OK, I never quite understood some of the finer points of the 125% largest motor load and 125% continuous loads.
I need to calculate the load on an existing system to see if I can add any load to it. The existing system has a chiller and some motor loads. I think I've narrowed my confusion down to a few questions.
430.24 states to use 125% largest motor, 100% other motors, 100% other non-continuous loads and 125% continuous loads.
210.19, 210.20, and 215.2 all state that the conductors and OCP shall be sized for 100% of the noncontinuous load plus 125% of the continuous load unless the OCP is listed for operation at 100% of its rating.
So here are the questions:
1) My chiller is basically one big motor. So for my total load calc. I'm figuring 125% of the chiller plus the other motor loads. Is that right, or do I need to add 125% of another motor, because my chiller isn't really just a motor?
2) What if some of the other motors run continuous? Do I ever need to count additional motors at 125% if they run continuous? 430.24 seems to say no, while the 210 and 215 requirements seem to say yes.
3) What about the transformer supplying the loads? Should it just be sized for the total load, or should I add figure 125% of any of the loads against the transformer size?
4) I I have 1000 amp feeder supplied by a 1200 AF breaker with the trip set at 1000 amps. So the breaker would be rated for 0.8 * 1200 = 960 amps continuous. So can I use the exceptions for a 100% rated breaker and place 960 amps of continuous load on this feeder without including any extra 25% load factors?
I need to calculate the load on an existing system to see if I can add any load to it. The existing system has a chiller and some motor loads. I think I've narrowed my confusion down to a few questions.
430.24 states to use 125% largest motor, 100% other motors, 100% other non-continuous loads and 125% continuous loads.
210.19, 210.20, and 215.2 all state that the conductors and OCP shall be sized for 100% of the noncontinuous load plus 125% of the continuous load unless the OCP is listed for operation at 100% of its rating.
So here are the questions:
1) My chiller is basically one big motor. So for my total load calc. I'm figuring 125% of the chiller plus the other motor loads. Is that right, or do I need to add 125% of another motor, because my chiller isn't really just a motor?
2) What if some of the other motors run continuous? Do I ever need to count additional motors at 125% if they run continuous? 430.24 seems to say no, while the 210 and 215 requirements seem to say yes.
3) What about the transformer supplying the loads? Should it just be sized for the total load, or should I add figure 125% of any of the loads against the transformer size?
4) I I have 1000 amp feeder supplied by a 1200 AF breaker with the trip set at 1000 amps. So the breaker would be rated for 0.8 * 1200 = 960 amps continuous. So can I use the exceptions for a 100% rated breaker and place 960 amps of continuous load on this feeder without including any extra 25% load factors?
The bulk of the load is a 500 FLA chiller that will run almost full out for several hours.