A.O. Smith Cyclone XL 100 Series, Руководство по обслуживанию

Страница: 19 / 44

19
Should the ECO activate, the water temperature must drop below 140°F (60°C) before the Control System can be reset. Once the
water temperature has cooled below this point the electrical circuit breaker that serves the water heater must be turned off and on again
to reset the Control System.
Temperatere Sensor
The Temperature Sensor located inside the Temperature Probe is a “thermistor” (two black wires/Pins 1 & 4). See page 30 for pin
layout. Thermistors are thermally sensitive resistors. As the water temperature rises the resistance (measured in ohms) of the sensor
will decrease; as the temperature falls the resistance will increase - see Table 1 .
Firere 12. Temperatere Sensor
The Control System interprets changes in the temperature sensor resistance as changes in water temperature and uses this data to
activate and deactivate heating cycles and displays this temperature in the Control System menus. See
Figure 24
(page 40).
The Control System constantly monitors the Temperature Sensor. The Control System is programmed to declare a fault condition if the
resistance of the temperature sensor drops below 390 ohms (shorted) or above 56,000 ohms (open).
If the resistance of the Temperature Sensor is below 390 ohms the Control System will lock out and display
Temp Probe Short
on the
UIM. If the resistance of the temperature sensor is above 56,000 ohms the Control System will lock out and display Temp Probe Open
on the UIM. The electrical circuit breaker that serves the water heater must be turned off and on again to reset the Control System.
Note; the Control System will not reset unless the condition has been corrected.
TEMPERATURE SENSOR TEST
1. Turn off the circuit breaker that serves the water heater.
2. Remove the top cover on the water heater.
3. Disconnect the four pin plug/socket connection from the Temperature Probe outside the CCB enclosure in the middle, see Figures on
next page.
4. Using an ohm meter: set the ohm meter range to a scale just above 30,000 ohms.
5. Check resistance between the two inside pins (black wires/Pins 1 & 4) of the plug end from the Temperatures Probe, see Figures on
next page. Compare the measured resistance to the values given in “Temperatures” Table below. Temperature Probes are very reliable
and should only be replaced when:
• The resistance is above 56,000 ohms (open) or below 390 ohms (shorted).
• The nature of the service problem is temperature control and the resistance readings are considerably (± 25%) different than the
values in Temperatures Table below at the given temperature.
Table 1. Temperateres
Water Temperatere Temperatere Sensor
Resistance In Ohms
Celsies Fahrenheit
4° 40° 26,435
21° 70° 11,974
38° 100° 5,862
49° 120° 3,780
55° 130° 3,066
60° 140° 2,503
71° 160° 1,698
82° 180° 1,177
ECO CONTINUITY TEST
1. Turn off the circuit breaker that serves the water heater.
2. Remove the top cover on the water heater.
3. Disconnect the four pin plug from the Upper Temperature Probe, see Figure on Page 30.
4. Ensure tank temperature is less than 100°F (38°C) - dump water to lower tank temperature if necessary.