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Residential PV w/ battery backup disconnect requirements

Question asked by john.szelog on Jan 6, 2017
Latest reply on Jan 14, 2017 by cdafd

I'm a homeowner, installing a 3kw PV array with battery backup for a critical loads circuit in the house.  I've been an electronics tech for 23+ years and I did the electrical in my house when we built it, so I'm familiar with installing all the equipment, etc.  The new code requirements are what I have questions about.

 

I'm using grid-tied micro inverters downstream of a utility-interactive (not a grid-tie) battery-based inverter.

 

When the mains go down, the micro-inverters shut down like they're supposed to and the battery-based inverter disconnects from the mains.  The battery-based inverter then uses the batteries to start producing 240VAC for the critical loads circuit.  During the day, this enables the micro-inverters to come back online  to run the loads and keep the batteries charged (the battery-based inverter throttles the micro-inverters, for anybody wondering about it).  The batteries by themselves will have sufficient capacity to run my critical loads for ~10 hours, so it's not designed or sized to be a whole-house off-grid system.   

 

The PV array will be ground mounted behind the house, the battery-based inverter and the batteries will be in a cargo container behind the house (between the house and the array).

 

Power will be tied to the house via a subpanel in the house.  

 

The line from the subpanel in the house, the output from the PV array and the output from the battery-based inverter will all meet at a distribution panel in the cargo container.

 

I just submitted my permits to the county and they said I need a rapid shutdown system as of 1 January.  I had seen rapid shutdown mentioned a couple of times previously while I was designing my system, but I didn't see anything saying it was required and the solar power part distributor and manufacturers didn't mention a requirement for it, so it didn't appear that my system would require it.  

 

Based on what I've read, rapid shutdown requirements only apply where you'd have a discharge time for caps, etc., in a circuit, not to a normal AC branch circuit, which is basically what the circuit going into the house from the cargo container will be. 

 

I did confirm that the micro-inverters are rapid shutdown compliant and on the output side of the micro-inverters and the battery-based inverter, it's just a standard 240VAC circuit, so as far as I can tell, my system should not need anything else to meet that requirement.

 

All that said, it made me realize that I didn't have a separate, external disconnect for the battery backup circuit that would meet the intent of the new requirements (de-energizing all the circuits in the house to protect fire fighters).

 

The backup circuit will have a disconnect inside the house at the subpanel, but the line between the subpanel and the cargo container would still be energized.  There is a disconnect on the battery-based inverter, but it (with the disconnect) will be locked in the cargo container (which would also create a problem if there was a fire in the cargo container).  

 

So my plan is to install a safety disconnect on the outside of the cargo container and run the output from the battery-based inverter through it.  Opening that switch would disconnect 240VAC from the distribution panel, which would then cause the micro-inverters to shutdown, thereby removing power from the line going to the house.

 

So, to my question:

 

The safety disconnect would be approximately 30ft and readily visible from the main service disconnect at the house.  I will also install plaques/labels on the main service disconnect clearly stating where it is and what it is.  Is that going to meet the new requirements?

 

Thanks.

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