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| Demand Rapid owner & installer guide 12949-B 02-19
Troubleshooting
troubleshooting without controllers or status monitor
Fault
Possible solution
Unit does not start
Check power is on at the unit. Check gas isolation valve at the unit and gas
meter are fully open.
Unit starts and then shuts down
immediately
Check power is on at the unit. Check gas isolation valve at the unit and gas
meter are fully open.
Unit starts then water goes cold
Check power is on. Open hot water tap fully.
Excessive temperature
fluctuation while water is flowing
Service call.
Excessive noise or vibration from
the water heater
Service call.
Faults caused by insufficient gas and/or water supply, gas quality, water quality, installation errors
or operation errors are not covered by the Rinnai warranty.
Troubleshooting
general system troubleshooting
What’s happening
Possible cause
Explanation and/or possible solution
Delivery temperature not
hot enough
No electrical or gas supplies to the heat
source
Check and turn on the power and gas
supplies
Insufficient gas
Check gas supply, availability and pressure
Temperature sensor has dislodged or failed Check temperature sensor is correctly
positioned and providing information to the
thermostat
Excessive load on system
Check maximum demand does not exceed
rated capacity
Inadequate heating circuit—pump not
working properly
Check all valves are fully open
Tempering or thermostatic mixing valve
malfunctioning
Service call
Delivery temperature too
hot
Tempering or thermostatic mixing valve
malfunctioning
Service call
Make-up water flowing
continuously
Leak in cylinder and/or heating circuit
Check for leaks
