pulling large wire through PVC

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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snipped-for-privacy@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
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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.
If you need more answers than you get on this newsgroup you could try posting on alt.home.repair which has several electricians.
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wrote:

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
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On Wed, 16 Jan 2008 19:29:55 GMT snipped-for-privacy@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?
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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/calculators/rf_calculator.html for additional electrician calculators try: http://www.electriciancalculators.com
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wrote:

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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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.
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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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