New Water heaters and singing circuit boxes...

a reply to: butcherguy

beats me,

Wire a hot water heater with wire that's sized to accommodate the heater's current requirement. For example, a 20-amp hot water heater needs 12-gauge wire, a 25-amp hot water heater requires 10-gauge wire, and a 30- to 40-amp hot water heater requires 8-gauge wire. Some large heaters draw up to 50 amps, requiring 6-gauge wire.
www.hunker.com...

A water heater of this type is required to be considered a continuous load meaning that the branch circuit needs to be calculated at 125% of the heater's rated ampacity. 4500/240 = 18.75 amps, will work on a 20 amp OCPD but, 18.75*125% = 23.4 amps, requires a 25 or 30 amp circuit
www.hunker.com...

we think it's a 12 guage wire, which would have gone with the 20amp breaker that was in in... but there's that 125% bit in there that made the 30 amp required....
the water heater itself is a 20 amp?

a reply to: dawnstar

If you have a 30 amp breaker, the wire going from it to the appliance should be a minimum of 10 awg, to satisfy the requirements of the national electrical code, no matter what the appliance minimum ampacity is.