Solar Photovoltaic (PV) Systems, Rapid Shutdown, NEC 2020 - [690.12], (31min:43sec)

The 2020 Code cycle brought many changes to Article 690, Solar Photovoltaic (PV) Systems. Some of the more notable changes were in section 690.12. Electricity poses a significant danger to firefighters when working with energized PV systems. To reduce this risk, the NEC has implemented requirements in 690.12 that include a rapid shutdown function for PV system circuits.
This video is an extract from Mike Holt’s Understanding 2020 NEC Requirements for Solar PV and Energy Storage Systems. Learn more about this topic www.MikeHolt.com/Solar or call 888.632.2633.
For almost 50 years, Mike Holt Enterprises has been providing quality electrical Code training to help electrical professionals learn the Code, prepare for exams, and improve their electrical knowledge. Visit www.MikeHolt.com​ for exam preparation tips and training, instructor and curriculum support, continuing education options, free videos and graphics, and so much more.
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[@pauldirschka7052]

26:35 was exactly the screen that brought 690.12(C)(1) into focus for me, satisfying pg 8 of Enphase IQ8 installation tech brief: "Service disconnecting means" functioning as "an initiating device"! TY!

[@do7hemath937]

Mike, I was in an electrical apprenticeship program from 2002 - 2006. All of my classmates & I watched your DVDs. For some reason, 1 of the main ones that I remember was Grounding vs Bonding. Lol. Before all of this social media you were trying to help & teach people & you did a great job! It's great to see over 20 years later you're still a part of the solution. 👍👍

[@MikeHoltNEC]

Thanks Brother.

[@do7hemath937]

@@MikeHoltNEC No problem.

[@ai4px]

It’s not that the initiator tells the dc dc converters to turn off… it tells them to turn on and in the absence of a ON signal they’ll shut off within 30 seconds.

[@user-dr2pg8fk2i]

1:20 Rapid Shut Down devices also help reduce fire risks, as they almost always include some form or arc/ground fault detection.

[@Senthiuz]

To play devil's advocate. RSD devices may increase fire risk. Plugging in an additional device to each panel doubles the number of connections on the roof. The risk of any one connection causing a short is very low, but not zero, especially over an expected 30 year lifespan, and now that's been doubled. I think extra connections is a minor concern, more than that it's putting a bunch of tiny circuitboards into an extremely hot environment, THWN-2 is rated to 194f, an asphalt roof in Texas can reach that in a hot day. The more complicated the electronics, the more kinds of failure modes they can have, on devices that haven't existed for their expected lifetime, it's hard to predict the results, especially as time progresses.

[@microcolonel]

Hey Mike, shoot me a message if you want to hear how this is being enforced in Northern Colorado jurisdictions. I talk to inspectors every business day, and work on both string inverter and microinverter systems, inspected against 2020 and (very soon) 2023 codes. It is fascinating, and there is a lot of variance between jurisdictions on their interpretation. MLPE like power optimizers (what the DC-DC converters are called in industry) and microinverters are still required to be equipped with an external AC disconnect, even if they inherently go down with the main service disconnect (which is not something that can be assumed in the case of supply side taps). The power optimizers on a SolarEdge string inverter solar system will automatically come down to "safety voltage" (in SolarEdge's case, 1 V DC per optimizer) when the DC circuit is opened. It is not based on the powerline communication, and the inverter does not have to succeed at communicating the intent to the optimizers in order for the string voltage to come down.

[@vpeters2647]

Great videos, thanks Mike and associates .

[@VylDZN]

I’ve never heard “DC to DC converters”. Most installers will know “power optimizers” are referencing a DC circuits that run down to a Inverter. Also most installers will understand “microinverters” are in reference to a AC system that runs down to a combiner.

[@MikeHoltNEC]

These are Code terms, I can’t use slang terms.

[@Tiersmoke92555]

Wow, this is making it harder to live off grid. Can I even still do a ground mount array with out all of this extra cost?

[@MikeHoltNEC]

Safety is not free...

[@user-dr2pg8fk2i]

14:55 Yeah, the whole conversation here about the why and what of the 80V part is entirely off based.

[@nothanks960]

I get that Mike is playing the role of the audience by asking questions, but we never got the info before the questions. Was it the edit? Why did we not get the presentation first? Why did Mike not let these guys actually answer fully?

