SOLAR PANELS ON MULTIPLE BUILDINGS

[Mavipo0221]

Morning everyone,

Lets say a combiner box fed from a service is on the house, and feeds solar with microinverters on the home, but also feeds solar with microinverters on a detached garage, would that garage require a disconnecting means located on it, or is the disconnecting means on the home feeding the combiner box sufficient?

Thanks

 

[pv_n00b]

NEC 690.15 requires a disconnect in sight of and within 10ft of the garage microinverters. But some AHJs accept the connector in the microinverter AC conductor as the required disconnect. So it depends.

 

[Mavipo0221]

After looking further into it, the microinverters are UL listed as rapid shut down devices in accordance with NEC 690 2014 and 2017, which I interpret as not requiring a separate disconnecting means

 

[ggunn]

After looking further into it, the microinverters are UL listed as rapid shut down devices in accordance with NEC 690 2014 and 2017, which I interpret as not requiring a separate disconnecting means

Check with your AHJ. Irrespective of the NEC, several we deal with require a disco on the outside of every building that has PV on the roof.

 

[pv_n00b]

The purpose of disconnecting means is so that people can work on the equipment denergised. It has to be in sight of or locked out so the worker knows it won't be turned on while they are working on the device.

 

[jaggedben]

If the AHJ wants to cite 225.31 you really have no argument against a disconnect being required. Also your logic on rapid shutdown is backwards. Arguably that section requires a rapid shutdown initiation device on the garage, which would mean a disconnect. (You could argue that the code just says 'outside the building' not 'on the building', but at best it makes no difference.)

These requirements may seem silly if the garage is just a few feet from the service panel on the house. But the farther the garage is from the house the more obvious it should be that someone should have a disconnect either for emergencies or to do work on the circuit at the garage. Also if the garage is also served by other power one should make it easier to figure out how to turn off all circuits at the garage.

 

[JoeNorm]

We have been required to tie the ground into whichever building the panels are on

 

[Carultch]

Arguably that section requires a rapid shutdown initiation device on the garage, which would mean a disconnect.

It doesn't necessarily need to be a disconnect that the system's full power runs through. An off-switch could be remotely operated via a shunt trip or contactor control circuit.

This is significant when your system is large enough, since there is a big difference between running hundreds of amperes to the location of an outside switch, and running a couple of #14's or a CAT5 cable to a push-button. Utilities may have their own requirements for shutoff switches, that logically might double as a rapid shutdown switch.

 

[Carultch]

After looking further into it, the microinverters are UL listed as rapid shut down devices in accordance with NEC 690 2014 and 2017, which I interpret as not requiring a separate disconnecting means

Microinverters are UL listed as rapid shutdown devices, because by their operation, they only energize the AC side when it is already energize with a voltage waveform to follow. Only the module-to-microinverter DC circuit remains energized after the system is shut off. You still need a device to initiate rapid shutdown, and in this case, this means cutting the grid power to the AC side.

 

[jaggedben]

It doesn't necessarily need to be a disconnect that the system's full power runs through. An off-switch could be remotely operated via a shunt trip or contactor control circuit.

This is significant when your system is large enough, since there is a big difference between running hundreds of amperes to the location of an outside switch, and running a couple of #14's or a CAT5 cable to a push-button. Utilities may have their own requirements for shutoff switches, that logically might double as a rapid shutdown switch.

Yeah, I know, but in the case of a single micro-inverter circuit nothing will be as low-cost and simple as a disconnect.

 

[ggunn]

It doesn't necessarily need to be a disconnect that the system's full power runs through. An off-switch could be remotely operated via a shunt trip or contactor control circuit.

This is significant when your system is large enough, since there is a big difference between running hundreds of amperes to the location of an outside switch, and running a couple of #14's or a CAT5 cable to a push-button. Utilities may have their own requirements for shutoff switches, that logically might double as a rapid shutdown switch.

But of course the AHJ may have something to say about it. I deal with some AHJs that require an external readily accessible bladed PV AC disconnect on every building that has an array on the roof irrespective of whether it is a complete PV system or part of a larger one.

 

[wwhitney]

I deal with some AHJs that require an external readily accessible bladed PV AC disconnect on every building that has an array on the roof irrespective of whether it is a complete PV system or part of a larger one.

So no DC between buildings, each building has to have its own inverter?

Cheers, Wayne

 

[ggunn]

So no DC between buildings, each building has to have its own inverter?

Cheers, Wayne

Yes, in CPS (San Antonio), anyway, which is the only jurisdiction where I have floated that trial balloon. In this case, however, the OP said up front that he is using microinverters.

 

[Ravenvalor]

Morning everyone,

Lets say a combiner box fed from a service is on the house, and feeds solar with microinverters on the home, but also feeds solar with microinverters on a detached garage, would that garage require a disconnecting means located on it, or is the disconnecting means on the home feeding the combiner box sufficient?

Thanks

Great content here.

This forum is great for helping me better understand pv systems especially given how fast the industry is evolving. For instance I find no reference to the term 'combiner box' in the 2020 NEC. I did find a definition in the book 'Install your own solar panels' by Burdick & Schmidt. It states
Combiner Box - Outdoor rated enclosure usually located at or near the pv array, where pv modules series strings are electrically connected and combined into parallel strings and where protector devices (such as fuses, breakers) are located. A Disconnecting Combiner Box can be shut down remotely by a rapid-shutdown control device, shutting off the power between the combiner box and the AC-DC inverter.

Thanks....

 

[Carultch]

Great content here.

This forum is great for helping me better understand pv systems especially given how fast the industry is evolving. For instance I find no reference to the term 'combiner box' in the 2020 NEC. I did find a definition in the book 'Install your own solar panels' by Burdick & Schmidt. It states
Combiner Box - Outdoor rated enclosure usually located at or near the pv array, where pv modules series strings are electrically connected and combined into parallel strings and where protector devices (such as fuses, breakers) are located. A Disconnecting Combiner Box can be shut down remotely by a rapid-shutdown control device, shutting off the power between the combiner box and the AC-DC inverter.

Thanks....

Glad we could assist.

Combiner boxes have been a mature term used in the industry for decades, even if it never was directly defined in the NEC. Their use is a logical consequence of other code rules about the need to parallel strings with fuses, and the need to enclose the busbars that parallel the current. The evolution of what you needed to do with a combiner box, has evolved over the course of the code cycles from 2008 to 2017. Due to rules about load-break disconnect co-location, AFCI, and rapid shutdown, that govern what you need to do for balance-of-systems on the DC side.