690.13 (D), Only 6 Disconnecting Means for Microinverter Systems?

[DerrickM]

I am installing a pole mount system here at our campus.
Here is where I am at:

I am using the new C-250 Enphase Microinverter as the basebuilding voltage is 480/ 277V.
I thought this was a good idea to use the higher voltagesource to help reduce voltage drop issues that could arise as our PV array isapprox. 350’ away from our electrical source.
I am installing an outdoor rated cabinet/panelboard thatwill be used solely for the distribution for solar arrays, this is only about 25' away.
The goal is to have a total of 8 pole mount systems, eachpole consisting of 12 modules and 12 microinverters, and installing 1 polearray per year for the next 8 years.
I like the microinverter system for the ease of addinganother branch circuit to our outside (within site) panelboard each year.

This brings me to my question:
Article 690.13 (A) requires me to have a PV disconnectingmeans installed at a readily accessible location on the outside of thebuilding. This I will have, as my outdoor rated panelboard will be with in siteof the pole mount arrays. I will be using the 3 pole circuit breakers for this.
I am struggling with 690.13 (D) which states that themaximum number of disconnects- switches or circuit breakers, allowed is 6. Why6? My goal was to have a total of 8 systems, each one having its own 3-phase,480 volt circuit breaker, all installed in one panelboard.

What am I missing with this code rule?
Thanks in advance.

 

[Carultch]

I am installing a pole mount system here at our campus.
Here is where I am at:

I am using the new C-250 Enphase Microinverter as the basebuilding voltage is 480/ 277V.
I thought this was a good idea to use the higher voltagesource to help reduce voltage drop issues that could arise as our PV array isapprox. 350’ away from our electrical source.
I am installing an outdoor rated cabinet/panelboard thatwill be used solely for the distribution for solar arrays, this is only about 25' away.
The goal is to have a total of 8 pole mount systems, eachpole consisting of 12 modules and 12 microinverters, and installing 1 polearray per year for the next 8 years.
I like the microinverter system for the ease of addinganother branch circuit to our outside (within site) panelboard each year.

This brings me to my question:
Article 690.13 (A) requires me to have a PV disconnectingmeans installed at a readily accessible location on the outside of thebuilding. This I will have, as my outdoor rated panelboard will be with in siteof the pole mount arrays. I will be using the 3 pole circuit breakers for this.
I am struggling with 690.13 (D) which states that themaximum number of disconnects- switches or circuit breakers, allowed is 6. Why6? My goal was to have a total of 8 systems, each one having its own 3-phase,480 volt circuit breaker, all installed in one panelboard.

What am I missing with this code rule?
Thanks in advance.

Think of it more as six MASTER disconnecting means, rather than 6 total disconnects. If you have branch breakers grouped in a panelboard, with a main breaker, only the main breaker counts toward your count of 6.

 

[DerrickM]

Ok, so its the total number of disconnects working your way back to the utility connection, that can not exceed 6?
That way your not running around trying to isolate a huge number of disconnect switches?
Thanks, that makes more sense.

Derrick

 

[ggunn]

Ok, so its the total number of disconnects working your way back to the utility connection, that can not exceed 6?
That way your not running around trying to isolate a huge number of disconnect switches?
Thanks, that makes more sense.

Derrick

Yes. If your 8 circuits are combined onto one switch or breaker, that handle is the only one that counts toward the six.

 

[DerrickM]

I was confused because I am going to have 8 separate branch circuit breakers (AC disconnects) in a sub panel for my 8 micro inverter systems. I thought that those circuit breakers counted towards my 6 disconnecting means for solar PV. I believe now that it is the master disconnect switches I need to be counting, like a main breaker for the electrical panelboard or the 600 volt ac disconnect ahead of the panelboard, not the branch circuit breakers.

 

[shortcircuit2]

690.13 confuses me too.

 

[shortcircuit2]

690.13 and 690.13(A) seem to apply to DC conductors.

Then 690.13 (C), (D), and (E) would seem to apply AC type disconnects from previous comments here?

My comment here is regarding grid interactive systems.

 

[ggunn]

I was confused because I am going to have 8 separate branch circuit breakers (AC disconnects) in a sub panel for my 8 micro inverter systems. I thought that those circuit breakers counted towards my 6 disconnecting means for solar PV. I believe now that it is the master disconnect switches I need to be counting, like a main breaker for the electrical panelboard or the 600 volt ac disconnect ahead of the panelboard, not the branch circuit breakers.

