a bunch of "run around red tape" doesn't it [Linked Image]

It begins to make sense after a little time!!

Since you are a DIY'er, please feel free to ask as much as needed before jumping into any project. We all appreciate this fact - you will get safe answers to go by [sometimes more than you expect [Linked Image] ]

By all means, if something is too overwhelming to do, or is suggested by persons in the group not to be done by you, please seek professional assistance. Use a qualified and licensed electrician to help out on the heavy duty stuff, plus to check your installations if you have doubts.

We don't want to discourage DIY work performed by competent persons on their own houses, but we also don't want DIY'ers to go out and install things beyond their capabilities.
If Electrical installs are interresting to you, please extend your knowledge base with some books or classes.

Thanks for asking and once again welcome to the group! Hope to see you in the future.

Scott SET


Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!
Joined: Mar 2001
Posts: 9
T
TRS Offline OP
Junior Member
Wow, most helpful and thanks for the welcome. Confirms my impression from reading the posts that the regular contributors are knowledgeable AND generous. I'll definitely stay tuned!

-TRS

Joined: Nov 2000
Posts: 2,148
R
Member
Scott,
The requirement that NM cable be constructed with 90°C conductors first appeared in the 1984 NEC.
Don(resqcapt19)


Don(resqcapt19)
Joined: Mar 2001
Posts: 2,056
R
Member
True enough. From what I understand, any NM Cable manufactured after 1985 is identified as NM-B. The "-B" suffix indicates 90C- rated conductors.
Quote
Originally posted by resqcapt19:
Scott,
The requirement that NM cable be constructed with 90°C conductors first appeared in the 1984 NEC.
Don(resqcapt19)


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