NEC 366.20 Conductors Connected in Parallel

[Jatavedas]

For my battery / inverter room the 6awg conductors @ 50a output from each of the EG4 18kpv's will have a combiner on one side of the room, to run the conductors from the furthest 18k it will be 25+ feet and the shortest 8 feet... But for NEC 366.20 should they all be the same length just bunching up the extra??? Seems odd but I understand keeping phases in sync.

 

[robbob2112]

you need the same round trip lengths to keep them the same, then the wire to the inverter will be the same

So if you put your combiner bars on opposite sides of the room you can use the same total length of copper between batteries and bus bars....

The inverters will have some minor imbalances, but once you hit the battery bus bars you would have even loading. The inverter/charger imbalance would just mean some of them provide more charge than others

 

[Jatavedas]

you need the same round trip lengths to keep them the same, then the wire to the inverter will be the same

So if you put your combiner bars on opposite sides of the room you can use the same total length of copper between batteries and bus bars....

The inverters will have some minor imbalances, but once you hit the battery bus bars you would have even loading. The inverter/charger imbalance would just mean some of them provide more charge than others

Sorry I should have been more clear, this is for the AC output of the inverters, there are 4x 18k PV's, all at varied lengths from the AC combiner, each 18k will supply 50 amps and be combined into a 200a output which will go to the whole house transfer switch. So is the same length statement for the round trip phase A and B, but each inverter can have a different total distance so long as both legs from each inverter are equal ?

 

[robbob2112]

I am gonna have to say @timselectric is the man to answer this question, I would only be guessing.

 

[timselectric]

If you want the inverters to evenly carry the loads. All conductors need to be the same length.
As in,
All L1's the same length.
All L2's the same length.
All neutrals the same length.
EGC's do not have to be the same.

 

[Jatavedas]

If you want the inverters to evenly carry the loads. All conductors need to be the same length.
As in,
All L1's the same length.
All L2's the same length.
All neutrals the same length.
EGC's do not have to be the same.

So the inverter that is 8ft from the combiner would also have a 24' set of matched length conductors that lead to the combiner as would all of the rest of the inverters?

 

[rogerheflin]

For my battery / inverter room the 6awg conductors @ 50a output from each of the EG4 18kpv's will have a combiner on one side of the room, to run the conductors from the furthest 18k it will be 25+ feet and the shortest 8 feet... But for NEC 366.20 should they all be the same length just bunching up the extra??? Seems odd but I understand keeping phases in sync.

It needs to be the same length for even load/resistance. if one set of wires was longer then then one phase/inverter will supply less power.

The amount the phases will be out of sync will not matter with a few feet extra. I have seen this matter with analog monitor cables (500ft run, some cables longer than others, so it caused the R/G/B to not be lined up, but this was a 50Mhz signal (.6meter pixel size), someone trial-and-errored adding cable length to get the signals to line up. 60hz has a wavelength of 5,000 meters, so a few meters off won't do anything important to the sync and is likely off less that variances in the electronics of the inverters themselves cause.

 

[Jatavedas]

It needs to be the same length for even load/resistance. if one set of wires was longer then then one phase/inverter will supply less power.

The amount the phases will be out of sync will not matter with a few feet extra. I have seen this matter with analog monitor cables (500ft run, some cables longer than others, so it caused the R/G/B to not be lined up, but this was a 50Mhz signal (.6meter pixel size), someone trial-and-errored adding cable length to get the signals to line up. 60hz has a wavelength of 5,000 meters, so a few meters off won't do anything important to the sync and is likely off less that variances in the electronics of the inverters themselves cause.

THANK YOU!!! In my head the intuition of wavelength synchronization shouldn't be out of step by typical measurements if the conductors are within 20ft of each other beyond that I'm sure the variance could be detected by likely not to any detrimental effect. But I'm not as well versed and I read the 366.20 and it was super specific so I wanted to make sure I wasn't misunderstanding anything

 

[timselectric]

So the inverter that is 8ft from the combiner would also have a 24' set of matched length conductors that lead to the combiner as would all of the rest of the inverters?

Correct
If you want the inverters to share the loads evenly.