Question about rapid shutdown and the NEC 2017 1ft and 3ft requirements

[bmw]

I am installing my own DIY system which consists of 6x 100-watt panels wired in series groups of 2 each to create a 24v system. These will go on my garage roof, into my garage, and into a charge controller (which then feeds a small battery bank of 2 batteries in series, about 2500w total storage and that feeds an inverter). There is no grid tie, so this is completely isolated from mains. Basically all I'm using this for is to power a heat pump and for aux power druing a mains outage.

My question is on NEC rapid shutdown requirements. My state has adopted the 2017 rules which state that 30 seconds after rapid shutdown is engaged, voltage inside the array as well as within 3 feet of the building entry point must not exceed 80 volts and voltage outside the array as well as outside of 3 feet of the building entry point must not exceed 30 volts.

690.12(B)(1) Outside the Array Boundary. Controlled conductors located outside the boundary or more than 1 m (3 ft) from the point of entry inside a building shall be limited to not more than 30 volts within 30 seconds of rapid shutdown initiation. Voltage shall be measured between any two conductors and between any conductor and ground.
...
690.12(B)(2)(2) Controlled conductors located inside the boundary or not more than 1 m (3 ft) from the point of penetration of the surface of the building shall be limited to not more than 80 volts within 30 seconds of rapid shutdown initiation. Voltage shall be measured between any two conductors and between any conductor and ground.

So ultimately I have 2 questions. First, because the open voltage rating of an individual panel is just over 24v, I don't believe any 2 points within the array boundary would ever exceed 49v (maybe somewhat higher in cold temps, but never over 80v even when applying the temperature factor multiplier), regardless of whether or not the array is fully energized by the sun or not. As such, would that effectively exempt the array from the RSD requirement as it pertains to inside the array? I can't think of any 2 connection points where this would even theoretically be exceeded.

Second, I obviously would exceed 30v outside the array when the array is energized. But if I install the outer-most solar panel within the array at the edge of the garage roof, can I combine that 1 foot allowance vertically down from there with the 3 feet allowance for building penetration location and simply mount a disconnect switch 4 feet down? By my interpretation of the rules, a switch in such a location would make it such that there is no point between the array and the switch (so long as both the switch and the building entry point are both within 4 feet of the panel edge) that would be subject to the 30v rule, and obviously everything on the other side of the switch, once in the off position, would be de-energized (at least up to the charge controller). Am I interpreting this all correctly?

And a smaller point - which actually applies? 1 meter, or 3 feet? Because 1 meter is 39.3 inches, thereby arguably giving me an additional 3.3 inches of allowance.

 

[zanydroid]

I can’t really help with the detailed rules lawyering, but if you are pulling permits racking 6 small panels to code compliant standards may not be as cost effective effective as doing 2 400W standard size panels plus RSD. And honestly the 400w are not that heavy to do, I solo’ed up 16 onto a single story ranch roof as a noob last month. Fewer panels address other balance of system costs like wiring, fusing, and adapters. With 3P you will usually need some fuses since you exceed the exemption of fuses given to 1P and 2P

You also have SCC AFCI and GFP to contend with, which is likely more complicated to retrofit than RSD (RSD having a cross vendor sunspec standard and plenty of hardware options). So hopefully you’re also looking into that rather than getting distracted by min maxing the more straightforward part.

You can potentially look at the NEC2014 installer hacks to see if you can make any of those work. I think some of those put the inverter at the boundary. If rapid shutdown means interlocked with flipping a readily accessible switch or losing AC power then a cutoff switch is unlikely to work.

 

[FilterGuy]

I am installing my own DIY system which consists of 6x 100-watt panels wired in series groups of 2 each to create a 24v system. These will go on my garage roof, into my garage, and into a charge controller (which then feeds a small battery bank of 2 batteries in series, about 2500w total storage and that feeds an inverter). There is no grid tie, so this is completely isolated from mains. Basically all I'm using this for is to power a heat pump and for aux power druing a mains outage.

My question is on NEC rapid shutdown requirements. My state has adopted the 2017 rules which state that 30 seconds after rapid shutdown is engaged, voltage inside the array as well as within 3 feet of the building entry point must not exceed 80 volts and voltage outside the array as well as outside of 3 feet of the building entry point must not exceed 30 volts.



So ultimately I have 2 questions. First, because the open voltage rating of an individual panel is just over 24v, I don't believe any 2 points within the array boundary would ever exceed 49v (maybe somewhat higher in cold temps, but never over 80v even when applying the temperature factor multiplier), regardless of whether or not the array is fully energized by the sun or not. As such, would that effectively exempt the array from the RSD requirement as it pertains to inside the array? I can't think of any 2 connection points where this would even theoretically be exceeded.

