2014 NEC 690.12 Emergency Shutdown

[shortcircuit2]

690.12 PV Arrays on Buildings Response to Emergency
Shutdown. . For PV Systems installed on roofs of buildings,
photovoltaic source circuits shall be deenergized from
all sources within 10 seconds of when emergency shutdown
is initiated or when the PV power source disconnecting
means is opened. When the source circuits are deenergized,
the maximum voltage at the module and module conductors
shall be 80 volts.

This is one product available...

http://www.solarbos.com/products/combiner-boxes/contactor-combiners


I'm looking for input from others on how they will comply with the new rule.

Thanks, shortcircuit

 

[GoldDigger]

690.12 PV Arrays on Buildings Response to Emergency
Shutdown. . For PV Systems installed on roofs of buildings,
photovoltaic source circuits shall be deenergized from
all sources within 10 seconds of when emergency shutdown
is initiated or when the PV power source disconnecting
means is opened. When the source circuits are deenergized,
the maximum voltage at the module and module conductors
shall be 80 volts.

This is one product available...

http://www.solarbos.com/products/combiner-boxes/contactor-combiners


I'm looking for input from others on how they will comply with the new rule.

Thanks, shortcircuit

I do not see one of these by itself meeting the quoted requirement. If you have a string of panels and the - end is grounded, opening the contactor will still leave more than 80 volts at some of the module connectors.
It seems to me that you would have to break both the + and - end of the string or be working with an ungrounded string in the first place to be able to meet the new requirement.
It is not clear to me at all how the requirement can be met when you have more than one panel in a series string unless you interpret the ambiguous language in the most favorable way.

Some designs of DC load breaking contactors are polarity sensitive, so you may not be able to just put an additional one of those units on the - end of the strings.

 

[Zee]

Only way is module level electronics.
=
Micro's or power optimizers.
(ENphase, TIGO, Solaredge)

Grounded or no, DC V is still over 80 V (doesn't have to be V to ground, line to line counts. I THINK)

 

[GoldDigger]

Grounded or no, DC V is still over 80 V (doesn't have to be V to ground, line to line counts. I THINK)

I thought about that, but since the + and - from a typical panel come out via separate connectors, there would not be 80 volts accessible at any one connector if the string were ungrounded. (Unless there is also a ground fault caused by fire fighter axing a panel.)

 

[SolarPro]

That's not the language that made it into the Code. The module-level disconnect requirement was replaced with this language:

690.12 Rapid Shutdown of PV Systems on Buildings PV system circuits installed on or in buildings shall include a rapid shutdown function that controls specific conductors in accordance with 690.12(1) through (5) as follows.
(1) Requirements for controlled conductors shall apply only to PV system conductors of more than 1.5 m (5 ft) in length inside a building, or more than 3 m (10 ft) from a PV array.
(2) Controlled conductors shall be limited to not more than 30 volts and 240 volt-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(B).
(5) Equipment thatperforms the rapid shutdown shall be listed and identified.

So disconnecting combiner boxes will meet the 690.12 requirements in NEC 2014, as will listed module-level solutions. (Module-level disconnecting requirements are expected to pass in the next Code cycle.)

 

[shortcircuit2]

690.12 Rapid Shutdown of PV Systems on Buildings PV system circuits installed on or in buildings shall include a rapid shutdown function that controls specific conductors in accordance with 690.12(1) through (5) as follows.
(1) Requirements for controlled conductors shall apply only to PV system conductors of more than 1.5 m (5 ft) in length inside a building, or more than 3 m (10 ft) from a PV array.
(2) Controlled conductors shall be limited to not more than 30 volts and 240 volt-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(B).
(5) Equipment thatperforms the rapid shutdown shall be listed and identified.

My 2014 book hasn't arrived yet. Is this the new 690.12 Rapid Shut down?

If so, would DC disconnects mounted to the roof within 10ft of an array satisfy this rule?

I don't see where it has to be readily accessible or even accessible.

 

[SolarPro]

Yes, the above is the exact language, cut & paste from a PDF of NEC 2014.

The acceptable solution is up to the AHJ. But in my opinion array segmenting disconnects will not meet 690.12, at least not the intention of the requirement. Keep in mind that the adopted language is a compromise solution. The original language called for module-level shutdown, and everyone involved in the Code-Making Process expects that the module-level shutdown requirement will included in NEC 2017. However, module-level technology is not simply ready for prime time, both in terms of pricing and reliability. So we have the current last-minute compromise language that wound up in NEC 2014, calling for rapid shutdown of dc PV circuits within 10 feet of the array or 5 feet of entering a building.

