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I believe this is the model number for my main panel: RC12L200C.

The breaker box is rated for 200 amp and lives under the meter, it feeds a 100 amp sub panel and three 240v circuits for appliances. They total up to 175 Amp. However, it does not seems to have a main disconnect.

My questions are:

  1. Am I able to install a 200 amp main breaker to the panel so I can turn it off?
  2. Assuming I must have the 200 amp breaker installed before I can feed another subpanel which would make it exceed the 200 amp rating, otherwise I'm limited with a 25A circuit, correct? or does the meter have a 200 amp breaker inside?

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    What are you trying to power? If it's an EV, you can't always get whatcha want, but if you try, sometimes you just might find you get what you need.
    – Harper - Reinstate Monica
    Mar 5 at 6:49
  • Nice reference, @Harper-ReinstateMonica!
    – FreeMan
    Mar 6 at 14:20
  • 2
    Please include a picture of your actual panel instead of something "similar" found on the internet. Often, the "something similar" isn't as similar as people think...
    – FreeMan
    Mar 6 at 14:21

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There is no breaker in the meter. You have a Rule of 6 panel. I double-checked in the Schneider Electric web site and the datasheet specifically says "INSTALL NO MORE THAN SIX BREAKERS", which is the tell-tale sign of a Rule of 6 panel. Without such a warning (e.g., the same panel section as a typical subpanel, except without the meter) could handle any combination of 6 double-breakers and/or 12 single breakers. The wiring diagram makes it quite clear that there is no way to slap in a main breaker.

Basically these date back to the time when breakers larger than 60A were very expensive. The idea is that you you would have a set of breakers for large devices (oven, dryer, water heater, HVAC) and one breaker for lighting/general receptacles. The total could be more than the service feed size, particularly if multiple subpanels are included, which is one of the problems with Rule of 6 panels. As far as I know, they are not allowed in new construction, and certainly not recommended.

In any case, you can't change that to have a true main breaker without replacing this entire panel. As far as how much you can add to this panel (based on the description you have two available spaces for double-breakers), that will depend on a load calculation, primarily dependent on what is handled by the 100A breaker as the other 3 breakers are likely rated at or close to their actual usage (or 125% derate thereof).

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Wow, they still sell that? Rule of Six panels have been illegal for decades.

Well, to be more precise... oversubscribing Rule of Six panels (the load breakers add up to more than 200A) have been illegal. Today the sum of load breakers must <=200A.

It specifically says "install no more than 6 breakers" so yeah. Rule of Six.

I can actually see a reason for such a panel today, with more and more spaces being filled with non-loads. You could fill it with a surge suppressor, three solar breakers adding up to 200A, and a 200A breaker going onward to loads. That would be a legal setup allowing 200A of solar.

Sorry. Back to your question, no, the docs on this unit do not indicate that a 200A main breaker can be retrofitted.

You'll either need to keep the other sub <=25A, or fork the 100A going to the existing sub (so the two subpanels share the breaker), or move some loads into one of the subpanels.

Remember, surge suppressors and solar are not loads.

For what it's worth, some people illegally wire 100A feeders with #4 copper (85A) or #2 aluminum (90A) wire. If that was done, you must down-breaker to 90A (since 85A breakers are not made). That will mean you actually have 35A or 40A of headroom in the panel.

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Harper briefly mentioned "a 200A breaker going onward to loads," but I thought the idea deserved a little more attention.

It appears you could install an HOM2200B or HOM2200 200-amp circuit breaker. This breaker could then feed a new subpanel with lots of spaces. (photo: amazon.com)

HOM2200B circuit breaker

A few notes:

  • Check the labeling in your panel to be sure a 200 amp branch breaker is allowed. There may be a specific position where it must be installed.
  • All other breakers in this panel would have to be moved to the new subpanel.
  • The subpanel, being protected by this single 200-amp breaker, would qualify to hold more than a sum of 200 amps of breakers.
  • The HOM2200 does not come cheap -- I'd strongly prefer to spend the money on replacing the RC12L200C panel. But when you consider the job as a whole, and the work required to replace the RC12L200C, maybe the path suggested here will make some sense.
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