Second, I obviously would exceed 30v outside the array when the array is energized. But if I install the outer-most solar panel within the array at the edge of the garage roof, can I combine that 1 foot allowance vertically down from there with the 3 feet allowance for building penetration location and simply mount a disconnect switch 4 feet down? By my interpretation of the rules, a switch in such a location would make it such that there is no point between the array and the switch (so long as both the switch and the building entry point are both within 4 feet of the panel edge) that would be subject to the 30v rule, and obviously everything on the other side of the switch, once in the off position, would be de-energized (at least up to the charge controller). Am I interpreting this all correctly?

And a smaller point - which actually applies? 1 meter, or 3 feet? Because 1 meter is 39.3 inches, thereby arguably giving me an additional 3.3 inches of allowance.

That is an interesting proposition.

The ultimate arbiter is going to be your inspector.... and he may not interpret the rules the same way you do.
The disconnect will have to be in a position that meets all the readily accessible rules.

 

[zanydroid]

For these under 30V single panels you can also put a RSD per 2S string. That will drop the voltage to under 30v and the switch/shutdown behavior will be perfectly standard. The voltage will be 1s +1V (the approximate standby output voltage from a RSD)

$100-150 for the transmitter (probably less with judicious eBay or Craigslist use) and $30 per module.

Another possible way your plans posted above can tank is if your AHJ/fire department mandates a specific externally accessible way to initiate the RSD

 

[bmw]

Just to clarify - my planned cutoff switch location would be on the same external wall as where the utility power comes in, and basically at eye-level. My lowest solar panel, measured 4 feet down from there, would put the switch at that height. And horizontally, it would be like 8 feet away from the mains power entry into the garage. So pretty sure this particular part would not be a problem.

As to AFCI requirements, those only apply to systems under 80v open circuit, so I think my system would be exempt from that. Of course I will be earth-grounding both my inverter shell (which is metal and electrically isolated) as well as my panel frames to a common earth ground. And the inverter is UL-listed and has GFCI protection built-in (it is a higher-end Samlex inverter).

Also as an aside, I think I'm in the rare subset of people who don't need a permit for this. The state of Michigan, via a 2004 law, defers building code management to the local level, and at the county level, electrical permit language hasn't been updated since 1999 and the language in the actual permit forms only pertains to utility services 100 amps and up. At least one city in my county enacted a solar power ordinance just last year that lays out permit requirements (a permit must be gotten from that city), but my city has no such ordinances. I suspect it is because literally nobody around here has solar panels and it is something that just hasn't been really discussed by my city. I'm sure the requirements are coming soon, but as of now, I certainly can't find any. Worst case scenario, if I'm wrong, per the language in the permit section at the county level, is a penalty whereby I get charged double for a permit and then have to pass a safety inspection.

 

[zanydroid]

Ok, looks like you’ve been doing your homework.

Though GFCI, is that the AC side or PV side. There’s no such thing as circuit interruption during all possible types of PV ground faults

Hmm, well you can give it a shot by sending plans through to plan check. Though if your town charges by revisions it may eat into your cost savings, along with taking more time (depends on how much you value the time).

 

[bmw]

Heh, turns out Michigan goes by 2 different NEC rule sets (2014 or 2017) depending on whether you are in a commercial building or a residential one. It appears I only have to meet the 2014 rules which allow for 80 volts within 10 feet of the array and 5 feet of the building entry point.

The rules really are quite vague when it comes to small, lower voltage systems. For example, it would seem that a 12v system is entirely exempt from all RSD requirements as it would never exceed 30v at any 2 points even when operating, yet, the rules are written in such a way that all solar panel systems must have RSD. There really should be exemption clarification to the 80v and 30v rules which clarify RSD exemptions when the "on" voltages are within the limits of what must be reached after RSD is activated.

 

[patrickparrott]

Heh, turns out Michigan goes by 2 different NEC rule sets (2014 or 2017) depending on whether you are in a commercial building or a residential one. It appears I only have to meet the 2014 rules which allow for 80 volts within 10 feet of the array and 5 feet of the building entry point.

The rules really are quite vague when it comes to small, lower voltage systems. For example, it would seem that a 12v system is entirely exempt from all RSD requirements as it would never exceed 30v at any 2 points even when operating, yet, the rules are written in such a way that all solar panel systems must have RSD. There really should be exemption clarification to the 80v and 30v rules which clarify RSD exemptions when the "on" voltages are within the limits of what must be reached after RSD is activated.

