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Home > Archive > Electrical Engineering > January 2008 > pulling large wire through PVC
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pulling large wire through PVC
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| I need to pull 3 lengths of 2/0 copper THHN through about 270 ft of 2 inch
PVC conduit with two 90 and two 45 bends in it. I've done this before, but
always with three separate lengths of wire pulled together. My supplier
says they may be able to get triplex wire cheaper than three separate wires.
Is the triplex going to be harder, easier or about the same effort to pull
as three separate wires pulled together?
How feasible would it be to pull 3 lengths of 4/0 aluminium wire through
this conduit? It's code-legal, but is it doable? Three 2/0 wires is the
biggest load I've tried through this length of 2 inch PVC, and that was
hard.
I was talking with an electrician friend recently, and he mentioned that
heavy pulling with nylon or poly rope can saw through bends of PVC conduit.
I've always used nylon or polyester rope with no problems. My friend
recommends cotton rope. Is this worth doing? Cotton is a lot weaker than
nylon or polyester, which is a worry, plus I'd have to go buy it.
Mike
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| Dean Hoffman 2008-01-16, 8:25 pm |
| newsman@att.net wrote:
> I need to pull 3 lengths of 2/0 copper THHN through about 270 ft of 2 inch
> PVC conduit with two 90 and two 45 bends in it. I've done this before, but
> always with three separate lengths of wire pulled together. My supplier
> says they may be able to get triplex wire cheaper than three separate wires.
> Is the triplex going to be harder, easier or about the same effort to pull
> as three separate wires pulled together?
>
> How feasible would it be to pull 3 lengths of 4/0 aluminium wire through
> this conduit? It's code-legal, but is it doable? Three 2/0 wires is the
> biggest load I've tried through this length of 2 inch PVC, and that was
> hard.
>
> I was talking with an electrician friend recently, and he mentioned that
> heavy pulling with nylon or poly rope can saw through bends of PVC conduit.
> I've always used nylon or polyester rope with no problems. My friend
> recommends cotton rope. Is this worth doing? Cotton is a lot weaker than
> nylon or polyester, which is a worry, plus I'd have to go buy it.
>
> Mike
>
>
I guess some people use steel elbows for this. A code class
instructor mentioned that the steel had to be grounded at one time even
if it was underground. Someone got electrocuted while doing repair
work because the steel elbow wasn't grounded. Code writers not familiar
with the history of the requirement later deleted the grounding provision.
Dean
| |
|
| Dean Hoffman > wrote:
> newsman@att.net wrote:
> I guess some people use steel elbows for this. A code class
> instructor mentioned that the steel had to be grounded at one time even
> if it was underground. Someone got electrocuted while doing repair
> work because the steel elbow wasn't grounded. Code writers not familiar
> with the history of the requirement later deleted the grounding provision.
>
> Dean
I believe metal elbows in a PVC run have to be grounded unless buried
below 18 inches, or a concrete requirement for non-service wires (NEC
250.80-ex, 250.86-ex3).
Damaging effect of the rope should depend partly on the rope diameter.
Soft nylon is probably less abrasive than polyester.
I wonder about the effect on triplex pulling it around a bend. The path
around the outside of the bend is longer and the wires can't easily slip
past each other to adjust. And with separate wires the 'longer' wire
tends to stay the same wire.
If you need more answers than you get on this newsgroup you could try
posting on alt.home.repair which has several electricians.
--
bud--
| |
| phil-news-nospam@ipal.net 2008-01-17, 1:25 pm |
| On Wed, 16 Jan 2008 19:29:55 GMT newsman@att.net wrote:
| I need to pull 3 lengths of 2/0 copper THHN through about 270 ft of 2 inch
| PVC conduit with two 90 and two 45 bends in it. I've done this before, but
| always with three separate lengths of wire pulled together. My supplier
| says they may be able to get triplex wire cheaper than three separate wires.
| Is the triplex going to be harder, easier or about the same effort to pull
| as three separate wires pulled together?
My guess is the triplex will be slightly easier because you will not
have as many points where separate wires are contacting the edges.
When the triplex is rubbing on one side of the inside of the conduit,
it is pulling the other wires with it and they will thus not rub on
the other side at that point. OTOH, triplex may not as easily like
to bend going around those conduit bends.
BTW, what is the radius of the four bends?
--
-----------------------------------------------------------------------------
| Phil Howard KA9WGN | http://linuxhomepage.com/ http://ham.org/ |
| (first name) at ipal.net | http://phil.ipal.org/ http://ka9wgn.ham.org/ |
-----------------------------------------------------------------------------
| |
| gfretwell@aol.com 2008-01-17, 1:25 pm |
| On Thu, 17 Jan 2008 10:39:56 -0600, bud-- <remove.budnews@isp.com>
wrote:
>Dean Hoffman > wrote:
>
>I believe metal elbows in a PVC run have to be grounded unless buried
>below 18 inches, or a concrete requirement for non-service wires (NEC
>250.80-ex, 250.86-ex3).
