B
Bobster
It's probably best to keep socket-outlets below 6,500 feet alright.
Funny you should mention this. I've had to redesign what VSDs I am using on a job in Albuquerque as the city is around 6000ft above sea level. (Higher than Ben Nevis anyway)
Many manufactures have de rating factors on components once you get over around 2000ft above sea level.
Not that this is ever really applicable in the UK.