Rapid-shutdown misinterpretation by AHJ

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Designer101

Senior Member
Location
California
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Solar and ESS Designer
Rapid shutdown 2017 requirement per NEC 2017
outside the array boundary 30 volts within 30 seconds of rapid shutdown initiation, when controlled conductors outside array boundary are more than 3 ft away.
Inside array boundary 80 volts within 30 second o rapid shutdown initiation, when controlled conductors are within 3 ft of array Boundary.

We have installed one Inverter 7.6 kw inside sub panel that is 90 Ft away from main panel
we have installed another inverter 7.6 kw in the main panel
4 Pole AC Disconnect switches off both the PV system at once to initiate rapid shutdown and is installed within 10 ft of main panel.

Now per my understanding Rapid shutdown is meant for fire fighters safety , so it should be limited to roof top only and it should be dc voltage that should be tested.
Plan reviewer is saying that we cannot install inverter breaker inside sub panel that's located inside house, it has to be readily accessible , Which is the misinterpretation of the code.
he said he will tell the inspector to test the voltage inside the sub panel to comply that with rapid shutdown voltage and I am sure it will fail the test. That sub panel is always energized so it will sure not pass the test.
They can test the voltage between any two conductors or any two conductors and ground in the Ac disconnect mounted outside but they cant test that inside sub panel.
I thought that's the whole point of mounting ac disconnect outside the main panel within 10 ft.

he gave us the conditional permit that the voltage will be tested at inspection at sub panel and is pretty confident to fails us at inspection. I wanted to take the suggestion from this group before we proceed..
Please give me your insights on this, thank you.
 

wwhitney

Senior Member
Location
Berkeley, CA
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Retired
Not so familiar with 690.12, but I note that 690.12 refers to "PV system circuits" and 690.12(A) refers to "PV circuits supplied by the PV system." In contrast, the definitions at the beginning of 690.12 are for PV Output Circuit, PV Power Source, PV Source Circuit, and PV System DC Circuit.

So it seems a bit sloppy to me that 690.12 is not using one of those defined terms. But PV System DC Circuit includes the other two PV Blah Circuit definitions, and is the only plausible meaning for the terminology in 690.12. You could also point to Figure 690.1(b) and note than the AC circuits on the AC side of the inverter are all referred to as Inverter Output Circuits, and that only the DC circuits on the DC side of the inverter are ever labeled with the term PV.

Cheers, Wayne
 

Carultch

Senior Member
Location
Massachusetts
Now per my understanding Rapid shutdown is meant for fire fighters safety , so it should be limited to roof top only and it should be dc voltage that should be tested.
Plan reviewer is saying that we cannot install inverter breaker inside sub panel that's located inside house, it has to be readily accessible , Which is the misinterpretation of the code.
he said he will tell the inspector to test the voltage inside the sub panel to comply that with rapid shutdown voltage and I am sure it will fail the test. That sub panel is always energized so it will sure not pass the test.
They can test the voltage between any two conductors or any two conductors and ground in the Ac disconnect mounted outside but they cant test that inside sub panel.
I thought that's the whole point of mounting ac disconnect outside the main panel within 10 ft.

he gave us the conditional permit that the voltage will be tested at inspection at sub panel and is pretty confident to fails us at inspection. I wanted to take the suggestion from this group before we proceed..
Please give me your insights on this, thank you.

The rule for rapid shutdown is geared toward DC conductors, because they remain energized when the array is exposed to sunlight. It applies to circuits ON or IN buildings, so it will apply even if you just bring the final 20 ft of DC circuits from a ground-mount array in to the building.

AC conductors of inverter output circuits shut off just like all other circuits on the premises, so the rapid shutdown rule doesn't really need to target them. Shut off the service as a whole, and you shut off the AC conductors. The inverters don't energize their output circuits, without first having a grid voltage waveform to follow. Since it is common to need an AC disconnect outside anyway for utility requirements, it is common that this disconnect doubles as a point of rapid shutdown initiation.

Readily accessible means you can get to it without a tool (other than a key), and that you don't need to remove any obstacles. Inside a house is just as readily accessible as outside at grade level. Climbing a staircase to get to it, is also just as readily accessible.
 

jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
What is your initiation device? Is it the service disconnect? Is the service disconnect readily accessible?

