RESIDENTIAL GAS AND ELECTRIC WATER HEATER
SERVICE HANDBOOK
Miscellaneous Residential Electric Water Heater Service Items:
•Watts divided by Volts = Amps
Supply wire gauge and fuse (breaker) protection must be at least 125% of the expected Amperage draw of the water heater.
•Volts times Amps = Watts
Replace elements with elements rated at the same wattage and voltage indicated on the heater model and rating plate. Installing an element with a higher voltage rating or wattage output may create a safety hazard by overloading the heater wiring or supply wiring or fusing. Installing an element with a lower wattage or voltage rating will reduce performance.
•Normally, a residential electric water heater with two elements will have only one element operate at a time. If the upper element or thermostat fails, the customer will be out of hot water. If the lower element or thermostat fails, the customer should still have 1/3 of the tank with hot water.
•With two element heaters, the lower element and thermostat will cycle more frequently than the upper element and thermostat. For this reason, the lower element will normally accumulate lime faster and fail more often than the upper element. Lower thermostats will fail more often than upper thermostats.
•Replacement elements:
Replace elements with an element having the most surface area (low watt density) available for your water heater. By spreading the heat of the element over a greater area, lime (calcium) buildup rate should be reduced.
Elements constructed of Incoloy are much more durable than elements made of copper with zinc coating.
•Many electric utilities offer discounts if you do not use electricity during certain times of the day. Contact them – by purchasing a larger storage water heater, with special wiring (see
Element with Links
Resistance of Element in Ohms (± 7.5%)
Rated |
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| Rated Wattage |
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Voltage | 600 | 750 | 1000 |
| 1250 |
| 1500 | 2000 | 2500 |
120 | 23.2 | 18.6 | 13.9 |
| 11.1 |
| 9.28 | 6.96 | 5.57 |
208 | 72.1 | 57.7 | 43.3 |
| 34.6 |
| 28.8 | 21.6 | 17.3 |
240 | 92.8 | 74.3 | 55.7 |
| 44.6 |
| 37.1 | 27.8 | 22.3 |
277 | 128 | 102 | 76.7 |
| 61.4 |
| 51.2 | 38.4 | 30.7 |
| Rated |
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| Rated Wattage |
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| Voltage | 3000 | 3500 | 4000 |
| 4500 |
| 5000 | 5500 | 6000 |
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| 120 | 4.64 |
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| 208 | 14.4 | 12.4 | 10.8 |
| 9.61 |
| 8.65 | 7.85* | 7.2 |
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| 240 | 18.6 | 15.9 | 13.9 |
| 12.4 |
| 11.1 | 10.1* | 9.28 |
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| 277 | 25.6 | 21.9 | 19.2 |
| 17.1 |
| 15.3 | 14.0 | 12.8 |
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| 480 | 76.8 | 65.7 | 57.5 |
| 51.1 |
| 45.7 | 41.8 | 38.4 |
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| A.O. Smith Water Products Company |
| 45 |
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| Training Department |
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| ©2002 |
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| Ashland City, Tennessee |
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