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Old 11-06-2019, 04:20 AM   #1
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Default Use of RHW-2 in EMT or other 2 hour fire rated Conductor

We have been asked to install conductors for and existing fire pump.
The installation as it sits is a 1970s designed electrical system with only normal power feeding it.
It has to be connected to a generator.
The inspector suggested MI cable. I have only seen this once in our jurisdiction. It's extremely rare. The more we looked into it, it's been suggested we look into RHW-2 in EMT with steel fittings.
This would be our first time using RHW-2 in EMT.
Does anyone here have experience with this conductor type? Is there anything to be aware of concerning up-sizing conduit, how hard is a short 75' pull with 2 90s and a 45. I was considering 3" EMT with a 4" standard LB through an exterior wall penetration.
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Old 11-06-2019, 08:59 AM   #2
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From long ago memory: RHW has a softer, rubbery insulation that creates more friction than THHN when pulled in. It is a larger diameter also.

However, I do not believe that RHW-2 in EMT will give you a code compliant , 2 hour fire rated installation. RHW-2 only has a 90C insulation - the same temperature rating as THHN. Please refer to NEC 695.8.
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Old 11-06-2019, 09:00 AM   #3
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Never used either method.


Was your inspector also the one to suggest RHW-2 in pipe?



What size conductors are you planning on going with?
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Old 11-06-2019, 03:35 PM   #4
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RWH is FAT.
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Old 11-06-2019, 05:44 PM   #5
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Quote:
Originally Posted by Cow View Post
Never used either method.


Was your inspector also the one to suggest RHW-2 in pipe?



What size conductors are you planning on going with?
There will be 4x 350s in 3" EMT. It fits
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Old 11-06-2019, 05:47 PM   #6
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Quote:
Originally Posted by varmit View Post
From long ago memory: RHW has a softer, rubbery insulation that creates more friction than THHN when pulled in. It is a larger diameter also.

However, I do not believe that RHW-2 in EMT will give you a code compliant , 2 hour fire rated installation. RHW-2 only has a 90C insulation - the same temperature rating as THHN. Please refer to NEC 695.8.
The manufacturer claims it has a 2 hour fire rating.

http://www.ckelectricalsales.com/pdf...arket37711.pdf

http://s3.amazonaws.com/zanran_stora...2529492530.pdf




Last edited by Southeast Power; 11-06-2019 at 05:54 PM.
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Old 11-06-2019, 09:13 PM   #7
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OK, always interested in new things.
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Old 12-07-2019, 10:31 AM   #8
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Quote:
Originally Posted by Southeast Power View Post
We have been asked to install conductors for and existing fire pump.
The installation as it sits is a 1970s designed electrical system with only normal power feeding it.
It has to be connected to a generator.
The inspector suggested MI cable. I have only seen this once in our jurisdiction. It's extremely rare. The more we looked into it, it's been suggested we look into RHW-2 in EMT with steel fittings.
This would be our first time using RHW-2 in EMT.
Does anyone here have experience with this conductor type? Is there anything to be aware of concerning up-sizing conduit, how hard is a short 75' pull with 2 90s and a 45. I was considering 3" EMT with a 4" standard LB through an exterior wall penetration.
Article 695.6(2)(3) gives us the option to use a " Listed electrical circuit protective system".
This "system is in the UL White Book under FHIT
There are more stringent rules to follow then just NEC chapter 3 . There are requirements for additional supports then the NEC requires, Type of conduit, type of fittings, what the conduit can be supported too. Its not just a case of using steel fittings and RHW
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Old 12-07-2019, 10:46 AM   #9
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MI is good stuff.
But it sure looks tempting to a plumber a few years down the road.
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