NEC 690.12 (A-D) Rapid Shut Down of PV Systems on Buildings.


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OffGridInTheCity

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Dec 15, 2018
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No extra wires to run, just plug the device in parallel with your solar panel. To close the relay they must be using the DC from the solar panel. I'm gonna search some youtube videos to get the fine details. If my theory is right then at night the array will be all disconnected as the sun come up and the panels start to generate a energy there must be a level of voltage and current that makes the receiver come on and maybe just maybe the relay is solid state. Still waiting on my answer to buy 5 or 10.
Sounds cool but I wonder... are the relays as robust as the panels as in 20+yrs of trouble-free service. How are the relays built - is there a link to one?
 

J_Mack58

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Apr 7, 2021
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What I have learned from a long boring APsmart video is the receiver operates on voltages from 7.7 volts up. They call the the signal from the transmitter to the receiver the "Keep Alive" Signal. The device switching mechanism be it contacts or solid state can switch 550 watts what ever your combination of voltage and current may be just long as it is 550 watts and below. That "Keep Alive" Signal may come standard in new inverters.

The video is a hour long, I scanned it for the info we are discussing
View: https://www.youtube.com/watch?v=VCwXo_BJ6tg

Sounds cool but I wonder... are the relays as robust as the panels as in 20+yrs of trouble-free service. How are the relays built - is there a link to one?
GOT IT! The negative is straight through and the positive is switched on through a MOSFET with a "Body Diode" or parasitic diode. That MOSFET can handle 15 amps so they say. Man! at 60 years old I'm learning way more than I care to learn. :)
 

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Korishan

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That doesn't make sense, tho. How do you disable them without running extra wire?? 🤔 Unless there's an AC signal running along the DC power lines to trigger them.
There'd have to be extra wires to trigger them on or off. Do you have an article that discusses these relays you're talking about? I'm really curious as to how they would function.
 

J_Mack58

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Apr 7, 2021
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That doesn't make sense, tho. How do you disable them without running extra wire?? 🤔 Unless there's an AC signal running along the DC power lines to trigger them.
There'd have to be extra wires to trigger them on or off. Do you have an article that discusses these relays you're talking about? I'm really curious as to how they would function.
Yes Korishan, they transmit on the DC line some FSK signal.. This reference design interfaces an AFE031 Powerline Communications Analog Front End with a C2000™ MCU to send and receive data over a wired coupled interface using frequency shift keying (FSK). The design demonstrates the SunSpec® standard protocol transmitting the specific 33-bit word packet using FSK (fM: 131.25 kHz and fS : 143.75 kHz). The purpose is to provide a keepalive signal with an integrated system solution that communicates from the solar inverter to photovoltaic (PV) module. LOL. All that above make me look like I know something... NOT! Here is the PDF.

https://www.ti.com/lit/ug/tidue68/t...%3FSYS-null-null-findchips-refdes-rd-null-wwe
 

J_Mack58

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I total get it now. At my day job we communicate with hundreds of sensors using our 475 HART Communicator.
“HART” is an acronym for Highway Addressable Remote Transducer. The HART Protocol makes uses Frequency Shift Keying (FSK) standard to superimpose digital communication signals at a low level on top of the 4-20mA. We can read and write parameters to the sensors, they took it a step further and made a MOSFET conduct.
 

Korishan

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Ahhh ok, that makes sense now. So you can't use commonly available relays then, gotta use the somewhat proprietary hardware. That sux
 
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