I'm building a new shop ( no metallic connections ) about 150' from my house. The shop will have a new 200amp service panel and I'll be feeding it from a 200amp disconnect panel at the house. My question is: How difficult is it going to be to pull the required 4/0 - 3 conductor aluminum wire through about 165' feet of 2.5" conduit? I've never done this before. Any tricks to making it easier?
I pulled in two 4/0 (hots) 2/0 (neutral) and a #4 (ground) XHW aluminum 115' from my yard panel to my house. It was in 2 1/2 PVC conduit with three 90° bends in the run. I bought triplex with the reduced size neutral and added the ground wire. You might want to use the reduced neutral because it will be easier to pull. As a separate building on the same premises you can skip the ground wire and just use a bonded neutral, but I would recommend separate ground wire. If you do run a separate ground, the panel will have a unbonded neutral bar that all of the white wires will go to and the ground wires will go to a ground bar you screw to the panel metal.
I used a come-along inside to pull with the come-along tied off to a ceiling joist. Make sure that you use a strong pull rope. Stagger the ends of the various wires and cut them off at a shallow angle so that the bundle gets progressively larger instead of forming flat front bumps. Either use a big enough pulling grip, or you can use lots of tape and make sure to wrap the rope around the wire several times with a timber hitch so the wires can't slide out of the rope. I used the knot with several timber hitches to pull mine. The whole taped off area will need to be several feet long to prevent one of the wires from slipping out.
When you go to pull, make sure to use lots of pulling lubricant. Lube the wires will to prevent chafing and make them slide easier. I can't over emphasize how important pushing is when you get to this size wire, particularly if you go with aluminum. It's very important to have two people working together so one can pull while the other pushes. Put the stronger person in the push position because the puller has the com-along to multiply force. The push person will literally climb the wires and use body weight to push them down.
I saw the contractor on "This Old House" use compressed air to blow a plug, with a rope attached, through a conduit (for a 200 amp outbuilding service), and then use the rope and his pickup to pull the wires for a 200 amp underground service, as a unit, through the installed conduit - as his partner aligned and fed the cables into the end.
Not my first choice, but if the ends of the conduit aren't sharp, and the wires are well gripped, etc., and they don't pull the wires so hard they stretch, and the rope strength was sized so it broke before the several cables stretched... I suppose... I remember the assistant was on the pole feeding the cable in, but I don't remember exactly how they routed it out of the conduit at the truck end - I think he ran the rope over a hook/pulley above the open end of the conduit (you don't need to bend the wires after they come out - just stop pulling then they are a foot or so straight up out of the end of the conduit.)
( I imagine if you are not careful and you did stretch the cable and it broke, you would be pulling cable back out of the conduit, or laying more conduit -and that would be more irritating to the contractor than just about anything else -- so on that basis alone I figured it must be a tried and true method in the northeast.)
(FWIW - you can pull the wire through from either end)
3-4/0 ? No equipment grounding conductor? Be sure and review the 2005 NEC Section 250.32 quoted below.
For 2 - 90 degree bends at 13 inch radii and using a pulling lubricant I come up with 100 to 153 pounds pulling tension. This assumes that some one is feeding the other end so the pulling tension into the first bend is zero. If you are pulling off a reel by yourself this could compound the required pulling tension since the bends have a mulitplying effect on the icoming pulling tension. I used my calculator based on a study by the ICEA at:
250.32 Buildings or Structures Supplied by Feeder(s) or Branch Circuit(s). (A) Grounding Electrode. Building(s) or structure(s) supplied by feeder(s) or branch circuit(s) shall have a grounding electrode or grounding electrode system installed in accordance with 250.50. The grounding electrode conductor( s) shall be connected in accordance with 250.32(B) or (C). Where there is no existing grounding electrode, the grounding electrode(s) required in 250.50 shall be installed. Exception: A grounding electrode shall not be required where only a single branch circuit supplies the building or structure and the branch circuit includes an equipment grounding conductor for grounding the conductive non- current-carrying parts of equipment. For the purpose of this section, a multiwire branch circuit shall be considered as a single branch circuit. (B) Grounded Systems. For a grounded system at the separate building or structure, the connection to the grounding electrode and grounding or bonding of equipment, structures, or frames required to be grounded or bonded shall comply with either 250.32(B)(1) or (B)(2). (1) Equipment Grounding Conductor. An equipment grounding conductor as described in 250.118 shall be run with the supply conductors and connected to the building or structure disconnecting means and to the grounding electrode(s). The equipment grounding conductor shall be used for grounding or bonding of equipment, structures, or frames required to be grounded or bonded. The equipment grounding conductor shall be sized in accordance with 250.122. Any installed grounded conductor shall not be connected to the equipment grounding conductor or to the grounding electrode(s). (2) Grounded Conductor. Where (1) an equipment grounding conductor is not run with the supply to the building or structure, (2) there are no continuous metallic paths bonded to the grounding system in each building or structure involved, and (3) ground-fault protection of equipment has not been installed on the supply side of the feeder(s), the grounded conductor run with the supply to the building or structure shall be connected to the building or structure disconnecting means and to the grounding electrode(s) and shall be used for grounding or bonding of equipment, structures, or frames required to be grounded or bonded. The size of the grounded conductor shall not be smaller than the larger of either of the following: (1) That required by 220.61 (2) That required by 250.122
I wouldn't mess with anything but the UL listed lubricant. You have to worry about the condition of the wire insulation for the next 50 years. The listed lubricant has been tested specifically for insulation degradation. Anything else hasn't.
