No, not really. The two hot legs can be opposite legs of a 120/240 V split phase power source. You still do need a protective earth ground, however, but the heater itself does not require a grounded neutral to run.
A stove, dryer, water heater, furnace, heat pump.
Any ground wire has to be connected to an independent ground wire that returns directly to the distribution panel and not to the neutral of the circuit.
VOLTS x (VOLTS/OHMS) = WATTS 240 X (240/8) = 7200 Watts = 7.2KWatts
yes and and no but you need to know how many amps the heater uses and how many amps the relay can with stand..
This will pull 20 Amps continuous so you will need a 30 A breaker and 10 AWG wire. You would have Black, Red, White and Ground. The 240 V would be on the black and red connected to the output from a two pole 240 A breaker. White would be neutral and green or bare wire would be ground.
no
20 amp
No. A water heater requires a 240 volt connection and cannot be re-wired to run on 120 volts. There isn't enough amperage in 120 volts to power the heating rods that are inside.
In the USA houses would have 120/240 volts. 120 volts at most receptacles and lights and 240 volts for larger equipment like your stove, dryer, hot 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.
In North America 240 volts.
The power rating and voltage for the pump will determine the size branch necessary to supply the power to the load and the over-current protection.For instance, a 1 hp pump would be 746 watts. At 240 volts, that would be a little more than 3 amps, when operating, and possible 10 amps during the first half-second when it starts up.