[RE-wrenches] Rapid Shutdown Compliance

Wed Apr 29 15:07:29 EDT 2020

I agree, 690.12 should have exemptions for lower voltage, lower power 
systems, and shorter runs; especially off grid.  10 years ago, I was 
promoting some type of remote controlled disconnect at the array, but 
that was for voltages over 400v, with unprotected conduit runs over a 
100 ft long, on systems over 10 kW.

For off grid where reliability is the number one safety issue, we've 
gone back to pole mounts to avoid 690.12.  If the temperature goes below 
zero, and the customer is snow bound, having the Rapid disconnect trip 
off is NOT creating a safer situation.  They need heat, unfrozen water 
supply, and communications.    Rural VFDs are not going to usually even 
get up on the roof anyway.  That's a scenario for in town, when they can 
respond in less than 10 minutes.

Actually for residential systems in rural areas, the only person that is 
going to get hurt on the roof is the customer trying to reset the Rapid 
Disconnect, not the Fire Department.  Maybe the NEC task groups will 
finally see that fire fighter safety needs to be balanced with the 
safety of the people they are trying to protect. I hope that the NEC 
could reach this conclusion before an untrained home owner breaks their 
neck.

Ray Walters
Remote Solar
303 505-8760

On 4/29/20 10:17 AM, drake.chamberlin at redwoodalliance.org wrote:
>
> Clearly, rapid shutdown increases cost and reduces reliability. Given 
> the excellent safety record of PV, prior to rapid shutdown being 
> required, it is unnecessary. The few anecdotal incidents of PV fires 
> were not enough to justify the requirement, especially on smaller 
> systems.
>
> According to a friend who worked for a local installation company that 
> went under, a big part of the reason for their failure was the chronic 
> replacement of microinverters and optimizers.
>
> What steps can be taken to create some balance in the rapid shutdown 
> requirements that are in the NEC?
>
>
> ---
>
>
> On 2020-04-29 07:27, Sky Sims wrote:
>
>> So far rapid shutdown has been a nightmare. It's added a lot of cost 
>> for no measurable benefit.
>> Using always off devices like midnight solar and Tigo makes it 
>> impossible to test open circuit voltages. Which opens the door to 
>> tons of problems when commissioning systems.
>> Also we've been trying out midnight Solar's product and have had an 
>> absurd failure rate. Which means lots of truck rolls and 
>> troubleshooting and system downtime. They send replacement product 
>> but they aren't paying for the lost weeks of productivity.
>> We have Tigo product in hand and are deciding which project to try it 
>> on. But our big concern about using it is not only the inability to 
>> confirm open circuit voltage of the strings but also the way panels 
>> bypass if the device doesn't allow the panel to connect properly. 
>> Both of these features are a recipe for problems and potential 
>> troubleshooting nightmares. The warranty from Tigo doesn't cover our 
>> expense if the product fails. And that's really what our reservations 
>> about the product boil down to right now. If we're on a job with 50 
>> units and one fails, the contractor or the homeowner will be the ones 
>> eating the expense of finding it and replacing it. There has to be a 
>> better option.
>>
>> Sky Sims
>> Https://EcologicalSystems.biz
>>
>>> On Apr 28, 2020, at 7:46 PM, Corey Shalanski <coresolar at gmail.com> 
>>> wrote:
>>>
>>> Now that 690.12 of the /NEC/ 2017 has been in effect for several 
>>> years, I am curious how designers and installers are meeting the 
>>> associated requirements with string inverter-based systems (*not* 
>>> considering microinverters or DC optimizers). I am generally a fan 
>>> of the KISS principle, and as best I can determine the /Tigo/ TS4-F 
>>> device is one of the simplest options currently available on the 
>>> market. What are others finding?
>>> I'd love to hear about favored options for complying with rapid 
>>> shutdown. Any success stories? or better yet, any early failures?
>>> --
>>> Corey Shalanski
>>> Jah Light Solar
>>> Portland, Jamaica
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