So for my main panel I want to upgrade it to 200 amps. Then have it feed to two subpanels. The subpanels that I have are rated for 150 amps but I am not going to exceed 100 amps of load for each panel. Do I need to change the main braker in each sub panel to 100 amps if they currently have 100 amps? Also the main panel that I have is rated for 225 amps because I do have a 4k solar system.
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2 Answers
No. Those main breakers in each sub panel will become a switch/disconnect.
It is the feed breakers to each sub panel from the main panel that are important/limit the power to each panel.
Could even use 200 amp panels fed by 40 or 60 amp breakers if you wanted.
For wire size if you want to go down to 90 amps, 2-2-2-4 aluminum is usually quite cheap compared to copper.
If your Load Calc comes in under 200A then you could feed 2 (or more) 200A panels. The catch is if you protect the service end of the feed 200A then you would have to feed them with 200A wire. Two 150A panels would require 150A wire to each Panels.
But first you need to do a Load Calc for each of those panels. It's possible one panel could exceed 150A and you would need a 200A panel for that feed.
If your Load Calcs determine either of the panels is less than 150A, you then could protect the service end of the feeder at that lower level allowing smaller wire (and conduit). The main breakers in the subs become disconnect switches. Actually if the subpanels are in the same building as the service the subpanels don't even need a main breakers or disconnects at all. They can be Main Lug Only as long as the breaker feeding the subpanel is the size of the panel or less.
answered Jul 30 at 20:52
