winnie
Senior Member
- Location
- Springfield, MA, USA
- Occupation
- Electric motor research
In a different thread, I asked about the possibility of running _two_ from an external disconnect to a home, one for high current loads that could tolerate voltage drop, and the other for loads where the voltage drop would be annoying but where current would not suddenly change drastically (eg. lighting circuits).
kwired had an interesting response which I thought merited further discussion, but I did not want to derail the original thread:
http://forums.mikeholt.com/showthread.php?t=182355&page=2&p=1810163#post1810163
kwired, are you basically saying that if you run _multiple_ sets of conductors to the detached structure, but you only have a _single_ OCPD at the supply end and all the conductors are tied together at the supply end, then this is a _single_ feeder. At the load end, you have multiple OCPD, one for each separate set of conductors, since 1-6 OCPD can be considered a single disconnect, you meet the disconnect rules. If I read this correctly, then you have what is legally a single feeder, with a 'single' disconnect at the detached structure, but with separate paths for the different loads.
The above seems plausible 'loophole' around 225.30, as long as each of the individual sets of conductors is properly protected by the OCPD. Consider a single OCPD where you have 2 sets of conductors, one leaving the panel going west and the other going east. One breaker means _one_ circuit, even if the circuit splits and goes 2 ways. Simply because the circuit splits at one building and both 'halves' go to a different building, IMHO you still have _one_ circuit.
For a long run where you need to upsize for voltage drop, the ampacity of each of the separate sets of conductors is likely sufficient to carry the full load, so proper protection doesn't seem an extra burden.
I like it and wonder what other think; would this have any place in a real world installation?
I understand that NEC 225.30 generally prohibits more than a single feeder to a detached structure. What I was hinting at in my question was the idea that one might pull off 2 feeders using 225.30(D) different characteristics, essentially same voltage, same frequency, same phase count, but _different_ voltage drop tolerance characteristics.
-Jon
kwired had an interesting response which I thought merited further discussion, but I did not want to derail the original thread:
http://forums.mikeholt.com/showthread.php?t=182355&page=2&p=1810163#post1810163
kwired, are you basically saying that if you run _multiple_ sets of conductors to the detached structure, but you only have a _single_ OCPD at the supply end and all the conductors are tied together at the supply end, then this is a _single_ feeder. At the load end, you have multiple OCPD, one for each separate set of conductors, since 1-6 OCPD can be considered a single disconnect, you meet the disconnect rules. If I read this correctly, then you have what is legally a single feeder, with a 'single' disconnect at the detached structure, but with separate paths for the different loads.
The above seems plausible 'loophole' around 225.30, as long as each of the individual sets of conductors is properly protected by the OCPD. Consider a single OCPD where you have 2 sets of conductors, one leaving the panel going west and the other going east. One breaker means _one_ circuit, even if the circuit splits and goes 2 ways. Simply because the circuit splits at one building and both 'halves' go to a different building, IMHO you still have _one_ circuit.
For a long run where you need to upsize for voltage drop, the ampacity of each of the separate sets of conductors is likely sufficient to carry the full load, so proper protection doesn't seem an extra burden.
I like it and wonder what other think; would this have any place in a real world installation?
I understand that NEC 225.30 generally prohibits more than a single feeder to a detached structure. What I was hinting at in my question was the idea that one might pull off 2 feeders using 225.30(D) different characteristics, essentially same voltage, same frequency, same phase count, but _different_ voltage drop tolerance characteristics.
-Jon
