Tapping wires between breakers

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Paul Joyce

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Somerset, NJ
We have a 200 amp service that has a 200 amp breaker at the meter as well as a 200 Main breaker in the panel. We wanted to perform a supply side tap, but between the meter and the first 200 amp breaker is busing, so we put our taps on the 4/0 SER wires between the 200 amp breaker at the meter and the 200 Main breaker at the panel. Our solar PV is supplying approximately 120 amps. The question is that since there is a breaker on each end of the 4/0 wire, does the wire need to be rated to carry the combined load of the service AND the PV or does the current limiting device on both ends mean that our tap is code compliant?
 

don_resqcapt19

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Location
Illinois
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retired electrician
Your connection is not a line side tap as it is on the load side of the service disconnect. You cannot connect a 120 amp solar source at that point.
 

jaggedben

Senior Member
Location
Northern California
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Solar and Energy Storage Installer
Under the 2014 NEC this is a compliant installation. The one area that is a bit grey is exactly how you are supposed to size the conductors for the tap you made.

Under previous codes this is NOT a compliant installation. At best, you could argue that those code allow the conductor to be loaded to 120% of it's rating, which you are way over. At worst, some AHJs don't allow this type of connection at all, and the code is too vague to made a very solid argument that they should.
 

Carultch

Senior Member
Location
Massachusetts
Under the 2014 NEC this is a compliant installation. The one area that is a bit grey is exactly how you are supposed to size the conductors for the tap you made.

Under previous codes this is NOT a compliant installation. At best, you could argue that those code allow the conductor to be loaded to 120% of it's rating, which you are way over. At worst, some AHJs don't allow this type of connection at all, and the code is too vague to made a very solid argument that they should.


I think our asker is going to have to ask for the AHJ's acceptance of future code editions, if 2014 doesn't apply. Not OK today, but will be OK 5 years from now? Should that mean that it is OK today?

The way I see it, a tap is a conductor that is protected, but only in excess of its ampacity, and will eventually be protected at its ampacity when it terminates at an OCPD. So either you protect a conductor at its ampacity, you are making a tap, or you made a mistake. Or it meets another section of the code.
 

jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
The way I see it, a tap is a conductor that is protected, but only in excess of its ampacity, and will eventually be protected at its ampacity when it terminates at an OCPD. So either you protect a conductor at its ampacity, you are making a tap, or you made a mistake. Or it meets another section of the code.

The relevant sections in 2014 are 705.12(D)(2)(1) and (2).

I don't think it's correct to call the feeder a tap even if the sum of the sources that can feed it is above its ampacity. But the tap to the solar is exactly that.
 

Buck Parrish

Senior Member
Location
NC & IN
I was wondering if he could have used a 125 amp breaker back fed in the outside panel. (Labeled alternate feed) But he might need to add 1.25. That would put him over.
 

jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
Because it does not appear to me, based on the original post, that there is an OCPD between the feeder and the inverter.

I figured they just left that out of the description. If indeed they didn't put an OCPD between the tap and the inverter, that's not a proper 240.21(B) tap. OTOH, it would be easily rectified, and it doesn't affect the question of whether it's compliant to tap the feeder for an inverter.
 

jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
I was wondering if he could have used a 125 amp breaker back fed in the outside panel. (Labeled alternate feed) But he might need to add 1.25. That would put him over.

I presume there was no place to put a breaker at the service panel. I run into a lot of houses where the service equipment contains only a single circuit breaker and the rest of the distribution is via a subpanel somewhere else in the house. It can be very annoying for us solar guys who usually want to avoid working in finished areas of buildings.
 

don_resqcapt19

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Location
Illinois
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retired electrician
I figured they just left that out of the description. If indeed they didn't put an OCPD between the tap and the inverter, that's not a proper 240.21(B) tap. OTOH, it would be easily rectified, and it doesn't affect the question of whether it's compliant to tap the feeder for an inverter.
It makes the tap a violation so it really does affect the question at to it being a compliant tap. They can make the tap at that location without a breaker if the size the feeder conductors to the sum of the upstream OCPD and 125% of the inverter output.
 

