PV Rapid Shut down Requirements -Ontario Canada

bedpan

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Hey folks... I am looking at diy'ing residential solar system and trying to wrap my brain around code. It's been a bit of a roller coaster as I got denied my grid tied application with Ontario hydro so I switched gears to building a smaller system. After a few phone calls though it seems like hydro might actually give me an approval after all and I am back to designing a larger system again....

So today's question is around rapid Shut down Requirements here in Ontario Canada'land. I have attached a ESA bulletin I found on the topic and I am trying to dissect it.

If I read it correctly rapid Shut down should only be required if the inverter is setup to run in Islanding mode. So a basic UL1741 listed string inverter would not require a seperate means of rapid Shutdown.

Now if I goto a hybrid inverter that supports a critical load sub panel does this now mean I need a means of external rapid Shutdown? If so what does this look like for say a solark style inverter?

My plan is to stage the my install.. starting with about 5-6kW of PV setup to hybrid inverter. No critical loads panel, just a breaker in my main panel. Once I have that working I will then move to a critical loads panel and likely at the same time add a small amount of battery. Then likely add another 5-6kW of panels...

Your thoughts and input are greatly appreciated!

Mike
 

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Hedges

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Just skimming it, I don't see grid-tie only vs. off-grid operation.
What I do see is the older version of U.S. requirement, where high voltage DC is OK if confined to the array, disconnected from wires going further.
That's just one disconnect switch.
The new U.S. requirement disconnect between each PV panel (or group of panels) so nothing in array is more than 80V from anything else.

Maybe just a mechanical switch within 3' of array (possibly mechanical extension to remote handle) might satisfy requirement.
 

Supervstech

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If rapid shutdown is an issue, aside from the inverter is the fire code for residence roof mounted array shutdown.
 

bedpan

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Just skimming it, I don't see grid-tie only vs. off-grid operation.
What I do see is the older version of U.S. requirement, where high voltage DC is OK if confined to the array, disconnected from wires going further.
That's just one disconnect switch.
The new U.S. requirement disconnect between each PV panel (or group of panels) so nothing in array is more than 80V from anything else.

Maybe just a mechanical switch within 3' of array (possibly mechanical extension to remote handle) might satisfy requirement.

Thanks Hedges,
In the US what does a Rapid shutdown entail with a traditional string inverter? I gravitate to the Sol-Ark (likely not buying due to price), what would be needed for a Rapid shut down on a solark system? I guess I can do some searching on it and try and wrap my brain around it.

Side note. My Fuse panel is in my garage. The garage is insulated but not finished so working in there is pretty easy.

If rapid shutdown is an issue, aside from the inverter is the fire code for residence roof mounted array shutdown.
Not sure I follow Supervs. Should I be checking local fire code as well regarding the solar installation? Had not even considered this beyond making sure panels are properly spaced from edges with walkways in between ridges, troughs and edges.
 

bedpan

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I am struggling with this wording. Anyone able to provide their interpretation for me?

Based on the intent of Rule 64-218, rapid shutdown process can be defined as a process that:  de-energizes PV source or output conductors that are more than 1m. in length on or inside a building, and  de-energized conductors to not more than 30 V within 30 s of initiation. If a combiner is close (not more than 1 m) to a PV array/module, Rule 64-218 does not require a PV module level shutdown. PV conductors within a PV array and up to a combiner box located within 1 m are permitted to remain energized.
 

bedpan

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I am struggling with this wording. Anyone able to provide their interpretation for me?
Alright.. starting to wrap my head around it. Soooo if all the panels run into a combiner box within 1m of the panels then I can have some form of switch to turn off the power from the panels at the combiner box. What Hedges said makes sense now. Just was not following for some reason..

Any idea what this disconnect would be? Something on the side of the house either electrical or mechanical that some how breaks a DC circuit likely about 100' away?
 

Hedges

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100' away? Is that panels on the roof 100 feet away from the switch, or ground-mount panels 100' away from the house?

I read the requirement as a roof-mount array having a switch within 3' of the array. Once switch is opened, nothing more than 3' from the array (and on the house) is energized. Could be mechanical lever, could be relay controlled remotely.

