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Supply side solar max disconnect/OCPD rating? I can only find minimum rating

Supply side solar max disconnect/OCPD rating? I can only find minimum rating


Old 07-04-19, 09:33 PM
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Supply side solar max disconnect/OCPD rating? I can only find minimum rating

Maybe I havent found it in the books or online yet, but I am looking for what the maximum disconnect/OCPD that would go on the supply side (between meter and main) for the use of solar is. The goal is to get away from / not have to consider the 120% rule at all and a whole new service is being put in and and really the only thing I can find is the 60A minimum listed in 230.79(D).

Siemens has a bunch of solar ready panels that have provisions for a 60A or 100A disconnect for solar purposes, MC0816S1200SCT or similar. The problem is that this panel isnt in the Duke/MEG approved equipment list and I would HIGHLY prefer a CSED that has feedthru lugs like the previous model number listed. MEG has an approval for a larger panel that doesnt have feed thru lugs.

The goal for components involved / how things would be connected for the ideal layout illustrated below. Main for the CSED panel is 200A, meter is 200A, inside panel and ATS are both 200A.

The problem now becomes that since I cant use that panel I either have to use a larger panel which has a lot more spaces that I am not going to use, add a 200A breaker between the service disconnect and ATS, or some other option.

Trudging through to find other solutions I found some 400A CSEDs, namely MC0816B1400RLTM, which is on the MEG list and going from 200A to 400A from duke for my project is only an extra $200 (I need to get clarification from Duke on this because on my quote its listed as a changout and I requested thicker wire so if I wanted to go 400A in the future I could, but I dont know if that included a 400A meter or if it was literally just the wire cost.) and leads me to the purpose of this post. While this CSED is essentially the exact same as the solar ready one I want, except instead of a QP style that is limited to 60A as the side for the solar, it is QN which can be 150-200A. The difference between both solar ready CSEDs and the 400A is also around $200, bringing the total to about $400 extra, but in reality the 400A would have greater flexibility in allowing me being able to use the solar 200A for anything instead of just solar if I should need to build an addition or something.

Another reason for a CSED other than moving some non-gen loads is to get the SPD connected as close to the meter as possible, especially since its not some small surge protector: SSP01EMA12

For now until I get confirmation from Duke on if paying the extra $200 to them upgrades the service as well, lets assume its a 200A meter / service.

Other less desirable solutions are separating the meter from the panel, over-rating the bus (200a OCPD on a 400A panel, which those arent cheap and I really dont want to upgrade the panel.)

Thoughts on this one? There was one place that I read on using a ranch panel (400a with 2 200a mains to go to 2 separate panels, basically what I am doing) and using 1 as a solar disconnect, however cant find it anymore, but I guess thats essentially what I would be doing, but this option would mean that I wouldnt be moving my non-generator loads from the inside panel to the outside panel. For the curious, MM0404L1400RLM which is actually only about $70 more than the solar ready one instead of $200.

Another tidbit: my OCD kills me on having snap in breakers for high amperages. My go-to panel of choice are bolt on style like NQ or NF panels where everything is bolt on including branch circuits. Ive seen enough loose bus side connections to form the opinion that all springs weaken over time. But I guess I cant have it all in the residential world.
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Old 07-08-19, 05:43 AM
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I'm not aware of a maximum OCPD in this situation, but it would generally be sized to reasonably match the system you're installing. The other options seem OK to me too, and you appear to have a good understanding of the trade-offs with each of those.

When using plug-on breakers in a "backfeed" arrangement, you have you install hold-down clips anyway. These are a small kit you can order with the breaker that has a clip and a metal screw to secure the breaker to the panel much like a bolt-on. There's no reason you can't use them for any breaker if you want.
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