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I need to replace my old panel now but I also have plans to add more circuits in the future. I suspect that I will need to upgrade my underground service from the current 100A to 200A in the next 5-10 years to accommodate the increased power demands of my future plans (hot tub, central air, etc.)

My question is simple. Can I buy a 200A rated loadcenter and swap the 200A main breaker for 100A to comply with CSA code (the main breaker can't exceed the maximum amperage of the service conductor - #2 aluminum btw)? This would allow me to install the original 200A breaker in the future once I finally upgrade the service conductor to 4/0 to allow me to draw 200A without having to buy another panel all over again.

If this is possible, which manufacturer/series panels support this "interchangeable main breaker" capability? (200A panels that can be downgraded to a 100A main breaker.)

Many thanks!!

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    I'll chip in the standard comment, even though you probably already know this since you're thinking this far ahead: Do NOT skimp out on spaces! You're already planning on upgrading the service in the future and the only reason you'd likely need that is because you'll be adding more circuits. Getting spaces now is cheap - replacing the whole panel in the future to get more spaces is much more expensive. – FreeMan Aug 8 '20 at 3:08
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You probably could do a breaker swap, assuming that a 100A breaker in the same case style as the 200A breaker could be found. I can't point to a manufacturer or product family, but I can at least say that Square D has decent drawings and technical specs available on their web site. Several of the drawings do indicate the case style of the main breaker, and some panels must be field-fitted with a main, so many of the drawings do include the information you'd be needing to match.

There are (at least) two other ways you could crack this nut. Supposing that your meter is located elsewhere, ie that you're not looking at meter-main combination type panels:

  1. Install the new 200A panel and a 100A panel also. Set it up so that the 100A is the main panel fed by the existing service and call the 200A panel a subpanel. Later, when you upgrade the underground service, remove the 100A panel and have the upgraded service connect directly to the 200A panel. There's nothing wrong with a subpanel being equipped with a main breaker that's rated higher than some upstream breaker. If you find a 100A panel with output lugs you could wire the subpanel feeder directly from those to the 200A panel; no branch circuit breaker needed.
  2. Install the new 200A panel with a 100A branch breaker rated for backfeed. Connect the service conductors to that branch breaker and mark it as the main breaker. Note: you'll probably be required to get a bolt-down bracket to retain the 100A breaker in the panel.
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    Manufacturer-wise: Eaton and Square-D have 100A breakers available in the 225A main frame size; notably, Siemens doesn't, and requires you to use a backfed 100A branch breaker as a main, instead, while GE has a "carrier" adapter used for 100A breakers in 225A main frame positions – ThreePhaseEel Aug 8 '20 at 2:35

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