Dual panels, ATS switch on one....

[HammaMan]

Home is a fully-gutted remodel, all old wiring removed, 2 new 200a panels installed indoors. First time using an ATS -- When Gen power is active, gen has 60a breaker and the next disconnect breaker in line is the 200a in panel 1. Can the neutral case ground bond occur in panel 1 with the neutral and ground bar in ATS remaining isolated? Customer wants all metal conduit and fittings, but I believe the ATS to panel 2 must include PVC at some point as to not maintain a conducting path. The meter is yet-to-be-supplied by the utility, and am waiting on clarity for what exactly they're providing. NEC 2014 applies. Previous 2 panel install used 2 outdoor disconnects, one to each panel with each outdoor disconnect bonded. They were connected separately to single meter via PVC. As of yet no outdoor equipment mounted.

 

[Little Bill]

Normally, if you have a "service rated" ATS the bond is made there and the panel is a subpanel.
But since you have a meter combo, you would need to bond there and isolate the grounds & neutral in both the ATS and panel(s). That's the way I see it anyway.

 

[GoldDigger]

If your ATS has to switch the neutral you are more limited in where the ground to neutral bond is located.

 

[HammaMan]

The combo box is what the home owner believed the utility was going to provide -- I've asked the home owner to clarify with the utility and see what options are available (the utilities own literature says meter bases are only supplied under limited circumstances, if at all). The ATS only switches L1/L2, and it is service rated. I believe I'll request the utility to supply just the meter base, and the customer purchase a separate 200a disconnect for panel 2. The meter will then separately feed the ATS (panel 1) and the 'new' disconnect (panel 2). I know there will be some grumbling--I don't think they've gotten over the sticker shock of the AFI and especially AFI/GFI combo breakers.

 

[cuba_pete]

Depending on whether or not you switch the neutral, and each of those panels power different devices which share a common bond outside of the safety ground i.e., coax or network cable...watch out for ground loops and circulating currents. It's likely, however, that the ATS panel will have things like refrigerators, freezers, etc. If the TV and computers are connected across the panels and bonded through their communications cables, there could be issues for sensitive devices.

Also if you have devices which cross that boundary when you are running the generator, the neutral could still be bonded back to the service.

 

[ceb58]

I see a problem with the conductors if you do it the way your diagram shows. You have the conductors in the same nipple from the meter/combo to the ATS. The conductors from the breaker in the meter to the panel are now feeders. The conductors from the meter to the breaker in the ATS are still service conductors. Cannot be mixed. 230.7 I also question the use of 2/0Cu from table 310.15 (B)(7) 2011nec

 

[texie]

View attachment 15097

Home is a fully-gutted remodel, all old wiring removed, 2 new 200a panels installed indoors. First time using an ATS -- When Gen power is active, gen has 60a breaker and the next disconnect breaker in line is the 200a in panel 1. Can the neutral case ground bond occur in panel 1 with the neutral and ground bar in ATS remaining isolated? Customer wants all metal conduit and fittings, but I believe the ATS to panel 2 must include PVC at some point as to not maintain a conducting path. The meter is yet-to-be-supplied by the utility, and am waiting on clarity for what exactly they're providing. NEC 2014 applies. Previous 2 panel install used 2 outdoor disconnects, one to each panel with each outdoor disconnect bonded. They were connected separately to single meter via PVC. As of yet no outdoor equipment mounted.

Among other issues, this is a non starter if you have a meter/main combo as you can't attach conductors directly to the meter ahead of the breaker. If you do end up with, say, a 400 amp meter/main it will have 2, 200 amp main service disconnects which would be fine-just use a standard transfer switch. If you are stuck with a service rated transfer switch you could use it if you remove the main bonding jumper. Just make sure is SUSE and not suitable ONLY as service equipment as you won't be able to remove the main bonding jumper. Or just use a standard meter socket with a separate 200 amp main and the service rated ATS as the second main.
Also noted is that your genset is considerably smaller than the feeder you are supplying so you will need automatic load shedding to keep the load on the genset within limits to comply with Art. 702.
Also as an FYI, note that all meter/main combo units are suitable for use ONLY as service equipment as they have a non removable main bonding jumper.

 

[ActionDave]

I see a problem with the conductors if you do it the way your diagram shows. You have the conductors in the same nipple from the meter/combo to the ATS. The conductors from the breaker in the meter to the panel are now feeders. The conductors from the meter to the breaker in the ATS are still service conductors. Cannot be mixed. 230.7 I also question the use of 2/0Cu from table 310.15 (B)(7) 2011nec

I see the same thing. Put a pair of breakers in the meter/main, one to feed the sub-panel, one to feed the ATS on to the other panel cleans all that up.

 

[HammaMan]

Thanks for the input, The HO has made it much more difficult than it should be. This is what I settled on, told them to have util to supply meter only. They're dragging their feet on a lot of other things on the home. Holding off on outside boxes until the utility does their thing -- still haven't even run the lines in since they're going from aerial to UG. 2,700 sqft, NO blue prints, just a single page rough drawing. Can't do anything in the kitchen as of yet. Total nightmare.

 

[HammaMan]

Would any of you mind takng a look at my other thread regarding the contactor panel... http://forums.mikeholt.com/showthread.php?t=177148