I have a manufactured building that is built like a mobile home. It is already wired with an A/C, outlets, lights, etc. through a 125 amp panel. The panel is very small and has no room for additional breakers. I need to run a few additional circuits for GFI's in the kitchen and bath, a 50 amp range plug and a 30 amp hot water heater.
So I have two options (may be more, two that I can come up with). The first option is to upgrade the existing internal panel box to 200 amp and run the additional circuits to the new inside panel. The second option is to treat the 125 amp panel box as a subpanel and then run the circuits to the outside load center (it's 200 amp with capacity for 20 breakers).
My thoughts, it would be more expensive to run to the load center (it's about 30' but only 10' to the interior panel). However, if I modify the existing panel box, I'm concerned it will expose me to a requirement to upgrade all existing wiring to current code (the building was built in 2000).
Between the two options, is one better than the other? Additionally, if the second option is employed, what is the best way to get all of the individual circuits to the load center? In essence, will they need to be in individual conduit? The building is block and tied about 30" off of the ground.
I checked 550 of the NEC and it doesn't seem to speak to running ancillary circuits (only the main feed).
Any help would be appreciated.