Another journeyman & I (with 2 helpers) are now into our 4th week of turning a new & empty 80'x30' into the control room of the soon to be largest switch on the biggest trunk (345KV) in Texas. I know they(the utility)are exempt from code but there ARE some strange things, such as using white (as well as green) for phase, but using black for ground. OK...I got over that one. Next, after installing the overhead trays, AC & DC panels, etc., I wire in the requisite 5 rows of the usual cheesy fluorescent fixtures and receptacles according to prints. At this point we still haven't received the panel schedules, but hey.... they show the circuit numbers on the lighting and receptacle prints (AC 43X, AC44X, AC45Y, AC46Y, etc.), and, knowing service will be 240v.(X&Y), I mount both panels (1-42)&(43-84)and terminate the 120v. stuff. This week the panel schedules finally show up...and when I saw how the engineer has arbitrarily choosen to number the circuits according to his idea of the actual number of circuits with no correlation to panel numbers, well........ Example, if the first breaker on the left hand side was a two-pole 240v breaker, one would normally number the first wire #1(X-black) and the red wire below it #3(Y-red). Said engineer instead chooses AC1X and AC1Y. OK.....I can learn to live with that. BUT....I'm running service this coming Monday and I wonder how AM I going to pull FOUR 4/0 THW's for a distance of 150' through a single 2" underground PVC with two 90's ? (from the 200 A. disconnect I installed out by the transfer switch all the way into the control room to my distribution panels). But this IS what the customer calls for...and the plans MUST BE FOLLOWED!!!

[This message has been edited by 3rd degree Burns (edited 02-09-2002).]

[This message has been edited by 3rd degree Burns (edited 02-09-2002).]

[This message has been edited by 3rd degree Burns (edited 02-09-2002).]

LOL!, 3rd Deg.........get the pull 1/2 way there, play the 'dope' and ask him how to do it.

Send a Request for Information to the engineer, detailing your problem.
(He'll try to shirk it off, of course)
Then, give them a price to run a properly sized conduit overhead. Make sure you get a signed Change Order before you proceed with the work.

Four 4/0 THWNs or XHHWs will fit in 2" schedule 40 PVC. Are the 90's PVC or rigid? The pull rope will probably cut through the 90's if they are PVC.
Don(resqcapt19)

In a pinch, buy some nylon webbing from a caver or mountain climbing supply, (or any other source if you can find it...) 1" to 1-1/4" wide is good. It will be less likely to cut into the PVC Sweeps.

Sparky,
In a rope rescue class I was taught that moving nylon straps on any type of pastic was something to avoid. They said there was too much heat build up and the nylon could fail. Of course this was for life safety not pulling wire. I've never tried a nylon strap, but often use rigid 90s in under ground runs. I've also had good luck soaping the pull rope.
Don(resqcapt19)

Hmmm!?!? Allegheny Power uses webbing for UG pulls, mabe it's not Nylon?

What about bonding concerns with the lone GRC sweeps in the middle of PVC runs?

[This message has been edited by sparky66wv (edited 02-09-2002).]

Sparky,
I've never used them above grade and the code permits them to be unbonded when they are covered with 18" of earth. See Exception #3 to 250.86.
Don(resqcapt19)

GRC sweeps so not need to be bonded if they are at least 18” underground.

I have found that mule tape works real good. It has footage marks every foot too.

What is "mule" tape.
If I'm pulling anything like that it would be with tugger and the rope that goes with it.
Don(resqcapt19)

Yeah, Resqcap...Schedule 40 PVC and I have no problem with 2"nipples or straight runs. Even the NEC table only shows a max. of two #4/0 RHW. One 90 is verticle, the other horizontal, both are buried leading into the control room....about 150-160 feet underground and an additional 75 feet up into the overhead tray and over into my distribution panels. We will see.....I'll keep you posted on how it goes.

3rd degree,
I agree that the Table C10 says that only2 4/0 RHWs fit in a 2" schedule 40 PVC conduit, it also says that 3 4/0 THWs fit and 4 4/0 THWNs or XHHWs fit. With the proper equipment I don't see any problem other than the pull rope and or conductors cutting through the inside of the 90s. If this happens the conducotrs will be damaged.
Don(resqcapt19)

Don,
Mule tape is used by datacom people allot. I don't remember the exact material it's made of but it is smooth and flat with footage numbers stamped on it. I think its nylon. I have found it works well on small and medium size feeder pulls. It does not cut into PVC 90's. If I find a link or manufacturer I'll post back with it.

Are you also including the #4 EGC in your calcs for conduit size? Doesn't it become 2-1/2"?

[This message has been edited by electure (edited 02-09-2002).]

Electure,
I didn't include an EGC. I see that this is after the service disconnect so an EGC required and you are correct that when the #4 EGC is added a 2 1/2" conduit is requried.
Good catch!!
Don(resqcapt19)

Like I said, tommorrow should prove interesting...........

I guess you would be referring to me and my fellow engineers. I woudl agree that a lot of engineers need to have field experience before entering into any job requiring design. I am very glad that I am still getting my field trainging while earning my degree. I have looked at designs from professors and fellow students that are almost impossible to do in the real world. The trouble always comes from the lack of field experience.

Electure, overheads are out of the question in a switchyard....EVERYTHING is buried in PVC (except for the high voltage transmission lines). I installed the disconnect about 20' below some comparatively small 38KV potential transformers....you get the picture.

Cool........we made our run today, a HARD pull, a tackle and a bucket of soap, but otherwise OK. Actually, we ended up pulling THW instead of RHW and only three 4/0's instead of four(2 hots & neutral). We will derive our ground somewhere else-son't ask, there are miles of grounded grid electrodes in a switchyard and the EGC will come into an overhead in an opposite direction than where I took our service-it gets complicated but the entire yard is fairly "flat" as a result). Really though, I don't think we could have negotiated that last PVC elbow if we had to pull four in that damn 2".

We did a small power plant last summer that I spent a few weekends at. The grounding (bonding) scheme was similar. Just tap into the ground grid anywhere. I did then and still do think it is a violation of 250.134(B). I don't understand why things suddenly change just because your we are inside a substation or power plant.

Nick...The reason why things CAN change is due to NEC Article 90.2(b)(5). The reason why things are done in their own fashion, aside from the technicalities, stem in part from the result of 50-80 years of having state-wide infrastructures/organizations/providers that were around long before we or our parents were born. I coaxed this truth out of a 29 yr.TXU Switch Manager in regards to the strange color code. Things have been done for so long state-wide, it is just how things are. You ought to have heard my fellow journeyman rant today about having to install white for positve and black for negative on the battery banks/chargers in the control room. Oh well....

[This message has been edited by 3rd degree Burns (edited 02-12-2002).]

Actually, the color code is the old vacuum tube circuit color code, where black was common, and white was some positive voltage. This electronics color code is still found in equipment today..as well as in the curriculum of the engineering students. Its not "practice", its just a different color code. They probably think WE are the one's who are backward.

Elzappr,

I have never seen any hot wires marked white. Our standard electrical engineering color code has always been balck for common, red for positive. Thats what we are taught here.