User Manual
35
PROBLEM CHECK THIS POSSIBLE CAUSE CORRECTIVE ACTION
Not enough hot water (cont.) Differential Controller Improper wiring or loose 
connections)
Compare with system 
schematic. Check for proper 
connections. Seal all splices 
against moisture
Isolation valves Closed Open
Thermostatic mixing valve Improper adjustment Check water temperature at 
house faucet and adjust valve 
setting
Valve defective Replace. System must not 
be run without thermostatic 
mixing valve due to scald risk.
Piping Insufcient Insulation Add insulation where required
High heat losses Check insulation for splits, 
deterioration, absence
Nighttime thermosyphoning Check for pump operation at 
night
Improperly plumbed Compare with system 
schematic. Check ow 
direction
Flow blockage Flush system. Check efuent 
for debris.
Low system pressure Check pressure gauge. Set 
system pressure to correct 
setting, check for leaks.
Pump No power Check breaker, pump cord, 
and controller fuse. Repair or 
replace
Flow rated too high or too low Adjust ow rate
Faulty pump Listen for irregular noises 
in pump operation. Feel 
collector feed and return line 
for temperature difference. 
Ensure all air is purged from 
system.
Runs continuously Check sensors for shorts
No hot water in the morning Storage water heater Circuit breaker shut off Turn breaker on
Differential controller Sensor wires reversed Ensure the collector and 
tanks sensors are wired to 
the correct position on the 
controller
Water too hot Thermostatic mixing valve Improper adjustment Check water temperature at 
house faucet and adjust valve 
setting
Valve defective Replace. System must not 
be run without thermostatic 
mixing valve due to scald risk.
No water Cold-water supply valve Valve closed Open valve
Pump does not start Differential controller Controller set to “off” position Set system operation to 
“Auto”
Unplugged Return power to controller
On and/or off temperature 
differential set points too high
Reset on and off 
differentials according to 
recommendations
Loose contacts Clean contacts and tighten 
connections or replace
Blown fuse Replace fuse










