On Sunday, September 21, 2014 1:07:53 PM UTC-4, Mikepier wrote:


There is no problem with a 100a sub panel on a 150a main. You would



feed that with #2 copper and off you go. You can protect the feeder



with a 100a breaker in the main panel and use an MLO sub panel as long



as you are in the same building.







The real limit is on the service as a whole. To know for sure whether



150a is enough you need to do a load calculation.



There are several load calculation templates on the internet you can



try.



If you have Excel the one from the city of Naperville seems pretty



good. There are 2 methods and they usually do not come out with the



same answer but you can use either one.,



Load calcs are something you measure with a micrometer, mark with



chalk and cut with an axe. Residential load calcs are just a wild



guess anyway. A frugal person would never get close to the calculated



load and a house full of people who never turn anything off will



easily exceed it.



Do I need to run #2 wire and use a 100A breaker? Or can I just run #6 to the sub-panel and use a 50A or 60A breaker in main?

That depends on if you want a 100 amp subpanel or a 50A subpanel.