explosion proof unions

[russ]

I asked UL if explosion proof unions were water tight.
Their reply was no they are not water tight fittings.

 

[Ed MacLaren]

Re: explosion proof unions

Neither is an explosion-proof box or cabinet.

There is no gasket, by design, so that in the event of an explosion within the enclosure, the pressure is relieved, and the hot gases are quenched as they escape through the metal-to-metal surface.

Ed

 

[jim dungar]

Re: explosion proof unions

While explosion proof enclosures are not automaticaly weatherproof, it is possible to purchase some.

 

[russ]

Re: explosion proof unions

My main concern that prompted my question to UL, is the fact that many electricians think these are acceptable for underground burial, even if they are in the fill below the concrete.

[ December 23, 2004, 05:32 AM: Message edited by: russ ]

 

[don_resqcapt19]

Re: explosion proof unions

Russ,
They are a lot more water tight than a standard conduit coupling. It is impossible to keep water out of underground conduit runs and that is way the code requires conductors rated wfor wet locations when installed in underground conduit.
Don

 

[russ]

Re: explosion proof unions

Don

I know many underground installations end up with water in them, but the code does require rain tight fittings.
If we're not trying to keep the water out, why not just allow set screw fittings.

I have in the past allowed the use of the unions under ground, but I'm convinced now that I was wrong.
Maybe they could sill be used if protected by some water proofing method/material, or by pouring concrete around them.

 

[don_resqcapt19]

Re: explosion proof unions

Russ,

I know many underground installations end up with water in them, but the code does require rain tight fittings.

There is no such item as a raintight coupling for rigid conduit. Rigid conduit couplings are much less raintight than the old EMT compression couplings that UL says we can no longer use in wet locations. I see no code problem with using standard or explosionproof unions in wet or underground conduit runs. Both are at least as watertight as the threaded conduit coupling. Remember that our couplings are straight thread and not taper thread like those the plumbers use.
Don

 

[charlie]

Re: explosion proof unions

Also remember that plumbing fittings are not water tight unless you use pipe dope around the threads. If we did that, we would lose the electrical continuity though.

 

[russ]

Re: explosion proof unions

If there is no raintight type couplings for RMC then the NEC 344.42 would prohibit threadless couplings in wet locations. The same would have to go for IMC.

 

[don_resqcapt19]

Re: explosion proof unions

Russ,
I'm not talking about the threadless couplings for rigid and I don't know if they are listed as raintight. I am talking about the threaded couplings and they are not raintight.
Don

 

[don_resqcapt19]

Re: explosion proof unions

Charlie,

Also remember that plumbing fittings are not water tight unless you use pipe dope around the threads.

The seal on plumbing pipe and fittings is by direct metal to metal contact between the male and female tapered threads. While pipe dope may help seal imperfections in the threads, its main purpose is to provide lubrication so that the joint can be tightened enough to get the required metal to metal contact.
Don

 

[russ]

Re: explosion proof unions

I am talking about the threaded couplings and they are not rain tight.

I had no idea that threaded couplings were not rain tight. Seems the code still specifically allows them in all atmospheric conditions, and in direct contact with the earth.

 

[petersonra]

Re: explosion proof unions

Originally posted by Ed MacLaren:
There is no gasketEd

But I think you can get at least some of them with an o-ring seal to make it more water tight.

 

[petersonra]

Re: explosion proof unions

Originally posted by russ:

I am talking about the threaded couplings and they are not rain tight.

I had no idea that threaded couplings were not rain tight. Seems the code still specifically allows them in all atmospheric conditions, and in direct contact with the earth.

After a few weeks in contact with the soil I'd bet they rust pretty mcuh watertight.

 

[don_resqcapt19]

Re: explosion proof unions

Russ,

I had no idea that threaded couplings were not rain tight.

That is why I have a real issue with the new EMT "raintight" fittings. The older EMT raintight fittings are more water tight than threaded conduit couplings. Why does UL and teh NEC require EMT couplings and rigid threadless couplings to be "raintight" when threaded couplings are not raintight
Don