a solar "String"?

[Blue Grouse]

Ok...when you see the term "string", would these be both the Pos and Neg pv wiring from an array? I sometimes get lost in the terminology.

I'm building a grid-tie system...which will use 4 - 9 panel arrays. I want to have a shutoff system before wiring hits the Inverter and am looking at an IMO Isolator.
You can get a 4-string Isolator so....will this handle the 8 wires (4 Pos, 4 Neg) coming from the panels?

 

[sunshine_eggo]

A string is a single set of panels wired in series.

I don't know for certain, but an isolator probably only interrupts ONE of the wires, typically (+) rather than both. Cut either, and the circuit is open, so there's no reason to cut both.

If you're subject to NEC2017 and installing on rooftop, you'll need shutdown modules on EACH panel as well. These cost about $60-75/panel.

 

[Hedges]

If that is four, 9-panel series strings, are all four connected in parallel at one MPPT input?
Three or more in parallel, all should have fuses or breakers. If just two in parallel (e.g. 2 strings into one MPPT, other 2 into another MPPT) then not necessary.

PV panels wired 9s is likely about 200V to 300V open circuit. If you use breakers, some are rated that high but it exceeds others. Using a 2-pole breaker, each pole rated 150V, you can interrupt both (+) and (-) to get 300V capability. (or use both poles in series to interrupt just (+).
It is nice to have both ends disconnected, safer to work on wiring that way. Once current flow interrupted or otherwise disabled, alternative is to unplug MC connectors to completely isolated PV.

If you use breakers for disconnect of multiple parallel PV strings, there are some issues with "polarized" breakers. I would rather see non-polarized breakers in that application.

My newer GT PV inverters already have a 2-pole disconnect built in. So I just use fuses.

Link to the isolator you're considering? And PV panels? And inverter or whatever has PV MPPT inputs?