Although it sounds like the AHJ may not fully understand rapid shutdown, we can't easily say he's wrong about the subpanel without knowing these details.
 

wwhitney

Senior Member
Location
Berkeley, CA
Occupation
Retired
FWIW, my understanding of the OP is that the 4 pole AC disconnect installed outside is the rapid shutdown initiating device and that both inverter output circuits are routed through it. Then one inverter output circuit goes on to interconnect in the main panel, and the other goes on to interconnect at the interior subpanel. [Not sure why you'd do that, maybe there is a partial backup ESS involved, or else a misapplication of the 120% rule.] The plan reviewer's concern seems to be that the subpanel will still have AC power from the grid when the rapid shutdown has been initiated.

Cheers, Wayne
 

jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
Sorry I read the original post too fast and missed the mention of the 4 pole disconnect. If that initiates rapid shutdown on the roof and if it is outside (which wasn't actually said explicitly) then the AHJ is wrong. Code does not require it to shutoff the subpanel or anything else. (If there is an ESS involved there is no rapid shutdown requirement for that, although shutting it off with an outside switch might be another way to meet the solar rapid shutdown requirement. )

I agree with Wayne that the 4 pole disco is odd, especially since code would allow it to be two 2-pole switches (which would surely be cheaper). It is not required to be within 10ft of anything.
 

Designer101

Senior Member
Location
California
Occupation
Solar and ESS Designer
What is your initiation device? Is it the service disconnect? Is the service disconnect readily accessible?

Although it sounds like the AHJ may not fully understand rapid shutdown, we can't easily say he's wrong about the subpanel without knowing these details.
initiation device will be AC DISCONNECT 4 pole Type that can switch off both inverter system at single throw.
 

Designer101

Senior Member
Location
California
Occupation
Solar and ESS Designer
Sorry I read the original post too fast and missed the mention of the 4 pole disconnect. If that initiates rapid shutdown on the roof and if it is outside (which wasn't actually said explicitly) then the AHJ is wrong. Code does not require it to shutoff the subpanel or anything else. (If there is an ESS involved there is no rapid shutdown requirement for that, although shutting it off with an outside switch might be another way to meet the solar rapid shutdown requirement. )

I agree with Wayne that the 4 pole disco is odd, especially since code would allow it to be two 2-pole switches (which would surely be cheaper). It is not required to be within 10ft of anything.

FWIW, my understanding of the OP is that the 4 pole AC disconnect installed outside is the rapid shutdown initiating device and that both inverter output circuits are routed through it. Then one inverter output circuit goes on to interconnect in the main panel, and the other goes on to interconnect at the interior subpanel. [Not sure why you'd do that, maybe there is a partial backup ESS involved, or else a misapplication of the 120% rule.] The plan reviewer's concern seems to be that the subpanel will still have AC power from the grid when the rapid shutdown has been initiated.

Cheers, Wayne
plans reviewer didnt understand hawaiian tie in option that i used, before explaining multiple times didnt help, so i have to use this 4 pole ac disconnect options, and route both inverter into it.
 

jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
You realize that 4 pole disconnects are very expensive special order items? Have you consulted with the person who has to buy that?

Sounds like your conversation with the AHJ has nothing to do with code. I sympathize, but I probably wouldn't give up just yet.
 

Designer101

Senior Member
Location
California
Occupation
Solar and ESS Designer
You realize that 4 pole disconnects are very expensive special order items? Have you consulted with the person who has to buy that?

Sounds like your conversation with the AHJ has nothing to do with code. I sympathize, but I probably wouldn't give up just yet.
yes, i used this option only after contacting the concerned person. Thanks jaggedben for your insight.
The plan reviewer send me 22 comments for the first review, 10 comments for the second review, 4 comments for the 3rd review, he simply doesn't understand Hawaiian tie in, says its a supply side connection and it will violate the UL listing of the main panel relocating the existing feed into new load center. we get permit on the first submission most of the time. This AHJ is in native Indian land and the plan reviewer is most difficult person i have ever dealt with. I have said and explained many times that the 200A breaker is filed installed on the upper bas bar of 400A rated,200/200 Split main breaker panel by Eaton and we have done that connection all over Midwest, south and here in California. Tried to qualify the Hawaiian tie in both as 120 percent rule and sum of breaker rule, didn't help. He thought this was feeder tap and wanted me to comply with 25 ft or 10 ft tap rule, he didnt understand 705.12(b)(2)(1)(b) for feeder taps, he is the type of guy who fought us saying flat portion of roof needs fire set backs and fire access pathways, wanted center line axis pathways for residential installation, wanted AFCI breaker installed on solar load center, said he wans sub panel solar breaker outside though AC disconnect was clearly shown outside as a means of solar disconnect. He raised so many code issues that he misunderstood, I never have up but customer was very anxious about everything and we had to come up with another solution. i also didn't want to argue for longer when you know you are dealing with fools and its better to run away from them once you know them.
 
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