Author Topic: Applicability of NEC 690.12 to pole-mounted off-grid PV systems  (Read 1619 times)

uniquebobc

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 ???What I am reading in NEC 690.12 seems to indicate that if the DC conductors run more than 10 feet from the pole-mounted array or run greater than 5 feet inside of the house before reaching the power center, a rapid shutdown is needed.
Does anyone else see this differently?
uniquebobc

vtmaps

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Re: Applicability of NEC 690.12 to pole-mounted off-grid PV systems
« Reply #1 on: June 27, 2014, 05:17:23 PM »
???What I am reading in NEC 690.12 seems to indicate that if the DC conductors run more than 10 feet from the pole-mounted array or run greater than 5 feet inside of the house before reaching the power center, a rapid shutdown is needed.
Does anyone else see this differently?

Welcome to the forum,  As I understand it, for a ground or pole mount array you do NOT need a rapid shutdown, UNLESS the DC goes more than 5 ft inside the house.  The 10 ft rule is for roof mount arrays. 

I'm sure Ryan "halfcrazy" will explain if I am wrong... he's been spotted over at MikeHolt's forum commenting on this very issue.

--vtMaps

Westbranch

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Re: Applicability of NEC 690.12 to pole-mounted off-grid PV systems
« Reply #2 on: June 27, 2014, 05:21:22 PM »
Is this a move to get all DC outside the house perimeter walls?
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vtmaps

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Re: Applicability of NEC 690.12 to pole-mounted off-grid PV systems
« Reply #3 on: June 27, 2014, 05:27:50 PM »
Is this a move to get all DC outside the house perimeter walls?

No, it's about firefighter safety... ideally a firefighter would press an easily accessible button and de-energize everything.  With the 5 ft rule, they would still have to enter the structure to de-energize the PV input.

It's not so terrible IMO, but if NEC ever requires that batteries be disconnected from a remote location... 
OMG, it's too horrible to think about.

--vtMaps

tecnodave

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Re: Applicability of NEC 690.12 to pole-mounted off-grid PV systems
« Reply #4 on: June 27, 2014, 08:31:43 PM »
vtMaps,

I think that the birdcage does have the capability of remote battery shutoff ,it sends a signal to shunt trip breakers to shut down system. Carlingswitch makes shunt trip breakers and I believe that these are used in the birdcage system

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uniquebobc

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Re: Applicability of NEC 690.12 to pole-mounted off-grid PV systems
« Reply #5 on: June 27, 2014, 08:52:45 PM »
"UNLESS the DC goes more than 5 ft inside the house"

There is the kicker!

The DC conductors will be longer than 5 feet inside the house.

uniquebobc

harryn

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Re: Applicability of NEC 690.12 to pole-mounted off-grid PV systems
« Reply #6 on: February 04, 2017, 03:23:37 PM »
Does that mean that if you make everything in a way that there is no DC inside of the house, then the rapid shutdown is not required?

For example, I could imagine putting it all in an exterior rated box, about 2 ft deep, mounted to the exterior of the house.  Only run AC into the house.  The main challenge I suppose is finding extended temperature rated components.

niel

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Re: Applicability of NEC 690.12 to pole-mounted off-grid PV systems
« Reply #7 on: February 04, 2017, 08:47:52 PM »
just my 2 cents,
firstly let me say that i think the nec is over bearing and bs at times. now that that is out of the way, going by the way the nec is thinking if the power source is external of the house and the generating source can't catch the house on fire (not attached) then they'd have to treat it just like a utility feed and have an external means of manually shutting off the ac to the house. most would pull the meter to do so for a utility.

this begets another scenario as the box or structure the batteries and electronics are housed in could catch fire. if it is an unoccupiable structure that they are in then nothing should be required for a rapid shutdown requirement.

mind you, this is my opinion and the nec and inspectors may think differently from my common sense answer. ::)

tecnodave

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Re: Applicability of NEC 690.12 to pole-mounted off-grid PV systems
« Reply #8 on: February 08, 2017, 11:14:19 PM »
I'm bootlegging the code here in California with my solar system mounted on an old class A RV.  The RV is a state registered motor vehicle which is registered as a housing unit by the STATE housing authority and therefore exempt from the building code and the county building authority. The entire system is within the RV and my house "plugs into the RV". There is no utility feed. The motor home has a 120 volt 6.5 kW. Generator so it is already approved as a mobile power plant.

The building inspector did his best to shut me down for not getting a permit but was stymied by government rules and regs that he gave up and attempted to shut me down by the fire department. My local CalFire captain paid me a courtesy call as one person  in this area was blamed for causing a massive wildlands fire with a non regulated system which caught fire causing the loss of dozens of homes. After a inspection of the system I was given the OK that it was not a fire hazard and have been allowed to operate it like that for several years now.

