Underground service installation (NH)

[DavidInNh]

I'm installing dedicated (not from the house) underground service for a new barn/shop and have a question.

PSNH requires 3" conduit, which I've installed per PSNH URD Conduit Installation (and its even passed town inspection). Next, I need to install a meter box and breaker panel. In this drawing, it appears that you go from the expansion joint to the bottom of a knockout in the meter box. When I look at meter boxes in HD or various online catalogs, I don't see any with 3" knockouts.

Does anybody know of a meter box with 3" knockouts? (and a 3" meter offset)
Does anybody know if it is OK to reduce to 2"? (The PSNH documents only mention 3")

-david

[jtd]

All of the boxes should have concentric rings knockouts for different size conduit up to 3". You'll probably want to locate the distribution box in the barn rather than outside with the meter. This requires two boxes versus a meter box/distribution box. It's best to get a friend with experience to help you if you don't want to hire an electrician. There are several important items - wire sizes, anticorrision grease (for aluminum wire), using the appropriate grounding rod clamp and proper grounding between the boxes as required by local code. Mistakes can be very costly. This is especially true with any internal wiring since it may not be inspected if you are doing the work yourself. I just wired my polebarn and am waiting for the power hookup. I hired an experienced neighbor to help.

[DavidInNh]

Thanks. I was already planning on two separate boxes. I'll do some more looking for a meter box with 3" knockouts. I looked at one at HD and it didn't go that big. I found one on the net with published specs that stopped before 3". I'll try a real electrical supply house later this week. I think it will all get inspected - our new town inspector is an electrician and he is pretty "meticulous". I've done plenty of interior wiring, but this is my first meter and panel. I may yet chicken out and hire a "consultant".

[DavidInNh]

I finally managed a trip to an electrical supply house today. The counter guy was surprised when I asked for a meter base with 3" knock-outs. He double checked with the boss and he said I was right - that is what PSNH requires for underground and they only had one model that had it. It seems strange that HD in NH doesn't carry meter boxes required by PSNH - but then again, maybe they were there and they were hiding, like the HD electrical department employees. [img]/forums/images/icons/smile.gif[/img]

Thanks for the pointer on the grease for aluminum wire.

[Pat]

Good luck to you. My first experience with 200 amp servie was to wire my moms meterbox and ran the HUGE wires 50 ft through conduit (now under the sun room slab) Not fun, trying to manhandle that big stiff wire. If you have a choice, choose enclosures with more room so it isn't so hard to fit the big wires.

Next week I'll be puting in temp service for my new house. It is 350 amp service, underground from the pole mounted transformer and the wires are really something... big, stiff, clumsy, and a pain to shape and fit. My builder suggested routing them around the house staying 10 ft outside any walls or slabs but that added over 150 ft to the run and got a veto.

I'm putting in 6 inch conduit to go under the foundation and util room floor. Overkill but shouldn't bind and should be able to be pulled in the unlikely event of a problem.

Pat

Pat

[DavidInNh]

PSNH doesn't let me have that bit of fun. The customer has to provide the conduit, meter socket, grounding and a pull cord. They pull the cable from the pole. Just laying the conduit has been a real adventure.

[Pat]

My utility is going to trench and lay direct bury cable. I have requested they trench as deep as possible to avoid conflicts with landscaping. I'll probably get 4 ft. I will put down 6 inch PVC conduit where and if the cable ends up under the doundation of the utility room. This will be for just in case.

Pat

[DavidInNh]

I was at PSNH's web site this morning and found a new document - it turns out that it is the customer's responsibility to install the meter base, but they will provide it. Sometimes I wish learning wasn't so painful. [img]/forums/images/icons/blush.gif[/img]

[jtd]

Yes, sometimes there are multiple documents regarding the complete installation and the when you don't do it right the companies act like "Well, it's obvious. Why does everyone install it wrong?" I got a little bit of this from the linesmen but they were nice enough to make the minor corrections required. I did go out of my way to make them know I appreciated their help. Courtesy goes a long way.

[CJDave]

[img]/forums/images/icons/smile.gif[/img] We have just recently finished an extensive "farm re-electrification" wherein we have literally changed everything and upgraded to higher amp services. [img]/forums/images/icons/tongue.gif[/img] We put everything in conduit and in each case we jumped up in size at least one size, sometimes two sizes. Conduit isn't that expensive and if you ever need to do any changes, the bigger the tube the easier it will be. [img]/forums/images/icons/tongue.gif[/img] We made sure that we used generous quantities of the 3M product called:WL-QT Wire Pulling Lubricant. That is a MUST. It makes the difference between sweating and grunting and just simply pulling wire. In most areas of the country, utility companies will require the customer to provide the raceway the meter can and base and the power company pulls their own conductors in. Sometimes if the run is a long one and the conductor size is way up there, you will need a "Pull Can" alongside the meter can for the pull rope to get a good shot at the pipe and to take the huge knock-out size. Because the utilities use mostly aluminum wire, conduit sizes have to be well above what you would install for copper. Bigger is SO MUCH better. And don't believe that stuff about not needing to use primer when you solvent-weld the pvc joints. USE IT and help keep seepage water out of your conduit. [img]/forums/images/icons/tongue.gif[/img]