what is the lettering for triplex or as its called out here in the west coast "URD"? a contractor(general)has poured the foundation for a house and ran 2 1/2" pvc under his garage slab and up into a interior wall in the garage (remote meter) well now the home owner wants electric heat and electric insta heaters for tub and kitchen, which the original 200 amp service wont handle (has a comp with a high locked rotor current) and now they want to bump up to a 400 amp servic(320 amp meter no doughnuts or ct can)but problem being one 2 1/2" pipe. will the 4/0x4/0x2/0 pair fit? not that it will be an easy pull mind you. i dont like what he is suggesting and depending on actual lettering of triplex will determine if it is even legal. when i tried to suggest putting service on exterior wall he just about blew a gasket. another problem is running though one panel to get to another ive never done this and wonder if a gutter below both panels will be required?
Legally, you can put up to 7 #4/0's in a 2 1/2" conduit. That's with an insulation suitable for a damp or wet location. I've never seen triplex installed underground. Someone else may be able to correct me on this, but since the neutral conductor is not insulated, you may not be able to use it this way. You are also not allowed to use the panel as a junction box to get to the other. 312.8 in the NEC prohibits this.
XtheEdgeX, why don't you feel that most panelboarsd have don't have space? I think that it would be very hard to exceed the allowable gutter space in most situations. In this case I could see more of a problem because of the wire size. I think wire bending space is going to be a bigger issue.
H2O, will the conductors from the remote meter be service conductors or feeders? (will there be overcurrent protection at the meter)
triplex is sorta a generic term we used back in mn. it isnt a bare neut(guy wire)it is 2-4/0's with a insulated neutral. guess thats why they call it urd here in the west coast. thanx guys appreciate the comments.
Never heard of URD.... (On the west coast) googled it and came up with mostly med. voltage cable. (KV) You're right though, "Triplex" is pretty generic, and means diferent things to people. I think of it as arial service drop wire. "Triplexed", would be concentric clockwise twisted conductors in my mind.
Anyway you would have more room than you need to pull 3 4/0....(yes it won't be easy with distance and bends) Unless you are dealing with POCO rules like PG&E. You might be looking at 4"....
Mark Heller "Well - I oughta....." -Jackie Gleason
You CAN NOT use a panelboard as a junction box. NEC 110-3(b) Installation and Use. Listed or labeled equipment shall be installed and used in accordance with any instructions included in the listing or labeling. UL-67, to which panelboards are tested listed and labeled, does not list a panelboard to be used in this way. Here is an interesting read on this subject, that includes a response directly from UL. http://www.isa-home-inspections.com/articles/tecspk08.pdf
XtheedgeX- I hope that your not saying what it looks like your saying because there are a bunch of panels out there with splices in the gutter space. I don't think UL will ever say that this panel is listed for allowing splices in the gutter space. BUT- the code is rather clear that you can splice in enclousures with overcurrent devices in them if you have the room and stay within the percentages called out. The words "Listed for the purpose" with respects to splicing are not found here. I'm wondering how we measure the 75% or 40%. I venture to say if you asked a pointed question of UL about "Listed for splicing" they will always say "No it's not Listed for splicing". Probably no manufacturer has ever submitted a producted and specified that it be Listed that way because the code doesn't ask that it be so Listed for splicing.