What size main panel?

[Guzzle]

….House built in ’64, panel permit pulled in ’71.
....The smart meter doesn't have any useful info and the elec. company refuses to tell us the main panel size.

….According to one method, I get 3 Watts per square foot for lighting and general outlets, then I added everything else.
….100% of the first 10,000VA = 10,000VA and 40% of the balance = 21,000VA gives 31,000 VA, then times 1.25 gives 39,000 VA.
….Divided by 240v = 160A, so I assume I have 200A service, then 80% is 160A.

….By loading this panel with 50A by turning on several 240v appliances and scaling up, pulling 160A from this main panel should drop the 240v by 3.3%.
….This leaves 5% - 3.3% = 1.7% drop for sub panel & wiring from that subpanel. That doesn’t seem enough. What am I doing wrong?

 

[Eddie_T]

I never performed an analysis. I just installed a 200A panel and never looked back.

 

[Guzzle]

Yeah, I should trust the NEC more often. They did the analysis.

I could pull 40A from the main panel for a while to get to 236v/118v but the sub panel and the last outlet would also have to be loaded pretty heavy to get down to 232v/116v and then to 114v. This must be what demand factor is about.