UL3741

[pv_n00b]

Unirac does have a page that has links to UL3741 installation guides for their different racking systems but the link for RM5 gets an "Oops! That page can’t be found" msg

That link I posted for you in #6 works for me. Not sure what link you are using.

How does one do that for a particular system? Does someone inspect it and green tag it after it is completed? I don't think so but I could be wrong.

Have any of us designed and built a UL3741 compliant PV system? If so, please speak up.

I've designed them, worked with contractors who build them, and I'm on the UL 3741 technical panel. So I'm speaking up, what do you want to know?
Basically as the designer and installer all you have to do is follow the manufacturer's instructions for their UL 3741 listed system and you have a UL 3741 listed installation. There is no special 3741 inspection, the AHJ does the same inspection as with any PV array, to verify that it was installed in compliance with the manufacturer's installation instructions.
As for how 3741 works, it's purpose is to reduce the electrical hazard the PV array presents to a firefighter based on current through the body of a firefighter in full firefighter kit. A process is followed that identifies hazards, ranks the level of hazard, and assigns a likelihood of occurrence. Higher level hazards that are more likely to occur must be mitigated by design changes or installation requirements. Lower level hazards that fall below a specific likelihood of occurring do not need to be mitigated. The end result is that the array has a reduced electrical hazard that is considered acceptable by the stakeholders. It's not zero hazard, it's reduced hazard.

 

[tortuga]

I've designed them, worked with contractors who build them, and I'm on the UL 3741 technical panel. .../..
As for how 3741 works, it's purpose is to reduce the electrical hazard the PV array presents to a firefighter based on current through the body of a firefighter in full firefighter kit. A process is followed that identifies hazards, ranks the level of hazard, and assigns a likelihood of occurrence.

That sounds pretty straight forward thanks, is it safe to say UL3741 is only for large systems?
have you designed any mini 3741 systems? What would a mini PV system thats small or special application need to qualify for example:

• 144 square feet or less of array,
• 2000 watts AC or less
• 120 volts DC nominal

 

[pv_n00b]

That sounds pretty straight forward thanks, is it safe to say UL3741 is only for large systems?
have you designed any mini 3741 systems? What would a mini PV system thats small or special application need to qualify for example:

• 144 square feet or less of array,
• 2000 watts AC or less
• 120 volts DC nominal

The 3741 listing is almost completely applied to racking and initiated by a racking manufacturer. It's expensive so a manufacturer may choose not to apply for listing of rack intended for smaller systems. So step one for the system you describe is to see if there is a racking manufacturer that has a listed system including an inverter that would work for that voltage. Since that's not an industry standard design it's going to be hard to find that. I am not aware of any available 3741 listed racking that would work for this system. That's not a limit of the standard, just not enough market for a manufacturer to go through the expense of listing.