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8 lut 2024 · Residential water heaters require a 240-volt dedicated 30-amp circuit and a 10 AWG wire size. The 30 amp breaker only powers the water heater and no other appliances. A 30-amp circuit breaker can power all 4500-watt water heaters regardless of gallon size.
15 sie 2016 · This can be done -- the subpanel still has load to spare, albeit only by an amp. Since you have a 100A service, I can use the simplified calculations from 220.84, which give you 3VA/ft^2 for the house, 1500VA per Small Appliance Branch Circuit (kitchen/laundry), and the fixed appliances at nameplate rating (it sounds like you have none though ...
14 lut 2018 · No problem. If you really want the 40 amp breaker check the wire size going to your 30 amp breaker (see above advice from ratchet freak: "you will need to know the gauge of the wire all the way from the breaker to the heater.") If it is #10 wire you'd have to re-wire with #8.
30 amp wire = 30A x 100% / 80% = 37.5A ampacity. So, with 37.5A ampacity, an 8 AWG wire after 10 AWG wire will perfectly fit 30 amps. The 310-16 code suggests adding an extra 20% of the wire’s ampacity for 30 amps every time the distance increases to 100 feet.
For a 40-gallon electric water heater, the wire size typically required is 10-gauge copper wire, which can safely handle a 30-amp circuit. However, always consult the water heater’s user manual for the manufacturer’s specific recommendations and adhere to local electrical codes.
For 30 amp service 100 feet away you would need a wire that can handle at least 45 amps. Luckily, the #8 AWG wire has a 50A ampacity. You can use the #8 AWG wire for sub panel 50 feet, 100 feet, and even 150 feet away.
That’s the right choice for 30-gallon, 40-gallon, 50-gallon, 60-gallon, 70-gallon, and 80-gallon electric water heaters as you will see in the all-encompassing chart below. You could also go with thicker 12 AWG or 10 AWG wires but that’s overkill.
