3 ms·
The article says that you're are not allowed to use the full rated capacity of a circuit. Can anyone tell me why? This seems weird to me. I think this is an NF
by mmt 14y ago
The article says that you're are not allowed to use the full rated capacity of a circuit. Can anyone tell me why? This seems weird to me.
I think this is an NFPA/NEC[1] standard.
You could look at it another way: circuits are breakered such that you can temporarily peak 25% above their normal capacity without tripping the breaker. I don't know why the standard isn't more conservative, except to guess that it's because typical household/office uses are likely to have low continuous and high intermittent loads (e.g. vacuum cleaner), making it a good trade-off.
[1] USA (and Canada?) only. Anyone know how it is in other countries?
- mindslight 14y agoYes, this is a requirement of the NEC. Branch circuits need to be rated at 125% of the continuous load. In general, wires are sized not only on their overcurrent protection, but also (overbuilt) for the planned load. Unplanned "noncontinuous" loads get a free pass as the only thing that really keeps them in check is the overcurrent protection. But kika's downthread comment is most on the mark - of course data centers would rather advertise the less relevant "circuit rating" as the number is higher. The load calculations are the same either way. (btw speaking of the NEC, http://bulk.resource.org/codes.gov/ http://bulk.resource.org/codes.gov/ is a fantastic resource)