Newer HVAC units are much more energy efficient than older. Not as much power is needed for newer air conditioners to function normally, this saves building owners money.When HVAC technicians install new air conditioners, seldom do they look at the circuit breaker or fuse rating in the sub panel or service panel protecting the new HVAC unit.New HVAC units have a minimum and maximum ampere rating on the data tag. If the maximum rating is 40 amperes, a 50 ampere breaker or fuse is not better, actually it’s a potential detriment.Facility managers and property owners should make sure the circuit breakers or fuses in older electrical panels are within the minimum and maximum rating of the over-current protection stated on the data tag of new equipment.In Arizona we inspect air conditioners, the over-current protection, and all components associated with conditioning commercial buildings and residential homes.

Source: Commercial Building HVAC Over-Current Protection | NACBI Community Forum