20 amp is perfect, 15 is fine
The wattage of the water tank is needed to size the breaker and the wire to feed the tank.
The wire size is dependent upon the wattage size of your water heater. The higher the wattage the larger the wire size. A standard 3000 watt heater will use a two pole 20 amp breaker connected to 2C #12 wire.
Yes the wire size is larger for that size breaker but will not effect the 30 amp breaker protection of that circuit.
To answer this question the wattage of the heater is needed.
15 amp
The wattage of the water tank is needed to size the breaker and the wire to feed the tank.
10/3 wire with 30 amp double pole breaker from panel box to water heater.
Assuming you are referring to a 240 volt residential hot water heater you will need to install 10/2 NM cable (Romex) with ground from the service panel to the water heater wired to a 30 amp circuit breaker in the service panel. If you cannot see the water heater from the service panel you will need to install a service disconnect at the water heater.
Usually 30 amp
The wire size is dependent upon the wattage size of your water heater. The higher the wattage the larger the wire size. A standard 3000 watt heater will use a two pole 20 amp breaker connected to 2C #12 wire.
Yes the wire size is larger for that size breaker but will not effect the 30 amp breaker protection of that circuit.
32amp 30ma rcbo
To answer this question the wattage of the heater is needed.
15 amp
Look on the heater and see what amps it is pulling. That will determine the wire size and breaker size. It must be on a dedicated circuit. 15 amps = AWG # 14 wire with 15 amp breaker 20 amps = AWG # 12 wire with 20 amp breaker 30 amps = AWG # 10 wire with 30 amp breaker 40 amps = AWG # 8 wire with 40 amp breaker
20 amp
The formula you are looking for is I = W/E.