Sub Panel to sub panel

[dshokoofi]

I am looking for a answer to what would be the max. amperage I could supply a secondary subpannel if my main panel is 200 amp. the home owner does not have all the specs. on the house yet and I need a general rule answer.

 

[charlie b]

That's easy. 200 amps. But that assumes there is no load on the existing upstream panel. :roll:

More to the point, the rating of any panel, whether upstream or downstream of another panel, is not the controlling factor. The only rule is that you must not load any component beyond its rating. If for example you have 150 amps of calculated (or measured) load on the existing panel, then you cannot add more than 50 amps on a new subpanel. The rating of the subpanel can be anything (e.g., it could be a 225 amp panel). But you cannot have a total load on the new panel that is so high that it overloads the old panel.

Welcome to the forum.

 

[haskindm]

There is no "general rule" answer. All items must be sized for the "load to be served". Until you know the loads ANYTHING you do will be a complete guess and a waste of time. The homeowner must realize that without the specifications you will need to "guestimate" and the only safe thing will be to oversize everything to the point of it being ridiculous.

 

[beanland]

Breaker

Breaker

You may run into a limit on the size of the branch circuit breaker you can get to install in the panel. If you can only get a 100A branch circuit breaker, and you use that to feed the subpanel, that is your limit.

You can always use a feeder tap or sub-fed breaker to avoid that issue.