Wiring ?

My house is over 100 years old and the cold air returns are simply sheet metal nailed between two joists.

I know that when running romex though holes bored in the joists according to the National Electrical Code I'd need to run type "MI" if wiring through the cold air return joists.

I was wondering it it would be OK to run conduit across the /outside/ of the return? I know that romex can only be run through holes in the joists.

Reply to
philo 
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I believe standard Romex is permitted to be used through bored holes, just as it would if it were not a return duct. See section 300.22C of NEC where they specifically exempt such spaces between joists. No need to make it more complicated.

Reply to
trader_4

This is the exception Trader is talking about

Exception: This section shall not apply to the joist or stud spaces of dwelling units where the wiring passes through such spaces perpendicular to the long dimension of such spaces.

Even if you do not want to exploit this exception, 300.22 allows these other wiring methods (besides MI)

Type MC cable employing a smooth or corrugated impervious metal sheath without an overall nonmetallic covering, electrical metallic tubing, flexible metallic tubing, intermediate metal conduit, or rigid metal conduit without an overall nonmetallic covering.

An easy fix is a short sleeve of EMT between the studs with bushings on the ends and shove your Romex through the sleeve.

Reply to
gfretwell

trader_4 wrote in news:2237ac43-dc59-4204-8134-f0e00d702aa4 @googlegroups.com:

As trader notes below, that is not actually necessary...

Of course it would. It's also OK to run Romex in conduit *through* the return, as long as it's metal conduit.

Not correct. Romex can also be run:

  • along the face of a joist
  • stapled to running boards nailed across the bottoms of joists
  • through conduit attached to the bottoms of joists.
Reply to
Doug Miller

Thank you both for the replies and helping me wade through the regulations. Now it's time for me to get to work.

Reply to
philo 

Or run a large enough conduit through the plenum to be able to call it a "raceway" instead of a conduit - which allows you to run Romex through it. I believe code also allows romex to be run through conduit for "protection"

Reply to
clare

But NOT if it is inside a plenum. (except in a conduit)

Reply to
clare

Conduit IS a raceway. (Article 100 Definition)

"Raceway. An enclosed channel of metal or nonmetallic materials designed expressly for holding wires, cables, or busbars, with additional functions as permitted in this Code. Raceways include, but are not limited to, rigid metal conduit, rigid nonmetallic conduit, intermediate metal conduit, liquidtight flexible conduit, flexible metallic tubing, flexible metal conduit, electrical nonmetallic tubing, electrical metallic tubing, underfloor raceways, cellular concrete floor raceways, cellular metal floor raceways, surface raceways, wireways, and busways."

... and this is not a plenum.

"Plenum. A compartment or chamber to which one or more air ducts are connected and that forms part of the air distribution system."

As for the original question,

Trader correctly cited the 300.22(C) exception.

Reply to
gfretwell

snipped-for-privacy@snyder.on.ca wrote in news: snipped-for-privacy@4ax.com:

Nobody's talking about a plenum here, just the space between joists which is often enclosed as a cold air return -- and is specifically excepted from those requirements by the section of the Code cited in the paragraph below. (You *did* read that before replying, didn't you?)

Reply to
Doug Miller

snipped-for-privacy@snyder.on.ca wrote in news: snipped-for-privacy@4ax.com:

It doesn't matter at all how large the conduit is, as long as it's large enough for the conductors being run through it. He's perfectly compliant with the NEC running Romex through an air handling space inside 1/2" EMT.

Reply to
Doug Miller

ote:

He's only got 3 1/2" inches. At some point you start interfering with the air flow.

Reply to
jamesgang

jamesgang wrote in news:1384a70e-1be9-4c69-9796- snipped-for-privacy@googlegroups.com:

Two points:

  1. Just ignore clare; as usual when attempting to give electrical advice, he's well wide of the mark. There simply is no reason at all to think that anything larger than 1/2" EMT is needed.
  2. The OP was asking about wiring through a cold air return between *joists*, not studs, so presumably he has at least 7 1/4" to work with (assuming 2x8s).
Reply to
Doug Miller

the plenum to be able to call

Well, I went down there the plan my work and saw that one of the cold air returns is double-wide ...so I'd have to remove the sheet metal... plus it's a long run and would require many holes.

I'm just going to run conduit, it's going to be a lot easier.

Reply to
philo 

the air flow.

Why?

Reply to
trader_4

trader_4 wrote in news:4b935964-d4d0-45a4-a372- snipped-for-privacy@googlegroups.com:

To drill through the center joist of three, obviously.

Reply to
Doug Miller

Doh! I was just picturing a wider space.

Reply to
trader_4

yep, three joists.

Anyway, I ended up talking to a friend of mine who is a retired building inspector and he gave me an easy work-around for Romex.

Though I cannot attach it directly to the joists, he said all I have to do is use a "running board" . Basically I just need to run a board across the joists then attach to Romex to that.

Reply to
philo 

A cold air return comprized of sheet metal nailed to 2 adjacent joists is considered to be a plenum. Air duct #1 connects it to the cold air intake of the furnace. Duct#2 opens to the conditioned living space - it is part of the air distribution system on the return side. Any communication cable installed through such an air return MUST be plenum rated cable by code, so I'm sure power cables would also need to be treeted as "in plenum"

Reply to
clare

You are right. I thought there was some reference to using romex in conduit where the fill ratio had to be a lot lower than with separate conductors but I've been wrong before. I know there is a fairly broad restriction on running romex in conduit - yet I know there are quite a few situations where it is allowed, and even a few where it is "required" for protection. OK - you don't NEED to use Romex - but if you use romex you DO need to protect it, and conduit is the simlest. cheapest, most effective solution.

Reply to
clare

I was thinking 3/4" was adequate for a "raceway" (or as someone else called it, a bushing) which would allow romex to be freely pulled through, yet both protect it and prevent fire and smoke from a damaged cable from being circulated through the "plenum" - or air handling system.

Reply to
clare

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