two questions

[graham123]

am doing a pir at a school which has a terrapin, the supply to the terrapin is a 3core 16mm, single phase. Question is somthing sticks in my mind thinking that externally supplied bulidings, sheds, garages etc used to require an earth stake?? Cannot find any answer to this in current regs. Im presuming as long as the earth going to the terrapin is of the same size as the equipotential bonding in the school its fine?

Also how do you calculate the maxium demand load on a PIR?

THanks

 

[SirKit Breaker]

I would agree with what you have said about the outbuilding, but i would prefer to shove an earth rod in just for good measure, and would also insist on full rcd protection for the supply to and the installation within the building. Belt and braces etc, there are kids and members of the public involved and your name is going to be all over it. You cant over do it in my humble opinion.

The calc i use for maximum demand is,

add up the sum of all the breakers, fuses etc. so lest assume your total comes to 350a, multiply it by 0.4, this equals 140a, so maximum demand is 140 amps. There are other methods, but this general rule of thumb is always acceptable.

Cheers.........Howard