ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
Shout Box
Recent Posts
VDE 0100 to introduce AFCIs
by sparky. 01/20/18 05:09 PM
MRI LED lights dimmer control replacement - wow!
by Potseal. 01/19/18 08:52 PM
Video: Inventor of the GFCI self-testing shocks
by Bill Addiss. 01/17/18 11:11 PM
FPE in Germany
by HotLine1. 01/17/18 07:07 PM
Fujifilm Recalls Power Adapter Wall Plugs
by Admin. 01/16/18 07:04 PM
New in the Gallery:
Housebilding DIY wiring
SE cable question
Who's Online Now
1 registered members (sparky), 10 guests, and 10 spiders.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
Page 1 of 2 1 2
MC cable in a damp location #209645
04/15/13 07:58 AM
04/15/13 07:58 AM
G
George Little  Offline OP
Member
Joined: Jan 2004
Posts: 1,489
Michigan USA
Do we have any information that makes it clear about running MC cable in a damp location. I can find wet locations and dry but nothing on a damp location?


George Little
2017 / 2014 NEC & Related Books and Study Guides
Re: MC cable in a damp location [Re: George Little] #209646
04/15/13 09:52 AM
04/15/13 09:52 AM
HotLine1  Offline

Member
Joined: Apr 2002
Posts: 6,918
Brick, NJ USA
George:
No, I can't see anything that is clear on this.
IMHO, the sheath materials should be clarified,between the steel and aluminum.

I have seen the aluminum sheath deteriorate in a few installs from condensation.



John
Re: MC cable in a damp location [Re: George Little] #209651
04/15/13 01:33 PM
04/15/13 01:33 PM
G
gfretwell  Offline

Member
Joined: Jul 2004
Posts: 9,166
Estero,Fl,usa
What is the question? If the MC is wet location rated, doesn't that encompass damp locations?

I looked at the MFG page for the Southwire MC-XHHW (one of the wet location MCs), it says that is an XHHW-2 conductor and that conductor is listed wet and damp (330.10(A)11(c)). I assume you would derate from the 75c column in a damp location like you do in a wet one.


Greg Fretwell
Re: MC cable in a damp location [Re: George Little] #209652
04/15/13 02:27 PM
04/15/13 02:27 PM
T
Tesla  Offline
Member
Joined: Jun 2004
Posts: 1,273
Sacramento, CA
Greg...

My Ugly's has XHHW-2 as a 90c conductor for derating purposes.

Even XHHW is rated 90c.



Tesla
Re: MC cable in a damp location [Re: George Little] #209655
04/15/13 04:46 PM
04/15/13 04:46 PM
G
gfretwell  Offline

Member
Joined: Jul 2004
Posts: 9,166
Estero,Fl,usa
I guess I "assumed" wrong wink

The box of EZ-MC I have says you derate at 75c when wet but that is not exactly the same stuff. Southwire did not even reference that on their page. Maybe it was a THHN/THWN product that was replaced by the XHHW


Greg Fretwell
Re: MC cable in a damp location [Re: George Little] #209701
04/18/13 10:17 PM
04/18/13 10:17 PM
M
mikethebull  Offline
Member
Joined: Mar 2007
Posts: 100
Rhode Island
330.10 (A)(11) gives conditions for MC in wet locations.

Re: MC cable in a damp location [Re: George Little] #209704
04/18/13 10:24 PM
04/18/13 10:24 PM
T
Tesla  Offline
Member
Joined: Jun 2004
Posts: 1,273
Sacramento, CA
Greg...

That XHHW-2 stuff is creeping in all over the place.

I first saw it with aluminum feeders. Now, it's popping up around stranded copper, from time to time.



Tesla
Re: MC cable in a damp location [Re: George Little] #209708
04/19/13 02:41 PM
04/19/13 02:41 PM
HotLine1  Offline

Member
Joined: Apr 2002
Posts: 6,918
Brick, NJ USA
George:
Are you refering to the sheath, or the conductor insulation?



John
Re: MC cable in a damp location [Re: George Little] #209709
04/19/13 03:23 PM
04/19/13 03:23 PM
G
gfretwell  Offline

Member
Joined: Jul 2004
Posts: 9,166
Estero,Fl,usa
The aluminum armor is considered suitable for wet locations if the wrapper and conductors are wet rated. I understand that salt air can eat it but when you are talking about the sea shore, galvanized rigid metal is not that great either.


Greg Fretwell
Re: MC cable in a damp location [Re: George Little] #209710
04/19/13 06:11 PM
04/19/13 06:11 PM
T
Tesla  Offline
Member
Joined: Jun 2004
Posts: 1,273
Sacramento, CA
Greg...

Carrying that thought further, any aluminum bussing installed near the ocean is at hazard for AlCl3 'rust.'

Aluminum is normally considered 'rust proof' because run-away corrosion does not occur -- unless chloride ions are present.

But, aluminum is, in fact, prone to ultra-rapid 'rusting' / oxidation. Bare aluminum metal oxidizes promptly in air. It acquires a THIN coat of Al2O3 -- aka alumina. It's so thin that you can see right through it. Unlike iron oxide rust, alumina expands to lock up tight, creating an air tight seal.

If salt air is misting in, the chlorine displaces the oxygen in the alumina. Now the metal loses its sheild. AlCl3 shrinks like common rust. Given enough time, aluminum metal becomes pitted -- with cruddy AlCl3 ( it's yellow ) crystals at the surface.

I've witnessed bussing that's picked up a 3 volt drop right at the rails (under load) over a twenty-year period.

The solution is to kill power, buff the crud off the rails, clean the breaker-rail contacts and re-assemble.

Where it's an issue, copper bussing is worth the premium. Copper does not rapidly react with salt air like aluminum.

This issue is why aluminum can't be totally trusted below grade. Some American soils are absolutely laden with old ocean salts. (Nevada, California, Utah, Arizona,...) So you can't trust aluminum to stay bonded as part of a GEC system.



Tesla
Page 1 of 2 1 2

Featured:

2017 Master Electrician Exam Preparation Combos
2017 NEC Electrician
Exam Prep Combos:
Master / Journeyman

 

Member Spotlight
waymag
waymag
dallas, texas, USA
Posts: 67
Joined: January 2002
Show All Member Profiles 
Top Posters(30 Days)
Admin 20
sparky 16
Potseal 15
Popular Topics(Views)
243,576 Are you busy
180,374 Re: Forum
170,852 Need opinion
Powered by UBB.threads™ PHP Forum Software 7.6.1
(Release build 20180101)
Page Time: 0.019s Queries: 16 (0.003s) Memory: 1.0245 MB (Peak: 1.2064 MB) Zlib enabled. Server Time: 2018-01-21 14:35:51 UTC