Our new module level requirement is either microinverter per PV module, or for string inverters a box per PV module that is controlled electronically. (some RSD devices have multiple PV panels plugged into one.) It either isolated between modules, or is a switching power supply (optimizer) that drops voltage of each module to about 1V.

Maybe you can have panels down to the eaves and a switch within 3' with pull handle or extension lever within reach.
Not many relays good for 600VDC, but there are some remote-trip breakers (several 150V poles ganged and wired in series.)
 

bedpan

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100' away? Is that panels on the roof 100 feet away from the switch, or ground-mount panels 100' away from the house?

I read the requirement as a roof-mount array having a switch within 3' of the array. Once switch is opened, nothing more than 3' from the array (and on the house) is energized. Could be mechanical lever, could be relay controlled remotely.

Our new module level requirement is either microinverter per PV module, or for string inverters a box per PV module that is controlled electronically. (some RSD devices have multiple PV panels plugged into one.) It either isolated between modules, or is a switching power supply (optimizer) that drops voltage of each module to about 1V.

Maybe you can have panels down to the eaves and a switch within 3' with pull handle or extension lever within reach.
Not many relays good for 600VDC, but there are some remote-trip breakers (several 150V poles ganged and wired in series.)


Cheers again Hedges.. I will need to seek professional help I think with someone that knows the code and what to expect from the inspection. I think you are right though about the disconnect 3' (1m) away. I am not keen however of having a weather exposed box/switch on the roof. I was hoping to go with something like the soladeck combiner on the roof underneath of the panels based on what I have seen so far. There may well be better options though, I am still learning..

I have done some reading on the Tigo Rapid shutdown equipment. It maybe an option as well. Part of the problem is the ESA code is all hidden behind payways. Maybe I just need to pony up and buy the code (which I have a download of) so that I can get access to all the bulletins and amendments.. I will continue to read the code and try and wrap my brain around it but I am hoping to find a Local (ontario based) installer that does not mind giving me an hour or two of time for some beer money.

Cheers,

Mike
 

macheung

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Wow, 30V is a pretty low voltage requirement. Pretty much it would prevent even a single normal sized roof panel (Voc 40-45V) without a disconnect switch located right there from working. Harsh...

As per the wording of the document, would it be possible to have a device that literally shorts the leads together to ground in a accessible location even if it is away from the roof on shut down? A single relay or switch per string would do that. If the PV leads are shorted and then grounded, then voltage would be by definition 0. The short circuit current isn't that much higher than normal operating current so existing wiring would still work. Am I missing something?
 

Wellbuilt

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Hmmm they don’t have us using the weather prof box any more
Our panels get turned off 12” from array
There are little boxes that go on each panel the box gets tied into others systems to turn every thing off at once .
I believe if you mount the charge controler on the out side of the building you are ok
The charging takes place at 63 volts or so
But I’m trying to figure this all out my self
It seams like a bunch of bull Sxxx
 

Supervstech

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Wow, 30V is a pretty low voltage requirement. Pretty much it would prevent even a single normal sized roof panel (Voc 40-45V) without a disconnect switch located right there from working. Harsh...

As per the wording of the document, would it be possible to have a device that literally shorts the leads together to ground in a accessible location even if it is away from the roof on shut down? A single relay or switch per string would do that. If the PV leads are shorted and then grounded, then voltage would be by definition 0. The short circuit current isn't that much higher than normal operating current so existing wiring would still work. Am I missing something?
Shorting a panel in full sun would RAPIDLY heat the panel and cause fire, etc...
 

macheung

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Shorting a panel in full sun would RAPIDLY heat the panel and cause fire, etc…
How come? The Isc is only 10% higher than Imp, if the panel can operate indefinitely at say 9A what would make it catch fire at 10A?
 

Hedges

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Shorting a panel in full sun would RAPIDLY heat the panel and cause fire, etc...

Not at all.

How come? The Isc is only 10% higher than Imp, if the panel can operate indefinitely at say 9A what would make it catch fire at 10A?

Yup.

No problem. Wire and connector have ampacity much higher.

If panel is open circuit, electrons generated just leak back through PV diode at Voc, and that 12% to 20% of suns energy heats the cell.
Shorted, it heats the conductors. Only about 10% more than at Imp as you note.