It really comes down to how many handles you have to throw to shut down the system. If, for some reason, you had all 8 circuits going to individual breakers in the MDP, then you'd be in violation of the six handle rule. Since you have the 8 circuits going into an AC combiner with a disco between it and the service, you are good - only one handle.

 

[GoldDigger]

For one PV system, the 6 handle rule would also require that those up to six disconnects be grouped together to form the required PV disconnect.

If you are running the branch circuits back to backfed breakers in a general load panel, the lack of a main disconnect that only affected the PV might be seen as an issue by some inspectors.

 

[ggunn]

If you are running the branch circuits back to backfed breakers in a general load panel, the lack of a main disconnect that only affected the PV might be seen as an issue by some inspectors.

Isn't that what I said, sort of?

 

[GoldDigger]

Yes.

 

[ggunn]

Yes.

Well then, great minds... oh, never mind.

 

[shortcircuit2]

When the Code refers to not more than six switches or sets of circuit breakers ... with regard to circuit breakers, what determines what a set is and how many are in each set?

 

[ggunn]

When the Code refers to not more than six switches or sets of circuit breakers ... with regard to circuit breakers, what determines what a set is and how many are in each set?

The bottom line is how many handles one would have to throw to shut down the system. If there are 8 breakers in an AC combiner, that's a set of 8, but if there is a single main breaker or AC disco that switches the connectivity of that set of breakers, that set is irrelevant to the six handle rule. If that AC combiner were MLO, however and for instance, and connected to the supply side of a service without a disco between them, that would be a violation of the six handle rule; you would have to throw all eight breakers to completely shut down the system.

 

[GoldDigger]

Well then, great minds... oh, never mind.

As I always say, great minds run in the same gutter.

 

[shortcircuit2]

Why say sets of circuit breakers then? Just say six switches or circuit breakers.

 

[jaggedben]

Why say sets of circuit breakers then? Just say six switches or circuit breakers.

Maybe because circuit breakers can be tied together with handle-ties, so that is a set but it's just one handle?

 

[shortcircuit2]

Maybe because circuit breakers can be tied together with handle-ties, so that is a set but it's just one handle?

Guess so...240.15(B) lists applications for handle tie use on circuit breakers. Seems like all Branch Circuit uses. I can't understand how Sets of Circuit Breakers applies to services as used in 230.71

Here is some new language for 690.12 of the 2017 NEC in the Second Draft Reports using the same language...

(C) Initiation Device.
Where multiple PV systems are installed with rapid shutdown functions on a single
service, the initiation device(s) shall consist of not more than six switches or six sets of
circuit breakers, or a combination of not more than six switches and sets of circuit
breakers, mounted in a single enclosure, or in a group of separate enclosures. These
initiation device(s) shall initiate the rapid shutdown of all PV systems with rapid shutdown
functions on that service. Where auxiliary initiation devices are installed, these auxiliary
devices shall control all PV systems with rapid shutdown functions on that service.



The above is just part of the revision to (C)...but here the Code is using the term (sets) again?

 

[ggunn]

Guess so...240.15(B) lists applications for handle tie use on circuit breakers. Seems like all Branch Circuit uses. I can't understand how Sets of Circuit Breakers applies to services as used in 230.71

Here is some new language for 690.12 of the 2017 NEC in the Second Draft Reports using the same language...

(C) Initiation Device.
Where multiple PV systems are installed with rapid shutdown functions on a single
service, the initiation device(s) shall consist of not more than six switches or six sets of
circuit breakers, or a combination of not more than six switches and sets of circuit
breakers, mounted in a single enclosure, or in a group of separate enclosures. These
initiation device(s) shall initiate the rapid shutdown of all PV systems with rapid shutdown
functions on that service. Where auxiliary initiation devices are installed, these auxiliary
devices shall control all PV systems with rapid shutdown functions on that service.



The above is just part of the revision to (C)...but here the Code is using the term (sets) again?

Yes, but still if there is a single switch between the panel with the CB's in it and the service, you can have as many CB's as you like because that single switch is the only one that counts. A couple of years ago I built a system with 42 inverters feeding a combiner panel (42 CB's) with a switch on the panel output. No problem.

 

[shortcircuit2]

Yes I understand the single switch logic.

I don't get what the Code means by "Sets of Circuit Breakers"...

I can have a set of golf clubs with 12 or a set of clubs with 18...so now I have 30 clubs in 2 sets.

If I have six "Sets of Circuit Breakers" with 6 in each set...I have 36 circuit breakers. Code Compliant...right??? The language says I can have six sets of circuit breakers.

I was just looking to understand this language. (Why not just say six circuit breakers)