AERCO SWDW68 U-Tube Double-Wall Heaters w/ECS - Manual (Page 53)

HE-
111 − TROUBLESHOOTING
Rev B Mar 2013 7-11
Table 7-3. TROUBLESHOOTING – ELECTRONIC CONTROL SYSTEM, continued
NO. FAULT INDICATION PROBABLE CAUSE CORRECTIVE ACTION
T20 Outlet water temperature is
far below setpoint
1. Incorrect Temperature
Controller setting
2. Defective Temperature
Controller.
3. Linkage not properly
connected.
4. Defective Actuator.
5. Control Valve shaft may be
binding
1. Refer to Chapter 4 and check the current setting of the Over-
temperature Switch. Readjust as necessary.
2. Disconnect the cable plug from the Valve Actuator and verify that the
Temperature Controller is generating a control signal greater than
4 mA. If not, replace the Temperature. Controller.
3. Check the Control Valve linkage to verify that it is properly connected
and that the pin in the linkage is in the correct position for the
selected Valve size.
4. Replace the Valve Actuator.
5. Refer to Table 7-2, Fault T12, Corrective Action 2c and perform the
indicated action.
T21 Wide fluctuations occur in Hot
Water Output water
temperature during large flow
changes.
1. Heat exchanger recirculation
pump is not operating.
2. Over-temperature Switch
setting is too low.
3. Over-temperature Solenoid
Valve is leaking or open.
1. Check the power to the recirculation pump.
2. Refer to Chapter 4 and check the current setting of the Over-
temperature Switch. Readjust as necessary.
3. Inspect the solenoid valve for evidence of leaks. If leaks are
detected, replace the solenoid valve.
T22 Wide fluctuations occur in Hot
Water Output water
temperature under low flow
conditions.
1. DHW Outlet Temperature
Sensor connected to the
Temperature Controller is
intermittent.
2. Mixed water temperature
sensor is open, shorted or
gives inconsistent readings.
3. Recirculation pump has failed
1. Replace DHW Outlet Temperature Sensor at the heat exchanger Hot
Water Output port.
2. Replace mixed water temperature sensor.
3. Replace recirculation pump.
T23 Hot Water Output
temperature above over-
temperature limit, but
solenoid (Dump) valve does
not open. 1. Disconnected or defective
solenoid
2. Defective Over-temperature
Switch
3. Solenoid valve wiring is loose
or reversed.
1. Verify that 24 VDC is present at the solenoid plug between leads
103(+) and 104 (-).
If voltage is present and the solenoid is connected, replace the
solenoid. If 24 VDC is not present, proceed to Item 2, below.
2. Replace Over-Temperature Switch.
3. Verify that solenoid valve wiring is secure and connected per
Figure B-1.