Rapid Shutdown 690.12 2014 NEC

[Efrain1]

If I have a roof mounted solar system in a commercial building, and the designer is installing the inverters within 10ft of the array, do the inverters need to be listed as rapid shutdown device? The Designer is stating they do not need to be listed since they are located withing 10ft of the array. Are the "controlled conductors" the conductors only from the array to the inverter, or are they the conductors from the array all the way to the service panel?

PV system circuits installed onor in buildings shall include a rapid shutdown function that controls specificconductors in accordance with 690.12(1) through (5) as follows:
(1) Requirements for controlled conductors shall apply only to PV systemconductors of more than 1.5 m (5 ft) in length inside a building, or more than3 m (10 ft) from a PV array.
“(2) Controlled conductors shall be limited to not more than 30 volts and 240volt-amperes within 10 seconds of rapid shutdown initiation.
“(3) Voltage and power shall be measured between any two conductors and betweenany conductor and ground.
“(4) The rapid shutdown initiation methods shall be labeled in accordance with690.56(C).
“(5) Equipment that performs the rapid shutdown shall be listed andidentified.”

 

[jumper]

Welcome to the forum.

We have some pretty sharp PV guys here, so someone should be able to help shortly.

 

[ggunn]

If I have a roof mounted solar system in a commercial building, and the designer is installing the inverters within 10ft of the array, do the inverters need to be listed as rapid shutdown device? The Designer is stating they do not need to be listed since they are located withing 10ft of the array. Are the "controlled conductors" the conductors only from the array to the inverter, or are they the conductors from the array all the way to the service panel?

As long as you are under the 2014 NEC, if you are installing your inverters within 10' of an array and you have no exposed conduits with DC conductors in them extending more than 10' from an array, you are fine. The inverters do not need to be specially listed. The AC conductors are already covered under UL1741. Under the 2017 NEC, however, it's a different story.

 

[Carultch]

If I have a roof mounted solar system in a commercial building, and the designer is installing the inverters within 10ft of the array, do the inverters need to be listed as rapid shutdown device? The Designer is stating they do not need to be listed since they are located withing 10ft of the array. Are the "controlled conductors" the conductors only from the array to the inverter, or are they the conductors from the array all the way to the service panel?

PV system circuits installed onor in buildings shall include a rapid shutdown function that controls specificconductors in accordance with 690.12(1) through (5) as follows:
(1) Requirements for controlled conductors shall apply only to PV systemconductors of more than 1.5 m (5 ft) in length inside a building, or more than3 m (10 ft) from a PV array.
“(2) Controlled conductors shall be limited to not more than 30 volts and 240volt-amperes within 10 seconds of rapid shutdown initiation.
“(3) Voltage and power shall be measured between any two conductors and between any conductor and ground.
“(4) The rapid shutdown initiation methods shall be labeled in accordance with 690.56(C).
“(5) Equipment that performs the rapid shutdown shall be listed andidentified.”

"Controlled conductors" means conductors that can be de-energized once rapid shutdown is initiated. De-energized means brought down within the 30 volt limit. These are on the building grid side of the device that does the rapid shutdown. "Uncontrolled" conductors would be the conductors coming directly off the PV array, and could remain energized up to the full open circuit voltage. Uncontrolled conductors are limited to no more than 10 ft from the PV array, or be longer than 5 ft in length inside a building, in projects where NEC2014 applies.

When the inverter is the device that "does" rapid shutdown, all AC-side conductors are "controlled", and all DC-side conductors are "uncontrolled".
When a contactor combiner does it, the little string wires are "uncontrolled", and the big output wires are "controlled".
When a power optimizer does it, the module factory wiring plugged into it is "uncontrolled", and the optimizer output wires are "controlled".

By omission, the text of the 2014 NEC doesn't specify whether the 10 ft is conductor length beyond the final module frame, or the absolute "as the crow flies" distance. By default, it is the absolute distance, when going by the exact NEC language. So as long as the inverter, combiner, or whatever else it may be, is within the 10 ft offset zone, you have a solution.

For 2014 NEC, the listing requirement just means that the equipment has to be listed in general. So if your inverters satisfy this by being within 10 ft of the array, even without any post 2014 technology, they will still work. Shutting off the electricity for the building in general, or at the outside-mounted disconnect that utilities typically require, would be your initiation method that has to be field labeled per 690.56(C).

 

[ggunn]

"Controlled conductors" means conductors that can be de-energized once rapid shutdown is initiated. De-energized means brought down within the 30 volt limit. These are on the building grid side of the device that does the rapid shutdown. "Uncontrolled" conductors would be the conductors coming directly off the PV array, and could remain energized up to the full open circuit voltage. Uncontrolled conductors are limited to no more than 10 ft from the PV array, or be longer than 5 ft in length inside a building, in projects where NEC2014 applies.

When the inverter is the device that "does" rapid shutdown, all AC-side conductors are "controlled", and all DC-side conductors are "uncontrolled".
When a contactor combiner does it, the little string wires are "uncontrolled", and the big output wires are "controlled".
When a power optimizer does it, the module factory wiring plugged into it is "uncontrolled", and the optimizer output wires are "controlled".

By omission, the text of the 2014 NEC doesn't specify whether the 10 ft is conductor length beyond the final module frame, or the absolute "as the crow flies" distance. By default, it is the absolute distance, when going by the exact NEC language. So as long as the inverter, combiner, or whatever else it may be, is within the 10 ft offset zone, you have a solution.

