It is lamentable that the code writers thought it was OK to write a requirement in the code for DC Arc fault breakers on the DC wires of a PV system when no such animal had yet been developed.
It's like asking for conduit made of unobtainium!
Many electricans lamented the introduction of ACFI's on AC circuits, for justifiable reasons of huge extra cost, lack of proof of need or effectiveness and spurious tripping issues. There is a getout on the AC AFCI usage however; you do not need to use AFCIs on branch circuitS that are wired entirely in metal conduit between metal boxes. We have checked a couple of AHJ's interpretations of the code on this point and they agree with this interpretation of exception 1 to 210.12(A). It may thus sometimes be cheaper to wire the whole place in conduit than to use a couple of thousand bucks worth of AFCIs.
Now we are already required by 690 to use metal conduit from a PV array up to the DC disconnect, precisely for arc-safety, so it seems that it is belt, suspenders and G-string also to require Arc fault breakers. Heaven only know how much they are going to cost for 200 volts DC at 50 amps.
I suggest that the 2014 code should introduce a similar exception for art. 690.11.
I would also like to see the voltage brought into line with 690.7(D) i.e. no arc fault breakers required for under 150 volts, as otherwise we get a lot of fragmentation into different voltage regimes that will hinder the emergence of products.
Exception 1: Where the DC conductors installed inside a building of a PV DC circuit with a maximum system voltage exceeding 150 volts are contained entirely within listed metal conduit or raceways, it shall be permitted to omit the use of DC arc fault circuit protection.
I think thie requirement for arc fault protection should also only apply to residential installations, as on the AC side.
It's like asking for conduit made of unobtainium!
Many electricans lamented the introduction of ACFI's on AC circuits, for justifiable reasons of huge extra cost, lack of proof of need or effectiveness and spurious tripping issues. There is a getout on the AC AFCI usage however; you do not need to use AFCIs on branch circuitS that are wired entirely in metal conduit between metal boxes. We have checked a couple of AHJ's interpretations of the code on this point and they agree with this interpretation of exception 1 to 210.12(A). It may thus sometimes be cheaper to wire the whole place in conduit than to use a couple of thousand bucks worth of AFCIs.
Now we are already required by 690 to use metal conduit from a PV array up to the DC disconnect, precisely for arc-safety, so it seems that it is belt, suspenders and G-string also to require Arc fault breakers. Heaven only know how much they are going to cost for 200 volts DC at 50 amps.
I suggest that the 2014 code should introduce a similar exception for art. 690.11.
I would also like to see the voltage brought into line with 690.7(D) i.e. no arc fault breakers required for under 150 volts, as otherwise we get a lot of fragmentation into different voltage regimes that will hinder the emergence of products.
Exception 1: Where the DC conductors installed inside a building of a PV DC circuit with a maximum system voltage exceeding 150 volts are contained entirely within listed metal conduit or raceways, it shall be permitted to omit the use of DC arc fault circuit protection.
I think thie requirement for arc fault protection should also only apply to residential installations, as on the AC side.