Isolation for backup output

[Skipper]

So ... maintained or backup outputs from the inverter to a distribution board in a different location.

I know for the main grid tie connection the current recommendation is an isolator on each end of the cable, one by the inverter and one by the distribution board ... enabling you to disconnect the inverter from incoming mains to work on it with an isolator directly under your cotrol ... and likewise isolate the distribution board to work on it with an isolator adjacent to it.

For the backup output, does anyone know if an isolator adjacent to the distribition alone is sufficient or should it be isolated both ends like the grid incomer? As it is an output only, isolating adjacent to the distribution board would appear to be sufficient, but I am uncertain what the current recommedation is.

 

[binky]

not seen any recomendations on that, but as the back up output is only live in the event of a grid fail, I would say an isolator by the inverter is enough, but one both ends is better. Mind you your dis board will have a main switch anyway.

 

[Skipper]

The "backup" output is better described as a "maintained" output and is live both in grid on and grid fail conditions. I don't have a lot of room at the inverter end so just considering options ...

Like you say, there is a switch on the board incomer ... you coud argue "what if you want to work on the incoming terminals" ... but the same would apply to "what if you want to work in the incoming terminals to the isolator" ...

 

[binky]

You aren't going to get a backfeed on that supply, so isolation would be more like standard wiring. The reason we install isolators both ends of the mains feed to the inverter is because you could have energy flowing both ways, so a local point of isolation is needed both ends, unless the inverter ir right next to dis board / meter equipment, It's a safety and ease of maintenance if , say, the inverter is in an attic.

 

[Skipper]

Jolly good, I have plenty of room for a isolator at the distribution board end, and like you say, there is no backfeed, so it makes sense to have one close to the distribution or not at all.