Tap length limitations

csoc64

Senior Member
Does 705.31 limit tap conductor length to a maximum of 10'? The conductors I am referring to are between the load side of a fused PV disconnect with the tap located between the utility meter and the MCB in the panel (i.e "supply side of the service disconnecting means"). I am seeing many mentions of being able to extend to 25' per 240.21.(B)(2) but have also seen posts that refer to 705.31 and say we are limited to 10' in the case of PV conductors.
 

jaggedben

Senior Member
They are not feeder tap conductors. They are inverter output conductors. 240.21(B) does not apply.

'Load side' can be a little vauge when referring to PV outputs. The conductors between the service and the disconnect are limited to 10ft by 705.31. The conductors on the inverter side are not limited at all.
 

Carultch

Senior Member
They are not feeder tap conductors. They are inverter output conductors. 240.21(B) does not apply.

'Load side' can be a little vauge when referring to PV outputs. The conductors between the service and the disconnect are limited to 10ft by 705.31. The conductors on the inverter side are not limited at all.
10 ft "as the crow flies", or 10 ft of actual wire length? In otherwords, must it account for the serpentine path that the wire might have to take, or is it OK as long as the fused disconnect is 10 ft away from the enclosure where interconnection happens?

In the event that you can't put the fused disconnect within 10 ft, the work-around for this situation is to put cable current limiters within 10 ft, and then extend the circuit as far as needed to install the fused disconnect.
 

ggunn

PE (Electrical), NABCEP certified
10 ft "as the crow flies", or 10 ft of actual wire length? In otherwords, must it account for the serpentine path that the wire might have to take, or is it OK as long as the fused disconnect is 10 ft away from the enclosure where interconnection happens?
The NEC is ambiguous on this point. I have always interpreted it to mean 10 feet maximum conductor length between connection point and OCPD, but that's not precisely what it says.
 

Carultch

Senior Member
The NEC is ambiguous on this point. I have always interpreted it to mean 10 feet maximum conductor length between connection point and OCPD, but that's not precisely what it says.
If you were an inspector, would you cite it as a violation if cable path makes it greater than 10 ft, even if absolute distance is less?

Do you know any inspectors who might be that strict to the wording of the NEC, even if no practical safety hazard due to the violation would exist?
 

jaggedben

Senior Member
I happen to be facing this conundrum myself this morning. I have to get a bit more info on the site, but we may looking at a disconnect that is less than 10ft away on an opposite wall, yet the conduit would have to go up 5ft to the ceiling, across the room and back down, and will end up like 15-20ft conductor length. I haven't faced this situation before.

I think strict to the wording would allow it as the code does not mention conductor length.
 

jumper

Senior Member
The NEC is ambiguous on this point. I have always interpreted it to mean 10 feet maximum conductor length between connection point and OCPD, but that's not precisely what it says.
I just read the ROP, that was the intent however I agree that is not what it says.
 

ggunn

PE (Electrical), NABCEP certified
If you were an inspector, would you cite it as a violation if cable path makes it greater than 10 ft, even if absolute distance is less?

Do you know any inspectors who might be that strict to the wording of the NEC, even if no practical safety hazard due to the violation would exist?
If I were an inspector and it were left totally up to me, yes, I would flag it, though I might be somewhat flexible if it were close. I don't know that my interpretation would stand up in court, though, seeing as the code is ambiguous.
 

jumper

Senior Member
If I were an inspector and it were left totally up to me, yes, I would flag it, though I might be somewhat flexible if it were close. I don't know that my interpretation would stand up in court, though, seeing as the code is ambiguous.
Very ambiguous gunny, one can certainly easily infer that it is distance.

The last sentence in the substantiation clearly said it was meant to limit the cable length, but the wording...did it change at all in the 2017?
 

ggunn

PE (Electrical), NABCEP certified
Very ambiguous gunny, one can certainly easily infer that it is distance.

The last sentence in the substantiation clearly said it was meant to limit the cable length, but the wording...did it change at all in the 2017?
I just looked and it appears to be unchanged.
 

pv_n00b

Senior Member
Looking at the NEC 2020 proposals and 705.31 was deleted and the requirements moved to the new section 705.11 which provides a lot more guidance on making supply-side interconnections than we had before. They updated it to specify that the distance is the conductor length. So that is probably what is coming.

In the 2017 NEC, it is up to the AHJ which interpretation they will accept. If I were going over 10' of conductor length I would ask first and not risk expensive rework later.
 

shortcircuit2

Senior Member
Do you know any inspectors who might be that strict to the wording of the NEC, even if no practical safety hazard due to the violation would exist?
If there were no safety hazard, service entrance conductors too would be allowed to run 10-feet or more in a building. But 230.70(A)(1) says "nearest the point of entrance" because the conductors have no protection.

Solar gets a buy on this rule by not calling these conductors what they are...unprotected service entrance conductors. Now for 2020 under the new 705.11, the distance is proposed to increase to 16.5 feet.

CMP-4 proposed the new 705.11 for 2020 with information gathered from public input's for the new cycle. IMO, the proposed 705.11 is a workaround of the safety rules in article 230 in the interest of cost savings for the solar installer.
 

GerryB

Senior Member
If there were no safety hazard, service entrance conductors too would be allowed to run 10-feet or more in a building. But 230.70(A)(1) says "nearest the point of entrance" because the conductors have no protection.

Solar gets a buy on this rule by not calling these conductors what they are...unprotected service entrance conductors. Now for 2020 under the new 705.11, the distance is proposed to increase to 16.5 feet.

CMP-4 proposed the new 705.11 for 2020 with information gathered from public input's for the new cycle. IMO, the proposed 705.11 is a workaround of the safety rules in article 230 in the interest of cost savings for the solar installer.
I agree, except "buy should be bye??":) The solar guys also use this to get around grouping of disconnects. They will tap inside the panel and jump outside to their fused disco.
 
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