Plenum Box installation: SO cord

[soundcon]

We are installing a ceiling mounted projector using a Da-Lite mfg product specified for plenum use. This device is NOT UL listed. The mfg lists this product as housing an electrician installed handy box with receptacle. The cord from the projector is run through the 1 1/2" NPT mounting pipe directly into the plenum box which is an integral assembly with the projector mount, and then plugs into the provided receptacle.

The local inspector indicates that this is not in compliance with code and cites the NEC 400.8 item 5. He also indicates that the installation might be acceptable if the plenum box/mounting assembly wer to be UL approved. The mfg vehemently declares that the configuration is in compliance with code and UL approval is not required. We are in the middle.

I have two questions: 1. Is the inspector is correct that this is not an acceptable installation? 2. Is there another way to configure this where we do not have to have the receptacle exposed to the room on the ceiling side?

Any help leading us to a better cleaner installation will be appreciated. Jim

 

[RUWired]

Not much you can do other than install a 1 gang s.s. blank plate at the ceiling and hard wire the cord.

Rick

 

[e57]

Think you could point out the offending item in a picture and describe a little more of the install????

Since you mention a projector - hard to think of one in a plenum... Cords - fans, just generally not allowed..... If I were to design such a beast - it would be a gigante box sealed from the plenum - thus removing it from the effluent - I mean 'environmental air'....

 

[soundcon]

Plenum Box installation: SO cord

Here is a drawing of the installation:

 

[iwire]

Great image.

It is also a perfect example of a 400.8(2) violation.

Article 400 Flexible Cords and Cables

400.8 Uses Not Permitted

(2) Where run through holes in walls, structural ceilings, suspended ceilings, dropped ceilings or floors

 

[SEO]

I agree with iwire . Nice clear diagram.

 

[alfiesauce]

I think you'd have a hard time getting a hard wire'd installation passed as well. Why such a desire to hide the receptacle? Seems like a really clean cheap and easy way to do it compared to what you are describing.

 

[e57]

Here is a drawing of the installation:

The product your using, if this is correct, is an accessory to another mounting plate and not intended for the use decribed by that picture above IMO. A 1G cut-in box mounts so it would face below the cieling....

Otherwise I would have expected to see somethin akin to a floor access box - where the outlet inside would be accessible from below the cieling - where the cord would not be going through a hole in the cieling, but a hole designed for the cord in the box....

 

[sandsnow]

Here is a drawing of the installation:

I think this enough of a new idea to warrant careful evaluation by the AHJ. Not saying I would or would not accept it, just that I'd take a good look at it and consult with staff on it.

If it were listed for the intended purpose, then DA-LITE might have something.

 

[soundcon]

Why is this a violation

Why is this a violation

I deeply appreciate all of the response here. i design very complex and high end A/V systems integration systems but have little experience with electrical installation codes. We are increasingly required to provide specifications for installation details and so it is now incumbent on me to know more of these details.

Does anyone have a logical, non code, reason this is a problem? The cable is fully encased in metal for the entire path exactly the same as it would be if it were running into a junction box for an HVAC sysem in the same plenum space. In my great ignorance I fail to see the difference. Again thanks for any help you can give. Jim

 

[iwire]

It is tough, if not imposable to pin down original reason that a code section was added. If it was a recent change you can find panel statements about it, but older code sections are tough.

A common explanation for this section (and one that I believe) is that the NFPA wants cord to be visible and not become a permanent part of a building wiring system. The cords of the past when left untouched for years deteriorated and would fall apart when later moved. Now your modern projector will break down and need replacement long before the cord on it deteriorates but until someone puts in a code proposal in to have this changed it is what it is for all flexible cored types.

 

[soundcon]

Plenum box configuration

Plenum box configuration

The product your using, if this is correct, is an accessory to another mounting plate and not intended for the use decribed by that picture above IMO. A 1G cut-in box mounts so it would face below the cieling....

Otherwise I would have expected to see somethin akin to a floor access box - where the outlet inside would be accessible from below the cieling - where the cord would not be going through a hole in the cieling, but a hole designed for the cord in the box....

You are absolutely right, this is a brand new option provided to us and this is our first effort at using it. The original ceiling mount plate provided a knockout(s) for through the ceiling receptacle installation, the way we have had to do it in the past. The new plenum box provided the oportunity to house the receptacle out of sight.

The reason we want this out of sight is for cleaner cosmetic/installion appearance. In this particular case the customer is spending $75,000 for very nice high end audio visual equipment in a very nice clean newly decorated conference/meeting room. While electricians may have fallen deeply in love with the good old NEMA, plug that affection is not shared by the populace in general. In addition there is always the requsite excess cord that is tied up with Panduit cable ties, another installer addiction, and which promplty sags within 20 seconds of the installer walking out of the door. And actually does NOT add to the beauty of the room, contrary to some opinions. The option of putting the power interface in the plenum box allows us to take all of the wires including the low voltage interfaces and hide them from view. The result is a visual of the projector and a few wires, wraped in flex wrap disappearing into the ceiling almost invisable from the seating area. A very good thing for us who have to design and sell these expensive installations.

At this point I have not been given a reason this is against code. I suppose things could catch fire up in the plenum box and the flames work their way backwards down the 6" of 1 1/2" pipe, turn and reach back up to the inflamable ceiling tile and catch it on fire. Anything is possible but inquiring minds want to know.

