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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 Insuffi cient 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 fl ow
direction
Flow blockage Flush system. Check effl uent
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 fl 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”
Uplugged 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