Dunkirk H2OI Single Coil Stainless Steel Indirect Water Heaters - Manual (Page 22)

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VII. Troubleshooting
PROBLEM CAUSE SOLUTION
No hot water at faucets
Boiler does not operate.
Press reset button
Check main cut-off switch
Check fuses or breakers.
Check power supply
Check shaft coupling
Circulator does not operate Check shaft coupling
Improper thermostat setting Turn thermostat to a higher setting.
Zone valve does not open Check power supply and valve
Electrical problem Check fuses and replace.
Check circuit breaker and reset.
Check power supply
Sediment and/or scale buildup If boiler, circulator, and thermostat are
operating properly, and the boiler is cycling
on the high limit several times before the
tank thermostat is satisfied, the coil may
have a coating of sediment and/or scale.
Clogged filter Clean or replace filter.
Insufficient or runs out of hot water
at the faucet
Thermostat setting too low. Turn the thermostat to a higher setting.
Undersized boiler with no priority to
domestic water heating.
Rewire for priority.
Peak draw of hot water is greater than
the tank storage.
Determine peak usage and compare to tank
volume.
Sediment and/or scale buildup Clean coil
Faulty water heater thermostat Replace thermostat
Water at faucet too hot
Thermostat set to high Lower thermostat setting.
Improper system plumbing
Compare plumbing to installation guide.
Inspect check valves.
Improper wiring. Compare wiring to installation guide.
Boiler cycles more than 5 times per
day in summer
Excessive demand Reduce demand or consider larger boiler
and/or water heater.
Faulty thermostat Replace thermostat
Boiler high limit set to low Increase boiler hi-limit setting
Sediment and or scale buildup Clean coil.