PV Load side tie-in, disconnect requirement

[Designer69]

If I am connecting my inverter on the load side using a breaker in the main panel (40A PV breaker)... Do I need a separate disconnect between this PV breaker and the inverter?


Lastly, what is special about this PV breaker (it must be backfeed rated?) what the heck does that mean?


Thank You!

 

[ggunn]

If I am connecting my inverter on the load side using a breaker in the main panel (40A PV breaker)... Do I need a separate disconnect between this PV breaker and the inverter?


Lastly, what is special about this PV breaker (it must be backfeed rated?) what the heck does that mean?


Thank You!

With the AHJ's I deal with, yes, they want a bladed PV AC disconnect (visible break, lockable in the off position, labeled) on the exterior of the building irrespective of the mode of interconnection. Fused if line side connected and unfused if backfed breaker connected, of course.

As for the breaker, if it is stamped line and load you cannot backfeed it, but if it is not so stamped you can. FWIW, I have never seen a stamped breaker, so most any load breaker is OK to use.

 

[Designer69]

With the AHJ's I deal with, yes, they want a bladed PV AC disconnect (visible break, lockable in the off position, labeled) on the exterior of the building irrespective of the mode of interconnection. Fused if line side connected and unfused if backfed breaker connected, of course.

As for the breaker, if it is stamped line and load you cannot backfeed it, but if it is not so stamped you can. FWIW, I have never seen a stamped breaker, so most any load breaker is OK to use.

Thank You Ggunn.


Lastly, this project is a nearby (to the house) ground mounted pv system. Would you use pvc underground from the arrays to the inverter (inverter located next to main service panel) or emt? about a 20 ft run

 

[ggunn]

Thank You Ggunn.


Lastly, this project is a nearby (to the house) ground mounted pv system. Would you use pvc underground from the arrays to the inverter (inverter located next to main service panel) or emt? about a 20 ft run

PVC. You can't bury EMT.

 

[jaggedben]

If I am connecting my inverter on the load side using a breaker in the main panel (40A PV breaker)... Do I need a separate disconnect between this PV breaker and the inverter?


Lastly, what is special about this PV breaker (it must be backfeed rated?) what the heck does that mean?

The NEC requires a disconnect that is 'grouped' with the inverter. It does not require those things that ggunn said and in my experience those things always come from the utility, not the electrical code. Around here the major utility does not require a disconnect for most residential systems. A couple city owned utilities do. These things will probably vary regionally.

We usually interpret 'grouped' to mean 'within sight' and a circuit breaker can usually meet that requirement just fine. One AHJ interprets 'grouped' to mean within 6ft, most others aren't too strict about it. The NEC requires at least one disco to be lockable; this can be accomplished with a device installed on the circuit breaker.

The line-load thing disqualifies AFCI and GFCI breakers but not ordinary ones in my experience.

 

[ggunn]

... in my experience those things always come from the utility, not the electrical code.

And that's what I said.

 

[pv_n00b]

With the AHJ's I deal with, yes, they want a bladed PV AC disconnect (visible break, lockable in the off position, labeled) on the exterior of the building irrespective of the mode of interconnection. Fused if line side connected and unfused if backfed breaker connected, of course.

If an unfused disconnect is used make sure it is rated for the available fault current. Most allow up to 10kAIC when protected by any upstream OCPD but to get a higher rating the OCPD and the disconnect have to be correctly series rated or a fused disconnect is needed. Not usually an issue on residential systems but often is on larger systems.

 

[Carultch]

The NEC requires a disconnect that is 'grouped' with the inverter. It does not require those things that ggunn said and in my experience those things always come from the utility, not the electrical code. Around here the major utility does not require a disconnect for most residential systems. A couple city owned utilities do. These things will probably vary regionally.

We usually interpret 'grouped' to mean 'within sight' and a circuit breaker can usually meet that requirement just fine. One AHJ interprets 'grouped' to mean within 6ft, most others aren't too strict about it. The NEC requires at least one disco to be lockable; this can be accomplished with a device installed on the circuit breaker.

The line-load thing disqualifies AFCI and GFCI breakers but not ordinary ones in my experience.

NEC2017/690.15 now requires the AC disconnect within 10 ft of the inverter, or a remote means to shutoff a more distant disconnect, that can be reached within 10 ft. I think this is overkill in many situations, as it is common to have a 20 ft long inverter line-up, and the inverters are clearly grouped with their branch breaker in the adjacent AC combining panelboard. By strict interpretation of the wording, this means half the inverters would need a redundant switch, or pushbutton to activate a shunt trip, and the other half are OK with only their branch breaker.

A criteria of 6 ft or 10 ft = "grouped" makes sense if there are only two pieces of equipment in the group. However, when there are a dozen related pieces of equipment in a group, separated by about a foot each, it is clear that the two farthest pieces of equipment in this group are still "grouped" with one another. 50 ft I could see as justifying them no longer being "grouped", since that is what the NEC considers as no longer "within sight".