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Old 02-13-2008, 12:28 PM   #1
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New Service

Hi Folks,

I was hoping to get a little input on my "weekend" project. I've been building a house for the last couple of years and have fought w/ the electric company most of that time. However, we have finally settled our differences w/ them agreeing to put a meter at the edge of my property at which point I will assume responsibility, step the 240 VAC service up to 600 VAC, run it 1300 ft to another xformer, step it back down to 240 VAC and run it into the house. To complicated things, I already have a 9kw generator that I have used to build the house and it is currently connected to my main panel. Codes has required that I have a EE design everything from the meter to the house.

Id like some input on what my service will look like at the point it comes into my basement. Codes has lots to say about the "main" disconnect, and I'm curious how you would interpret where my "main" disconnect is.

I know you will want lots of info, but here are some preliminary details:

The meter is approx 1450 ft from the house. The meter will be mounted at/near the step-up transformer and there will be a disconnect between the meter and xformer. This will be a 200 amp service, so they are 50KVA xformers. They will be connected via 2, 3/0 AL lines and run in 2 schedule 80 conduit. There will be grounding rods at both xformers bonded to the neutrals. The step-down xformer will be approx 150 ft from the house, as is the generator, which has its own grounding rod. Both will run 2 hots, and 1 neutral (underground in 2 sched. 80) thru my basement wall and then approximately 30 to my main 200 amp panel (with disconnect), and from there I go to a sub-panel about 50 away (100 amp panel w/ disconnect). I will have a switchgear so that both the generator and service cannot be on at the same time.

So for starters, do I need a separate disconnect where the service comes into the basement, or can I run both services the 30 to a switchgear mounted next to my panel? Next, do I have to put a 100 amp breaker in my main panel prior to branching to my sub-panel, or since the sub has its own disconnect, can I run the 2-2-2 AL from the lugs of the main panel to the lugs in the sub? Third, do I tie the grounding rod(s) located at the house to the grounding rods located at the generator and step-down xformer? And finally, is there anything Ive described above that should/could be done differently to head off any future problems?

Thanks in advance for the help!



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Old 02-13-2008, 02:08 PM   #2
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Wow, this is a complicated setup, and I'm sure there is a better way to do it. Why can't the POCO put the meter closer to the house?

But with the setup you describe:

At the meter, you only need the two hot conductors to the first xfmr, no neutral. You need a disconnect for it, and a separate grounding conductor to bond the case. One leg of the secondary will bond to the case and a grounding electrode. You need a separate grounding conductor from the case to a secondary disconnect (appropriately fused) , which only needs to be single pole. In this case, you will have 600 volts between a hot and grounded (neutral) conductor, and a grounding conductor. These three wires will run to your step down.

At the step down, the secondary XO will bond to the case and a grounding electrode. A separate grounding conductor will run along with your two hots and neutral to a disconnect (fused), this time a two pole. Do not bond the ground and neutral here. It is already bonded in the xfmr.

You need to run 4 wires to your house from here. You need a main breaker in your panel, but no neutral bond. Unless you plan on using 200 A rated conductors to your subpanel and a 200 A rated panel, you need a 100 A breaker to feed it.

If your ground and neutral are bonded at the generator, you need a separate grounding conductor to your transfer switch, and the neutral must switch with the other conductors.



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