expanding foam

[jross_45365]

can you tell me if you are allowed to use expanding foam to seal an out door conduit this is not going to keek water out of the conduit (the conduit is a stub up that transition into a cable tray)If allowed where is it in the code
thank you

 

[russ]

Re: expanding foam

I don't think there is a code that specifically will address this. I imagine any sealing compound whould have to be approved by the inspector.

Russ

 

[tom baker]

Re: expanding foam

Expanding foam is not typically allowed as it may be detrimental to the conductor insulation. Duct seal is what is normally. Conduits entering from the outside where condensation may be a problem are required to be sealed. See Section 300.7

 

[mikeackley]

Re: expanding foam

If you really need/want to use an expanding foam, there is a 3M product I've used called "Fire Barrier Silicone RTV Foam 2001". It's UL listed for cable bundles, trays, conduits, etc. Reentrable, repairable, and no ampacity derating required. A two-part system with 1 to 5 minutes of working time before it kicks off. Comes 7oz tubes, 40lb. buckets, whatever you want. There is also a latex foam out there that's UL listed for electrical use but I can't remember the name. Check supply house.

As Tom points out, be wary of using any non-listed product - I would think most of the common expandable polystyrene or urethane foams would be a big no-no. Point made by Russ is also a good one. Even if you use a listed product, get AHJ approval.

[ March 28, 2003, 09:37 PM: Message edited by: mikeackley ]

 

[flightline]

Re: expanding foam

I would have to agree with Tom. We do enforce the sealing of conduits from the exterior, and generally only accept Ductseal, as we know that it has been approved for use with insulated cables. And while the price has come down on foam-in-a-can, I bet Ductseal is still cheaper and, and the unused portion easier to transport and install on the next job.

 

[bphgravity]

Re: expanding foam

Are we talking about sealing the inside of the conduit around the conductors to stop the passing of air from each location, or around the outside of the conduit to fill the air space surrounding the conduit from the penetration?

 

[roger]

Re: expanding foam

I have always used Ductseal too, OR, a weatherhead if the particular installation allows.

Mike, the 3M Fire Barrier materials are a little on the costly side if not needed for the purpose.
Although, like you said, if a "foam" were really "needed or wanted" this would do the trick.

Roger

 

[romex jockey]

Re: expanding foam

I've always figured dux seal to comply with 230.8, but am unaware of any listing pro's or cons

 

[mikeackley]

Re: expanding foam

While we're waiting for jross to clarify exactly what he is trying to seal (bph's question), let me ask you guys this: What do you use to seal penetrations through fire rated assemblies?

 

[roger]

Re: expanding foam

Mike, I always use an assembly listed by manufacturers such as Hilty, 3M, Tremco etc...

These assemblies are offered in detail by these manufacturers and covered in the UL orange books.

Roger

 

[mikeackley]

Re: expanding foam

Roger: How about EZ Path?

 

[roger]

Re: expanding foam

Mike, that's one I'm not familiar with.

Roger