This post might apply to my friends north of us. I watch Holmes on Homes on TV and I know that the show is filmed in Canada. I see where most of the service panels are installed sideways. I was just wondering why they do it that way? Is it force of habit? Or is it as per NEC? Or just preference?
It's strictly a matter of convenience. CEC does not require that 'down' mean 'off.'
You'll also see a number of other differences, especially regarding specific GFCI and AFCI requirements. You'll often hear that it's required to remove / disconnect knob&tube. You'll hear of a limit on the number of lights or receptacles on a circuit.
You'll learn that it's OK to wire-nut aluminum to copper using what appear to be ordinary wirenuts (specific nuts are approved for the use). You'll see new FPE-like panels being installed. Panel-mounted surge protecters are described as 'necessary.'
They do this because Canadian code requires a separate sealed compartment to contain the feeders and main breaker. This is to protect people from exposure to the mains. Because of this, the branch circuits must enter the panel through the sides or the bottom. By mounting it sideways, all (or most) of the cables can come straight down, thus reducing labor required to dress and fasten them.
Well i can tell you this living in Canada, the only code requirement regarding panels is the height, no breaker can be mounted higher than 5 feet...i see panels upside down and right side up but very rarely do we see them sideways..i guess some guys can't dress a panel properly and do it that way for speed...