PV isolators, where and what?

[mciholas]

Given a residential roof array in Florida with Tigo TS4-A-S rapid shutdown devices, does that satisfy NEC 690.13? That is, I don't need an isolator on the exterior wall of the building for fire fighter operation, just an RSD button which shuts down the inverter and the panels.

That being said, do I still need a PV isolator between the panels and the inverter? That is, can I wire the panels (with RSD boxes) to the inverter directly? The inverter has a PV isolator switch on it which I think satisfies 690.15, right?

Even if that's legal, would it be best to run the PV through a manual isolator switch just before the inverter or is this just extra stuff I don't need? It kind of feels like the ability to manually shut off the array while working on the inverter is a good idea even if the RSD *should* make those wires "safe".

It also seems a shutdown box could include surge protectors as well.

What can I get that will isolate 3 strings and surge protect them? Something that will mount on an interior wall (not outside).

Mike C.

 

[zanydroid]

Maybe a DIN mount IMO next to some DIN mount DC SPDs rated for solar string voltages.

Having a disconnect on the correct side of stuff you need to service is a good idea. Within reason. I think the forum zeitgeist turned against roof mount isolators (so you can turn it off conveniently up there; required overseas some places I think) due to the high risk (known fire issue) / questionable reward.

The RSD will still leave up to 30V on the circuit.

 

[mciholas]

Maybe a DIN mount IMO next to some DIN mount DC SPDs rated for solar string voltages.

It seems most DIN stuff is not UL rated.

The European stuff all looks so much nicer than what we can buy here in the USA.

Having a disconnect on the correct side of stuff you need to service is a good idea.

Seems so. Seems just a tad risky to depend on the Tigo TS4-A-S RSD devices on a sunny day to be able to disconnect the PV inputs and not have 400 volts available there.

The Tigo manual says things like:

"Always assume that TS4 units are in an ON state."

I guess on could limit servicing of the PV wires until it is totally dark, but even a moon lit night can generate meaningful voltages if there is no load on them.

I guess the best approach is to assume the PV wires are always live and handle them that way with insulating gloves and protections.

I think the forum zeitgeist turned against roof mount isolators

Roof mount isolators seem like a bad idea. They don't isolate anything except the run of PV wires to the inverter. The panels are still "hot" if RSD isn't active.

I'm debating if I want a manual isolator or not. if the code doesn't require it (given I have RSD), maybe I don't put one in. I can always add one later if that turns out to be the wrong decision.

Mike C.

 

[Hedges]

I will rely on the built-in switch to isolate what is downstream.

To work on connections between PV panels and switch, I will climb on roof and disconnect MC4 connectors for both PV+ and PV-.

Roof mount isolators seem like a bad idea. They don't isolate anything except the run of PV wires to the inverter. The panels are still "hot" if RSD isn't active.

Output of string is not hot (except for 0.5V ~ 1V per panel) unless RSD transmitter is active.
But don't bet on it; assume they are hot.

 

[zanydroid]

It seems most DIN stuff is not UL rated.

The European stuff all looks so much nicer than what we can buy here in the USA.

Yeah I guess there are a lot of Amazon combiners with fuse holder + SPDs in them, that are not UL listed.

Or you can get a regular IMO and hang a lot of midnite 600V SPDs off the side of it.

Roof mount isolators seem like a bad idea. They don't isolate anything except the run of PV wires to the inverter. The panels are still "hot" if RSD isn't active.

They isolate the roof conductors from the voltages coming back through the non-isolated inverter. I agree it's kind of dumb esp for residential, I'm not sure why those countries required it or did it as standard practice in the past. Seems like just an extra failure point. Just climb back down the ladder and flip the disconnect in the inverter or other protected location.