don_resqcapt19

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Location
Illinois
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retired electrician
.... It can be very annoying for us solar guys who usually want to avoid working in finished areas of buildings.
It may be annoying, but there is no reason to expect the original installer to make it easy for the next guy, no matter what the next guy is wanting to do.
 

jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
It makes the tap a violation so it really does affect the question at to it being a compliant tap. They can make the tap at that location without a breaker if the size the feeder conductors to the sum of the upstream OCPD and 125% of the inverter output.

I don't agree with that at all. Its the tap conductors that have to sized to that sum as calculated in 240.21(B). And the tap for the solar has to have a breaker at the end of the tap conductors for both 705.12(D)(1) and 240.21(B).

It may be annoying, but there is no reason to expect the original installer to make it easy for the next guy, no matter what the next guy is wanting to do.

It's not a criticism of the original installer, it's a question of whether there are code compliant solutions that allow the customer to save a lot of money and the installer to compete with other installers. Sometimes it's a question of whether the customer is even willing to go forward with a job.
 

don_resqcapt19

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Staff member
Location
Illinois
Occupation
retired electrician
I don't agree with that at all. Its the tap conductors that have to sized to that sum as calculated in 240.21(B). And the tap for the solar has to have a breaker at the end of the tap conductors for both 705.12(D)(1) and 240.21(B). ...
It appears to me that 705.12(D)(1)(a) specifically permits a connection without an OCPD at the inverter as long as the feeder conductors on the line side of the inverter have an ampacity that is at least equal to the sum of the feeder supply OCPD and 125% of the inverter output.
(1) Feeders. Where the inverter output connection is made to a feeder at a location other than the opposite end of the feeder from the primary source overcurrent device, that portion of the feeder on the load side of the inverter output connection shall be protected by one of the following:
(a) The feeder ampacity shall be not less than the sum of the primary source overcurrent device and 125 percent of the inverter output circuit current.
 

jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
It appears to me that 705.12(D)(1)(a) specifically permits a connection without an OCPD at the inverter as long as the feeder conductors on the line side of the inverter have an ampacity that is at least equal to the sum of the feeder supply OCPD and 125% of the inverter output.

The part you quoted specifically permits a connection without an OCPD on the load end of the feeder, given the condition.

Please keep reading to the (b) part for the other option.

In either case, you need an OCPD between the inverter and the tap location, to meet various article 705 requirements if not 240.21(B) requirements.
 

don_resqcapt19

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Staff member
Location
Illinois
Occupation
retired electrician
The part you quoted specifically permits a connection without an OCPD on the load end of the feeder, given the condition.

Please keep reading to the (b) part for the other option.

In either case, you need an OCPD between the inverter and the tap location, to meet various article 705 requirements if not 240.21(B) requirements.
I don't agree and therefore see no need to look at the "or" in (b).

I don't see any need for an OCPD other than the two that are on the existing feeder as long as the conductors are sized per the rule I quoted.
The conductors both from the inverter and the original feeder would have an ampacity so that they would be fully protected without any additional OCPD. The rules in this section modify the rules in 240.21 as permitted by 90.3 so there is no need to look to 240.21.
 

jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
Your opinion baffles me. :blink:

You only need to look to the section right before the one you quoted (i.e. 705.12(D)(1)) to see that a dedicated OCPD is required for the inverter(s) no matter which way they are connected.

I don't agree and therefore see no need to look at the "or" in (b).

It's weird that you don't want to discuss the provision that applies to the OP's question.

...The rules in this section modify the rules in 240.21 as permitted by 90.3 so there is no need to look to 240.21.

And you only need to look at the section right after the one you quoted (705.12(D)(2)(2) to see that 240.21(B) is still in force. The rules don't modify the rules if they don't actually modify them.
 
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