# dielectric connectors



## goose134 (Nov 12, 2007)

We're doing some work at a hospital, in particular, some MRI rooms. The specs call for some of the equipment to be connected by dielectric EMTconnectors. I've had no luck searching for these. I've used isolation fittings in the past (basically a squeeze connector made of thick rubber) but I didn't order them and don't know where to get them or if they'll pass muster with Siemens. The only other thing I was considering was a PVC to EMT connection. Any thoughts?


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## brian john (Mar 11, 2007)

They are trying for COMPLETE ISOLATION?

Some who doo voo doo spec?


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## goose134 (Nov 12, 2007)

> They are trying for COMPLETE ISOLATION?


The Siemems rep didn't have a good answer for this. He's not even sure how to achieve it and had to RFI this question himself. I do know that there is an grounding conductor and and isolated grounding conductor in the raceway, both of them the same size as phase conductors

Aside from the PVC to EMT idea, I'm not sure there is a way to isolate the equipment. I agree that it may be a bit of snake oil, but I'm no engineer.


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## MDShunk (Jan 7, 2007)

An actual dielectric coupling is only available from a plumbing supply house. I get the same spec on federal jobs, and I just do it with a short PVC section. Passes muster with the Army and the CIA so far.


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## MDShunk (Jan 7, 2007)

brian john said:


> They are trying for COMPLETE ISOLATION?
> 
> Some who doo voo doo spec?


Brian, it's an anti-wiretapping spec. Bad guys can use the pipe as one conductor of the mic. I have no idea why it's in an MRI room spec.


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## KayJay (Jan 20, 2008)

I don't believe there is a need for any special dielectric fitting, since 250.96* allows one or more listed nonmetallic fittings to be installed on a metallic raceway at the equipment enclosure for that purpose, as long as the raceway encloses only the conductors supplying that piece of equipment.
It appears that this gets around the requirement of 358.6 for listed EMT fittings.

BTW: 300.10, Exception #2, references 250.96.
*


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## RePhase277 (Feb 5, 2008)

Maybe you could use a junction box adapter slip fitting into a female adapter, then screw the EMT fitting into it.


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## goose134 (Nov 12, 2007)

> Maybe you could use a junction box adapter slip fitting into a female adapter, then screw the EMT fitting into it.


This is right along the lines of what I was thinking. It is probably the least ghetto of my options.


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## KayJay (Jan 20, 2008)

I don’t see that there’s any specific way to do it as long as the nonmetallic fittings are listed.
If the equipment has a threaded enclosure, go ahead and use a T/A and an F/A back to back with just enough RNC between them to butt the two together. If it’s just a KO in a sheet metal box, use the F/A and a box adapter like you were talking about. Unless Siemens has there own specifications, I can't see any issue.

What is interesting and kind of ghetto though, is that it sounds like the previous inspector allowed you to use those black rubber Fernco, no-hub DWV plumbing fittings for electrical work and it passed it. :whistling2:


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## goose134 (Nov 12, 2007)

> What is interesting and kind of ghetto though, is that it sounds like the previous inspector allowed you to use those black rubber Fernco, no-hub DWV plumbing fittings for electrical work and it passed it. :whistling2:


I probably didn't describe them well, but these were not plumbing fittings. There was a locknut on a threaded base that was part of an assembly that LOOKED like a plumbing no-hub. Again, I've searched for these a bit and can't find them so maybe they're not what I thought they were.


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