- Location
- Seattle, WA

- Occupation
- Electrical Engineer

- Existing installation: A 400 amp breaker and 500 MCM conductors provide power to an old rooftop HVAC unit that is about to be replaced.
- The new HVAC unit has an MCA of 152 amps and an MOCP of 175 amps. The manufacturer recommends dual element 175 amp fuses.
- New installation: We will retain the 400 amp breaker and 500 MCM conductors, install a new disconnect switch with the recommended fuses.
- Question: Does the disconnect switch have to be rated at 400 amps, given the upstream OCPD is 400 amps, or can it be rated at 200 amps, given the downstream load is lower than 200 amps?

I could not find the answer in article 404 or 240, and I am allergic to article 430.