Islanding. grid protection, and whole house UPS

[zanydroid]

Is it an acceptable compromise if Chinese inverter makers can be convinced to make the undersized transfer relays easy to access for user servicing?

Are there theoretical blockers to doing that?

 

[Cmiller]

Back 25 years ago, Trace used a Deltrol 375 three pole, 30A/pole 3PDT relay with the three poles connected in parallel for their 60A pass-through AC current spec on inverter.

They had a debate with UL over using 3x 3 pole 30A relay contacts to achieve a 60A capability. They won the debate with UL by arguing the three poles were mounted to same mechanical rocker bar within the single relay and would have simultaneous opening and closure.

The Schneider XW relays in my picture above are 3 pole relays as well. Passthrough is rated at 60A, but I'm almost thinking they might actually be 30A. That would theoretically give a total of 90A, which would give some "headroom" to help the relays live longer and healthier lives. That could be a feature that has been carried over from those Trace days!