Hi, I just posted this as a reply in an existing topic, but perhaps I should also post it here in its own new topic? I'm not sure.

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I'm doing a major renovation on my house and what I have had here is a 40 position 200 amp main panel. An electrician told me I need to have a sub panel next to that to deal with all the circuits I'm adding. Its not that any of them will have anything big here or there, but for convenience I have made many little circuits (for example, a separate one for microwave in kitchen, etc)

I want to put a subpanel next to the main one and have hopefully 40 more circuits to be able to cover everything in the house...

The electrician told me to get a MLO for this... and so I'm assuming to put something like a 100-125-150 or so amp breaker in the main panel and feed to the subpanel next to that... that part makes sense... but what I'm confused by is this part where I have to isolate the neutral bar from the ground bar... could you explain that to me a little bit? Basically I have a murry 200 amp main panel right now... if I purchase a 40 position murry mlo box, how should I connect the two? Then can I just have a bunch of 20 amp circuits on that?

-Dave

Dave, how much did you advising electrician say he'd charge to do this for you? I do stuff like this all of the time. My rule of thumb for home owners is 110 V is worth a try, 220 V you could die.

Once you take the cover off the main panel, you may as well be installing a 2 pole breaker as a single one, which is the difference between 120 and 240. The older panels had one buss for grounds and neutrals. Current code calls for separate ones although they are connected at the main panel only. So you will be running 4 fat wires to the sub panel. The 2 hot ones run from a double pole breaker to the main lugs.