The intent of 690.12 is to enable fire fighters and first responders to confidently de-energize PV system conductors outside of the array area, rapidly and on demand. One way to accomplish this is using contactor combiners within 10' of the array area. In this scenario, you have a big red emergency shutdown button at ground-level that firefighters can trigger to open all of the contactors simultaneously and shutdown the dc circuits outside the array area. Another way to meet 690.12 is to locate string inverters within 10' of the array area, such that only ac inverter output circuits leave the array area. That way when firefighters shutdown the facility's ac service disconnect, the energized dc circuits are isolated to the array area, no special equipment required.

FWIW: here's the associated explanatory text (not very elucidating) from the Handbook:

First responders must contend with elements of a PV system that remain energized after the service disconnect is opened. This rapid shutdown requirement provides a zone outside of which the potential for shock has been mitigated. Conductors more than 5 feet inside a building or more than 10 feet from an array will be limited to a maximum of 30 V and 240 VA within 10 seconds of activation of shutdown. Ten seconds allows time for any dc capacitor banks to discharge. Methods and designs for achieving proper rapid shutdown are not addressed by the NEC but instead are addressed in the product standards for this type of equipment.

 

[GoldDigger]

I do not see one of these by itself meeting the quoted requirement. If you have a string of panels and the - end is grounded, opening the contactor will still leave more than 80 volts at some of the module connectors.
It seems to me that you would have to break both the + and - end of the string or be working with an ungrounded string in the first place to be able to meet the new requirement.
It is not clear to me at all how the requirement can be met when you have more than one panel in a series string unless you interpret the ambiguous language in the most favorable way.

Some designs of DC load breaking contactors are polarity sensitive, so you may not be able to just put an additional one of those units on the - end of the strings.

1. If the module connectors are still more than 80 volts above ground or there is more than 80 volts difference between two module connectors, there is still no violation of 690.12 as long as those connector or the wires attached to them do not extend more than 10 feet from the array. Module connector leads usually do not do that. Put the contactor combiner within 10 feet of the outer boundary of the array.
2. For an ungrounded system which may be subject to a ground fault, you would have to put a contactor on both + and - leg. But the section does not say that the disconnect also has to protect against a panel or wiring fault that creates a mid-string ground. If you want to go that far, you would also need a contactor that protects against contactor failure!
3. As for polarity sensitivity, you have a point there, but the listed unit does not seem to be that kind.

If a later code cycle removes or tightens the 10 foot exception, then there will indeed be problems with anything but a module level solution. Probably built into the panel itself so that there would not be even an inch of exposed wire before the disconnect. :happysad:

 

[shortcircuit2]

Yes, the above is the exact language, cut & paste from a PDF of NEC 2014.

The acceptable solution is up to the AHJ. But in my opinion array segmenting disconnects will not meet 690.12, at least not the intention of the requirement. Keep in mind that the adopted language is a compromise solution. The original language called for module-level shutdown, and everyone involved in the Code-Making Process expects that the module-level shutdown requirement will included in NEC 2017. However, module-level technology is not simply ready for prime time, both in terms of pricing and reliability. So we have the current last-minute compromise language that wound up in NEC 2014, calling for rapid shutdown of dc PV circuits within 10 feet of the array or 5 feet of entering a building.

The intent of 690.12 is to enable fire fighters and first responders to confidently de-energize PV system conductors outside of the array area, rapidly and on demand. One way to accomplish this is using contactor combiners within 10' of the array area. In this scenario, you have a big red emergency shutdown button at ground-level that firefighters can trigger to open all of the contactors simultaneously and shutdown the dc circuits outside the array area. Another way to meet 690.12 is to locate string inverters within 10' of the array area, such that only ac inverter output circuits leave the array area. That way when firefighters shutdown the facility's ac service disconnect, the energized dc circuits are isolated to the array area, no special equipment required.

