Code Required Disconnect outside.

I am in the very early stages of planning out a Hybrid solar system, this will be a single inverter, with Solar, Batteries and grid tied.


I am planning to put my Inverter and Batteries in a garage, so they will not be accessible outside. What disconnects do I need to place outside?

I am a little confused on what exactly needs to be outdoor accessible based on NEC 2020 requirements.

The grid tied disconnect is easy and can be place right next to my power meter. But the PV and DC battery disconnects I am unsure if that is required to be outside accessible or not.

If outside disconnects are required are relays or some kind of electronic disconnect an option? So I don't need to have long cable runs of massive battery wire just to add disconnect outside?

This is a very confusing thing, and I'm not sure I have it entirely figured out, but here is what I think:

1. External RSD button/switch

NEC 690.12 rapid shutdown requirement. A button on the exterior of the building, near the utility meter, shuts down the PV array, the inverter, and any battery system when pressed.

2. Accessible AC disconnect

A breaker or switch that disconnects the PV system from utility power. This does NOT need to be outside per NEC, it just has to be "readily accessible". In the main breaker panel meets the definition of "readily accessible" (which is what the main panel main breaker has to be as well).

3. PV DC disconnect

For a system with RSD, it isn't clear this is required, but most inverters have a switch that disconnects the PV inputs. I believe NEC 690.12 RSD says the RSD system meets the requirements even without the inverter switch.

4. Battery DC disconnect

Not clear this is required if the battery shuts off with RSD. If the battery has a breaker on it, that should meet the requirement.

I am not very secure in my understanding of these things, but I just had plans drawn and stamped for FL which had no external AC disconnect, no added PV DC disconnect (over the inverter switch), and no added battery DC disconnect switch (over the battery built in breaker). So the only thing I need to add to the outside of the house is the RSD button which signals the inverter, battery, and RSD boxes under each panel to shutdown.

Mike C.

mciholas said:

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Thanks for the response. I will have to do some research on the RSD button/switch. I haven't heard of that before.

From what your describing is sounds like it is more of a low voltage 12/24 volt software kind of button that would trigger the equipment to shutdown. Is that correct?

Am I the only one that finds the idea of having an easily pressed button right on the outside of your house that turns off all your power, including the whole house UPS, upsetting?

Maybe put the button in an "In case of fire break glass type enclosure". Or, are you allowed to put it in a metal box, clearly labeled, with a padlock? You can padlock your main breaker box can't you? My main breaker box on the outside of my house has a padlock hole on it, and the meter at least has a little locking clip security seal on the bottom of it.

I imagine firefighters can break a small padlock on a metal box.. though the delay might cause the destruction of your home and/or your death.

I intend to have an internal bypass, so I can restore power if inside.

GT PV, a switch disconnecting AC is all that's required to trigger RSD of PV modules by taking away keep-alive signal.
With a hybrid/AIO, it would keep operating as battery backup when grid goes down. Some have an RSD input, which shuts down the inverter and stops the keep-alive. That is probably the case for OP.

RSD stickers are supposed to have a map of what doesn't get shut down.

Since I'm using older Sunny Island, my plan is to use 3-pole disconnect. Two disconnect to prevent backfeed to grid, 3rd pole will interrupt keep-alive so PV does RSD. Could also disconnect load-shed so no AC reaches anything in house, just supplies AC coupled GT PV (wires in conduit) and monitoring/communication hardware (12V immediately after AC connection at breaker panel.)

cs1234 said:

Am I the only one that finds the idea of having an easily pressed button right on the outside of your house that turns off all your power, including the whole house UPS, upsetting?

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No.

It worries me, too.

I want to put the button under a cover to make it less obvious and to avoid a nuisance switch if someone leans on it.

Note that anybody could cut your meter security tag and pull your meter to shut off your power, but that's a lot more commitment than flipping a switch.

cs1234 said:

Or, are you allowed to put it in a metal box, clearly labeled, with a padlock?

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I think a security seal would be sufficient. Something someone has to cut to get to the switch.

That has to be okay since the meter has one already.



Mike C.

mciholas said:

This is a very confusing thing, and I'm not sure I have it entirely figured out, but here is what I think:

1. External RSD button/switch

NEC 690.12 rapid shutdown requirement. A button on the exterior of the building, near the utility meter, shuts down the PV array, the inverter, and any battery system when pressed.

2. Accessible AC disconnect

A breaker or switch that disconnects the PV system from utility power. This does NOT need to be outside per NEC, it just has to be "readily accessible". In the main breaker panel meets the definition of "readily accessible" (which is what the main panel main breaker has to be as well).

3. PV DC disconnect

For a system with RSD, it isn't clear this is required, but most inverters have a switch that disconnects the PV inputs. I believe NEC 690.12 RSD says the RSD system meets the requirements even without the inverter switch.

4. Battery DC disconnect

Not clear this is required if the battery shuts off with RSD. If the battery has a breaker on it, that should meet the requirement.

