Code Question: NEC 690.17(A) vs 690.10(E) vs 705.12(D)(4)

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forresthuynh

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Article 690.17(A) talks about not backfeeding circuit breakers marked "line & load", however I am under the impression that it is not enforced and more informational. However, in Article 690.10(E) it is enforced. Then in article 705.12(D)(4) it says breakers are suitable for backfeeding unless otherwise stated.

What is the general consensus on how to approach these three articles? I've been told its best to consult the manufacturer but I would like to see if there is a more solid thought toward these three articles and what devices are suitable for backfeeding that are makred line and load.

thanks!
 
General rule

• Cannot be Reverse-Fed:
When a UL Listed molded case circuit breaker and a molded case switch (not shown) are marked showing “Line” and “Load,” the power supply conductors must be connected to the end marked “Line.” These devices cannot be reverse-fed.

• Can be Reverse-Fed:
If “Line” and “Load” are not marked on the UL Listed molded case circuit breaker, the power supply conductors may be connected to either end. These devices are suitable for reverse-feed applications.
Click to expand...

Source: Eaton white paper "Reverse-Feed Applications for Circuit Breakers"
 
Among the OCP devices which may not be compatible with backfeeding are AFCI and GFCI devices, and shunt trip breakers which are wired such that the opening of the breaker interrupts the shunt current supply to limit coil loading.
To some extent grid interactive inverters do not create the same potentially problematic conditions when they are the source of the reverse feed because, unlike generators or non-interactive inverters, their outputs do not continue to supply power after the breaker opens.
 
The difference between 690.10(E) and any of the other sections is with respect to the hold-down requirement. 690.10(E) is for a stand alone inverter output, and applies the same hold down requirement as for any plug-on breaker in a panelboard that could be unplugged and still be live. The hold-down requirement does not apply to interactive inverter outputs that go dead just like load breakers when unplugged from the primary source. See 705.12(D)(5).

Other sections are simply concerned that power does not flow in a direction that the breaker is not approved for. This is actually a slightly different meaning of 'backfed'. As mentioned, other than AFCI and GFCI breakers, most breakers have no limitations on which direction power can be fed through them, which is important for feeder breakers on service disconnecting means which may see powere going one way or the other at different times.

Note: all references are 2014 NEC, and all of them in this thread (so far) changed numbering, at least, in the 2017 NEC.
 
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SolarPro said:
Source: Eaton white paper "Reverse-Feed Applications for Circuit Breakers"
Click to expand...

So in order to determine if a breaker is suitable for backfeed, you have to prove a negative. Prove that it isn't marked line and load, in a place you probably cannot see on the device itself, if it is the existing main breaker at a service that is energized on your initial visit.

Is there a requirement for datasheets to be marked as such? Or just the device itself?
 
Carultch said:
So in order to determine if a breaker is suitable for backfeed, you have to prove a negative. Prove that it isn't marked line and load, in a place you probably cannot see on the device itself, if it is the existing main breaker at a service that is energized on your initial visit.
Click to expand...

Why would you think that you probably could not see it if it was marked?
 
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