2014 NEC Public Comments

[don_resqcapt19]

Julie,
I don't understand. It is first by Code Making Panel and then by code Article and Section. And if you are looking for a comment on a proposal that was accepted at the ROP stage it is even easier. You first download the draft copy. Each proposed change is show along with the proposal number for that change. You then just search the ROC for that proposal number.
If the following is the change you are talking about, you would search the panel 4 comment for proposal 4-253. There were two comments submittd on that change.

690.12 PV Arrays on Buildings Response to Emergency Shutdown. . For PV Systems installed on roofs of buildings, photovoltaic source circuits shall be deenergized from all sources within 10 seconds of when emergency shutdown is initiated or when the PV power source disconnecting means is opened. When the source circuits are deenergized, the maximum voltage at the module and module conductors shall be 80 volts. [ROP 4?253]

 

[shortcircuit2]

I'm not sure how that would work for string inverters since they usually wire from panel to panel, with a home run back to the string combiner. As I read the proposal, no portion of that entire string could be above 80 volts. Since Voc on a 72 cell module is over 40 volts, that means EACH AND EVERY module would have to be individually disconnectable.

Yes, a very difficult situtation for string inverter design.

There will have to be more use of micro inverters and AC panels.

Maybe this will be delayed till 2017 for the industry to adjust?

 

[tallgirl]

Yes, a very difficult situtation for string inverter design.

There will have to be more use of micro inverters and AC panels.

Maybe this will be delayed till 2017 for the industry to adjust?

I suspect it will be "delayed" only because there is no readily available solution, short of requiring microinverters. I don't expect it to be deferred until 2017.

This can be handled by panel vendors including control circuitry inside the junction box on the back of the panels, which is what I expect they'll do. Bringing every single last PV module to some kind of control box is unworkable, and other solution is more difficult than adding some form of switch to the inside of the module junction box.

The entire industry is undergoing a lot of very rapid change, and learning to cope with roof-top fires is just part of that process. It's not like they're a secret -- the string inverter vendors have only been in major denial about arc-fault related fires since Enphase entered the market and made it an issue. And while microinverter vendors would =love= to see this become a requirement (ESD requirements making string designs nigh on impossible), there isn't enough total manufacturing capacity for microinverters to meet the demand.

 

[tallgirl]

Maybe the solution would be to allow an ungrounded PV array in that case, so that no point would ever be 80 volts (or any other voltage) from ground.
Seriously, if you just disconnect both + and - leads from the string, you could argue that the requirement had been met.

For an ungrounded array, that would definitely be the case. I'm not a believer in ungrounded PV systems -- solar arrays and panel frames are essentially giant metal objects, waiting to gather static electricity and release it somewhere. Allowing the other electrical components to be ungrounded is unsafe for all the usual reasons such things are unsafe.

 

[tallgirl]

Julie,
I don't understand. It is first by Code Making Panel and then by code Article and Section. And if you are looking for a comment on a proposal that was accepted at the ROP stage it is even easier. You first download the draft copy. Each proposed change is show along with the proposal number for that change. You then just search the ROC for that proposal number.
If the following is the change you are talking about, you would search the panel 4 comment for proposal 4-253. There were two comments submittd on that change.

Don,

Do you have a hyperlink for that comment?

No?

Then it's not easy There's a reason us geeks invented the interwebs -- so we could be lazy and use it.

 

[don_resqcapt19]

Don,

Do you have a hyperlink for that comment?

No?

Then it's not easy There's a reason us geeks invented the interwebs -- so we could be lazy and use it.

Directly to the comment, no as it is part of a larger PDF, but here is a link to the Panel 4 ROC.
You can access all of the currently available information on the 2014 NEC here.