Feeder installation

[w6259]

Help! I have an 'engineer' wanting to install a feeder to a disconnect that is to be used for power to a Sea/Land storage unit. The disconnect will be fed from a building 700 feet away. He wants me to install conduit run across the top of the ground. He is intending this to be a permanent installation. It doesn't feel right to me but I cannot put my finger on a code article to slap him with. The supports will be short pieces of strut with stakes driven into the ground. I don't feel that this qualifies as supported as per 300.11. I appreciate any input.

 

[txsparky]

Re: Feeder installation

Hmmmm...
I'm thinking 1/2 allthread cemented in, unistrut, and RMC.
If it is "permanent", why doesn't the engineer want it buried? Ground conditions maybe?

 

[BAHTAH]

Re: Feeder installation

Have installed cable (MC) above ground in ski areas for lifts. It is on on the ground (rock)exposed in the summer and under 10ft of snow in the winter. If its protecdted from physical damage like they say, burial depth only applied if you bury it.

[ December 08, 2003, 12:18 PM: Message edited by: grant ]

 

[tom baker]

Re: Feeder installation

Rigid conduit could be laid on top of the ground, its considered suitable for protection from severe physical damage.
On the other hand, Art 330 tells us MC cable:
330.10 Uses Permitted.
(A) General Uses. Where not subject to physical damage, Type MC cables shall be permitted as follows:

It can be run exposed but not subject to physical damage.

It really hinges on how it runs and what damage it will be exposed to. Typically it can be buried 6" deep. To me, it would be faster to run it 12" underground then to fool around with strut and stakes.

And if you want to really do it fast, run pvc, if you are worried about damage encase it in concrete, say a one sack mix.

Pehaps someone with some experience estimating can run the numbers, comparing running 700 ft of rmc to pvc - buried.

 

[w6259]

Re: Feeder installation

Thanks for the replies. The engineer doesn't want to pay for the dig, either direct burial or in pipe. Also, there is no provision for anchoring the strut in concrete. I just thnik that he's trying to short-cut the job. I really want a code violation if it is installed this way. If I can show him that we could likely spend the $ to do it right, which is what I feel obligated to do...although he (Engineering Department) is the AHJ. This is a gov't facility.

 

[iwire]

Re: Feeder installation

It is not a great job but I can not think of any code violations.

This is the sameway raceways are often run across roofs.

 

[ranger12]

Re: Feeder installation

How does he intend to protect people from tripping over this conduit?And assuming it is schedule 80 pvc{for physical protection} how many expansions joints does he want in this run?Rigid metallic conduit would be more expensive to buy.We do the stake method for securing pvc feeders under mobile homes once in a while but this is always covered with a skirting so one does not see it.I would be a bit worried about my own liability in a case like this.

 

[tom baker]

Re: Feeder installation

Heres an angle you can use. RMC does expand due to temperature, see 300.7 FPN for expansion of RMC, it is 20% of PVC determine the min to max temp change from winter to summer. You'll have to install an expansion coupling and they will be expensive.

 

[tshephard]

Re: Feeder installation

Even out in the wild blue yonder, how do you protect from vehicle damage with conduit slightly above ground?
If the RMC is allowed, it would be best protected long term, just laying, rather than raised. Most vehicles would just roll over it.
Talk 'em into oversize for later expansion.

 

[w6259]

Re: Feeder installation

My feeling exactly, vehicle traffic, tripping hazard and oversize for future. I don't feel good about it but he's the AHJ. I have no liability if I express my concern and he over-rules me. Looks like I'm going to have to do it this way...wish me luck. BTW, I don't feel so stupid now since you smart people couldn't find me an out either. thanks again.

 

[hurk27]

Re: Feeder installation

700' away

I hope you did your voltage drop caculations.
Had a contractor bid a pump house 780' from the main service where he wanted to feed from. three large motor loads and electric heat to boot. the POCO wanted 9K to drope a primary to the pump house he thought he could do it for 6K and this was a 600 amp load. boy was he wrong.