spare capacity

davelerave · May 16, 2011

how would i determine quickly if i have sufficient spare capacity on

a TPN final board for an additional load?

also i'm working off 4% total allowable VD(16volts)- should i allow a percentage for the 3P final circuit as the length/VD on sub-main isn't obvious?

telectrix · May 16, 2011

worst case is if all existing circuits are pulling rated current all at same time. add up breaker ratings . too vague a question to know if and what diversity can be allowed.

davelerave · May 16, 2011

you mean add up 'total connected load' for worst case?

only just looked at it
it's a school sub-board with a mix of lighting .sockets. hand dryers mostly

prob not much diversity on lighting here

telectrix · May 16, 2011

i'd take 100% lighting, 60% sockets, 30% hand dryers. add that up, then subtract from max. board amps.

davelerave · May 16, 2011

it's 63amp tpn

i'd agree with lighting and dryers- but more diversity on sockets imo

is this the only way of doing this?

prob the easiest way to get the lighting demand is to clamp it during school hours

telectrix · May 16, 2011

ok. go for more on sockets. there's no hard and fast rule. as they say, you're the one on siter. it's your decision. try a clamp meter on the incomer/s and get someone to go round switching things on and off, see what it reads.