Cutting unfused wires from Main (line side)and installing Polaris taps in main panel for new solar.

[jaggedben]

I thought you could use 230.82(1) instead of (6) when installing without the last part, "if provided with a disconnecting means listed as suitable for use as service equipment, and overcurrent protection as specified in Part VII of Article 230."

But I don't think it would be compliant anymore. I went back to 705.11 and realized it specifies 230.82(6).

I have seen them spec-ed out on solar plans before, but now I don't know why. (P.S. They had SUSE for the solar install). I thought they did it to limit available fault current or something. The install was based on the NEC 2017. This was a couple of years ago. Maybe it was required by the UL inspector.

The 2017 NEC had distance limits between where the service conductors were tapped and the PV disconnecting means. Cable limiters allowed one to increase the distance.
This was before NFPA finally went in the direction of treating a PV supply side connection as basically just another service disconnect.

 

[don_resqcapt19]

The 2017 NEC had distance limits between where the service conductors were tapped and the PV disconnecting means. Cable limiters allowed one to increase the distance.
This was before NFPA finally went in the direction of treating a PV supply side connection as basically just another service disconnect.

What code section said that?

 

[electrofelon]

What code section said that?

In the 2017:

705.31 Location of Overcurrent Protection. Overcurrent protection for electric power production source conductors, connected to the supply side of the service disconnecting means in accordance with 705.12(A), shall be located within 3 m (10 ft) of the point where the electric power production source conductors are connected to the service. N Informational Note: This overcurrent protection protects against short-circuit current supplied from the primary source(s) of electricity.

Exception: Where the overcurrent protection for the power production source is located more than 3 m (10 ft) from the point of connection for the electric power production source to the service, cable limiters or current-limited circuit breakers for each ungrounded conductor shall be installed at the point where the electric power production conductors are connected to the service.

I dont know if they appeared in other editions, maybe JB knows.

 

[don_resqcapt19]

In the 2017:



I dont know if they appeared in other editions, maybe JB knows.

Thanks.

I never read that section. I wonder if they really meant current limiters or did they really mean current limiting fuses to match up with the current limiting circuit breaker?

 

[electrofelon]

Thanks.

I never read that section. I wonder if they really meant current limiters or did they really mean current limiting fuses to match up with the current limiting circuit breaker?

Yeah that section always seemed non-sensical to me. Why the different rules for conductors feeding a "Pv disconnect" vs feeding a "normal" service disconnect? Also why cant we use these rules for "normal" service conductors then? Again, what is the difference? And like you said, what about CL fuses, they are not an option ? ITs just bizarre.

 

[jaggedben]

I dont know if they appeared in other editions, maybe JB knows.

It first appeared in 2014. 2020 has a somewhat different version (in 705.11(C)) that makes a distinction between dwellings and non-dwellings. Gone in 2023.

 

[ggunn]

Thanks.

I never read that section. I wonder if they really meant current limiters or did they really mean current limiting fuses to match up with the current limiting circuit breaker?

They meant current limiters. I used that section of code a couple of times when there was no physical room to set a PV disco close enough to a supply side point of interconnection.

 

[electrofelon]

They meant current limiters. I used that section of code a couple of times when there was no physical room to set a PV disco close enough to a supply side point of interconnection.

Was that more economical than just putting a "regular" OCPD there? Did you use cable limiters?

 

[ggunn]

Was that more economical than just putting a "regular" OCPD there? Did you use cable limiters?

It was a physical limitation; there was not enough room close enough to the POI to mount a "regular" OCPD in a very crowded electrical room. The section of code I used is no longer there, but it allowed for the length of the conductors between the POI and the OCPD to be significantly increased if cable limiters were installed at the POI. It was vetted and approved by the POCO.

 

[electrofelon]

It was a physical limitation; there was not enough room close enough to the POI to mount a "regular" OCPD in a very crowded electrical room. The section of code I used is no longer there, but it allowed for the length of the conductors between the POI and the OCPD to be significantly increased if cable limiters were installed at the POI. It was vetted and approved by the POCO.

Yeah I can certainly see that with cable limiters, as my understanding is they crimp right on to the cables and dont require significant space or a separate enclosure. The "current limiting circuit breaker" option is what I am not clear on and how that would be any different than a "regular" OCPD.

 

[ggunn]

Yeah I can certainly see that with cable limiters, as my understanding is they crimp right on to the cables and dont require significant space or a separate enclosure. The "current limiting circuit breaker" option is what I am not clear on and how that would be any different than a "regular" OCPD.

"Current limiting" apparently means something different when it applies to fuses and breakers. Google says:

A current limiting circuit breaker is a protective device that not only breaks the circuit when the current exceeds a safe threshold, but also acts quickly to limit the severity of the fault current, protecting the electrical system from damage and reducing the risk of fire.

Current limiting fuse types are designed with a special element that gradually melts when subjected to sustained overcurrents, which prevents the fuse from blowing instantaneously during short-duration surges or inrush currents

I read them as sort of being opposite from each other - faster breakers but slower fuses.

 

[electrofelon]

"Current limiting" apparently means something different when it applies to fuses and breakers. Google says:

A current limiting circuit breaker is a protective device that not only breaks the circuit when the current exceeds a safe threshold, but also acts quickly to limit the severity of the fault current, protecting the electrical system from damage and reducing the risk of fire.

Current limiting fuse types are designed with a special element that gradually melts when subjected to sustained overcurrents, which prevents the fuse from blowing instantaneously during short-duration surges or inrush currents

I read them as sort of being opposite from each other - faster breakers but slower fuses.

Note the NEC has a definition of "current limiting over current protective device" which is:

Current-Limiting Overcurrent Protective Device. A device that, when interrupting currents in its current-limiting range, reduces the current flowing in the faulted circuit to a magnitude substantially less than that obtainable in the same circuit if the device were replaced with a solid conductor having comparable impedance.

My point is that, unless I am missing something, a CL fuse or CL breaker is just going to be whatever frame size and enclosure size you need for the circuit size, so will essentially be the same thing as what a "normal" OCPD would be, right?

 

[ggunn]

Note the NEC has a definition of "current limiting over current protective device" which is:

Current-Limiting Overcurrent Protective Device. A device that, when interrupting currents in its current-limiting range, reduces the current flowing in the faulted circuit to a magnitude substantially less than that obtainable in the same circuit if the device were replaced with a solid conductor having comparable impedance.

At first reading that makes no sense to me. "...when interrupting currents in its current-limiting range" means that the current in the faulted conductor is shut off, not reduced "to a magnitude substantially less than that obtainable in the same circuit if the device were replaced with a solid conductor having comparable impedance."