Solar edge 11.4 on high leg shutting down

ggunn said:
Ignoring your hyperbole for a moment, are the transformers themselves balanced? Have you asked the POCO if they would allow the system to be connected to only the A and C phases? Are you sure that whoever at the POCO told the solar contractor to balance the PV system across all three phases knew what they were talking about?
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Birken Vogt said:
What would happen if you just moved the troublesome inverter to a more stable phase and did not tell anyone?
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ggunn said:
Moreover, did the POCO tell you personally that the PV system needs to balanced over all three phases, or is that what the solar guys are telling you that the POCO said? This is an unusual configuration for a system, it could be that the solar guys have got it wrong. I would check out the simpler solution that we know would work (connecting to the A and C phases) thoroughly before discounting it.
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I was on a conference call with the POCO guy and the solar developer. Yes the Poco specifically wanted the inverters balanced as much as possible, I heard it straight from his mouth. As I said in a previous post somewhere, just moving the troublesome inverter off the open phase would be the simplest solution assuming the Poco allows. We wouldn't even need to avoid B completely we would just need to avoid BC. However, The feeder serving the combiner panel is not large enough to accomplish any rearrangement. I'll leave it to the solar developer and the Poco to hash out whether they want to go that route. Birken, yes if this was my install and job, I would probably just move it and upgrade the wire and not tell anybody and be done with it.
 
electrofelon said:
I think all they care about is whether their infrastructure can handle the load...
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Yeah exactly and its difficult to balance on a primary line thats not there thru a transformer thats not there.
Like my sink analogy in post 58 you only have two sinks to dump power down.
 
electrofelon said:
Perhaps, but didn't someone else say the Poco doesn't really care whether your inverters work or not? 😂. I think all they care about is whether their infrastructure can handle the load, and if their costs are as low as possible.
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Correct me if I'm wrong but theoretically I believe the difference in current on the B leg between two inverters on AB and one inverter on each of AB and BC is 2/(sqrt3), or a ~15% increase. This does seem like not a big deal to get the whole system working.
 
All I'm saying gunny is I I don't see any reason to avoid connecting to the high leg on a Delta service, provided the Poco allows, it doesn't limit my choice or preference of inverter, and it's a closed Delta (or maybe if it's open and POCO is cool with identifying and avoiding the open jaw).
 
jaggedben said:
Correct me if I'm wrong but theoretically I believe the difference in current on the B leg between two inverters on AB and one inverter on each of AB and BC is 2/(sqrt3), or a ~15% increase. This does seem like not a big deal to get the whole system working.
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Inverter current is 48A x 4. So say 2 on AB and 2 on AC if we want to avoid BC. Doesn't A see 96 x 1.866?
 
tortuga said:
Yeah exactly and its difficult to balance on a primary line thats not there thru a transformer thats not there.
Like my sink analogy in post 58 you only have two sinks to dump power down.
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Right so to gunny's point, in theory it doesn't really make sense for them to want all three phases balanced. Seems like they should want it connected in such a way that would balance the load across the two transformers.
 
electrofelon said:
Inverter current is 48A x 4. So say 2 on AB and 2 on AC if we want to avoid BC. Doesn't A see 96 x 1.866?
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No, the factor is not 1+sqrt(3)/2 =1.866, it's just sqrt(3) = 1.732. So 166A.

Versus sqrt(962+482+48*96) = 127A on A if you have 2 on AC and 1 on AB. [Law of cosines for phase angle difference of 60 degrees, as cos(60 deg) = 1/2.]

Cheers, Wayne
 
jaggedben said:
Correct me if I'm wrong but theoretically I believe the difference in current on the B leg between two inverters on AB and one inverter on each of AB and BC is 2/(sqrt3), or a ~15% increase. This does seem like not a big deal to get the whole system working.
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That's correct if there were 2 inverters. But there are 4 inverters. So the ratio for A between not using BC versus using BC is 2*sqrt(3)/sqrt(7) = 131%.

Cheers, Wayne
 
electrofelon said:
Like most high leg Delta services, I imagine the load is highly unbalanced. I agree it is likely inconsequential whether the PV system is balanced or not, but if I may quote you, it is not our place to ask or question, we just have to do what the POCO says.
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But I have also said many times that we must choose our battles wisely; sometimes it is indeed worth it to challenge a POCO on a ruling when it makes a big enough difference to the project.
 
wwhitney said:
That's correct if there were 2 inverters. But there are 4 inverters. So the ratio for A between not using BC versus using BC is 2*sqrt(3)/sqrt(7) = 131%.

Cheers, Wayne
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How does the POCO think he is going to balance four inverters on three phases?
 
ggunn said:
How does the POCO think he is going to balance four inverters on three phases?
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Obviously not possible without adding a transformer (Scott-T would work), but two on AC and one each on AB and BC would be the most balanced, particularly if the AC (lighting) transformer is larger. It gives you a balanced 3 phase supply plus a single phase supply on the transformer designated for single phase loads.

Cheers, Wayne
 
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wwhitney said:
No, the factor is not 1+sqrt(3)/2 =1.866, it's just sqrt(3) = 1.732. So 166A.

Versus sqrt(962+482+48*96) = 127A on A if you have 2 on AC and 1 on AB. [Law of cosines for phase angle difference of 60 degrees, as cos(60 deg) = 1/2.]

Cheers, Wayne
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Oops, ok , thanks for the correction. But it would still not work without upgrading the feeder, as currently there is 2/0 CU installed.
 
wwhitney said:
That's correct if there were 2 inverters. But there are 4 inverters. So the ratio for A between not using BC versus using BC is 2*sqrt(3)/sqrt(7) = 131%.

Cheers, Wayne
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Totally forgot to think about the A leg. 😄 I was just thinking in terms of the effect on the B leg because that's handled by the presumably smaller stinger transformer.
 
wwhitney said:
If you had to, you could make that work with a 175A 100% rated OCPD.

Cheers, Wayne
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ggunn said:
All I can say at this point is that I am glad that this is someone else's problem. :D
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Actually its not just the conductors that would need to be upgraded. It's a supply-side tap to a 200 amp fused Disco. I forgot about the fused Disco. Unfortunately putting all four inverters on AB and AC exceeds 200 amp, so the switch would need to be changed to a 400 amp. 😞. another option would be Wayne's 200 amp 100% rated enclosed circuit breaker. I'm guessing not a huge cost difference either way.
 
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