Different Wire Insulation

[ItsMattsFault]

Good morning all

I work on a site where they are making the conversion from THHN to XHHW wire as a standard.

However, we have some THHN wire they don't want to just throw away, and as such are informing us to pull a mix of XHHW and THHN to use it up

I was curious if I had some sort of code reference to be able to push back?

The craftsman and common sense side of me doesn't want to pull a mix of insulation wires to a single piece of equipment.

 

[don_resqcapt19]

There is no code or real world issue mixing insulation types for a singe circuit.

 

[jim dungar]

The only possible requirement for identical insulation would be with the conductors in a parallel run, but even here any one phase conductor insulation could be different than the other phases.

 

[AC\DC]

What’s the reason for the conversion?

 

[don_resqcapt19]

I specify XHHW for all wet location locations and for all conductors between a VFD and the driven motor. It is a more robust insulation.

 

[hornetd]

What’s the reason for the conversion?

Maybe it will help if I point out that a lot of THHN wire is also listed as THWN. That means that when you use it in a wet location it is 75 degree rated conductor. XHHW is 90 degree wire even when used in a wet location. Although it is generally true that 90° degree terminals are not readily available the ampacity for 90° wire is were you start the derating for such factors as ambient temperature, number of conductors in a raceway, and so forth. That works out so that in many cases the XHHW works out to a smaller wire size being able to handle the load. That is a real money saver.

 

[electrofelon]

Maybe it will help if I point out that a lot of THHN wire is also listed as THWN. That means that when you use it in a wet location it is 75 degree rated conductor. XHHW is 90 degree wire even when used in a wet location. Although it is generally true that 90° degree terminals are not readily available the ampacity for 90° wire is were you start the derating for such factors as ambient temperature, number of conductors in a raceway, and so forth. That works out so that in many cases the XHHW works out to a smaller wire size being able to handle the load. That is a real money saver.

XHHW is only 75 degree wet. For both T and X types, the "-2" get you 90° wet or dry. It's really just academic now essentially all conductors are XHHW-2 or THWN-2. IIRC, it's only small sizes like 14 through 10 you may find conductors that may only be THHN or THWN.

 

[hornetd]

XHHW is only 75 degree wet. For both T and X types, the "-2" get you 90° wet or dry. It's really just academic now essentially all conductors are XHHW-2 or THWN-2. IIRC, it's only small sizes like 14 through 10 you may find conductors that may only be THHN or THWN.

Than You. Live and learn. At 73 maybe I should say live and relearn.

 

[AC\DC]

Unless there chaning old thwn out. The new wire is thwn-2 plus dual rated so the 90 degree rating wet applies to that also.

 

[don_resqcapt19]

You do have to watch out for conduit fill issues, the area of XHHW is greater than that of THHN/THWN in the smaller sizes. I think up to 6 AWG'

 

[AC\DC]

I specify XHHW for all wet location locations and for all conductors between a VFD and the driven motor. It is a more robust insulation.

would that matter in Pipe?

 

[don_resqcapt19]

would that matter in Pipe?

The interiors of all raceways in wet locations are also wet locations.

 

[AC\DC]

ya but why would a more Robust insulation really matter in raceway? should be protected in raceway.

 

[don_resqcapt19]

ya but why would a more Robust insulation really matter in raceway? should be protected in raceway.

It just lasts a lot longer in outside wet location installations, maybe because of the freeze thaw cycles we have. As far as the VFDs, I use that because that is the insulation type used in all of the shield VFD cables. My installations are always in rigid conduit, so there is no need for the expensive shielded VFD cables, as the conduit takes care of that issue.

 

[garbo]

The large hospital/research center that I retired from had over 500 VFD'S that were all on THHN/THWN wire. Some original plain jane NEMA frame motors were still running from when the building was built back in the early 1970's. Never had to replace any of the wire between VFD & motors. Wires were in EMT and a copper ground wire from panel, drives to motors. I asked the option of at least three different drive techs about thier opion on expensive shielded drive cables. Told me in far majority of the time they were not needed. In our newest building every drive over 40 HP was 18 pulse and every tech I asked thought they created too many problems and thought in most cases were overkill.

 

[don_resqcapt19]

The large hospital/research center that I retired from had over 500 VFD'S that were all on THHN/THWN wire. Some original plain jane NEMA frame motors were still running from when the building was built back in the early 1970's. Never had to replace any of the wire between VFD & motors. Wires were in EMT and a copper ground wire from panel, drives to motors. I asked the option of at least three different drive techs about thier opion on expensive shielded drive cables. Told me in far majority of the time they were not needed. In our newest building every drive over 40 HP was 18 pulse and every tech I asked thought they created too many problems and thought in most cases were overkill.

Most of the VFDs I installed were run using THHN/THWN without any real issues....all in rigid conduit. However in talking with various VFD experts, I changed my specifications to require XHHW a number of years ago.

 

[garbo]

Most of the VFDs I installed were run using THHN/THWN without any real issues....all in rigid conduit. However in talking with various VFD experts, I changed my specifications to require XHHW a number of years ago.

Just curious being retired over five years have no ideal on prices but is there a big price difference between THHN/THWN & superior type XHHW wire? A few years ago when I saw a 250' roll of 12/2 NMB cable selling for $250 ( $1 a foot ! ) at a big box store glad that I'm retired. Last 25 years I moonlighted was lucky to only do commercial work so last roll of 12/2 that I purchased maybe only cost $25 and still have some of it.

 

[Knightryder12]

I specify XHHW for all wet location locations and for all conductors between a VFD and the driven motor. It is a more robust insulation.

Its also great for conductors exposed to sunlight. No need to derate for temp.

 

[don_resqcapt19]

Just curious being retired over five years have no ideal on prices but is there a big price difference between THHN/THWN & superior type XHHW wire? A few years ago when I saw a 250' roll of 12/2 NMB cable selling for $250 ( $1 a foot ! ) at a big box store glad that I'm retired. Last 25 years I moonlighted was lucky to only do commercial work so last roll of 12/2 that I purchased maybe only cost $25 and still have some of it.

Not sure, I just spec it and don't purchase it
One site shows 6AWG copper THHN at $0.92/foot and XHHW at $1.11/ft