DXR Drainback
Page 23
TROUBLESHOOTING GUIDE
The homeowner will know that the solar system is operating if both pumps are running and the water level in the
sight glass is at the marked running level. This indicates that the pump has pumped the water from the reservoir
through the collectors.
Problems with systems usually fall under two categories: system leaks or lack of sufficient solar heated water.
LEAKS
If leaks exist, the system should be shut down for repair. Make sure the electrical circuit to the controller is
unplugged. Close off the cold water inlet to isolate the solar system, until a suitable repair can be made.
There is a possibility that what may appear to be leaks may be condensation on the pipes. Also, water escaping from
the T&P relief valve, on the water heater, may be an indication of proper function as they are designed to vent off
excess temperature and pressure. Discharge from the T&P relief valve can happen, but it should be checked if it
happens frequently.
INSUFFICIENT HOT WATER
If insufficient hot water is available, a system malfunction may not be indicated. A low amount of solar radiation or
heavy water demand can be the cause. If no excessive demands are put on the system and ample solar radiation is
available, the system should operate properly. The pump should run each sunny day until a full supply of hot water
is stored. If the pump does not run, there is a problem on the electrical end of the system. Either, the pump,
controller, or sensors may be malfunctioning. The controller can be bypassed by running a power cable directly to
the pump and checking its function separate from the control system. Make sure that the problem is not a blown
fuse or a tripped breaker or GFI outlet. If the pump runs normally when powered externally, the control circuit is
the problem area.
Differential controllers use thermistor sensors to determine modes of operation. To verify proper sensor operation,
refer to the Temperature vs Resistance Conversion Chart for 10k Thermistors included in the controller installation
manual. Check sensor wiring. If no faulty wiring can be discovered, replace the sensors.
If the pump is running all the time, even when the collectors are cool, then the storage sensor or collector sensor may
be open. It is also possible that the sensor wire itself is at fault. To check this, service personnel should test the
continuity with an ohm meter. Be sure to disconnect the sensor when performing this test. Test the wire with both
ends open, then retest after twisting the 2 sensor wires together at one end. The system can be set on a timer or
switched on manually until the controller is properly functioning.
SYSTEM TROUBLESHOOTING AND OPERATIONAL CHECK
The system can be checked to determine that it is operating by noting the temperature difference between the
collector feed and collector return lines. The return line should be hotter than the feed line. In addition, the owner
should periodically check the drainback reservoir sight glass to make sure that there is sufficient water in the
drainback reservoir.
