Installing Water heater (existing wiring)


Old 04-15-08, 06:01 PM
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Installing Water heater (existing wiring)


My family just moved into a place an the water heater was a bit small for us (30gal probably because it was older and had problems). I have a 40gal heater that I took out of the place we moved from (yes it was mine lol).

Now the old location (where I originally had this 40gal heater) had existing wiring for it (2-20amp breakers) and the wire was 10 gauge.

The new location also has existing wiring of a heater (2-20amp breakers) but the wire is 12 gauge.

Is this ok?

The heater is a Reliance 6-40-DORT (4500watt upper and lower heating lements).

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Old 04-15-08, 06:44 PM
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You will probably find the water heater operates off a 30 amp breaker (double) for 240 volts. That being the case, you will need to run 10-2 to the location.
Old 04-15-08, 06:58 PM
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I'll have to recheck my original breakers, but I am pretty sure it was 2-20amps.
Why don't the stupid manuals mention the requirements?

Old 04-15-08, 07:43 PM
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If my calculations are right (I'm a little rusty), this heater has TWO 4500 watt elements running on 240v so:

9000 watts / 240 volts = 37.5amps
Old 04-15-08, 08:50 PM
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Typically though, both elements aren't on at once.The top portion of the tank heats, then the lower.
Old 04-16-08, 12:24 AM
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Electric water heaters are almost always wired for non-simultaneous operation.

However, the NEC requires that water heaters be considered a continuous and therefore the circuit powering the water heater must be designed for 125% of the applied load.

A 4500 watt heater draws 18.75 amperes and multiplying that by 125% equals 23.44 amperes. Since the NEC requires #14, #12 and #10 wire to be protected to 15, 20 and 30 amperes respectively it is clear that a 4500watt water heater requires number 10 wire and either a 25 or 30 ampere circuit breaker or fuse.

HOWEVER, if the heater in question WAS wired for simultaneous operation of the upper and lower elements then the circuit would require a circuit rated at no less than 46.88 amperes and that would require #8 wire and a fifty ampere circuit breaker or fuse PROVIDING that the connections, wire and circuit breaker are all rated for operation at 75 degrees C.
Old 04-16-08, 12:40 AM
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Majorty of resdentail water heaters are non simultaneous operation and i will just say a hand full are simultaneous operation.

however with 4500 watt heating element @ 240 v you will run 18.75 amps but however if run in diffrent voltage like 230 or 208 [ not change the element size ] the amparage will drop some.

anyway let stick with the 240 figures [ this is most common voltage ]and you can run with #10 wire size [ NM or THHN/THWN if in area that reqired conduit ]

you can use 25 amp two pole breaker or 30 amp [ 30 amp two pole breaker is more common to find in most big box store ]

but however there is a " overlooked " code that if you installed the waterheater and not in line of sight to the breaker box like example water heater in diffrent room or dived wall or diffrent floor.,, then you need a disconnect switch to safisfay the code requirement most common methold is

1] use the A/C pullout disconnect switch [ or non fused disconnected lever switch ]

2] use double pole switch in 4X4X1 1/2 rasised single toggle cover

those two methold is most common to meet the code


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