Backfeeding Main Breaker

[SCSE]

We're an installer in AR/OK working on a grid-tied job. We subcontract with a local licensed elec to do the bottom-side work. Work is similar to residential electrical work EXCEPT when we get to the line tap. That's always something new for them. We've never worked with this particular elec contractor before. At this job, the line side comes directly off meter into a 200A main breaker. There is a metal connector from the meter to this breaker. From load side of breaker, the wires leave this meter/brkr box and travel into the load center. I'm not sure if the LC has main breaker or not.

We've asked elec to line tap in the meter box downstream of the 200A breaker where there is room to do it. I'm getting pushback that we need to be on the line side of this breaker...but since it is a meter ring/breaker combo with a metal connector we can't attach on the top side. We're not in any electrical jurisdiction (no permit or inspection req'd), but when we install in places where we are inspected in AR, we've backfed through the main breaker. Case in point...the meter box on my house inside city limits of Little Rock where we did exactly that.

I understand the 120% rule as it applies to bus bars and breakers. Here we are backfeeding JUST through a 200A breaker. Googled it and everything found relates to 120% rule. Absent of any local jurisdiction rqmts, what is NEC say about backfeeding just through a breaker? We do it when we backfeed smaller systems directly into the load center. Why would this be any different...it's just a larger breaker.

Looking for some kind of guidance to get this elec off my back and just finish the job.

Sorry I would upload pics, but the upload attachments link here gives me an error.

[solarix]

Problem is that for the 20% backfeed rule to apply the backfeed point has to be at the end of the chain (bottom of the load center buss). If you inject the solar power in just after the main breaker, the 200amp utility power can add to the solar power and potentially melt the buss in the load center if more than 200amps of load happens. If the load center happens to have a main breaker in it, then you are safe except the code doesn't address this case. What you probably have to do is backfeed the bottom of the load center. btw, what size is the inverter?

[foo1bar]

I'm not sure if the LC has main breaker or not.

Fairly important question to be answered.

If there isn't, you could have 200A coming from the meter, 60A (or whatever your inverters can produce) coming from the tap, all going through the wire and bus to the load center.
And the wire between the meter/main breaker and the load center might be sized only for 200A, but it's carrying 260A. (which would be bad)

IF there's a main breaker on the load center then you can't have >200A going into the load center, and therefore you couldn't have >200A on the wire going to it. (So should be safe, but .)

If there isn't a main breaker on the load center, then possibly you add another panel in between the meter/200A breaker and the loadcenter. Something that has a 200A breaker for the downstream LC and an appropriately sized breaker for the inverters. (Then you know that you're going to be OK as far as current on any set of wires between breakers.)

I think this is a relevant article for what you're looking at:
https://iaeimagazine.org/magazine/fe...pliant-or-not/

[bob-n]

We're going to see many more installations like this in the future. This new style meter box with breaker is for NEC 2020 compliance.

I'm not an electrician and yield to experts on this subject. But from my vantage, the contractor's advice is bad practice. The meter box 200A breaker is there to protect from a fault past the box and so that the utility can completely disconnect stuff from the grid in an emergency. Tapping ahead of it defeats those purposes.

Yes, you have rapid shutdown and that will solve disconnect when the grid drops, but if the rapid shutdown fails or there is a wiring fault in the solar, you want that 200A breaker/disconnect to save you.

Rendundancy is unnecessary, until something goes wrong.

In addition, as you describe, the meter box is not engineered for tapping ahead of the breaker.

My suggestion is to contact Milbank or your preferred meter box manufacturer and get their suggestion, then bring that to the contractor.

[SCSE]

Thanks for the feedback. Total screw-up on my end. The LC does not have a main breaker just lugs and we need OCPD on the wires to it. The 200A breaker below the meter provides this protection (as well as service disconnect) and tapping after it potentially doubles the amps available to the load center without any OCPD. We'll put a new meter base in with a separate 200A main breaker box below it that will feed the LC. We'll tap between the new meter base and 200A brkr box.

If LC had a main breaker, we could have line tapped as I wanted. Without it, elec is correct we needed to do something different. This is old construction where I didn't pay close enough attention to existing electrical. Again, thanks all for the help.

[peakbagger]

FYI, the local utility got upset when folks were doing line side taps in the actual utility meter boxes. There was room to do it but the utility argued that they did not want any other source outside of their control in the meter box. They insist the tap be made in separate box downstream of the meter box. Reportedly several solar installers had to go back and revise their taps.

[PVAndy]

As others have suggested, either add a 200A main in the Main Lug Only (MLO) panel or add an inline 200A breaker. Do a supply side connection between the 2 breakers with a fused disconnect.
Pretty much all utilities will not allow any connections in meter cans or CT cabinets. You can tap in the breaker portion of the meter can if it has a partition between it and the meter.

Andy

[inetdog]

If you are upstream of the Service OCPD you have a line side connection and the only limit is that the PV power cannot exceed the rating of the service from POCO.
If you are downstream but not at the end of the bus you can either use the 100% rule on the sum of the load breakers or the 100% rule of the sum of main breaker and PV not to exceed the bus ampacity.
I have seen pictures of a meter-main combo butchered by a solar installer by cutting and bending the bus connection between meter and main breaker. and bolting to drilled holes in both stub ends to make a line side connection, This is not cool!!!