Off grid house bonding sanity check

[jaggedben]

Hmm. If you have no service, and just one electrical source, it is by definition an SDS.

If you have no service, and two electrical sources, then you have 0 or 2 SDSs. 0 SDSs would be the case where the two sources have a solidly connected circuit conductor, e.g. the grounded conductor. While 2 SDSs would be the case where there is no non-grounding/bonding connection between the two sources. ...

Lol there you have it. 250.4 thru 250.20 apply, but 250.24 and 250.30 do not. Notably, 250.142(B) also does not apply because of how it’s worded. So, codewise you can ground this system anyway and anywhere you want that meets the very generally stated intents in 250.4.

I would still go with the main panel myself. Keep it simple.

I'm pretty sure the Sol-Ark inverter syncs with the generator when it turns it on. I believe it will not behave like a grid-tied inverter in this configuration, but is capable of acting as a parallel voltage source. As Birken will tell you this is not a particularly new. Actually I'm just assuming it has similar capabilities to the old Trace or Sunny Island.

 

[pipe_bender]

I would still go with the main panel myself. Keep it simple.

Agreed

I'm pretty sure the Sol-Ark inverter syncs with the generator when it turns it on. I believe it will not behave like a grid-tied inverter in this configuration, but is capable of acting as a parallel voltage source.

The way 250.30 reads to me is this parallel voltage source would be one SDS.

 

[jaggedben]

Agreed

The way 250.30 reads to me is this parallel voltage source would be one SDS.

What Wayne has brought our attention to is that the definition of an SDS isn't written that way.

Actually it really ought to be fixed because it could be read as saying that 250.30 doesn't apply to a system supplied by both a transformer and a grid-tie inverter, but it's industry standard to treat the transformer as an SDS and I'm strongly of the opinion it should stay that way.

 

[pipe_bender]

What Wayne has brought our attention to is that the definition of an SDS isn't written that way.

Actually it really ought to be fixed because it could be read as saying that 250.30 doesn't apply to a system supplied by both a transformer and a grid-tie inverter, but it's industry standard to treat the transformer as an SDS and I'm strongly of the opinion it should stay that way.

Sorry I am confused 250.30 it says "Multiple separately derived systems that are connected in parallel shall be installed in accordance with 250.30". So just for my education what makes them in parallel or not in parallel ? I would think a inverter syncing with a SDS makes it all one SDS?

 

[wwhitney]

Actually it really ought to be fixed because it could be read as saying that 250.30 doesn't apply to a system supplied by both a transformer and a grid-tie inverter

Well, the second sentence of (2017) NEC 250.30 may reasonably be taken to mean that if you have two or more sources connected in parallel, and they would individually be SDSs if they weren't in parallel, 250.30 still applies.

Cheers, Wayne

 

[jaggedben]

Well, the second sentence of (2017) NEC 250.30 may reasonably be taken to mean that if you have two or more sources connected in parallel, and they would individually be SDSs if they weren't in parallel, 250.30 still applies.

I see. But subsequently they went ahead and muddled that with 'of the same type.'