For 2014 NEC, the listing requirement just means that the equipment has to be listed in general. So if your inverters satisfy this by being within 10 ft of the array, even without any post 2014 technology, they will still work. Shutting off the electricity for the building in general, or at the outside-mounted disconnect that utilities typically require, would be your initiation method that has to be field labeled per 690.56(C).

I'm pretty sure that's the long way of saying the same thing that I did. Put your inverters within 10' of an array (it doesn't necessarily have to be the array that the inverter is connected to) and don't have DC conduits extending more than 10' from an array, and you'll be fine.

 

[GoldDigger]

:thumbsup:

IMHO the "in accordance with 690.12(1) through (5) " makes it appear to me that the PV system conductors as used in the context of Rapid Shutdown do not include inverter output conductors, but those are covered for Rapid Shutdown anyway by the anti-islanding circuitry in the grid interactive inverters.

 

[pv_n00b]

I'm pretty sure that's the long way of saying the same thing that I did. Put your inverters within 10' of an array (it doesn't necessarily have to be the array that the inverter is connected to) and don't have DC conduits extending more than 10' from an array, and you'll be fine.

Maybe I am misunderstanding what you mean, but I’m not sure about this one part of your statement, "it doesn't necessarily have to be the array that the inverter is connected to.” If there are multiple arrays on a roof and the inverters are grouped together all within 10’ of one of the arrays, then the arrays more than 10’ away from their inverters will need a disconnect within 10’ of those distant arrays.

 

[pv_n00b]

:thumbsup:

IMHO the "in accordance with 690.12(1) through (5) " makes it appear to me that the PV system conductors as used in the context of Rapid Shutdown do not include inverter output conductors, but those are covered for Rapid Shutdown anyway by the anti-islanding circuitry in the grid interactive inverters.

NEC 690.12 refers to “PV system circuits” so it applies to AC as well as DC circuits. In grid connected non-backup systems the AC circuits will be deenergized on loss of the grid so it is self activating RSS. But for backup systems the AC circuits from the inverter will still be hot and need a separate RSS shutdown other than removal of grid power.

 

[ggunn]

Maybe I am misunderstanding what you mean, but I’m not sure about this one part of your statement, "it doesn't necessarily have to be the array that the inverter is connected to.” If there are multiple arrays on a roof and the inverters are grouped together all within 10’ of one of the arrays, then the arrays more than 10’ away from their inverters will need a disconnect within 10’ of those distant arrays.

A disco within 10' of the array doesn't help you with rapid shutdown unless it is remotely activated either by the inverter shutting down or by a plainly labeled ground level button or switch grouped with the building disco.

But that isn't what I was talking about. If you have, for example, three subarrays side by side, each feeding a separate inverter, you can group the three inverters at one end of the array within 10' of it as long as all their DC conductors run under the array, even though two of the inverters aren't within 10' of the subarrays that are feeding them.

 

[pv_n00b]

A disco within 10' of the array doesn't help you with rapid shutdown unless it is remotely activated either by the inverter shutting down or by a plainly labeled ground level button or switch grouped with the building disco.

But that isn't what I was talking about. If you have, for example, three subarrays side by side, each feeding a separate inverter, you can group the three inverters at one end of the array within 10' of it as long as all their DC conductors run under the array, even though two of the inverters aren't within 10' of the subarrays that are feeding them.

The 2014 code does not require remote shutdown for RSS. I have seen all kinds of manual switches used to comply with it, including one on the second story outside wall with no access other than a ladder.

For your array layout, that interpretation is up to the AHJ. Some would accept it and some would say each inverter has to be within 10' of the modules it is connected to. Lucky for you that you have not run into one of those AHJs, yet.

 

[ggunn]

The 2014 code does not require remote shutdown for RSS. I have seen all kinds of manual switches used to comply with it, including one on the second story outside wall with no access other than a ladder.

For your array layout, that interpretation is up to the AHJ. Some would accept it and some would say each inverter has to be within 10' of the modules it is connected to. Lucky for you that you have not run into one of those AHJs, yet.

690.12 expressly says that RSS requirements apply to "PV system conductors of ... more than 3m (10 ft) from a PV array" [emphasis mine]. I believe that the system I described fulfills both the letter and the spirit of the regulation, and I have designed systems that made use of that interpretation in several jurisdictions without a single challenge.

Conversely, all the AHJ's I have dealt with have required that the RSS disco be remotely operable from a switch on the ground even though the NEC does not say that, exactly. Perhaps I could fight with them about it, but it's not a battle I would choose to have. I stand corrected on the code, though.

 

[Carultch]

Conversely, all the AHJ's I have dealt with have required that the RSS disco be remotely operable from a switch on the ground even though the NEC does not say that, exactly. Perhaps I could fight with them about it, but it's not a battle I would choose to have. I stand corrected on the code, though.

2014's rules were so open to interpretation on this, that you could have the switch on your neighbor's house and still comply with the wording of the code. This was not a careless omission from the CMP, but it was intended to not specify such details so that installers, fire departments, and AHJ's could decide on a location together, instead of being constrained to rules that would be intended to apply in all cases.

In 2017, the NEC offers some common-sense guidance on this:
1. Service disconnecting means
2. PV system disconnecting means
3. A readily accessible switch that plainly indicates the on and off positions