I have heard that the friction from the pulling rope can cut into a PVC elbow but I don't have experience with runs like this. NEC 250.80 permits isolated metal elbows in service runs (but presumably not feedeers) to avoid this problem if there is a minimum cover of 18". You could use a metal elbow with metal conduit to the panel.
An electrician would probably use a pulling grip. Without that I would strip the wire ends and bend one back through a loop in the end of the pulling rope. I would reduce the number of strands on the rest of the wires and bend the ends of them back through the loop in the pulling wire staggering the full size ends away from the end of the rope. Use tape to keep the wires bent through the pulling loop and use plenty of tape to keep the bundle smooth. As Michael said, use plenty of wire lube and push the wires in. Be careful to avoid crossovers. The loop in the pulling rope is the weak point.
Particularly if using mechanical advantage consider the forces on the panel and conduit.
There are some electricians at alt.home.repair if you want advice beyond this thread.
Dave I have bad news for you. Your shop will either have to be supplied through a rather expensive special order 180 ampere breaker or you're going to have to run 250 MCM cable. A shop is not a dwelling unit. You cannot use the amperage table for dwelling unit services from Table
310.15(B)(6) to select your conductor size. You must use the size called out by table 310.16.
Tom, I disagree. The 200 ampere breaker protects both the 90 degree 4/0 aluminum rated at 205 amperes terminated on a 75 degree terminal rated at 180 amperes and a 75 degree C. insulated conductor rated at 180 amperes since we can size up per sect 240.4.
240.4 Protection of Conductors. Conductors, other than flexible cords, flexible cables, and fixture wires, shall be protected against overcurrent in accordance with their ampacities specified in 310.15, unless otherwise permitted or required in 240.4(A) through (G). (B) Devices Rated 800 Amperes or Less. The next higher standard overcurrent device rating (above the ampacity of the conductors being protected) shall be permitted to be used, provided all of the following conditions are met: (1) The conductors being protected are not part of a multioutlet branch circuit supplying receptacles for cordand- plug-connected portable loads. (2) The ampacity of the conductors does not correspond with the standard ampere rating of a fuse or a circuit breaker without overload trip adjustments above its rating (but that shall be permitted to have other trip or rating adjustments). (3) The next higher standard rating selected does not exceed
You probably won't believe this, but when we built the trans-alaska pipeline pump stations and north slope facilites we had to pull in sub zero temperatures. UL listed pulling lubricant froze solid, so we made our own using glycol anti freeze, soap and water. I guess it didn't hurt anything because most of those runs are still in service some 30 years later.
All right you got me. I had, incorrectly obviously, believed that 180 amperes was a standard size under the code. So since the conductor ampacity is 180, and thus five amperes over the next lowest standard fuse or breaker size, you can protect it with a two hundred ampere breaker. That assumes that the computed load is actually only 180 amperes or less which seems likely. It would be a good idea to label the building disconnecting means with the actual ampacity of the circuit.
Tom, I too was a working electrician that recently got tired and retired. I finally just finished putting the finishing touches on two webpage calculators that read Table 310.16 and most of the related requirements. I swear the thing took me about 2000 hours over ten years. It was a bitch to wite!