Originally Posted By: jonofrey
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Anyone know of a reference that speaks to wiring run within a return air plenum?
Thanks.
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Inspection Nirvana!
We're NACHI. Get over it.
Anyone know of a reference that speaks to wiring run within a return air plenum?
Thanks.
Originally Posted By: pdacey
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John,
I couldn't find anything on it. I'm interested in that also because we have homes here that have a small electric water heater in a closet below the furnace and the WH closet acts as the return air chamber. The homes that have this tend to be 10+ years old.
By the way, are you going to the TAREI seminar this weekend? I opted not to. Too much $$.
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Slainte!
Patrick Dacey
swi@satx.rr.com
TREC # 6636
www.southwestinspections.com
Originally Posted By: kwilliams
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You mean like this
Originally Posted By: pdacey
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WOW!
It also looks like you need to duck coming down the stairs as to not hit your head on the light bulb.
As Mr. Wiley once stated....Job Security!
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Slainte!
Patrick Dacey
swi@satx.rr.com
TREC # 6636
www.southwestinspections.com
Originally Posted By: rsummers
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I’m not sure if its ok but if you think about there is electrical running thru every blower compartment on units with direct drive motors. I would think that if they used the wright connectors and its air tight what could it hurt.
Originally Posted By: Guest
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I’m sure Jerry’ll have the code but the romex is allowed to pass through the return air duct, but not run along inside it… you can’t use the duct like a conduit.
Originally Posted By: rpalac
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It in it self is not illegal to run wire in a return air plenum.
The problem is the type of wire.
NEC Article 300-22 Miring in Ducts, Plenums, and Other Air Handling Spaces.
Section (B) Ducts or Plenums Used for Environmental Air.
Basically NM Or Non-Metallic sheathed cable (Romex) is not allowed. The reason being, is that if it were exposed to fire or excessive heat the molded plastic cover and wire insulating would break down. The insulation type is made of PVC. The over heating releases Poly-Vinyl Gas.
Poisonous to breath.
That is very typical and known in the electrical trade. A definite No-No.
There are some wire types that can be used. Another problem that is not very often sited is phone and Cable TV wire of the same type of outer PVC casing.
Bob p.
Originally Posted By: Mike Parks
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In a nutshell.
Nm can cross a cold air but can not run with it.
The above picture "might" be code compliant. The only way to know is to remove the panning. I'll bet it is a violation and the light was probably run before the panning was installed. I doubt if the electrician could have installed a j-box if the panning was present first.
Mike P.
Originally Posted By: jonofrey
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Robert,
Nice find. Thanks. Here's a photo of a recent inspection with a light switch wired inside the return air plenum. I recommended that the switch be moved.
http://www.nachi.org/bbsystem/usrimages/DSC01309.JPG
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Inspection Nirvana!
We're NACHI. Get over it.
Originally Posted By: Blaine Wiley
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John,
Was that in a stud cavity being used as a return air duct?
Originally Posted By: jfarsetta
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Can only run low smoke producing cable in supply or return plenums. The cable must be rated as low smoke producing. In the old days of telecom, we used to refer to communications cable with these characteristics as “teflon”
Romex is not rated for this type of use. Certain types of armor sheathed cables are, however.
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Joe Farsetta
Illigitimi Non Carborundum
"Dont let the bastards grind you down..."
Originally Posted By: Bob Badger
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Guys Mike already gave the correct NEC answer.
The NEC never as clear as you think. 
Exception to 300.22
| Quote: |
| 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. |
In a dwelling unit any type of wiring method may pass perpendicular through this type of duct made from joist or stud spaces.
As Mike also pointed out the wiring in this case does not pass through but is terminated at the light, this is a violation.
But had it just passed straight though it would be fine.
It is a funny thing about the added smoke from NM cable in a home.
90% plus of it is behind Sheetrock and the few pounds of plastic that the NM contains is well spread out. In other words you better be out of the house before the smoke from the NM becomes a problem, or you are already dead.
Look at your home furnishings, the smoke added by just one easy chair will probably be more than all the NM in the house.
It seems the fire codes should get onto the furniture makers, just food for thought.
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Bob (AKA iwire)
ECN Discussion Forums
Mike Holt Code Forum
Originally Posted By: roconnor
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Now riddle me this Batman … would the code permit that wire passing through a separate metal duct (i.e. not a joist space used as a plenum)? Does it make sense?
