The Electrical Contractor Network

ECN Electrical Forum
Discussion Forums for Electricians, Inspectors and Related Professionals

Books, Tools and Test Equipment for Electrical and Construction Trades

Register Now!

Register Now!

We want your input!

Featured:
   

2017 NEC and Related
2017 NEC
Now Available!

   
Recent Posts
Live Chat Feature
by Admin
01/19/17 09:52 PM
Safety at heights?
by gfretwell
01/19/17 07:16 PM
failed home inspection.
by gfretwell
01/19/17 07:03 PM
Webmaster > Admin
by Admin
01/19/17 05:49 PM
Old Bath Fan
by gfretwell
01/19/17 01:38 AM
New in the Gallery:
Desk-mounted "power-board"
Top Posters (30 Days)
Admin 33
HotLine1 21
Ruben Rocha 16
gfretwell 15
Trumpy 13
Who's Online
2 registered (Ruben Rocha, gfretwell), 0 Guests and 187 Spiders online.
Key: Admin, Global Mod, Mod
Topic Options
Rate This Topic
#30094 - 10/04/03 12:39 PM GRC Underground
golf junkie Offline
Member

Registered: 04/22/01
Posts: 511
Loc: York, NE
When using GRC (galvanized ridgid conduit) underground what do you use for a sealant at the threaded couplings?

Is there a listed sealant for this application?

thanks,
GJ

Top
Work Gear for Electricians and the Trades

Work Gear for Electricians and the Trades
Work Gear for Electricians and the Trades
Arc Flash Clothing, Gloves, KneePads, Tool Belts, Pouches, Tool Carriers, etc. etc....

#30095 - 10/04/03 01:19 PM Re: GRC Underground
iwire Offline
Moderator

Registered: 01/05/03
Posts: 4343
Loc: North Attleboro, MA USA
Maybe I will get slammed for this, but I do not use any sealant.

It is a given that water will get in the conduit or will accumulate inside the conduit from condensation.

It is my belief that this is the reason for 300.5(D)(5)

Quote:
300.5(D)(5) Listing. Cables and insulated conductors installed in enclosures or raceways in underground installations shall be listed for use in wet locations.
_________________________
Bob Badger
Construction & Maintenance Electrician
Massachusetts

Top
#30096 - 10/04/03 01:44 PM Re: GRC Underground
Roger Offline
Member

Registered: 05/18/02
Posts: 1779
Loc: N.C.
Got to agree with Bob again. I could count on one hand the jobs I have been involved with that required special treatment at the couplings. With a perfectly sealed conduit system condensation will still exist and will add up to gallons.

I installed one job where the engineer spec a TEE fitting at the lowest part of any underground conduit in a 2'x 2' gravel pit
(french drain if you will)

Roger

Top
#30097 - 10/04/03 07:35 PM Re: GRC Underground
golf junkie Offline
Member

Registered: 04/22/01
Posts: 511
Loc: York, NE
That's a good one Roger!

I had a very bad experience one time. The engineer spec'd GRC for the service and would not allow PVC.

A large parking area drained into the service trench, even after backfilling our service counduit made a very nice drain for the parking lot. And of course it drained right into our brand new service equipment.

We dug the trench out twice before we were able to stop the water. First time we tried to seal the couplings with a rubber sealant........that didn't work. Second time we encapsulated the coupling in bentonite (sp?) that did the trick.

Since that time I've avoided using GRC underground, but I'm looking at a job now where it's in the spec again.

GJ

Top
#30098 - 10/04/03 07:39 PM Re: GRC Underground
Bjarney Offline
Moderator

Registered: 04/10/02
Posts: 2561
Loc: West-Southern Inner-Northeast ...
Suggest T&B “Kopr-Shield” or Fel-Pro C5A for conduit threads. Don’t expect a perfect watertight seal, but preservation of raceway continuity during faults.

Page 3 of www.tnb-canada.com/catalogues/pdf/en/t_b/fittings_01a_eng.pdf
or www.newmantools.com/felpro/c5a.htm

For hazardous-location installations, Crouse-Hinds HTL compound is useful.

Top
#30099 - 10/04/03 08:25 PM Re: GRC Underground
Roger Offline
Member

Registered: 05/18/02
Posts: 1779
Loc: N.C.
GJ and Bjarney, do either of you or anyone know or have an opinion of a reason GRC would be used over PVC in an underground installation in todays world?

I can't personally justify it in my simple mind.

Roger

Top
#30100 - 10/04/03 08:57 PM Re: GRC Underground
Bjarney Offline
Moderator

Registered: 04/10/02
Posts: 2561
Loc: West-Southern Inner-Northeast ...
Some A&E firms and institutional/industrial facilities have GRC standard in their construction specifications. It’s likely some feel that the durability of steel over non-metallic is a better investment at a small additional cost. The criticality if the contained circuits has a big effect on the decision. One concern facility owners have is what telecom guys call “backhoe fade” or the unfortunate effect of dig-ins. Unscheduled power or communications outages can be staggeringly disruptive and exceedingly costly to some operations.

Running subsurface steel conduit is not that much of a task, and becomes far easier when you ‘get in the groove’ for lack of a better term. [A hydraulic bender at the trench edge is de facto for some jobsites and clients.]

It may be possible to offer a substitute proposal of nonmetallic below minimum specified burial depth, with GRC sweeps extending above ground. Concrete encasement of buried nonmetallic raceway—with or without rebar—might be acceptable to the client’s engineer.




[This message has been edited by Bjarney (edited 10-05-2003).]

Top
#30101 - 10/05/03 04:23 AM Re: GRC Underground
iwire Offline
Moderator

Registered: 01/05/03
Posts: 4343
Loc: North Attleboro, MA USA
No matter what is inside the raceway I would rather run PVC.

If what is in the raceway is critical have me concrete in-case it.

The reason for this is PVC will not change, at least in any of our life times, RMC ends up rusting inside and seems to bond with the conductors making it imposable to remove them if needed.

Greater care must be exercised with the back fill material, most times the site guy owns sand for the back fill on the jobs I work.
_________________________
Bob Badger
Construction & Maintenance Electrician
Massachusetts

Top
#30102 - 10/05/03 05:30 AM Re: GRC Underground
walrus Offline
Member

Registered: 07/25/02
Posts: 671
Loc: Bangor Me. USA
I use Kopr-sheild on cut threads otherwise nothing. It won't stop leaks into the conduit as conduit couplings seem to be(are) running thread(no taper) so they won't seal anyway.

I can think of a reason for steel over PVC if transistioning out of a deep hole. If compaction of the the dirt isn't done right the PVC will shear off where it hits native soil. I've seen it many times around tank holes. even rigid will shear if their's a coupling at the transistion

Top


ECN Electrical Forums - sponsored by Electrical Contractor Network - Electrical and Code Related Discussion for Electrical Contractors, Electricians, Inspectors, Instructors, Engineers and other related Professionals