XHHW 90 degree copper conductors in hospitals

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mshields

mshields

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Can anyone tell me, is it a common practice to use 90 deg rated conductors in hospital applications. I'm reviewing a project that calls for this and I'm wondering why?

thanks,

Mike
 
Are these conductors for Isolated Power Panels?

Roger
 
I don't know if this has anything to do with hospitals, but I spec 90? cable for underfloor raceway due to the derating required near the panels with the large number of conductors in the headers.
 
It is not common because 90 degree terminations are not common.


The only place I have seen this typre of insulation is in the IPU where the better current leakage charateristics are needed.
 
THHN/THWN have a PVC insulation whereas a XHHW will have a flame retardant XLPE insulation. Should also be specified with a non-halogen jacket.

PVC has a very high % of Chlorine especially compared to XLPE. In a hospital, where life safety is a big concern, if the cable were to catch fire, the PVC will give off a great amount of black smoke that contains a toxic amount of hydrogen chloride gas. Not to mention that it is very corrosive as well. This could be catastrophic to life, but also could damage millions of dollars worth of high tech equipment because of indirect fire damage due to the corrosiveness. The insulation of XHHW is thicker then THHN/THWN, and can withstand rougher installation techniques, otherwise known as abuse.
 
Very interesting King. OP...Does the spec call for a specific XHHW or similar 90 degree, or just a 90 degree cable in general? If the latter, it's not because of King's explaination since THHN is a 90 degree cable.
 
Back to the Isolated Power Systems (IPU in Ricks post) XHHW must be used because of it Dielectric strength, SQ D even recommends Rome Cable model # VW-1XHHW2 Spec 2110 for their systems, because of it's consistant Dielectric Constant of 3.5 or less.

Roger
 
mshields said:
Can anyone tell me, is it a common practice to use 90 deg rated conductors in hospital applications. I'm reviewing a project that calls for this and I'm wondering why?

thanks,

Mike
Click to expand...


As has been posted, this is generally the temperature rating of the conductor insulation for most installations.
Was a specific insulation Type listed in the specs?

I guess, based on Roger's post, that the dielectic of the insulation may be somewhat important for the specific installation.
 
Great input - thanks

Great input - thanks

My assumption, evidently wrong, when posing the initial question was that THHN is rated for 75 deg C and that XHHW was rated for 90 deg C.

Sounds like the practical answer to my question is that THHN/THWN is fine for all but IPP applications where XHHW is recommended for it's higher dielectric properties hence lower associated leakage current.

True?

Thanks,

Mike
 
mshields said:
Sounds like the practical answer to my question is that THHN/THWN is fine for all but IPP applications where XHHW is recommended for it's higher dielectric properties hence lower associated leakage current.

True?

Thanks,

Mike
Click to expand...

True.

Mike, we use THHN/THWN conductors for all wiring in Hospitals with the exception of the aforementioned Isolated Power Systems.

Roger
 
You do have to make sure that the THHN you are using is rated for 90 deg C in wet or dry locations.

Some THHN, including multiconductor may ony be rated ror 75 deg C in wet locations. (i.e. UG)
 
kingpb said:
You do have to make sure that the THHN you are using is rated for 90 deg C in wet or dry locations.

Some THHN, including multiconductor may ony be rated ror 75 deg C in wet locations. (i.e. UG)[/quote]


Take a look at the 90C column in Table 310.16 (conductor Types)
Also take a look at 310.8(B) &(C) - THHN is not permitted in wet locations.


You may be thinking of todays conductors with the Copolymers that are dual rated as THHN/THWN, where the THHN part is 90C in dry locations and the THWN is 75C in wet locations.
Click to expand...
 
Pierre C Belarge said:
You may be thinking of todays conductors with the Copolymers that are dual rated as THHN/THWN, where the THHN part is 90C in dry locations and the THWN is 75C in wet locations.
Click to expand...

Or add the -2 and it becomes both.
 
A 90 deg conductor is not really necessary, even in Medical equipment most terminations are only 75 deg.

Roger
 
Pierre C Belarge said:
kingpb said:
You do have to make sure that the THHN you are using is rated for 90 deg C in wet or dry locations.

Some THHN, including multiconductor may ony be rated ror 75 deg C in wet locations. (i.e. UG)[/quote]


Take a look at the 90C column in Table 310.16 (conductor Types)
Also take a look at 310.8(B) &(C) - THHN is not permitted in wet locations.


You may be thinking of todays conductors with the Copolymers that are dual rated as THHN/THWN, where the THHN part is 90C in dry locations and the THWN is 75C in wet locations.
Click to expand...

Actually, no I wasn't:

"Southwire's Type TC Power Cable is used to supply power to motors, or for connection to other power devices in industrial settings. Primary installations include cable trays, raceways, and outdoor locations where supported by a messenger wire. Type TC Power Cable is listed for direct burial and for use in Class 1, Division 2 hazardous locations and Class 1 control circuits. This cable may be used at temperatures not to exceed 75?C in wet locations and 90?C in dry locations. 6 and 8 AWG constructions with insulated grounds (standard) and 4 AWG and larger with bare or insulated ground are UL Listed for exposed runs (ER) per NEC 336.10."

Also, I think you may have forgotten about 310.8(C)(3) since the cable in reference is listed for wet locations, and it does have a PVC (THHN) insulation.

http://appprod.southwire.com/ProductCatalog/XTEInterfaceServlet?contentKey=prodcatsheet67
Click to expand...
 
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