THHW OR XHHW ?

[m sleem]

My question is ((material of the elctrical wires in healthcare facilities better to be 600v THHW or 600/1000v XHHW)) WHAT CODE SAYS?

 

[augie47]

The only Code reference I can think of is in 517.160(A)(6) in a FPN that discusses conductor insulations.
As I recall, XHHW meets those specs where THHW does not.
Note this is a FPN and not a "requirement" and is noted in relation to isolated power systems.

 

[m sleem]

The only Code reference I can think of is in 517.160(A)(6) in a FPN that discusses conductor insulations.
As I recall, XHHW meets those specs where THHW does not.
Note this is a FPN and not a "requirement" and is noted in relation to isolated power systems.

Forgive me but (FPN) means what?

 

[jumper]

Forgive me but (FPN) means what?

Fine Print Notes.

Information that is provided for a person to consider, but not required to follow.

(C) Explanatory Material. Explanatory material, such as
references to other standards, references to related sections
of this Code, or information related to a Code rule, is included
in this Code in the form of fine print notes (FPNs).
Fine print notes are informational only and are not enforceable
as requirements of this Code.

 

[kwired]

Fine Print Notes.

Information that is provided for a person to consider, but not required to follow.

(C) Explanatory Material. Explanatory material, such as
references to other standards, references to related sections
of this Code, or information related to a Code rule, is included
in this Code in the form of fine print notes (FPNs).
Fine print notes are informational only and are not enforceable
as requirements of this Code.

What Jumper has there is the content of 90.5(C).

In the 2011 NEC the FPNs have been renamed to "informational notes".

 

[tom baker]

XHHW and XHHW-2 (rated 90 Deg C wet or dry) is a far better insulation than THHW/N. THHW is a PVC and the insulation is very thin, easy to damage and in my experience does not hold up well in wet locations, and the insulation can melt. XWWH is cross linked polyethylene, thicker insulation and is direct bury rated. So using it in conduit is a win win situation. Some don't like it as its harder to pull.
I spec it for any run in a wet location, inside or out. Go to a mfgs website and look at the properties for each type.

 

[roger]

XHHW and XHHW-2 (rated 90 Deg C wet or dry) is a far better insulation than THHW/N.

Tom, that a sums it up in a "to the point" way.

Thanks

Roger

 

[curt swartz]

XHHW and XHHW-2 (rated 90 Deg C wet or dry) is a far better insulation than THHW/N. THHW is a PVC and the insulation is very thin, easy to damage and in my experience does not hold up well in wet locations, and the insulation can melt. XWWH is cross linked polyethylene, thicker insulation and is direct bury rated. So using it in conduit is a win win situation. Some don't like it as its harder to pull.
I spec it for any run in a wet location, inside or out. Go to a mfgs website and look at the properties for each type.

I frequently read post here about THHW but have never seen this type of wire. It is basically the same thing at THW but has a 90C dry rating. I would be surprised if any one still made THW or THHW. I'm sure it would be made to order if they do. My suppliers stopped stocking THW about 25 years ago and moved exclusively to THHN/THWN and XHHW.

THW and THHW have a much thicker insulation than XHHW. THHN or THWN not thinner. About twice as think depending on the size.

XHHW is NOT rated for direct burial applications.