Peter Clausen
09-10-2016, 01:58 AM
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:
http://www.cstone.net/~dk/400A%20Disconnect%20and%20400A%20Transfer%20Switch .png
Pdf version:
http://www.cstone.net/~dk/400A%20Disconnect%20and%20400A%20Transfer%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:
http://www.cstone.net/~dk/400-Trio-02.JPG
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:
http://www.cstone.net/~dk/400-Trio-Wire-Layout.JPG
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:
http://www.cstone.net/~dk/Asco-400-02.JPG
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.
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:
http://www.cstone.net/~dk/400A%20Disconnect%20and%20400A%20Transfer%20Switch .png
Pdf version:
http://www.cstone.net/~dk/400A%20Disconnect%20and%20400A%20Transfer%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:
http://www.cstone.net/~dk/400-Trio-02.JPG
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:
http://www.cstone.net/~dk/400-Trio-Wire-Layout.JPG
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:
http://www.cstone.net/~dk/Asco-400-02.JPG
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.