That was to have a full bath with a grinder and lift station for the sewage along with a kitchenette, bedroom and living room. Doing a visual inspection of the original 200 amp grid tied Main Breaker panel that was entirely filled with circurit breakers.
Nothing can ever be easy when dealing with residential original wiring issues and this project was a classic example of this because the LB conduit body underneath the old subpanel had to be relocated also because the new 24 space subpanel was twice the size of the old subpanel. The obvious choice was to relocate the LB conduit body to the top of the new subpanel which meant having to pull the wiring out of that conduit raceway to be able to cut the original raceway as needed along with redrilling a new entrance hole. All these repairs had to be done before any new work could begin for all the new recessed light cans, outlets, switching, AFCI bedroom outlets, GFCI bath outlets. exhaust vent with light kit and all the other new wiring needed for the remodel.
All that still leaves numbers to be taken into consideration as total wattage load determines Main Breaker sizing. Even with these 3 circurit breakers panels operating the Main Breaker is only going to take its amperage rating and then trip from overload. Before that even comes close to happening further testing 7 24 is needed on meter load side to original Main Breaker cables. to determine how much amperage and wattage is really being operated. Than that bridge can be crossed when those numbers are known? A grid tied original meter at 120 240 volt 200 amperage single phase is 48,000 watt (voltsXamperage=wattage) (wattage/voltage=amperage).
Personally I do not operate any Main Breaker to no more than 80% of its capacity leaving 20% in reserve for startup of motors, compressors, pumps and other large loads which require more voltage at startup. By doing this you see far less flickering in lighting. (200X80%=160). If the 7 24 load reports come back within those ranges than my next step would be to consider to upgrade the utility grid meter, weather head connections and necessary components for a larger amperage to grid tied connection.
A to Z D B Electric performs quality craftsmanship and services for clients.
Update Aug 3 2017
The task was 21 man hours and materials to do the heat sink step down method. Clearly shows the improvements completed. The original 200 amp Main had all piggyback breakers removed and transferred to 100 sub panel that was removed from 12 space and upgraded to 24 space. As well as placing each large 240 volt breaker highest amperage closest to the main breaker on down aka heat sink step down method . Allowing additional breaker space for basement walkout remodel electrical loads. 7 24 data loggers are gathering data for total current wattage usage more to follow after remodel loads are applied.