2nd SMA rapid shutdown that is not working for me

tortuga

Senior Member
Location
(44.057116, -123.103394)
Occupation
field supervisor
Greetings all this is the second time I have gone out to a site to replace an inverter and am unsuccessful at getting a rapid shutdown to shut the DC off.
My understanding is the rapid shutdown acts as a DC PV disconnect? You just hit the button and the system opens a contactor?
When I did that the LED still glows red and I measure 480VDC at the inverter.
Part numbers are SMA RSB-2S-US-10 and RSC-1X-US-10
Anyone have any tips or experience with these on here?
I notices in the manual it says:
8 Checking the Function of the Rapid Shutdown System
The Rapid Shutdown System is supplied via the PV array. If there is insufficient irradiation on the PV
array, the supply voltage of the Rapid Shutdown System is too low and the function of the Rapid
Shutdown System is not able to be checked.
Requirements:
• The Rapid Shutdown System must be commissioned.
• Wait a minimum of 60 seconds from powering on the system before testing the Rapid
Shutdown System functionality.
There must be sufficient irradiation on the PV array.
So does this thing not work if there is not enough sun? It was pretty early AM when we got there and cloudy.
There is of course a 'DC disconnect' however its part of the inverter being replaced.
Thanks in advance.
 

jaggedben

Senior Member
I only did one of these once, but if I recall, you wouldn't see the red LED if there weren't enough array voltage to operate. In other words, it's malfunctioning. I could be wrong but I believe it is supposed to work even if it is too dark to check that it worked. I.e. once the sun comes up it will respond to the push button.
 

synchro

Senior Member
Location
Chicago, IL
Occupation
EE
The manual mentions resetting the rapid shutdown function with a key. If the key is available it might be worth trying it to see if proper operation is restored.
 

tortuga

Senior Member
Location
(44.057116, -123.103394)
Occupation
field supervisor
They discontinued those.
Ok they also dont make my truck anymore and I still drive it. These are still installed out in the wild all over the place, the times I needed it they failed to work.
The manual mentions resetting the rapid shutdown function with a key. If the key is available it might be worth trying it to see if proper operation is restored.
Yeah tried the key dozens of times, you hit a red button to trigger it and it glows green if it works (not) and then use a key to reset.
Just like an e-stop. The rapid shutdown unit itself is installed under PV modules so you have to unrack stuff to get to it.

My ideal inverter would look like a transformer; grey box, no display, nothing sexy, no OCPD just one function convert DC to AC per UL spec.
My idea of rapid shutdown is run conductors in a raceway as in 230.6 and have a disco next to said inverter, no fancy stuff. All the other fluff can be mounted next to the inverter.
H36.JPG-smaller.jpg
 

ggunn

PE (Electrical), NABCEP certified
Location
Austin, TX, USA
Occupation
Electrical Engineer - Photovoltaic Systems
My idea of rapid shutdown is run conductors in a raceway as in 230.6 and have a disco next to said inverter, no fancy stuff. All the other fluff can be mounted next to the inverter.
It would not be NEC compliant. It is not enough to stop current from flowing in the DC conductors, you must reduce the voltage between any two conductors to less than 30V. A DC disco next to the inverter won't do that.
 

tortuga

Senior Member
Location
(44.057116, -123.103394)
Occupation
field supervisor
It would not be NEC compliant. It is not enough to stop current from flowing in the DC conductors, you must reduce the voltage between any two conductors to less than 30V. A DC disco next to the inverter won't do that.
My apologies if that seemed like code advice, thats just my opinion.
Rapid shutdown has only been in the NEC since 2014 and onwards (690.12). 690 has only been in the NEC since 1984.
Unfused outdoor DC conductors (service) were strung on and entering a buildings for over 100 years before that as regulated in article 230 (or 225 for feeders).
For the first 60 years DC conductors were as common as AC. (Con Edison in NYC turned off its last DC grid in Manhattan in 2007).
 

PWDickerson

Senior Member
Location
Clinton, WA
Rapid shutdown has only been in the NEC since 2014 and onwards (690.12). 690 has only been in the NEC since 1984.
Unfused outdoor DC conductors (service) were strung on and entering a buildings for over 100 years before that as regulated in article 230 (or 225 for feeders).
For the first 60 years DC conductors were as common as AC. (Con Edison in NYC turned off its last DC grid in Manhattan in 2007).
Rapid shutdown wasn't added to the code because PV circuits are DC. It was added to the code because, without it, you can't reduce the voltage in the conductors coming from the array.
 
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