wwhitney
Senior Member
- Location
- Berkeley, CA
- Occupation
- Retired
215.3 (Feeder OCPD), for example, requires us to know both the continuous and non-continuous load on a feeder. And Article 220 tells us how to calculate the load on a feeder, but doesn't discuss continuous loads, except as part of a single provision in 220.82(C)(6). So after calculating the total load on a feeder, how do we determine the breakdown into continuous vs non-continuous loads?
If there are no factors involved, and the feeder load is just the sum of individual loads, it's straightforward. We can categorize each individual load as continuous or non-continuous. But more complicated computations, as far I can see the NEC doesn't specify how to do the breakdown.
For example, take the Annex D2(a) example, an optional calculation for a single family dwelling. The calculated service load is 90A, of which none is continuous.
Say we add a 48A (output) EVSE on a 60A branch circuit to the load calculation. An EVSE is a real continuous load, mine often runs for more than 3 hours at maximum current. Adding it to the optional calculation in D2(a), we get a new service load that is 40%*48A = 19.2A higher, or 109A.
What portion of that 109A load is continuous? Is it 48A, irrespective of the "first 10 kVA @ 100%, rest at 40%" part of the optional calculation? Or is it 41.7A (10 kVA/240V) + (48-41.7)*40% = 44A? Or is it just 19A, amount the service load increased?
Thanks,
Wayne
If there are no factors involved, and the feeder load is just the sum of individual loads, it's straightforward. We can categorize each individual load as continuous or non-continuous. But more complicated computations, as far I can see the NEC doesn't specify how to do the breakdown.
For example, take the Annex D2(a) example, an optional calculation for a single family dwelling. The calculated service load is 90A, of which none is continuous.
Say we add a 48A (output) EVSE on a 60A branch circuit to the load calculation. An EVSE is a real continuous load, mine often runs for more than 3 hours at maximum current. Adding it to the optional calculation in D2(a), we get a new service load that is 40%*48A = 19.2A higher, or 109A.
What portion of that 109A load is continuous? Is it 48A, irrespective of the "first 10 kVA @ 100%, rest at 40%" part of the optional calculation? Or is it 41.7A (10 kVA/240V) + (48-41.7)*40% = 44A? Or is it just 19A, amount the service load increased?
Thanks,
Wayne