Couldn't resist, but the code actually says wires that "pass through such spaces perpendicular" to the joists ... that wire probably doesn't pass through.
I don't think either one is a big deal in a home though.
Just my 2-nickles
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Robert O'Connor, PE
Eagle Engineering ?
Eagle Eye Inspections ?
NACHI Education Committee
I am absolutely amazed sometimes by how much thought goes into doing things wrong
Originally Posted By: jonofrey
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Blaine,
I guess you could call that a stud cavity but it was specifically built to be the return air plenum.
Bob and Robert, Points well taken!
Joe, teflon? Never heard of it! 
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Inspection Nirvana!
We're NACHI. Get over it.
Originally Posted By: jpeck
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| jonofrey wrote: |
| Blaine,
I guess you could call that a stud cavity but it was specifically built to be the return air plenum. Bob and Robert, Points well taken! Joe, teflon? Never heard of it!  |
John,
If specifically constructed for use as a return air plenum, then (technically), no, it is not allowed. However, as shown by the above posts, there really isn't much difference between that and a stud or joist cavity, so it is not really anything to make a big deal over.
That said, it would still be technically wrong if specifically built as a return air plenum.
Unless ... you wanted to consider the framing for the return air plenum as studs or joists, then ... you can see why it really doesn't matter. It is basically meeting the 'stud and joist' meaning. This would be one of those lose-lose things.
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Jerry Peck
South Florida
Originally Posted By: roconnor
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| jonofrey wrote: |
| Joe, teflon? |
I think JF may have been referring to what some may call the plenum rated cables due to the durability/toughness of them. They have a special sheath that is both fire rated (will not wick fire through spaces) and low smoke producing (will not give off significant smoke or toxic fumes when exposed to fire). These are used a lot for longer communication cables runs in air handling spaces above "false ceilings" of commercial buildings. Very tough cables, as long as they are not exposed to sunlight for long periods ... 
About the post, my read is that the 300.22.C code exception specifically permits house wiring to pass through a joist/stud air handling space covered with metal or drywall to make it a plenum. That?s usually the only time a joist/stud space would be used for air handling in a home, and as long as the exception provisions are met it supercedes the other sections.
However, the code would not allow house wiring to pass through a metal duct, as the exception provisions wouldn't be met (it?s no longer only "joist or stud spaces") ... and I think that restriction makes sense for safety reasons. Imagine romex sitting on a sharp edge of a field cut hole in a large metal element that runs throughout the house, where there is possibly inadequate bonding or wire protection at the sharp edged hole, or that protection is dislodged (does "laundry hanger" ring a bell) ? 
I think the important provisions are that any wiring only pass through those joist or stud spaces/plenums to limit the exposed length, and that the wires not penetrate metal ducts at all ...
--
Robert O'Connor, PE
Eagle Engineering ?
Eagle Eye Inspections ?
NACHI Education Committee
I am absolutely amazed sometimes by how much thought goes into doing things wrong
Originally Posted By: jonofrey
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Robert,
I was messing with Joe about Teflon since we both have seen entirely too much of it over our lifetimes. Being familiar with low smoke cable, plenum rated cable is probably what raised my suspicions about non-plenum rated being inside the duct.
After reading the comments on this thread and the code, I don't think the toxic fume piece of this thing is a large concern given all the other toxic fume material in the home that exists.
After reading the opinions on this thread I was able to modify my report and remove the recommendation for moving the light switch (client had not accessed the report yet).
I appreciate you guys showing me the code reference and your interpretations.
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Inspection Nirvana!
We're NACHI. Get over it.
Originally Posted By: pgudek
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John,
Be aware that under TREC rules it says "Report in need of repair a return chase and plenum that are not free of hazardous conditions, such as gas pipes, sewer vents, refrigerant piping or electrical wiring."
Originally Posted By: jonofrey
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Peter,
That's a good find. My warning bells were going off but this old fuzzy brain has trouble nailing down sometimes. See you on the 19th.
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Inspection Nirvana!
We're NACHI. Get over it.
Originally Posted By: roconnor
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Be careful there, because those things may be allowed to cross a plenum (sometimes a duct too if done right), but it usually can not be run inside them for any significant distance …
–
Robert O’Connor, PE
Eagle Engineering ?
Eagle Eye Inspections ?
NACHI Education Committee
I am absolutely amazed sometimes by how much thought goes into doing things wrong