Rinnai Tankless Water Heater Error Code 16: Meaning and Fix
Applies to: Rinnai RL75i and RL94i condensing tankless water heaters (Rinnai installation guide U287-1817); the code numbers are shared across Rinnai's range but the steps vary by series.
Reading the tankless water heater display
A tankless water heater shows its fault as a number or letter code on the unit display or on the wired remote controller, and some models keep a short history of past codes. Write the code down exactly as shown before you reset the unit, and check the rating plate for the model number, because the same number can mean different things between series.
Rinnai makes gas tankless water heaters that report faults as two-digit diagnostic codes on the unit or the wired controller. The codes are shared across its range, but troubleshooting steps vary by series, so use the series in your manual. The codes apply to model numbers such as RL75i and RL94i; check the label on your unit to confirm yours.
What causes 16
- Scale in the heat exchanger
- Temperature sensor fault
- Low water flow or restricted supply
How to fix it
If you smell gas, leave the building and call your gas utility from outside; do not touch switches or the unit. Switch the water heater off and let it cool before you touch any internal part, and call a licensed plumber or water heater technician if you are not sure.
The code meaning comes from the manufacturer document listed under Sources. The causes and steps below are general troubleshooting guidance, not the manufacturer's service procedure.
- Switch the water heater off and let it cool before you touch anything inside it. If you smell gas, leave the building and call your gas utility from outside.
- Open the hot tap fully and check flow. Clean the inlet water filter if the flow is weak.
- Turn the unit off for a few minutes, then restart it.
- Have a technician descale the heat exchanger and check the sensors if it returns.
- If the code returns after these checks, call a licensed plumber or water heater technician and give them the code and the model number from the rating plate.
Questions
What does Rinnai tankless error code 16 mean?
Code 16 on a Rinnai tankless water heater is an over temperature warning. The unit sensed water or heat exchanger temperature above its safe limit.
Can I reset the water heater myself?
Turning the unit off and back on, or unplugging it for about 30 seconds, clears some codes. If the same code comes back, the fault is still there and the unit will shut down again. Do not bypass a safety device to keep it running.
When should I call a technician?
Call a licensed plumber or water heater technician for anything involving gas, venting, the heat exchanger, a thermal fuse or the circuit board, or when the code keeps returning after the simple checks.
Other brands with code 16
The same code can mean something different on another maker's appliance. Check the brand before you act.
Other Rinnai tankless water heater codes
Sources
Part numbers are OEM references; confirm fit by your model number before ordering. Meanings compiled from manufacturer and parts-retailer documentation; see sources below. Unplug the appliance before opening it.
Applies to models including RL75i, RL94i.