I am trying to find some guidance on the following: I have a customer who will be moving a small chiropractic business into a building that has two apartments on the second floor, and office space on the first. The main service is 200 amp, single phase, 3 wire. There is one subpanel for an apartment that has a 50 amp disconnect (breaker), one has a 30 amp disconnect (two 30 amp fuses in parrallel) and finally the panel my customer will be using is a 100 amp disconnect. She needs to have a 60 amp two pole breaker added for an x ray machine. My question...can I safely and legally upgrade her panel to 150 amp disconnect? I cannot find any clear guidance in the NEC.
Upgrading a subpanel
- Thread starter GeorgeW
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- Chapel Hill, NC
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- Retired Electrical Contractor
You can upgrade all you want as long as the total load does not exceed 200 amps. You need to calculate the loads.
tryinghard
Senior Member
- Location
- California
You should calculate the load see Article 220 and examples in the Annex. The breaker amperes don?t play a role in feeder/service size, the calculated load does. The calculated load qualifies the ampere size for service, feeder, & distribution.
You can install a larger ampere panel or service and under-serve or supply it. Many installations need breaker quantity and lower ampere subpanels are limited with low quantity spaces.
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