I've replaced several meter panels and subpanels over the years but I never had to figure out amp ratings for a new dual meter main. Here is what is existing:
125A meter main panel feeding house
1 1/4" pvc underground pipe to garage feeding 50A sub
Here is a description of the finish product:
- Main panel that feeds front house is replaced
- Garage is converted to a single family dwelling unit, will now call it "rear unit"
- Rear unit new 125A sub panel is feed on its own meter from new dual meter main panel at front unit
Questions:
How do I size the main panel? 200A or 400A?
Does the optional ampacity calculation in the NEC give a more reliable answer?
What is the best formula for converting the total wattage of the front unit to find the amp rating for this new main panel?
