From a 100 amp main panel (load center) in a residential house U.S. a circuit or space goes to a subpanel within the basement. The subpanel (going from memory) is about 12" or 14" square and I think has 8 or 10 spaces, and is 50A or 60A, and was installed many years ago. Something like 6 of those spaces have 15A breakers, the remaining spaces were marked with magic marker "do not use". This subpanel has a large main breaker in it, that when opened it disconnects power to all the 15A breakers in it.
- Has there, or is there, a limitation on the number of breakers that can be in a sub panel? And has that changed over the years?
- Why did someone write "do not use" on the remaining used spaces in the sub panel?
- What reason would prohibit using one of unused spaces in the subpanel, using a 15A breaker, to wire some LED ceiling light fixtures in an unfinished basement? Or to anything else?
- If you buy a sub panel with however many spaces, can you always make use of every space in that sub panel, If not why not?
update: no main breaker in sub panel, see pic below. It is a 50A breaker feeding this from the main panel. Sub panel doesn't have a main breaker in it, my mistake when I said it did. This was done 20+ years ago. Is this that rule of 6 thing, and does that still apply can it fill this box with breakers?