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The first electrician who installed the 200 amp panel didn't want to connect the 2 stage HVAC, so only connected 1 stage. However, now the heating hasn't been able to keep up in winter. The new electrician seems to think he can hook up the second stage without tripping the panel and the main breaker. Let me know if this is incorrect?

Our licensed electrician installed a 200amp subpanel in a condo off of a 150 amp building main breaker panel. Is there any issue with this? I tried looking in article 220 of the NEC, but haven't found anything yet.

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    Having a bigger panel than the feed breaker is okay. The price difference between the big panel and a smaller panel is quite low. The problem seems to be if the heating circuit is close or more than the 150 amp breaker can deliver/handle along with the rest of the electric needs of the condo. A load calculation should/will need to be done.
    – crip659
    Oct 20, 2023 at 12:52
  • Welcome. If you take the site tour you will find it says each post should be a single question. For that this question will likely get "closed". Really if you formatted or even titled it differently you might not trigger this event, your title really misses the central question. I'll take some liberty here to help this survive and change the title, and swap the paragraphs. Oct 20, 2023 at 13:46

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Your service is limited by that 150A main breaker, it won't allow items connected to subpanel to draw more than 150A. 150A is generally quite adequate for most condos, the minimum legal size of your service is determined by an intimidating formula called a "load calc". For a single family residence it isn't that hard, but the typical licensing exam has a section that makes you calculate some multifamily unit with odd configurations and many electricians freak out. Often people don't actually use near the capacity determined by this formula. The electrician who didn't want to hook up 2nd stage likely didn't want to try to calculate the legal load. It would be good for your current electrician to do the calc, it may just put the issue to bed.

Subpanels are kind of like tires, putting 200+ mph tires on a Mustang won't make it go any faster, but if you can buy them for less than 130 mph rated tires then go for it. 200A panels are often cheaper than 150A and usually larger making circuit terminations easier, but the main breaker at the service limits the current to 150A.

All that being said if you are supplementing your heat pump with electric resistive heat you are likely adding more load on your panels than connecting 2nd stage, kind of a Catch 22. It may not be legal to connect the heat pump, but it may result in lower power consumption. What do you do?

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    I get the feeling that the second stage is a big toaster. First did not connect it, the second is hoping it does not trip the main.
    – crip659
    Oct 20, 2023 at 13:35
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    @crip659 I did contemplate that the OP could mean Aux Heat, which would be a bigger issue, but decided it didn't really change my answer so I let it go. Oct 20, 2023 at 13:41

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