I am currently running my 3.5 ton Payne Central AC unit from a sub box that is feed by #6 wire straight from the main panel. The sub box is using a 40 amp breaker for the AC with a 50 amp breaker at the main panel. My question; can I add my 40 gallon electrical hot water heater (4500 watts) to the sub box and add a 30 amp breaker in the sub box for it? I know you would have to allow for a start up surge on the AC. Would the sub box handle both units? Thank you!

What is the A/C unit rated at?
Is there electric heat involved?

A 40A circuit seems big for only a 3.5T unit.

What is the A/C unit rated at?
Is there electric heat involved?

A 40A circuit seems big for only a 3.5T unit.

The specification tag on the back of the unit states:

LRA: 102.0

RLA: 19.2

I assume the former is related to startup and the latter associated with running amperage? The unit is only for Air Conditioning. There is no heat pump as I use a gas furnace with a 110 v. blower. I hope this info is helpful.

Does your A/C show the "FLA" value? Also what is the min and max values for the fuses or breakers?

The feeder to the loadcenter from the main service loadcenter is 50 Amps, correct?

What is the amperage require by the water hearer X 125%? Water heaters are a continuous" load and must have there amperage multiplied by 1.25 to make sure the conductors are sized correctly.