This conversation is quite interesting to me, because I live in Michigan. I am building my 3rd system all of which are visible from the roadway where an inspector would be able to see them when driving by. Noone has ever said anything to me yet. All are off-grid and I do try to make sure that they are code compliant. My next system will be an off grid 5kw array to power the cottage which I will be applying for a permit for. It will be interesting to see what the inspector's reaction is when he gets even closer to the existing arrays. I doubt if he makes much of a fuss at all. Last time that I pulled a permit to do some work on the cottage he signed off on the final without ever showing up! I guess he must have been too busy!

 

[zanydroid]

The way that panel is mounted will raise red flags for places with solar installers going by. They know that not going parallel to roof escalates the engineering and racking costs.

If nobody does solar around you then you might be safe. Around here with high solar adoption it gets reported

 

[OffGridForGood]

Around here with high solar adoption it gets reported

SPIES!!

 

[zanydroid]

SPIES!!

Well that one person on the forum here that got snitched on and fined deserved it for the unanchored solar panels on their roof…

 

[HarryN]

Well that one person on the forum here that got snitched on and fined deserved it for the unanchored solar panels on their roof…

I am not sure - they were experimenting and learning, not finished with the install.

The city could have sent them a "fix it" ticket instead of a large / ridiculous level fine. That would have made much more sense and been much more in line with the risk. The way it was done is more like a mafia action than a safety action.

 

[HarryN]

I have been studying these fire raptor units, but no experience with them.

I like the wired control vs wireless concept.

FireRaptor - UL Approved Solar Panel Rapid

Shutdown Safety Solution (Monitored). NEC2017 & NEC2020

imoautomation.com

 

[HarryN]

Perhaps this can be helpful ?

FLEXmax 100 Rapid Shutdown Kit - OutBack Power Inc

OutBack provides a fully-compliant PV rapid shutdown equipment plus combiner solution with the FLEXmax 100 Rapid Shutdown Kit.

outbackpower.com

 

[Hedges]

I am installing my own DIY system which consists of 6x 100-watt panels wired in series groups of 2 each to create a 24v system.

My question is on NEC rapid shutdown requirements. My state has adopted the 2017 rules which state that 30 seconds after rapid shutdown is engaged, voltage inside the array as well as within 3 feet of the building entry point must not exceed 80 volts and voltage outside the array as well as outside of 3 feet of the building entry point must not exceed 30 volts.

So ultimately I have 2 questions. First, because the open voltage rating of an individual panel is just over 24v, I don't believe any 2 points within the array boundary would ever exceed 49v (maybe somewhat higher in cold temps, but never over 80v even when applying the temperature factor multiplier), regardless of whether or not the array is fully energized by the sun or not. As such, would that effectively exempt the array from the RSD requirement as it pertains to inside the array? I can't think of any 2 connection points where this would even theoretically be exceeded.

Second, I obviously would exceed 30v outside the array when the array is energized.

I think there is a wattage limit together with 80V limit. But 600W may be low enough.
And then that 30V limit beyond 3'.

A 3-pole disconnect within 3' of the array, actuated electrically or with extension handle, should comply.
Also need inverter capacitors to get discharged.

Two 3-pole disconnects would make everything < 30V.

You can get a remote-trip breaker and have 6 poles ganged.

 

[ScrotusGobbleBottom]

a large / ridiculous level fine

How much was the fine?

 

[HarryN]

How much was the fine?

I don't remember the exact number but IIRC ~ $1 - 2K.

Basically a solar contractor doing a job on another roof turned him in and the city just sent out a fine.

Would not give a discount for trying to fix it and be compliant.

And this is in a state that is spending money on subsidizing solar like there is no tomorrow and claiming to be really solar friendly.

 

[zanydroid]

If I saw somebody YOLOing unsecured 400W panels on a roof (the only securement IIRC was the PV cables) I would report it too or at least talk to them. It is only 3-5 ft to the shared friendly neighbor fence in that city

If you want to test it, benchtest on the ground / use a lux meter & PVwatts

 

[HarryN]

If I saw somebody YOLOing unsecured 400W panels on a roof (the only securement IIRC was the PV cables) I would report it too or at least talk to them. It is only 3-5 ft to the shared friendly neighbor fence in that city

If you want to test it, benchtest on the ground / use a lux meter & PVwatts

So would you also endorse the idea that if you go over 55 mph, the drivers around you should also turn you in and the city will just send you a fine for $100?

Or perhaps a more similar version - your car is parked with the tires 7 inches away from the curb instead of 6 inches. Instead of either letting it go or similar, your neighbors turn you in each time - and you get a $500 fine? Or would a fix it ticket or just mentioning it to you be sufficient?

 

[zanydroid]

Those are kind of extreme examples, I suppose to make a point. I wouldn’t put them in the same risk bucket

I’m going to withdraw from the politics so that we can have productive discussions in the future and withdraw from this convo/other related convos. Neither between us is going to act that way anyway so it doesn’t matter in practice