Is the Classic 250 isolated? DC Transfer switch with grounded battery and ungrou

[joepr]

I have a Midnite Classic 250 charge controller. Would like to interconnect it with a string grid tied inverter. In order to use the panels if the grid is down (inverter not AC couple compatible). The rated MPPT voltage range is 155-480V. Will limit string voltage to 200v (tropical weather, no winter spikes). To do this I will use a UL approved 600v DC transfer switch (one pole, can only transfer the positive). According to the instructions of the grid tied inverter the solar array conductors cannot be grounded. The battery bank is DC negative grounded in order to comply with NEC. My question is. Are the solar array inputs isolated or do they share the negative with the battery negative like most MPPT charge controllers? Can I use the Classic 250 safely in this scenario? Thank you very much.

[Vic]

Hi joepr,   welcome to the Forum.

The PV negative,  and the battery negative are tied together on the power board in the Classic.

Vic

[joepr]

Thank you! That complicates things. But I think that can be resolved by using a double pole transfer switch (transfer both negative and positive). Again, thank you very much Vic.

[australsolarier]

yes i am using a non polarised 2P breaker to do exactly what you are doing.
and keep in mind the earth is connected to the neutral, so there is a direct connection of the neutral everywhere on the negative and consequently to a lesser degree to the positive of your system.