FWIW: here's the associated explanatory text (not very elucidating) from the Handbook:

First responders must contend with elements of a PV system that remain energized after the service disconnect is opened. This rapid shutdown requirement provides a zone outside of which the potential for shock has been mitigated. Conductors more than 5 feet inside a building or more than 10 feet from an array will be limited to a maximum of 30 V and 240 VA within 10 seconds of activation of shutdown. Ten seconds allows time for any dc capacitor banks to discharge. Methods and designs for achieving proper rapid shutdown are not addressed by the NEC but instead are addressed in the product standards for this type of equipment.

Thanks SolarPro... I wish they didn't leave the gray area for interpretation. Unfortunately, interpretations don't alway's go by intent, they go by the language of the article. I have talked to another contractor who said his company just wants to locate DC disco's on the roof to comply with 690.12...so now if installed like this, the fireman have to climb up on the roof to manually shut them off.

I know this was not the intent...but that's what may be attempted on some of the smaller systems.

 

[SolarPro]

Small systems can use module-level solutions to meet the 690.12 requirements. Systems deployed using microinverters or ACPV modules meet the 690.12 requirements, because there is no power outside the array other than the ac input to the inverter, which first responders can shut down using conventional practices. Most systems deployed using dc-to-dc converters will also output less than 30 Vdc when the ac input to the inverter is lost.

 

[Zee]

Thanks Solarpro,
This RAPID SHUTDOWN is a great idea, because the ability to de-energize a significant section of conductors is always a good thing.

My only problem: a big switch or CB on the roof of a house next to a sleek pv array = UGLY.

(Since that will only be needed for high V strings...I'll be considering moving to more micro.s or solaredge type electronics. In that case, no disco needed at all. (assuming, of course, an ac disco is installed on the inverter output circuit :dunce

 

[shortcircuit2]

Micro Inverters, DC to DC converters, AC panels, Shunt Trip Combiner Boxes are all options as well as a simple NEMA rated DC Disconnect. But on a small residential 1 or 2 string system, the DC Disconnect may be the least expensive way for some budget conscious installers.

They should have required the Rapid Shutdown Function be readily accessible...

 

[SolarPro]

This is worth a look:

http://www.youtube.com/watch?v=sUXShMZJorQ

 

[Zee]

Shortcircuit2,
I am curious, what do you mean by, "They should have required the Rapid Shutdown Function be readily accessible..." ? As in, for what reason?

Other Q's: can anything qualify as "readily accessible" if on a roof?

Is "readily accessible" always a matter of opinion/interpretation?

Also, is a roof specifically excluded , or something i remember vaguely about needing a ladder won't qualify as readily accessible.....

 

[GoldDigger]

Shortcircuit2,
I am curious, what do you mean by, "They should have required the Rapid Shutdown Function be readily accessible..." ? As in, for what reason?
.....

As mentioned at the end of the MH video, the intention of this provision is to increase firefighter safety by allowing them to remove voltage hazards from water and contact before they go about fighting a building fire by working on the roof or putting water on the roof.
As such, it makes a lot of sense that they be able to do that before going onto the roof.
But there is not yet anything in the Code that addresses that.
A secondary question is how they would go about locating this shutdown switch if it is not placed near the POCO service entrance.

The current alternative for emergency shutdown of a PV system without optimizers or microinverters is to put an axe through each of the panels. ¹

1: Credit to Dereck for this reference.

 

[shortcircuit2]

Shortcircuit2,
I am curious, what do you mean by, "They should have required the Rapid Shutdown Function be readily accessible..." ? As in, for what reason?

Other Q's: can anything qualify as "readily accessible" if on a roof?

Is "readily accessible" always a matter of opinion/interpretation?

Also, is a roof specifically excluded , or something i remember vaguely about needing a ladder won't qualify as readily accessible.....

Zee...if there is a DC Disconnect located on the roof to perform the Rapid Shutdown Function, this meets the wording of the code.

But it won't do what code making panel intended to do...

Therefore if they had required the RSF to be readily accessible, it would serve the intent.

shortcircuit

 

[Zee]

aha i see, i had previously thought that firefighters can be expected to go on the roof, so i didn't see the shutoff being up there as a problem.
I see now that often they cannot go on the roof because of fire.

 

[shortcircuit2]

Ok how about some Listed and Identified products to install for this 690.12 Rapid Shutdown function?

 

[GoldDigger]

They will be available shortly after the Class A fire rated PV systems now required in CA for use on Class A roofs.


Sent from my XT1080 using Tapatalk

 

[shortcircuit2]

Ok then...PV systems have to be ground mounted for awhile...