wiring in return air ducts

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jshaw

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Question: 2005 Nec 300.22 (B) wiring in ducts or plenums used for environmental air.

The heating installers in a basement panned both sides of a wall in a bathroom to create a return air duct, ceiling to floor. The 3 gang plastic Pass and Seymour box for the switches is now inside this return air duct. The wiring method is NM cable. Does anyone have an opinion as to whether this violates the above code reference?

This is a residential application.

Thanks
 
jshaw said:
Question: 2005 Nec 300.22 (B) wiring in ducts or plenums used for environmental air.

The heating installers in a basement panned both sides of a wall in a bathroom to create a return air duct, ceiling to floor. The 3 gang plastic Pass and Seymour box for the switches is now inside this return air duct. The wiring method is NM cable. Does anyone have an opinion as to whether this violates the above code reference?

This is a residential application.

Thanks
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300.22(B) states it as being a violation.
 
Can you make a plywood box around the nm cable in the corner so that it is technically outside the plenum and then do the same around the switch box.

You could just box in the switch box and possibly reroute the cables in the next stud space, if possible.
 
ryan_618 said:
The installation you describe is an "other space for environmental air", a 300.22(C) application. Either way, you can't have a plastic box in it.
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Are you saying that you can't box in the switch box with plywood to effectively keep it out of the space?
 
Dennis Alwon said:
Are you saying that you can't box in the switch box with plywood to effectively keep it out of the space?
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No, I am saying that a plastic box can't be used in the area that is for air handling. If you box around it, that area is no longer used for air handling.
 
ryan_618 said:
No, I am saying that a plastic box can't be used in the area that is for air handling. If you box around it, that area is no longer used for air handling.
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Okay, I was hoping I wasn't going to have to let my cats loose on you.:D
 
I would rather see 5/8 drywall and fire calking if you cant do it any other way.Allow it ,no way.Ijust ran a call something to this same problem.What you will have is with heat the box is being cooked.I was handed a call for bad plug /receptacle in fast food restraunt.They had a 208 20 amp receptacle and plug almost directly over a grill.Was replaced 6 months ago.Told manager that this will never last for long as heat is destroying this.Made fast temperary repair so they could run tonight.Still not sure what to suggest as final repaire but no way can we be heating up boxes,switches,outlets and plugs.
 
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Jim W in Tampa said:
I would rather see 5/8 drywall and fire calking if you cant do it any other way.Allow it ,no way.
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This is a dwelling unit Jim...what code section prohibits it? The IRC does not, if that is the code that governs in your area.

*And why fire caulk? What does this have to do with fire?
 
I always have a major problem in understanding why residential gets a relaxed code over commercial.Exsplain Lucy !!! people sleep in buildings with the least protective systems and buisnesses with hopefully wide awakes need extra protection.Am i miss understanding something about value of life ?If a fire broke out right now in my home we would likely not get harmed or major damage ,but at 3 am things are changed alot.At 3 am i try to sleep nice knowing that i personally am in control of hazards such as FPE.While nothing is perfect i must rely on faith of what is installed.My house is not romex free but 1 by 1 any opened walls turn into emt or mc.I refuse to allow romex.
 
Jim the answer is simple....money.

People do not want codes that make housing more expensive.

In my area it is the housing builders who lobby against rules requiring residential sprinkler systems.
 
I always use a metal 4 square box with greenfield going into the next stud space. Then I firecaulk the hole in the stud it's pretty fast and easy. I have seen some people use thermopan and wrap it around the box, say 10" above the box to about 6'' below the box. I just like the idea of greenfield and a metal box. Hope this helps!
 
iwire said:
Jim the answer is simple....money.

People do not want codes that make housing more expensive.

In my area it is the housing builders who lobby against rules requiring residential sprinkler systems.
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Exactly.Luckilly i can afford to wire my own a bit better.
 
I tend to disagree with the money issue this time. If you think about the rules in 300.22, they are in place to prevent items that produce noxious fumes while on fire from entering the air system. In commercial, this is a VERY real issue. You have hundreds of people trying to egress, and there is already smoke. Now make that smoke even more deadly, and see how many people get out alive.

In a dwelling unit, however, there are some things to consider:
1) the amount of people in the dwelling
2) the familiarity the people have of the environment that they are in
3) the small amount of noxious producing items that could physically be installed in such a small air system.

If you go back and re-read the post, the air handling space itself is made of wood! Why would a small amount of PVC or plastic be a big deal?
 
ryan_618 said:
I tend to disagree with the money issue this time. If you think about the rules in 300.22, they are in place to prevent items that produce noxious fumes while on fire from entering the air system.
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Ryan, IMO the NECs rules where we can use and not use NM and plastic boxes make a lot of sense.:)

When I gave Jim the money answer I was looking at it from a larger perspective.

Jim said:
I always have a major problem in understanding why residential gets a relaxed code over commercial.Exsplain Lucy !!! people sleep in buildings with the least protective systems and buisnesses with hopefully wide awakes need extra protection
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I took this question to go well beyond the issue of a box in a plenum.

If houses where built like commercial buildings (metal studs, masonry walls, cement floors) they would be much safer.

If houses where required to be constructed out of non-combustible construction the existing NEC rules would not allow plastic boxes or cable.

The reason the building codes do not require non-combustible housing is all about money.
 
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My point is mostly about people sleeping.It is them hours that concern me the most.Even if all we have in this house is 4 people and a dog they still might find getting out not so easy at 4 am.Even with smoke detectors in place a fire could be well into consuming the house before we wake up.I am not saying it will likely ever change.Florida and some other states have a bigger issue for now over insurance rates and high taxes.New house market is hurting real bad now.
 
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