[@MikeHoltNEC]

It's hard to decide what part of the video to make free. We put a lot out there but we have to cut it somewhere ;-) This is a small excerpt from the solar video library. Was there a specific question you didn't see answered about rapid shutdown? - Brian House

[@user-dr2pg8fk2i]

5:30 False again. It's called a Keep Alive Signal because without it the circuit goes cold and only allows the minimum per device signal voltage to be present. If a command to shut down were required, severing the lines would render the system pointless.

[@Armenian]

I have a 2 wire DC Outdoor Service disconnect at my stand-alone Solar Panel and another 2 wire dc fused switch at the entrance to my home where i bring the DC wires inside to my homemade power station.

[@microcolonel]

Do you have power optimizers on the modules? Because long DC runs especially without optimizers is a recipe for big inefficiency.

[@Armenian]

@@microcolonel nope dont need that. I sized the wire appropriately for the length of the run and the voltage. On a clear day and when my battery needs a charge, my mppt controller receives full power from my solar panel.

[@jimbob100-d3l]

Seems like most people have a DC disconnect after solar panels and an AC/service disconnect after the inverter, but is this saying that only the service disconnect is required?

[@MikeHoltNEC]

This is a very complicated topic. I suggest you review the video with the NEC a few times to better understand the purpose of the RSS and how it's intended to operate.

[@user-dr2pg8fk2i]

3:45 False. It does not depend on the design of the system. All modules are shut down and there is very definitely not any voltage beyond a signal voltage (usually 0.5-1V per device) seen at the inverter or on any given string.

[@klott88able]

I was changing out an SMA inverter. I have three strings the open circuit voltage on three strings read 15 volts, 422 v, and 17 volts,. I have 39 panels. I felt the power of the second string which I believe has a failed inverter or optimizer because that did not feel great. In other words the conductors on the DC array and fault condition are a shock hazard

[@klott88able]

In other words rapid shut down did is only at the inverter which conductors are connected to

[@milusosandmore7506]

SMA has no optimizers.

[@joemomma7]

Mike keeps his notes over his head

[@erichamilton4512]

Does anyone else think that Mike is trying to talk at a thousand miles an hour. Will also trying to learn, explain, and understand the code at the same time. As someone in the Solar Industry this is almost unbearable to watch.

[@MikeHoltNEC]

Did you know you can adjust the play speed?

[@steven7650]

It's incredibly painful as an electrical engineer to watch. Also shutting off my inverter because we lost grid is stupid. It should isolate to protect linemen NOT power down to increase profits because the poco doesn't want solar and this will make it look unreliable esp as the grid gets worse.

[@user-dr2pg8fk2i]

@@MikeHoltNEC The issue is your continual interruption and slap talk, i.e. not thinking then speaking, but figuring it out as you are speaking over others.

[@eliaslemus4037]

How about the neutral from a transformer

[@MikeHoltNEC]

?

[@user-me6zj8vk3x]

This Rapid Shutdown is not necessary, why would firefighters need this?, this is the most important question in this video. This requirement ended up giving a great advantage to the microinverter manufacturer over the string inverter. That is not a regulator's job, a regulator should keep a competitive market and avoid bringing unnecessary standards that benefit completely one of the manufacturers.

[@MikeHoltNEC]

So you think that the firefighters should not have the ability to turn off the power of the array so that they work around energized electrical parts? Really?

[@user-me6zj8vk3x]

Okay, but what about if this standard is getting out of the market all the residential string inverters manufacturers? The technical solution is very difficult to achieve in an string inverter, nine (9) years after this standard first appeared and you can see that there is still a huge advantage for the microinverter in residential systems. This standard changed completely the residential market share. I don't think the regulators should do something like this. Moreover, take into consideration that this standard does not exist in any other country in the world. @@MikeHoltNEC

[@MikeHoltNEC]

It's driven by the firefighters to protect themselves so that they can go home to their families after their shift. Maybe if you were a firefighter you would feel differently

[@Tiersmoke92555]

These systems are needed but have already killed off american companies already. The cost of going green is so high you will only see it on folks homes with a lot of green.

[@MikeHoltNEC]

I don't care if we go green, I care that we are safe...

[@PeymanSultan-wn6iw]

What a MESS