As of 2017 NEC requires panels mounted on the roof of living quarters have a rapid shutdown of less than 30V...

For all wires more than 12" from the array? While wires inside the array could be 600V.

New requirement (2020 or whatever) is any two wires even within the array no more than 80V apart.
I think that is usually met by Voc being within that limit, and possibly isolation, or buck converter. SolarEdge drops it to 1V per panel.
 

macheung

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Not at all.



Yup.

No problem. Wire and connector have ampacity much higher.

If panel is open circuit, electrons generated just leak back through PV diode at Voc, and that 12% to 20% of suns energy heats the cell.
Shorted, it heats the conductors. Only about 10% more than at Imp as you note.



For all wires more than 12" from the array? While wires inside the array could be 600V.

New requirement (2020 or whatever) is any two wires even within the array no more than 80V apart.
I think that is usually met by Voc being within that limit, and possibly isolation, or buck converter. SolarEdge drops it to 1V per panel.
Given that, if I only have panels that are not connected in series with Voc around 42V, can I satisfy the rapid shutdown requirement by having a shutdown switch that effectively shorts each of the panels out? Note the switch will be installed quite always from the panel, but once it is engaged and shorts there panel, the entire line would be at ground voltage.
 

Hedges

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That might fly (until a wire burns open and goes back to 42V)
Shorting out charged up capacitors in SCC might not be a nice thing to do to them.

I think the typical solution when that code applied was a mechanical disconnect at the array with extension lever.
There are also some remote-trip circuit breakers. I think Midnight's "Birdhouse" controls that.
 

macheung

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That might fly (until a wire burns open and goes back to 42V)
Shorting out charged up capacitors in SCC might not be a nice thing to do to them.

I think the typical solution when that code applied was a mechanical disconnect at the array with extension lever.
There are also some remote-trip circuit breakers. I think Midnight's "Birdhouse" controls that.
Note that I am not shorting an entire 600V string to ground. I am looking at a few individual panels wired separately with Isc 10A and Voc 42V.
 
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Hedges

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Do your PV panels wire to the input of a charge controller? It probably has a bank of capacitors. Those may or may no suffer damage if instantly discharged into a short, due to high current. It does happen, but I'm not sure what capacitor value and voltage makes it most likely. High voltage capacitor on AC input of switching power supply I've heard of it.

A switch or relay rated for that DC voltage and current could perform the disconnect.

At 44V, I'd hardly be worried. That's below usual hazard threshold. But it is a figure specified in some revisions of code.

I looked for pictures of an electrical switch box with extension lever, but can't find one.

Does the code allow > 30V to extend beyond array if inside metal conduit?
 

macheung

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I actually have a pretty unusual setup. I have 45 panels connected in 3 strings through SolarEdge optimizers to a SolarEdge grid tie inverter. The grid tie inverter shuts down when grid is lost and the optimizers shuts off at the panel. This is normal and all good. Rapid shutdown, no issues.

However, I want the ability to have some power when grid is lost, so for 6 of the panels, I installed a Y split between the panel and the SE optimizer to also connect the panel down to a secondary "off-grid" inverter unit with 2 MPPT inputs in the garage that can supply power to critical loads when grid is down. This "off-grid" inverter is manually connected when the grid is off and the SE system is down, and will be disconnected before I reconnect the SE main inverter so there never exist a situation where 2 MPPT (hybrid inverter and SE Optimizer) is both managing the panel. Note that secondary lines for these 6 panels are not connected in series before coming down, their lines are wired separately down from the roof to the garage in a metal conduit. The panels have Isc 10A and Voc 42V (Imp is 9A).

Therefor, I am wondering whether the rapid shutdown requirement would apply to these secondary lines, and if so, what's the best way to do that.
  1. No rapid shutdown required for 42Voc 10Isc in a metal conduit in side the building
  2. Simple switch in the garage to "ground" the lines when shutdown, brining the line voltage to 0V (though up to 10A would flow in each)
  3. Relay installed in the attic right under the panels that would disconnect the lines when in shutdown state
#1 is easiest, no work required. #2 isn't hard to do, #3 is possible but the most work.
 
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