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Old 07-31-2020, 02:20 PM   #1
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Default Rapid shutdown (off-grid, Manitoba Canada)

I'm trying to determine real-world requirements for rapid shutdown in small "cottage" off-grid systems in Manitoba, Canada.


If you're off-grid, code compliance falls to the Office of the Fire Commissioner. As far as I can tell, there is currently (no pun intended, but I'll pretend it was) only one guy covering electrical inspections for the entire province(?!)


I've read the codes, but there seems to be little clear distinction made between (relatively) high voltage grid-connected systems and (relatively) low voltage (e.g. 48V array) small-scale systems.


Just looking for practical information on-line has been frustrating.


I'm trying to sort out whether it is adequate to have an externally-accessible disconnect for an array that is not mounted on the dwelling, or do I need a full-on rapid shutdown system that disconnects the array and batteries remotely.


Anyone have any links, experience, commiseration...
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Old 08-13-2020, 11:45 PM   #2
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My experience is the rapid shut down (when installed on a grid tie system) is fed from the grid. Power goes down, the rapid shut down opens the circuit.

Not sure how you'd achieve that with an off-grid system.

I don't know what code says, but you'd likely be okay without a rapid shutdown if they're not mounted on the structure. If they're mounted to a racking system that's not on the building I'd just install a disconnect on the feed from the panels.
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Old 08-14-2020, 02:54 PM   #3
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Quote:
Originally Posted by Kevin_Essiambre View Post
My experience is the rapid shut down (when installed on a grid tie system) is fed from the grid. Power goes down, the rapid shut down opens the circuit.

Not sure how you'd achieve that with an off-grid system.

I don't know what code says, but you'd likely be okay without a rapid shutdown if they're not mounted on the structure. If they're mounted to a racking system that's not on the building I'd just install a disconnect on the feed from the panels.
I'm still waiting for a response from the Office of the Fire Commissioner, but here's what I'm thinking:

The important thing from the standpoint of firefighters is that there is no dangerous live power in the building they're going to try to save.

In a grid-connected home without independent power, the meter can be pulled or the farm service disconnect thrown or worst case, the power company can cut the lines. Then the building is dead.

In an off-grid situation, the array is only part of the picture; the batteries and any DC branch wiring represent a potential hazard, and by virtue of an inverter supplying (potentially) 120 or 240V to the house wiring, yet another.

What I half-know at this point is that shutdown can be initiated from a "birdhouse" manual shutdown location, like an e-stop in a little red box, that talks over some signal lines (maybe ethernet?) to remote disconnect devices.

As I understand it at the moment, this includes a remote disconnect at the solar combiner (or thereabouts, by code has to be fairly close to the array) to de-energize the solar output circuit. But ALSO, I believe this has to communicate to a battery remote shut-down gizmo, presumably a pulse-operated contactor or some such thing, that pulls the plug on the batteries and thus kills any DC branch circuits and the inverter.

Both of these items are likely to be expensive.

Another question I included in my submission to the OFC was if the entire power system (charge controls, batteries, inverter) is contained in a shed or sea can separate from the home, supplying only garden-variety AC to thereto, surely then it would be acceptable to have a simple external AC disconnect to cut supply to the home.

Either way, I have to admit the idea of an accessible, presumably obvious external means of cutting power to the building makes me uncomfortable, but I understand the concern and I can't really argue with it.
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Old 08-14-2020, 04:32 PM   #4
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How about just shunt breakers and a big red shutdown button in a WP box?
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Old 08-14-2020, 05:01 PM   #5
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How about just shunt breakers and a big red shutdown button in a WP box?

A perfectly good question. Functionally that's all we're talking about. I watched a demo on YouTube and the birdhouse box was issuing spoken status reports fer pete's sake. For me, an off button would be just fine.
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