Should AC modules be exempt from Rapid Shutdown requirements?

JoeNorm

Senior Member
It is my belief that if AC modules are used they should be exempt from Rapid Shutdown requirements.

I could be missing something, so if I am let me know. It seems to me that AC modules are inherently as safe as a PV system can be.

Why should rapid shutdown apply to an AC module system? And why should said system ever need an exterior disconnect?

thanks for your thoughts.
 

ggunn

PE (Electrical), NABCEP certified
That's two different questions. AC modules are already inherently rapid shutdown compatible, so that is a non-issue. As to a microinverter PV system not needing an exterior disconnect, that is a POCO requirement, not a code compliance point.
 

Carultch

Senior Member
It is my belief that if AC modules are used they should be exempt from Rapid Shutdown requirements.

I could be missing something, so if I am let me know. It seems to me that AC modules are inherently as safe as a PV system can be.

Why should rapid shutdown apply to an AC module system? And why should said system ever need an exterior disconnect?

thanks for your thoughts.
It's not that they are exempt from rapid shutdown, it's that without specifically intending to address rapid shutdown, you solve the problem of rapid shutdown by the nature of their theory of operation.

As of NEC2017, there are several initiation methods that can comply with rapid shutdown, and 690.12 has a section that spells them out. You do not necessarily need your exterior disconnect to do it. It's just that due to POCO's often requiring it regardless of what kind of system you have, it is most common to have this device double for the purpose of rapid shutdown as well.
 

jaggedben

Senior Member
It is my belief that if AC modules are used they should be exempt from Rapid Shutdown requirements.

I could be missing something, so if I am let me know. It seems to me that AC modules are inherently as safe as a PV system can be.

Why should rapid shutdown apply to an AC module system? And why should said system ever need an exterior disconnect?

thanks for your thoughts.
The code making panel decided that you need an exterior readily accessible switch to denenergize solar arrays. You don't seem to be arguing against the general merits of that requirement, so I don't understand what your issue is with AC modules in particular. I think you need to think through the issue a little more. Note that DC module systems can also be installed with technology that initiates rapid shutdown from the AC side, and in such cases the issues with providing an exterior disconnect are the same.
 

jaggedben

Senior Member
You need an exterior switch but not due to rapid shutdown.
That is not correct for the 2017 NEC and onward. Rapid shutdown requires an exterior switch. If the service disconnect or the otherwise required utility disconnect initiates rapid shutdown happens to be exterior then that will fulfill the requirement, but not all services and utilities will be having that.

Also note that when there's a battery backup, becoming a lot more common in my work, the service disconnect will no longer qualify.
 
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