I’m installing 150 amp breaker for solar. 400 amp 208 system. There are sets
of 300 per phase on lone and load side. I’m taping each phase set to keep it
balanced. Can I parallel # 4 copper off each phase set then tag those together
on my feeder to 150 amp breaker
Also, it is rare that equipment 200A and less has the capacity for two conductors per phase. Even if you can fit it, terminals are rated for just one conductor unless listed and labeled otherwise.
You'll most likely need to use insulated tap connectors, like those from Polaris, to accomplish what you are trying to do. The alternative is if there are spare lugs on the main breaker for the feeder/service you are tapping.
I'm assuming you are tapping onto 2 sets of 300. This means you'll need 5-terminal blocks to parallel the existing conductors, and the remaining terminal to tap on the solar. 2 sets in, 2 sets out, 1 remaining for the solar tap. Maintain the symmetry and keep the lengths as equal as you can.
