# 17KV at Expansion Joint



## BigCL (Jun 19, 2009)

Does anyone know if 17KV feeders can be installed in Flexible Metal Conduit? I have a 800' run of 25KV medium voltage cable installed in 4" rigid conduit. Per the detail on the drawing, any conduit crossing the expansion joint has to be in FMC or LFMC. I have no issues with any of the branch and feeder conduits under 600V, but 17,000V installed in flex just doesn't seem right.

!7KV feeds an new ER department at a hospital in California.


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## nolabama (Oct 3, 2007)

http://www.okonite.com/Product_Catalog/section2/section2-pdfs/2-23.pdf
that stuff above is gonna cost a fortune and it is not listed for your application

this is sorta listed for your app
http://www.okonite.com/Product_Catalog/section2/section2-pdfs/2-36.pdf
it will work tho


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## nolabama (Oct 3, 2007)

this cable is rated and listed for your app - and lead free for the california folks
http://catalog.proemags.com/publication/54eb2963#/54eb2963/127


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## wildleg (Apr 12, 2009)

are these cables premise wiring or utility owned ? what's wrong with a rigid expansion ? (ask the engineer, in writing, so you get a written response). If you use fmc, how do you propose to bond it ? this isn't being embedded in concrete is it ?

I don't do MV, but I think that 310.60 A precludes the use of FMC based on 348.12 ? (if the cable falls under the NEC)


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## BigCL (Jun 19, 2009)

nolabama said:


> http://www.okonite.com/Product_Catalog/section2/section2-pdfs/2-23.pdf
> that stuff above is gonna cost a fortune and it is not listed for your application
> 
> this is sorta listed for your app
> ...


Southwire has a similar cable but require a minimum purhase of 3,000'. I need less the 70'. Thanks for the reply.


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## BigCL (Jun 19, 2009)

nolabama said:


> this cable is rated and listed for your app - and lead free for the california folks
> http://catalog.proemags.com/publication/54eb2963#/54eb2963/127


Thanks for info, but we don't have a problem with cable. The problem is with installing 25KV cable in Flex. Do FMC have a maximum voltage rated? I've never seen a 17KV line installed in flex.


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## bobelectric (Feb 24, 2007)

Refer to the approved engineered drawings.


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## micromind (Aug 11, 2007)

I've installed plenty of 15KV cable in sealtite. Usually short pieces going from the underground stub to a generator. 

Depending on the installation, possibly you could build a skirt around whatever the flex is going to.

I don't see any reason why 15KV cable cannot be installed in flex. 

I've also ran miles of 15KV TEK cable in cable trays; TEK cable is basically 3 cables factory installed in sealtite.


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## MidwestJW (Oct 13, 2011)

BigCL said:


> Does anyone know if 17KV feeders can be installed in Flexible Metal Conduit? I have a 800' run of 25KV medium voltage cable installed in 4" rigid conduit. Per the detail on the drawing, any conduit crossing the expansion joint has to be in FMC or LFMC. I have no issues with any of the branch and feeder conduits under 600V, but 17,000V installed in flex just doesn't seem right.
> 
> !7KV feeds an new ER department at a hospital in California.


 Rigid pipe and rigid expansion joint?


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## Big John (May 23, 2010)

There's nothing inherently wrong with it, the only consideration is if the environment calls for rigid because of the possibility of physical damage, then flex doesn't measure up to that level of protection. 

I'd also ask to use rigid expansion couplings. But be ready to pay an arm-and-a-leg.

-John


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## wildleg (Apr 12, 2009)

well, I don't see how you can use FMC if it is a violation.


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## goose134 (Nov 12, 2007)

+1 on the expansion fittings. +1 also on their cost. 6 years ago we bought a pair for around $500 a piece.


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## nolabama (Oct 3, 2007)

BigCL said:


> Thanks for info, but we don't have a problem with cable. The problem is with installing 25KV cable in Flex. Do FMC have a maximum voltage rated? I've never seen a 17KV line installed in flex.


If your cable is listed for use in conduit.....


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## LightsOn81 (Jan 6, 2012)

Sound like you need expansion fittings. Cooper Crouse-hinds makes them and the company I work for gets them so they have got to be cheaper than the competition. I don't think FMC would go for the same reasons others have said and LFMC at least in my encounter with it has a tendency no matter how tight you get it initially seems to work it's way loose over time


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## BigCL (Jun 19, 2009)

micromind said:


> I've installed plenty of 15KV cable in sealtite. Usually short pieces going from the underground stub to a generator.
> 
> Depending on the installation, possibly you could build a skirt around whatever the flex is going to.
> 
> ...


 
Thanks for reply.


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## BigCL (Jun 19, 2009)

MidwestJW said:


> Rigid pipe and rigid expansion joint?


Did that. IOR want flex.


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## BigCL (Jun 19, 2009)

goose134 said:


> +1 on the expansion fittings. +1 also on their cost. 6 years ago we bought a pair for around $500 a piece.


The hospital's owners rep wants us to use back to back combo deflection/expansion fittings. The part recommended is almost $3,000 each.


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## BigCL (Jun 19, 2009)

bobelectric said:


> Refer to the approved engineered drawings.


I wish I could comment on the approved drawings, but it wouldn't be nice and I don't think I have the room.


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## nolabama (Oct 3, 2007)

Put it in flex, and label it.


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## knob_d (Dec 3, 2011)

We always use expansion/deflection fittings...Ive never seen flex for mv applications....these are things that should be picked up on the estimate...good luck


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## wildleg (Apr 12, 2009)

nolabama said:


> Put it in flex, and label it.


read the section in my post above. it is a violation for >600v


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## nolabama (Oct 3, 2007)

wildleg said:


> read the section in my post above. it is a violation for >600v


If his AHJ requires the flex......


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## nolabama (Oct 3, 2007)

wildleg said:


> are these cables premise wiring or utility owned ? what's wrong with a rigid expansion ? (ask the engineer, in writing, so you get a written response). If you use fmc, how do you propose to bond it ? this isn't being embedded in concrete is it ?
> 
> I don't do MV, but I think that 310.60 A precludes the use of FMC based on 348.12 ? (if the cable falls under the NEC)


If that troubles you, use a PVC expansion fitting.


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