We currently have a 100 amp main breaker box and need to add an outside disconnect to meet code requirements. We would like to use. 150 amp single pole disconnect since we plan to upgrade to 150 at a later date. Service company said existing line comings into house is only good for 100-110 amps, so need to know if there are any issues with using the 150 amp disconnect with the lower rated panel until we get the service line and main panel upgraded.

  • Usually using a larger rated disconnect is no problem. Doing all that work just for 50 extra amps, I might think of going to 200 amp service. It will depend on what you need/want but the cost should not be that much more to go big now, than to do it again in the future(this for the panel upgrade).
    – crip659
    Commented Jun 16, 2023 at 19:23
  • 3
    single pole disconnect? Really? Not double-pole? A single-pole disconnect would leave one of the hots live and any 120V loads on that hot would still be active so neutral would be live too. What jurisdiction? Unusual for code requirement of an outside disconnect to kick in unless/until you do a panel or service line upgrade. Commented Jun 16, 2023 at 19:24
  • Sounds like we need to go with the double-pole. It is a small cabin in Park County, Co. State inspector said we need outside disconnect for fire department at the meter since main breaker box is inside.
    – Fleet
    Commented Jun 17, 2023 at 4:29

1 Answer 1


Futile, since everything will need to be upgraded to go 150A. Including service entrance wires in and out of the meter and to the old main.

I agree, I've never heard of a 150A single-pole disconnect. Note that the cheap Alibaba crud found on eBay and Amazon Marketplace are unsafe and illegal, and will result in inspection failure and the power company refusing to energize it.

I would actually "lean in" to the bigger amps thing and instead of a disconnect, use a 200A panel with some breaker spaces at the meter. Make one of them a 100A breaker feeding the old panel. Now you don't need to replace the old panel. That's $2000 you never need to spend :) And when you upgrade service later, big stuff can go in the 200A panel.

  • Interesting idea on adding the panel to the outside. Existing 100 amp panel is inside and is a zinsco panel that works fine, but has recall issues. My understanding is that it is ok to leave in unless we “upgrade” and at that point they will probably make us replace it.
    – Fleet
    Commented Jun 17, 2023 at 4:38
  • @Fleet -- zinsco panels do not "work fine", they just look OK on the surface. Commented Jun 17, 2023 at 4:54
  • Lol ~ ok. I get your point. It probably just makes sense to get the service company out here and upgrade the service line, add the outside disconnect and replace the zinsco panel all at once. I was just hoping to get the minimum done for the short term.
    – Fleet
    Commented Jun 17, 2023 at 5:10
  • So just confirming - if we move the new panel to the outside of the house next to the meter we don’t need to add a disconnect? The main on the breaker panel acts as the emergency shutoff?
    – Fleet
    Commented Jun 17, 2023 at 15:16
  • @Fleet right. I'm not a super-fan of putting most breakers outside, since the weather is not kind to AFCI, GFCI and the "smart" breakers I'm expecting to see come down the pike. But the Zinsco has gotta go, to be sure. An outside panel or disconnect would make that possible to DIY. Commented Jun 17, 2023 at 16:55

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