I am not very secure in my understanding of these things, but I just had plans drawn and stamped for FL which had no external AC disconnect, no added PV DC disconnect (over the inverter switch), and no added battery DC disconnect switch (over the battery built in breaker). So the only thing I need to add to the outside of the house is the RSD button which signals the inverter, battery, and RSD boxes under each panel to shutdown.

Mike C.

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You post matches with my best understanding of the codes as well. But the NEC 2020 code has a fair amount of vagueness around this topic. NEC 2023 added a little bit of clarification, but not enough that it's not still vague overall IMO.

Unfortunately, the net result, from a practical perspective, is it ends up being the interpretation of the local inspecting authority. It's typically not the best approach to try to convince them the code doesn't require it. It's just best to provide what they demand. Solar installers typically know what the local inspectors will and won't sign off on and adjust the system plan based on their experience with inspectors in the jurisdiction where they are doing the install.

What I've found is if you want to be absolutely sure it'll pass inspection, design your RSD system to shut it all down. That's what I ended up doing on my system. Relays and low voltage wiring don't typically seem to be an issue as long as the system is designed such that it faults to disconnected. That typically means all the relays and contactors are normally open and have to stay energized to keep the power flowing. And if any part of the RSD system breaks, that results in the power shutting off.

The one thing I have seen to be very consistent now, is making sure you have an RSD module installed on every panel. Stupid requirement IMO, but it seems to be being pretty universally enforced.

jpwhit said:

Unfortunately, the net result, from a practical perspective, is it ends up being the interpretation of the local inspecting authority.

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Sometimes the utility also forces requirements.

In Florida, if above 10 KW AC capability, they require an external AC disconnect. Below 10 KW AC, they don't. They measure AC power by taking 85% of the panel nameplate capacity, which is a bogus way of doing it since it penalizes those who have to install more panels due to non ideal orientation.

jpwhit said:

What I've found is if you want to be absolutely sure it'll pass inspection, design your RSD system to shut it all down. That's what I ended up doing on my system. Relays and low voltage wiring don't typically seem to be an issue as long as the system is designed such that it faults to disconnected. That typically means all the relays and contactors are normally open and have to stay energized to keep the power flowing. And if any part of the RSD system breaks, that results in the power shutting off.

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An exception to this seems to be batteries. The RSD input on most batteries I look at tend to require contacts to be closed to shutoff whereas most inverters require open to be shut off.

In practical terms, this means your RSD button has a DPDT switch in it. One pole is inverter shutdown and it uses the NC contact. One pole is battery and uses the NO contact. RSD button pressed causes inverter contacts to open, battery contacts to close.

jpwhit said:

The one thing I have seen to be very consistent now, is making sure you have an RSD module installed on every panel. Stupid requirement IMO, but it seems to be being pretty universally enforced.

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Yes, it is a stupid rule and was promoted by the makers of microinverters and module electronics. Even when common sense shows up, like UL 3741, the code writers leave in a "business related requirement" like the fact UL 3741 requires inverters to be included in the approval, thus now allowing makers of stuff to manipulate which things get approved with which other things. Thus, my racking and panels are fully UL 3741, but my inverter is not, so I'm still out of luck and have to spend $1500 on stupid RSD boxes that, in fact, don't increase safety for anyone.

PV solar has been attacked by code writers, AHJs, utilities, and scam artists to the point it is very difficult to get things done. If gas cars were a new invention, the rules for garages where you keep them would be onerous indeed with tons of new rules.

Mike C.

mciholas said:

In Florida, if above 10 KW AC capability, they require an external AC disconnect. Below 10 KW AC, they don't. They measure AC power by taking 85% of the panel nameplate capacity, which is a bogus way of doing it since it penalizes those who have to install more panels due to non ideal orientation.

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PG&E computes power of my system as number of PV panels times California CEC listed PTC wattage of panels times CEC listed efficiency of inverters.

So yes, wattage can be well above inverter AC rating.

Makes sense when determining annual power production, not for safety rules.
I'm not sure if they tie it to disconnect requirements or not. I think disconnects aren't required, just recommended because otherwise yanking meter is their only 100% option to ensure disconnect.

Switch is handy for disconnect. Of course breaker provides same function. Switch allows lock-off (breaker, you can get a hasp).
But more important, breaker is fed by main panel, which switch I've wired as line-side or load-side tap. That lets me backfeed main panel as grid-backup.

I'm using Square-D 60A or 100A fused visible-blade safety switches, in 3R enclosure. Found at a discount through eBay.
I'm now getting 3-pole in anticipation of RSD requirement, to make that work even with battery backup.
I've also picked up handle-position microswitches, to retrofit 2-pole systems. Or I can swap the switch guts inside the box.

cs1234 said:

Am I the only one that finds the idea of having an easily pressed button right on the outside of your house that turns off all your power, including the whole house UPS, upsetting?

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Oh yeah. Mine is at least going to have a 9V battery and a Sonalert in the box on the second set of contacts.

wpns said:

Oh yeah. Mine is at least going to have a 9V battery and a Sonalert in the box on the second set of contacts.

Amazon.com

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Not a bad idea. It's a shame we can't just energize the box to keep troublemakers out. Firefighters wear thick gloves..