I do have a home made rapid shutdown built out of surplus rapid disconnect switches bought from midnite ....... It does battery disconnect and panel disconnect and system cross-connect as separately controlled systems or complete panic shutdown but is not listed by any testing agency as it is homemade.......its inspired by the birdhouse design but I don't think it would quality as one.
I call it my "doghouse" as it is basically for shutdown in case of a short circuit on the DC busses, I'm not worried about the pv busses as there in not that much power there.

Bottom line: It all depends on your local building authority as it states in the NEC  "when in dought, refer to the person in authority".......your local building inspector!

I've been given a pass, I did not pay any government agency for any permit but I have been a local electrician here for 40 years, I'm known for the quality of my work!

David



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Halfcrazy

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Re: Applicability of NEC 690.12 to pole-mounted off-grid PV systems
« Reply #9 on: February 10, 2017, 03:00:08 PM »
So on a pole mount the wires usually go under ground and then through a DC disconnect before entering the dwelling, That disconnect would be your rapid shut down. Basically in a nut shell if the PV wires are inside the building more than 5ft they need a way to shut them down
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TomW

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Re: Applicability of NEC 690.12 to pole-mounted off-grid PV systems
« Reply #10 on: February 10, 2017, 04:13:13 PM »
Basically in a nut shell if the PV wires are inside the building more than 5ft they need a way to shut them down

Just curious, our rack mounted grid tie install has no DC disconnect outside at all. It only has the DC disconnect on the Sunny Boy which is mounted on the wall just inside from the buried DC conduit entry. It probably has 6 or 8 feet of actual cable inside conduit but the connection to the inverter is only a couple feet from the conduit entry point.

There is an A.C. disconnect on the outside of the house. Installed last November, no one thought we needed any exterior DC disconnects at all. If they were on a  roof mount or otherwise mounted on the house they wanted the rapid disconnect setup? This grid tie system pushes 3X circuits of ~300 VDC to the inverter. Frankly, I wish I had a disconnect at the panels for maintenance as the DC circuits are lethally hot whenever they are illuminated.

I asked the inspector(s) lots of questions, including about disconnects but they were pretty clueless on the exact needs so we did what the solar installer usually did and the inspector was unconcerned with a disconnect but they had never done a grid tie solar setup before.

I guess that falls under "ask your local authority".

So this topic is interesting to me.

Just from here.

Tom

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mike90045

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Re: Applicability of NEC 690.12 to pole-mounted off-grid PV systems
« Reply #11 on: February 10, 2017, 08:14:49 PM »
Would a combiner box on the pole before the 90' of conduit to the structure housing the battery gear, count as a disconnect, 3 breakers to flip off.
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Halfcrazy

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Re: Applicability of NEC 690.12 to pole-mounted off-grid PV systems
« Reply #12 on: February 14, 2017, 05:19:53 AM »
Basically in a nut shell if the PV wires are inside the building more than 5ft they need a way to shut them down

Just curious, our rack mounted grid tie install has no DC disconnect outside at all. It only has the DC disconnect on the Sunny Boy which is mounted on the wall just inside from the buried DC conduit entry. It probably has 6 or 8 feet of actual cable inside conduit but the connection to the inverter is only a couple feet from the conduit entry point.

There is an A.C. disconnect on the outside of the house. Installed last November, no one thought we needed any exterior DC disconnects at all. If they were on a  roof mount or otherwise mounted on the house they wanted the rapid disconnect setup? This grid tie system pushes 3X circuits of ~300 VDC to the inverter. Frankly, I wish I had a disconnect at the panels for maintenance as the DC circuits are lethally hot whenever they are illuminated.

I asked the inspector(s) lots of questions, including about disconnects but they were pretty clueless on the exact needs so we did what the solar installer usually did and the inspector was unconcerned with a disconnect but they had never done a grid tie solar setup before.

I guess that falls under "ask your local authority".

So this topic is interesting to me.

Just from here.

Tom
Tom
That is correct, Every jurisdiction is different, Most times the inspector will require a DC disconnect at the point of entry but not all the time. So in your case if the physical length of the cable inside the house is longer than 5ft than you would fall under the 690.12 stuff.
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Halfcrazy

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Re: Applicability of NEC 690.12 to pole-mounted off-grid PV systems
« Reply #13 on: February 14, 2017, 05:22:00 AM »
Would a combiner box on the pole before the 90' of conduit to the structure housing the battery gear, count as a disconnect, 3 breakers to flip off.
In my opinion yes, As long as no tools are needed to get to the breakers and as long as there are 6 or less breakers and as long as it is placarded properly
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