>
>Damaging effect of the rope should depend partly on the rope diameter.
>Soft nylon is probably less abrasive than polyester.
>
>I wonder about the effect on triplex pulling it around a bend. The path
>around the outside of the bend is longer and the wires can't easily slip
>past each other to adjust. And with separate wires the 'longer' wire
>tends to stay the same wire.
FPL pulls 4/0 triplex through 2" around here all the time but they
usually cheat and put the elbows and risers on after they pull the
straight run. That is not really legal
| |
| Gerald Newton 2008-01-18, 3:25 am |
| On Jan 16, 10:29=A0am, <news...@att.net> wrote:
> I need to pull 3 lengths of 2/0 copper THHN through about 270 ft of 2 inch=
> PVC conduit with two 90 and two 45 bends in it. =A0I've done this before, =
but
> always with three separate lengths of wire pulled together. =A0My supplier=
> says they may be able to get triplex wire cheaper than three separate wire=
s.
> Is the triplex going to be harder, easier or about the same effort to pull=
> as three separate wires pulled together?
>
> How feasible would it be to pull 3 lengths of 4/0 aluminium wire through
> this conduit? =A0It's code-legal, but is it doable? =A0Three 2/0 wires is =
the
> biggest load I've tried through this length of 2 inch PVC, and that was
> hard.
>
> I was talking with an electrician friend recently, and he mentioned that
> heavy pulling with nylon or poly rope can saw through bends of PVC conduit=
..
> I've always used nylon or polyester rope with no problems. =A0My friend
> recommends cotton rope. =A0Is this worth doing? =A0Cotton is a lot weaker =
than
> nylon or polyester, which is a worry, plus I'd have to go buy it.
>
> Mike
3 each 4/0 in 2 inch PVC has a jamming ratio of 3.189. This is not
advised by Chapt 9, Table 1 FPN No. 2.
REF:
http://www.electrician2.com/calcula...calculator.html
for additional electrician calculators try:
http://www.electriciancalculators.com
| |
| Long Ranger 2008-01-18, 3:25 am |
|
<newsman@att.net> wrote in message
news:SWsjj.441353$kj1.203294@bgtnsc04-news.ops.worldnet.att.net...
>I need to pull 3 lengths of 2/0 copper THHN through about 270 ft of 2 inch
>PVC conduit with two 90 and two 45 bends in it. I've done this before, but
>always with three separate lengths of wire pulled together. My supplier
>says they may be able to get triplex wire cheaper than three separate
>wires. Is the triplex going to be harder, easier or about the same effort
>to pull as three separate wires pulled together?
>
> How feasible would it be to pull 3 lengths of 4/0 aluminium wire through
> this conduit? It's code-legal, but is it doable? Three 2/0 wires is the
> biggest load I've tried through this length of 2 inch PVC, and that was
> hard.
>
> I was talking with an electrician friend recently, and he mentioned that
> heavy pulling with nylon or poly rope can saw through bends of PVC
> conduit. I've always used nylon or polyester rope with no problems. My
> friend recommends cotton rope. Is this worth doing? Cotton is a lot
> weaker than nylon or polyester, which is a worry, plus I'd have to go buy
> it.
>
> Mike
That is what "Mule Tape" is for. It is strong enough to pull in your wire,
but since it is flat like a ribbon, it doesn't eat the inside out of your
plastic bends. The stuff I have is rated at 12,000 #, if memory serves.
| |
| Gerald Newton 2008-01-18, 8:25 pm |
| On Jan 17, 9:08=A0pm, Gerald Newton <electric...@electrician2.com>
wrote:
> On Jan 16, 10:29=A0am, <news...@att.net> wrote:
>
>
>
>
>
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>
>
> 3 each 4/0 in 2 inch PVC has a jamming ratio of 3.189. This is not
> advised by Chapt 9, Table 1 FPN No. 2.
> REF:http://www.electrician2.com/calcula...calculator.html
> for additional electrician calculators try:http://www.electriciancalculato=
rs.com- Hide quoted text -
>
> - Show quoted text -
I should add the jam ratio for schedule 40 PVC is 3.189 but the jam
ratio for schedule 80 PVC is 2.98.
For rigid it is 3.2. Jam ratios of 2.8 to 3.2 are considered a
problem.
If you want to find out what a bad jam ratio will do try pulling 3 No.
8s through 1/2 inch EMT with a few 90's in it.
REF:
2005 NEC Chapt 9 Table 1
FPN No. 2: When pulling three conductors or cables into
a raceway, if the ratio of the raceway (inside diameter) to
the conductor or cable (outside diameter) is between 2.8
and 3.2, jamming can occur. While jamming can occur
when pulling four or more conductors or cables into a raceway,
the probability is very low.
| |
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| Thanks for all the replies. Particularly for info on jam ratios and mule
tape. I'll either use 3 2/0 copper wires, 2/0 copper triplex, or 4/0
aluminum triplex (hope to avoid the latter, but $ may dictate it), and pull
with mule tape.
Mike
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