EMT - UL Heads Up [RE-wrenches]

Joel Davidson joeldavidson at earthlink.net
Tue Mar 16 12:27:33 PST 2004


The screened knock-out is an trick used by people who live in muddabber
(wasp) country.

Editorial - It's nice to have knowledgeable, cooperative PV system
inspectors, but too often they become nit-pickers showing off what they
recently learned but do not understand. In most cities, it is easier to get
a 1200 amp service panel installaton signed off than a 10.4 amp PV inverter.

----- Original Message ----- 
From: "Jason Fisher" <jfisher at nahbrc.org>
To: <RE-wrenches at topica.com>
Sent: Tuesday, March 16, 2004 7:34 AM
Subject: RE: EMT - UL Heads Up [RE-wrenches]


> A not so often followed NEC requirement is to provide expansion fittings
> on longer PVC runs (NEC 1999 347-9, don't have 2002 with me). These
> fittings (slip coupled pipe with o-rings and Vaseline, that are still
> not "watertight"!) are hard to find in supply shops but are essential
> for applications like wiring piers. Generally, I'd hope we keep our runs
> shorter but one still should keep in mind just how much this stuff moves
> over temperature swings (see table). Frequently, you'll find pipes
> popped out of glued connectors at enclosures. While one might blame the
> helper for not putting enough glue on the joint, often times this is due
> to the conduit being installed during the hot summer, strapped down
> tight, then shrinking during the winter. You also see this a lot when
> PVC comes out of the ground, especially if it wasn't supported by
> undisturbed earth. And yes, all the old PVC I've messed with shatters
> easily.
>
> It is sad to hear that the rumors of this EMT-fitting issue are now
> being played out in CA. I do not look forward to the day when inspectors
> here start pulling this out of their hats. Anyone who has done
> electrical service work on equipment in wet applications knows that no
> conduit system is watertight, even the expensive PVC coated steel. The
> conductors need to be rated wet for a reason and we have always drilled
> weep holes in our exposed boxes. I had an inspector once, take issue
> with this (not in line with the box's listing) and suggest that we
> rather leave out a threaded plug and install screening to keep out the
> bugs. Huh? OK, thanks for the tip. I said I'd make sure I did that "next
> time".
>
> Jason Fisher
>
> -----Original Message-----
> From: William Miller [mailto:wrmiller at slonet.org]
> Sent: Monday, March 15, 2004 10:27 PM
> To: RE-wrenches at topica.com
> Subject: [SPAM] - RE: EMT - UL Heads Up [RE-wrenches] - Email found in
> subject
>
> At 06:08 PM 3/15/2004, you wrote:
>
> >I don't know if my experiences come from UV or heat-related exposures,
> >or a combination thereof.  What I do know is that I have seen and
> >replaced too many exposed horizontal PVC conduit installations with
> >sagging runs, split fittings, disfigured shapes, separated connections,
>
>
> That's easy to fix!  Just strap the PVC to some EMT!
>
> William
>
> PS:  With PVC you can't ignore thermal expansion effects.  (Not so
> familiar with EMT-- Is this also an issue?)  I don't ever figure any
> pipe, on a roof or underground, will stay dry.  And it's true, PVC can
> sag, it requires better support than EMT.
>
> Wm
>
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