'Load side tap'

[Jeff Greef]

I'm an inspector and just saw what the installer is calling a load side tap. This is a residential PV instal that needs a 30 amp protected connection to the system.

200 amp main service panel does not have space for a breaker, so he tapped into the feeders to the only subpanel, after the 100amp breaker on the service bars protecting the subpanel feeders. The tap leads to the inverter via a separate 60 amp fused disconnect (as though it were a line side tap). No place to connect for a true line side tap.

Load side connections must be made AT a breaker or fusible disconnect, is my interpretation, so his feeder tap that leads to a fusible disconnect is not compliant, since the connection is made at a tap, not a breaker or fuse/switch.

Opinions?

Further, if the tap is compliant, the feeders could now be overfed by 20.3 amps (actual system capacity). He suggests reducing the feeder breaker from 100 to 80 amps. The sub only handles 15 and 20 amp lighting and receptacles so it should handle it at 80. Needs load calcs.

Is such a 'load side tap' compliant in this or any other way shape or form? There are of course several other solutions to this particular instal but I'm wondering specifically if tapping into conductors (or lugs) on the load side of the service disconnects can be code compliant.

Thanks

 

[augie47]

Did he actually connect to the feeder conductors ? (split-bolt, polaris, etc)

 

[jeffgreef]

Yes, connected directly to the feeder conductors, inside the service enclosure, 5 inches below the breaker, with a tap connector the name of which I don't know.

 

[jaggedben]

I don't see any general problem with his method, so long as his tap complies with 240.21(B). Reducing the sub breaker is technically necessary, but it seems unfair to ask him to do so when he is only exceeding the 120% rule by .3 percent.

 

[Jeff Greef]

I don't see a functional problem so long as wire sizes are correct. But, the code does say the connection must be made at a circuit breaker or fusible disconnect. So, I guess the question is, is this a violation since the connection is made at a tap rather than the breaker or disconnect. The tap leads to a fused disconnect (4 feet of wire away), and the installer says that therefore he is connected with a fused disconnect. But the connection to the system is not made AT the fused disconnect, it is made at a tap.

Is this a violation? If so, why could it be a problem?

 

[Smart $]

... But the connection to the system is not made AT the fused disconnect, it is made at a tap.

...

But the connection to the system IS made at an ocpd... the fusible disconnect (i.e. its load side terminals). From the perspective of the utility-fed system, the line side tap conductors are part of that system, not the PV system... same as the busbars when connecting to a panelboard breaker.

Why is it there are so many people that think a connection carries through to the other side of a device?

 

[jaggedben]

I have worked on numerous systems that were done with a load-side tap and I have never heard either anyone in the industry or an AHJ suggest that it was not a valid method.

I agree with Smart$; the system complies with 705.12(D)(1) because it has a fusible disconnect. Ask yourself these questions: If one is not allowed to tap conductors to provide the connection to a fusible disconnect, then under what circumstances would anyone actually use a fusible disconnect? Doesn't the fact that the code includes a fusible disconnect as a means of connection imply that the method in question is valid?

I will take back what I said earlier about the unfairness of downsizing the breaker; I was overlooking the 30amp fuse rating for the PV system. Unless the feeders to the sub are rated greater than 108.3 amps, the installer should downsize the sub breaker if he can, and then I think it is fine.

 

[Rich D]

The tap is being made in the main service panel at at 100A breaker which feeds to the main lugs of a sub panel. What is the rating of the bus at the subpanel? If this is exceeded by the allowable 20% then the OCPD device for the PV system needs to be positioned at the opposite end of the bus bar as the feeder.
This is not a code compliant interconnect, unless there is an additional OCPD at the sub panel to protect the bus in that panel.

 

[jaggedben]

If this is exceeded by the allowable 20% then the OCPD device for the PV system needs to be positioned at the opposite end of the bus bar as the feeder. This is not a code compliant interconnect, unless there is an additional OCPD at the sub panel to protect the bus in that panel.

I think this is open to interpretation. 705.12(D)(7) refers to "a connection in a panelboard", which this is not. There are concerns about panelboard thermal loading that go beyond simple ampacity ratings. With that said, you're correct that the subpanel rating does matter.

This is not a code compliant interconnect, unless there is an additional OCPD at the sub panel to protect the bus in that panel.

..or unless the sub breaker is downsized. Supposing we agreed that that the sub rating must be 100% of the OCPDs, then the sub breaker would need to be downsized to 70A instead of 80 (assuming it is a 100A panel).

 

[jeffgreef]

The feeders are #2 aluminum SE cable. According to article 338 on SE cable, when used inside walls it must be rated at 60 degrees on 310.16. In which case, the feeders must be protected at 75 amps before the tap, with the tap and 120% the total amperage on the feeders can only be 90, minus the 30 for the PV, means the feeder breaker has to be 60 amps. Subpanel is rated at 100 amps, so protection of the busbars is no problem in this scenario.

Given this, does the load on the subpanel have to be calculated for the possibility of using too small an OCPD on the feeders? Does the NEC prevent you from using too small a breaker for a given load?

 

[jaggedben]

Given this, does the load on the subpanel have to be calculated for the possibility of using too small an OCPD on the feeders? Does the NEC prevent you from using too small a breaker for a given load?

I always assumed the answer to the second question was yes. If it is, then the answer to the first question is also yes. Don't know what clause of the code to quote though.

From what you've described I'd say the installation in question has some legitimate problems. The installer probably should have used a different method (such as installing a new subpanel to handle solar and some existing loads). The load-side tap method is still a valid method, but as with anything the conditions for it have to be correct.