705.12 - 120% rule avoidance - Self Supply battery based applications

[Andrei]

Hey Code gurus, any tips, tricks or talking points, of how anybody is dealing with 120% rule in zero feedback battery based applications?

Example here is 3 x 7.6 SolarEdges (StorEdges) programmed to operate in zero feed back mode permanently, hooked up to intercepted 200A feeder via 200A MLO. 200A going in 200A going out, subfed with 120A from SE (3 X 40/2) into the same MLO. Basically MLO serves as a feeder tap, but I know AHJ might be referring to 120% rule here.. In some states people are putting "No additional loads" placard, does anybody know if we can get away with it in HI for example or other states.. Any thoughts..

Thanks

 

[ggunn]

Hey Code gurus, any tips, tricks or talking points, of how anybody is dealing with 120% rule in zero feedback battery based applications?

Example here is 3 x 7.6 SolarEdges (StorEdges) programmed to operate in zero feed back mode permanently, hooked up to intercepted 200A feeder via 200A MLO. 200A going in 200A going out, subfed with 120A from SE (3 X 40/2) into the same MLO. Basically MLO serves as a feeder tap, but I know AHJ might be referring to 120% rule here.. In some states people are putting "No additional loads" placard, does anybody know if we can get away with it in HI for example or other states.. Any thoughts..

Thanks

deleted

 

[jaggedben]

I don't think you get around any code rules here. Here are the options I see:

- Get an MLO panel that's 225A rated or higher.
- Downsize the breaker ahead of the panel to 175A.
- Do an actual feeder tap instead if you can insert a 200A overcurrent device somewhere else downstream.

 

[ggunn]

I don't think you get around any code rules here. Here are the options I see:

- Get an MLO panel that's 225A rated or higher.
- Downsize the breaker ahead of the panel to 175A.
- Do an actual feeder tap instead if you can insert a 200A overcurrent device somewhere else downstream.

I didn't follow exactly what he was doing, but could he perhaps qualify the bus under 705.12(D)(2)(3)(c) where the sum of all breaker ratings (supply and load), not including the breaker protecting the bus, sum to less than the bus rating? That's how we normally configure AC combiner panels and the 120% rule does not apply.

 

[SolarPro]

The normal rules will apply:

Interactive Inverter Interconnections: Identifying the Optimal Point of Connection

Self-supply is simply a software function. The Code is going to consider the hardware capability, regardless of the operating mode on Day 1.

 

[jaggedben]

I didn't follow exactly what he was doing, but could he perhaps qualify the bus under 705.12(D)(2)(3)(c) where the sum of all breaker ratings (supply and load), not including the breaker protecting the bus, sum to less than the bus rating? That's how we normally configure AC combiner panels and the 120% rule does not apply.

I understood him to be saying that the breakers in his panel are 3x20A for the solar plus a 200A load breaker to supply the downstream section of the existing feeder. In which case at 260A of supply and load exceeding 200A bus rating you can't use 705.12(D)(2)(3)(c). Perhaps he's proposing something else, although I can't really see how anything else under his description wouldn't be a feeder tap. (And in any case his real question seems to be about the self-supply programming, and I agree with SolarPro).

 

[ggunn]

I understood him to be saying that the breakers in his panel are 3x20A for the solar plus a 200A load breaker to supply the downstream section of the existing feeder. In which case at 260A of supply and load exceeding 200A bus rating you can't use 705.12(D)(2)(3)(c). Perhaps he's proposing something else, although I can't really see how anything else under his description wouldn't be a feeder tap. (And in any case his real question seems to be about the self-supply programming, and I agree with SolarPro).

Me, too. The code is specific about backfed breakers from an inverter irrespective of how you program it. I don't see that it's any different from trying to connect an inverter through a smaller breaker because you have it underloaded with modules. Can't do it.

 

[shortcircuit2]

Looked to me like he said 3 x 40amp 2-pole breakers.

Depends how he did the "interception" of the feeder for the new 200-amp MLO panel. Only way to do 200-amp out of a small panel like that is with a lug kit. Branch breakers on most only go to 125-amp.

If it is a full size tap to feed the new MLO panel...then he needs protection of the downstream panel with a 200-amp breaker ahead of it. Then label the new MLO panel with 705.12(D)(2)(3)(c) language restricting panel to sum of overcurrent devices not to exceed panel bus rating.

(2014 NEC)

 

[jaggedben]

Looked to me like he said 3 x 40amp 2-pole breakers.

You're correct. Oops. While it does not affect my last point, I have to retract that a 225A busbar or a 175 main breaker downsize would be adequate.

Depends how he did the "interception" of the feeder for the new 200-amp MLO panel. Only way to do 200-amp out of a small panel like that is with a lug kit. Branch breakers on most only go to 125-amp.

Not really true. See for example Square D HOMxxxBB type or Eaton BJ type. The panel would of course have to be listed for these but if a new panel that is not unlikely.

If it is a full size tap to feed the new MLO panel...then he needs protection of the downstream panel with a 200-amp breaker ahead of it. Then label the new MLO panel with 705.12(D)(2)(3)(c) language restricting panel to sum of overcurrent devices not to exceed panel bus rating.

(2014 NEC)

Agreed.