EMT - UL Heads Up [RE-wrenches]

[Matt Tritt]

This is sure to get a rise from someone, but on one of the first PV jobs
I did back in 80, I worked with an "old time" electrician who insisted
that the couplings on our underground run be left un-glued at the lowest
point in the trench. He said that this allowed the water, which would
inevitably show up in the conduit, to find a way out. PVC was pretty new
at the time so I don't know where he got his idea.

I thought that what goes out would also come in the same way, but I've
never had a call-back, so who knows.

I have also had very good success with oxidation prevention by painting
PVC with good latex house paint. This can look really crappy if done in
a hurry. 

I would like to add that PVC, being non-conductive, has always seemed a
lot safer to work around than e.m.t after getting hit a couple of times
from old e.m.t. installations with ground faults.

Matt T

-----Original Message-----
From: Bruce Geddes [mailto:b.geddes at clear.net.nz] 
Sent: Tuesday, March 16, 2004 12:33 PM
To: RE-wrenches at topica.com
Subject: Re: EMT - UL Heads Up [RE-wrenches]


Hi All,
            Following this thread with interest.

Being in New Zealand complete with ozone hole exposes us to some of the
highest UV levels to be found.  PVC conduit is used widely here but it
is stamped UPVC for UV stabilised.

I have seen installations exposed that are older than 20 years and the
conduit is intact.  The surface does go faded and a powdery layer forms
but it is only very thin.  The underlying material is good.  We use two
colours, grey and orange and both behave the same.  The biggest problem
is impact damage as PVC is relatively brittle.

As pointed out in other posts if it is not supported frequently the
conduit will sag between fixings.  If there is enough of this sagging
the glue together joints can seperate if not glued properly.

Condensation is an issue and even the moistureproof boxes I use on
rooftops still develop some moisture inside after years of use.  I now
drill small drain holes at low points and ensure that there are low
points before every termination or penetration.

I use rigid for the main runs and have a length of flexible jointed on
to run up to PV junction boxes.  This allows the panels to be tilted and
lay over for maintenance work.

Metal conduit has not been widely used here for decades.  I know that
this is not the USA and your NEC is different, but electricity is
electricity. Incidentaly we use 230/400VAC 50Hz.

So at the end of the day PVC conduit has a place and can do the job.
Longevity has as much to with installation techniques as with the
material.

Just my NZ$0.02 worth  (US$0.013)

Bruce Geddes
PowerOn

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