Thread: 320A Meter Base -> 400A Fused Disconnect -> 400A Transfer Switch for 3 200A subpanels

Hey guys,

I'm working with the county inspector and the POCO on doing a solar array on my shop building. I used to have a 400A service at the shop and a 320A service at the house (200 feet apart).

The POCO would not let me run the solar array through the shop meter, since I would be putting way more energy back on the grid that I'm using. So I arranged for them to come out and disconnected the service to the shop and I then dug up the 3 x 500 MCM Al cabling and swung it up to the house.

Here's a riser diagram of sorts of the overall layout:



Pdf version:

http://www.cstone.net/~dk/400A%20Dis...r%20Switch.pdf

My question is mostly about the details of how to wire the meter base, disconnect and transfer switch together, especially the neutral and grounds.

Here are the 3 cabinets sitting next to each other:



Since I'm "only" using 300 MCM Cu between the 3 cabinets, the inspector had me swap the 400A fuses with 300A ones. Also, all the ground wiring is 1/0 Al.

The disconnect came with 750 MCM lugs (CMC LA 750-2) which are also rated for landing 2 cables up to 300 MCM and is stamped as such right on the lug. But the inspector said to only land one cable per lug. So I picked up some dual 350 MCM lugs, as can be seen in the above pic. The disconnect, btw, is an Eaton Cutler Hammer DH225NRK.

So here's how I envision wiring everything together:



As can be seen, my neutral to ground bonding is taking place in the service disconnect switch.

The transfer switch is an Asco 300G 2 pole. On the load side, I forced to land both 3/0 Cu cables under the single L1 and L2 lugs, since there is really no way to swap those out for dual lugs that I can see. But again, as with the disconnect, Asco states in their docs, that each lug is rated to accept up to a single 600 MCM or up to dual 250 MCM cables. So landing dual 3/0 would not be a problem I would think.

In the Asco, there are only 3 neutral connectors as seen here:



So I'm planning on landing both 3/0 Cu neutrals going the house sub-panels under 1 lug. I have read here that NEC allows landing 2 neutrals under the same screw if the cable is at least 1/0, which would be the case here.

Are there any other issues with my planned wiring layout? Btw, I'll be using 3" PVC conduit between the 3 cabinets. The L1, L2 and N feeding the shop, gets spliced to the 500 MCM Al as soon as it leave the cabinet. Just can't bring that thick stuff into the cabinet and terminate it there.

Line and load wires do cross in the meter base, but I see no way around that as they don't make a "mirror image" version. The guy from the POCO that came out said that was perfectly acceptable.

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Originally Posted by Peter Clausen

Hey guys,

I'm working with the county inspector and the POCO on doing a solar array on my shop building. I used to have a 400A service at the shop and a 320A service at the house (200 feet apart).

The POCO would not let me run the solar array through the shop meter, since I would be putting way more energy back on the grid that I'm using.

Peter, sorry to interrupt the thread. I can not help you but others chiming in will and I thought I might learn a thing or tow along the way.

1: When is returning energy on the grind a bad thing? This is low voltage.
I though the utility would be happy for any extra energy they could profit from for free.

Thank you for your patients.

Hi Robert,

No worries. I don't know if it is a Virginia thing or not, but I'm only allowed to put up a 20kw system, which isn't enough to wipe out my monthly bill completely.

Net metering is otherwise pretty cool in that I get credited the exact same amount that I pay, for each kwh I put back on the grid. My electric co-op does not charge more during certain hours of the day like I have heard some places do. My panels will be facing almost due South and produce about 15 kwh.

I'm thinking about adding panels to my West facing roof with a gentle slope on the main house as well. Since those will peak out late afternoon, when demand is highest, I really don't understand why the POCO won't let me produce more than I consume.

On my shop meter, I was only consuming about 240 kwh PER YEAR, and they would not just credit my account and let me apply it to the house account. Hence the need to do all this work. At least I know longer have to pay $40/month on the shop account just for having the meter (base distribution charge and misc taxes).

Peter, thank you for the reply.
Ontario is the only province I know that has solar energy rebate program for residential consumers that I know of.
Sorry I can not help you out. Also I am personally am surprised no one has chimed.

If those are your illustrations you are a very smart man and my hat is off to for being so intellectual.

Good luck.
Best regards.

Originally Posted by Peter Clausen

The L1, L2 and N feeding the shop, gets spliced to the 500 MCM Al as soon as it leave the cabinet. Just can't bring that thick stuff into the cabinet and terminate it there.

That splice will have to be made in a box, or other thing rated for connections.You can't just sneak it into your conduit.

Originally Posted by ROBERT YOUNG

Peter, thank you for the reply.
Ontario is the only province I know that has solar energy rebate program for residential consumers that I know of.
Sorry I can not help you out. Also I am personally am surprised no one has chimed.

If those are your illustrations you are a very smart man and my hat is off to for being so intellectual.

Good luck.
Best regards.

Hydro Quebec as a similar plan as Ontario except that it does not refund any excess that you produce.

Originally Posted by Marcel Gratton

Hydro Quebec as a similar plan as Ontario except that it does not refund any excess that you produce.

Thanks, Marcel.
I did not know that.

Originally Posted by ROBERT YOUNG

Thanks, Marcel.
I did not know that.

More info at:

Residential Rates | Net Metering Option