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Rinnai gas heater code 73: Communication error
Gas heater, Australia
Parts of the heater's control system cannot communicate with each other.
This needs a licensed gasfitter. There are a few safe checks you can do first, marked below. Anything inside the unit is a job for a professional.
What causes it
-
A communication fault inside the heater. A service call is required.
Turn the Energysaver heater off and on againYou can do this
- Turn the heater OFF using its On/Off button, then turn it ON again.
- If the error returns on the next operation, contact Rinnai or a service dealer for a service call.
How to read this code on your unit
Booking a licensed gasfitter
Book a licensed gasfitterlicensed gasfitter
- Turn the unit off and leave the covers on. Gas components must only be serviced by a licensed technician.
- Note the code, how often it appears, and the model and serial numbers from the rating label.
- Book a licensed gasfitter and give them those details.
Models that show this code
6 models in 2 ranges
| Range | Models |
|---|---|
| Energysaver FDT commercial flued gas heater | RHFE-559FTSN (Energysaver 559FDT), RHFE-1005FTSN (Energysaver 1005FDT) |
| Energysaver FT flued gas heater | RHFE-309FT3 (Energysaver 309FT), RHFE-559FT3 (Energysaver 559FT), RHFE-561FT3 (Energysaver 561FT), RHFE-1005FT3 (Energysaver 1005FT) |
Where this comes from
- Error codes for Energysaver flued gas heaters (HE Gas Energysaver FT FDT ERR) , page 2
- Energysaver FT gas heater operation and installation manual , page 21
Checked against the manufacturer's manual on 15 October 2026.
Other Rinnai gas heater codes
| Code | Meaning | What you can do |
|---|---|---|
| 34 | Overheat temperature sensor fault | Safe checks first, then a pro |
| 35 | Overheat temperature sensor fault | Safe checks first, then a pro |
| 40 | Sensor tube failure | Call a pro |
| 49 | Sensor breakdown | Safe checks first, then a pro |
| 53 | Spark sensor fault | Call a pro |
| 61 | Combustion fan fault | Safe checks first, then a pro |
| 62 | Convection fan fault | Safe checks first, then a pro |
| 70 | On/Off switch fault | Call a pro |
| 71 | Gas solenoid fault | Call a pro |
| 72 | Flame detection circuit fault | Call a pro |
| 81 | Gas solenoid fault | Call a pro |
| 99 | Flue terminal blocked | Safe checks first, then a pro |