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.chamber...@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 <coreso...@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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