[RE-wrenches] #10 THWN-2

[Peter Parrish]

Just a minor point: the dash-two appendage brings a wet-rated wire from 75
deg C to 90 deg C. 

If you are not in a locale that argues for wet-rated wire and your specific
application does not argue for wet-rated wire, IMHO it is perfectly
acceptable to use THHN wire (90 deg C rated for damp environments) for
outdoors, attics and other extreme temperature conditions. Of course you
have to use good 3R boxes and rain-tight EMT connectors.

For us, it is easier to purchase and inventory just one wire type for
conduit runs, and we usually get the same price for THWN-2 as we do for
THHN, or close enough. In fact we almost never use #12 either for the same
reason.
 
Peter T. Parrish, Ph.D., President
California Solar Engineering, Inc.
820 Cynthia Ave., Los Angeles, CA 90065
CA Lic. 854779, NABCEP Cert. 031806-26
peter.parrish at calsolareng.com  
Ph 323-258-8883, Mobile 323-839-6108, Fax 323-258-8885

 
________________________________________
From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Allan
Sindelar
Sent: Friday, July 23, 2010 10:04 AM
To: RE-wrenches
Subject: Re: [RE-wrenches] #10 THWN-2

Mick,
-2 means 90 degrees C rather than 75. THWN-2 thus means that it is wet-rated
at 90C.  That is generally considered Code for arrays, such as if it is run
in NM flex conduit to a traditional module j-box. The j-box area may be
considered to be able to get hot enough to require 90C rated wire. Nowadays
with MC-type module leads, combiner boxes aren't subject to the same high
temperatures on the THWN as when they terminate in module j-boxes, and the
higher temperature rating isn't generally necessary.

Much of what I'm saying here is older John Wiles stuff.
Allan
 
Allan Sindelar
Allan at positiveenergysolar.com
NABCEP Certified Photovoltaic Installer
EE98J Journeyman Electrician
Positive Energy, Inc.
3201 Calle Marie
Santa Fe, New Mexico 87507
505 424-1112
www.positiveenergysolar.com

On 7/23/2010 10:52 AM, Mick Abraham wrote: 
I'm sorry to broadcast my ignorance, but:

Could someone explain to me the significance of the -2 marking? Reply
off-list if you wish to save bandwidth...but other List members may also be
wondering... 

Thanks, 

Mick Abraham, Proprietor
www.abrahamsolar.com

Voice: 970-731-4675

On Fri, Jul 23, 2010 at 10:48 AM, Nick Soleil <nicksoleilsolar at yahoo.com>
wrote:
I have specified THWN-2 for years, but occasionally will not be able to
source it!

Sent from my iPhone

On Jul 23, 2010, at 11:37 AM, "Peter Parrish"
<peter.parrish at calsolareng.com> wrote:
We went through a similar problem with some beach communities here in SoCal.
Because of the high humidity (all winter and summer mornings) they wanted
THWN-2 for all conduit runs (as well as PVC instead of EMT). At first we
were charged a premium for THWN-2 compared to THHN. But then we found a
source at All Phase Electrical Supply Burbank CA (a part of CED) for THWN-2
#10 stranded @ $162.40/k-ft. Brand is En(m?)core Wire. THWN-2 listing is
printed on the insulation.
 
- Peter
 
Peter T. Parrish, Ph.D., President
California Solar Engineering, Inc.
820 Cynthia Ave., Los Angeles, CA 90065
CA Lic. 854779, NABCEP Cert. 031806-26
peter.parrish at calsolareng.com  
Ph 323-258-8883, Mobile 323-839-6108, Fax
323-258-8885                                                              
                                    
 
 
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