Thanks very much for your interest in my dilema. Jim

 

[iwire]

Here is a good example of a deteriorated cord, I have seen ones above ceilings in worse shape then this.

However clearly a modern projector will have a different type of insulation on its power cord.

It code be worth putting in a code proposal to have an exception made for this situation.

 

[soundcon]

I think this enough of a new idea to warrant careful evaluation by the AHJ. Not saying I would or would not accept it, just that I'd take a good look at it and consult with staff on it.

If it were listed for the intended purpose, then DA-LITE might have something.

This is exactly what I have been thinking. I revised the drawing to include some additional details that might shed light on how this is installed. I have sent an email to Da-Lite regarding the fact that we are not allowed to install it as their spec sheet implies and have also spoken with them about UL approval. At this point they say approval is not required but then I suspect they don't want to pay the cost to have it done either.

Hopefully this dialog will lead to some serious evaluation of this installation method and, if safe, then the code be modified to allow this much cleaner installation.

Again, thanks to you and all who have participated in this threat. It has been most enlightening. Jim

 

[iwire]

The reason we want this out of sight is for cleaner cosmetic/installion appearance. In this particular case the customer is spending $75,000 for very nice high end audio visual equipment in a very nice clean newly decorated conference/meeting room.

Be that as it may, the purpose of the NEC has nothing to do with how something looks.

The stated purpose of the NEC is the practical safeguarding of persons and property from the hazards arising from the use of electricity.

Often the following the NEC is inconvenient but until someone can put in a code change proposal with good substantiation why it would be safe and necessary to make the change it will remain as it is.

 

[iwire]

At this point I have not been given a reason this is against code.

Quite honestly the reason is entirely irrelevant.

 

[soundcon]

Here is a good example of a deteriorated cord, I have seen ones above ceilings in worse shape then this.

However clearly a modern projector will have a different type of insulation on its power cord.

It code be worth putting in a code proposal to have an exception made for this situation.

OK, that makes perfect sense to me. I have done a fair amount of vintage electronic device restoration and certainly have seen what you are refering to. And clearly this kind of cable should not be left in a flamable or other unsave location to rot un-noticed.

I believe I have seen a shielded A/C cable at one time or another in use on computer or power supply gear that was probably built to reduce RF interference. I woulder if a cable of that sort where there would be clearly and permanently contained power wires might be the answer.

 

[soundcon]

Quite honestly the reason is entirely irrelevant.

I understand that cosmetics is not a reason to be unsafe. Also understand you might take the position that the reason is irrelevant however, someone decided the reason relevant enough to include it in the code in the first place. Knowing the reason will help you or I or someone else understand what is of concern and if necessary create a solution to overcome the concern in a safe manor and maybe present an even more safe solution. Problem situations have always been the genesis of a better and safer product. Just because someone said so once does not necessarily mean that is still the best solution for a current situation. It seems to me we have been having a national dialog about exactly that concept. Somone once though it a good and safe idea to open up the requirments to give more people homes. In itself not a bad goal but it ended up with a bad result. Taking a fresh look at a code requirement with new materials and installation methods is not a bad idea. It does not mean that the new concept or material will result in a code change. But it also doesn't mean it won't. Safety is always the highest concern always and that is the reason we have testing and codes to cover us all.

I have to make decisions every day regarding what piece of equipment is to be used, how it is to be installed and if it is the right choice. Knowing the resaon behind a regulation is important to me to save time and money and to be able to be in compliance. My company is in the business of using the newest and latest in technology to provide better solutions for my customers. We do not ever do something just because someone else does it that way or because it has always been done that way. We have been in business for over 20 years and have only done four or five rooms the same as another. Each project is revisited with an eye toward a better way which brought up this discussion.

Thanks again for sharing you great wealth of knowledge and experience. Jim

 

[e57]

Soundcon, what I think you are looking for in appearance is available in the floor..... Get one for the ceiling approved and you got a market....

However the reasoning - and I am now stepping into very deep water here - ceilings of the plenum flavor serve as environmental air for the HVAC system, and thus become part of the breathable air in a building when the worst happens. i.e. Fire.... And the propose of not allowing flexible cords in that area above the ceiling is to limit smoke, and fire travel on combustible materials. e.g. Plenum rated Cat-5 cabling is both lower in toxic smoke when burning, and has a lower rate of flame travel by UL testing. The chemical compounds in just about all flexible cords that make them 'flexible' are not produced in a way that could qualify as 'low smoke or flame spread'.... The NFPA and UL are not looking to add any more load to that type of area where it would be both concealed, more prone to fire, and be more toxic, and be inside essentially part of the duct work.... And as Iwire mentioned - the NEC does not want to open the pandora's box of allowing cords being used as premise wiring, as not only are the life-spans of said cordage lower, but the installation of said would then allow many other nasties into the pool - next thing you know we'll be using the non-methods of the hack.... cords to flying splices in walls - whole buildings wired in lamp cord with various voltages and we soon become Bangladesh.....

 

[e57]

I have sent an email to Da-Lite regarding the fact that we are not allowed to install it as their spec sheet implies and have also spoken with them about UL approval. At this point they say approval is not required but then I suspect they don't want to pay the cost to have it done either.

After reading the spec sheets for a few related items, I do not see them as implying that - did they provide you with that drawing????