Rigid Steel Conduit as Light Pole

[jcook980]

Is rigid galvanized steel conduit used as a light pole and secured only at one end a listed application? I've seen several examples of ten and even twenty foot (with a coupling in the middle) lamp poles in industrial settings made out of RMC. This appears to me to be a violation of the requirement to support the conduit every ten feet since it is free standing and supported only at one end.

 

[charlie]

Re: Rigid Steel Conduit as Light Pole

If you wish to use any piece or electrical equipment to serve a mechanical purpose, it is permitted. It is generally not up to the electrical AHJ to turn down that type of use. However, if it is being used for supporting a luminaire, the structural AHJ may want to see the calculations that show that the installation is safe.

 

[steve66]

Re: Rigid Steel Conduit as Light Pole

Charlie:



400.15 seems to apply, and I agree that I don't see anything in there that prohibits this.

But how is the conduit supported? From a box with locknuts, or what?

Steve

 

[bphgravity]

Re: Rigid Steel Conduit as Light Pole

I agree with Charlie with the addition that 410.15(B) may needed to be followed.

Think of a service riser installation. The raceway in this case is usually only supported on one end.

 

[jcook980]

Re: Rigid Steel Conduit as Light Pole

The conduit is welded (is welding to a conduit permissible?) to the outside of a steel handrail along a catwalk and separated from the rail by 3"x6" plates. The lower end of the conduit terminates on a T but the load is supported by connection to the rail. The luminare is being supported by the free end of the conduit. In the design I'm currently reviewing only a single 10' conduit is being used. As I noted, I have seen similar installations with a threaded coupling in the center of a 20' conduit "pole". AFAIK, no structural calc has been made on this design.

 

[bphgravity]

Re: Rigid Steel Conduit as Light Pole

I think you are viewing this from the wrong perspective. Instead of thinking the installation is that of a raceway being used as a pole, I would think of it as a pole that is being used as a raceway.

It seems to me that the primary purpose of the rigid pipe is for the purpose of a structural body and not as a raceway system. I don't think any of the requirements of 344 would apply.

 

[charlie]

Re: Rigid Steel Conduit as Light Pole

A piece of any kind of conduit may be used to support other raceways, sprinkler systems, duct work, etc. just the same as a piece of 2 X 4 would be used. A piece of any electrical equipment may be used for whatever purpose you see fit and as long as it is not being used for its original purpose, it may be OK.

For instance, I could commandeer a piece of 2" RMC, weld it end to end, and use it as a hand rail. I could use EMT for fence posts or anything else I deemed necessary. The building inspector may take exception to the way I used it but the electrical inspector could not turn it down.

 

[mpd]

Re: Rigid Steel Conduit as Light Pole

I would have to say this would have to comply
with 410.15 (B), and as far as a 20ft of conduit
with a coupling in the middle, I would never
accept it, I do not think you would find any
architects or engineers siging & sealing there
name to that.

 

[steve66]

Re: Rigid Steel Conduit as Light Pole

Charlie:

I feel a lot better now that I understand what you were saying

But I don't think it applies here because:

1) The conduit is still being used as a raceway for the wiring.

2) The conduit is supporting a luminaire, which must be supported per the NEC or its listing.

If I look at 300.8(B)(3) - Raceways used as a means of support, it points me to 314.23, which I think applies. And Exception #2(a) seems to limit the unsupported length of conduit to only 3 feet.

So I have changed my mind, and I now think this is a violation.

Steve

 

[mhulbert]

Re: Rigid Steel Conduit as Light Pole

What about one of the light fixtures at the link below (Go to page 7)??? It is designed to be supported by rigid supported on one end only.
Appleton Mercmaster Lights

 

[tshea]

Re: Rigid Steel Conduit as Light Pole

How do you know the installation is conduit? Could it be water pipe? Could it be tubular steel?

 

[dillon3c]

Re: Rigid Steel Conduit as Light Pole

If it has any bearing on this conversation thread,I infact installed a simular installation back in 95/96 at a Waste Water Treatment Plant in my hometown.It was raceway(conduit mounted) Luminares next to walkway around the Sludge Tanks.The listed assembly we received was Aluminum Heads w/ Aluminum Pole Bases alone,no pole riser between.We infact installed, either 2" or 1.5 Aluminum Raceway (10' length conduit),between bases and luminare heads.As I remeber it well,but do not recall Manufacturer of the assembly being long ago.I do remeber putting them together w/ my strap-wrench,as not to marr the aluminum conduit between fixture and base..This was "free-standing installation,anchored at base as any pole fixture.

 

[rbalex]

Re: Rigid Steel Conduit as Light Pole

Originally posted by jcook980:
The conduit is welded (is welding to a conduit permissible?) ...

Not usually; see 300.18(B)

 

[steve66]

Re: Rigid Steel Conduit as Light Pole

mhulbert:

I think 314.23(F) exception #2 applies to these fixtures (2002 NEC). That means it has to comply the a through f. I read that to say you can only have 3' of conduit rising above the last support, and you need another support more than 12" below the highest support.

I also read this to require the fixture to be less than 20lbs. But the fixtures you found are about 25 lbs.

[ February 03, 2005, 04:46 PM: Message edited by: steve66 ]

 

[nhee]

Re: Rigid Steel Conduit as Light Pole

314.23(F) seems to only apply to enclosures that are supported by raceways and which in turn support fixtures. The Appleton fixtures would actually be supported by the raceway, and not by another enclosure. So I don't think any of the rest of 310.23(F) or associated exceptions apply.

I think 410.15 would apply. Or maybe 410.16 (F)?

 

[steve66]

Re: Rigid Steel Conduit as Light Pole

nhee:

I thought about that also, but if you look at the definition for an enclosure in article 100, it seems that an "enclosure" is an integral part of those light fixtures.

Steve