A.O. Smith TC-049R3 Service Handbook page 53

RESIDENTIAL GAS AND ELECTRIC WATER HEATER
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
A-7 wiring circuit) for time clocks or "off peak meters", you may save on monthly operating
costs.
Rated
Voltage
600
120 23.2
208 72.1
240 92.8
277 128
Rated
Voltage
3000
120 4.64
208 14.4
240 18.6
277 25.6
480 76.8
A.O. Smith Water Products Company
©2005
SERVICE HANDBOOK
Element with Links
Resistance of Element in Ohms (± 7.5%)
750 1000
18.6 13.9
57.7 43.3
74.3 55.7
102 76.7
3500 4000
12.4 10.8
15.9 13.9
21.9 19.2
65.7 57.5
Rated Wattage
1250 1500
11.1 9.28
34.6 28.8
44.6 37.1
61.4 51.2
Rated Wattage
4500 5000
9.61 8.65
12.4 11.1
17.1 15.3
51.1 45.7
Technical Training Department
52
2000 2500
6.96 5.57
21.6 17.3
27.8 22.3
38.4 30.7
5500 6000
7.85* 7.2
10.1* 9.28
14.0 12.8
41.8 38.4
Ashland City, TN