The thermal fuse in a Rinnai HD55i continuous flow water heater is a fail-safe within the overheat protection circuit. If a combustion or airflow fault causes the unit to run hotter than it should, the fuse trips and cuts power, stopping the appliance before any further damage occurs rather than letting it continue running in an unsafe state.
It works alongside the other sensors and switches in the HD55i's safety system, so if the fuse itself fails or becomes faulty, the water heater will simply stop operating until it's replaced and the underlying cause has been checked and resolved. This is the genuine Rinnai replacement, made to the same specification as the original, restoring that overheat protection properly rather than working around it.
⚠ Important: This is a safety-critical component and must only be installed or serviced by a Gas Safe registered engineer or suitably qualified professional. Always isolate the gas supply and disconnect the electrical power before starting work.
Key Features & Benefits
Genuine Rinnai Part: Made to Rinnai's own specification for a correct fit and reliable operation.
Overheat Protection: Cuts power to the appliance if it runs hotter than the safe operating threshold.
Part of a Wider Safety Network: Works alongside the HD55i's other sensors and switches to prevent overheating.
Stable Electrical Connection: Maintains a reliable link within the safety circuit.
Straightforward Fault Fix: Restores appliance operation once a blown or faulty fuse has been replaced and the root cause addressed.
Ideal For
Rinnai HD55i continuous flow water heaters.
Replacing a blown or faulty thermal fuse.
Gas Safe registered engineers and heating professionals.
HVAC servicing and repair work.
Common Problems This Part Will Fix
Water Heater Won't Turn On: A tripped thermal fuse will stop the appliance operating until it's replaced.
Overheat Warning Indicators Active: Resolves faults where the overheat safety circuit has been triggered.
Fault Codes Linked to Thermal Protection: Addresses error codes tied to the overheat safety circuit.
Shutdown Following Overheating: A common sign the fuse has done its job and needs replacing.
Electrical Faults in the Safety Circuit: Restores a stable connection within the overheat protection network.
Why Buy This Product?
If your HD55i has shut down and won't restart, or you're seeing overheat-related fault codes, a blown thermal fuse is a common cause — and this genuine part restores that protection properly rather than bypassing it. It's a low-cost, safety-critical fix, and worth pairing with a check of what triggered it in the first place so the same fault doesn't repeat.
Order the Rinnai HD55i Thermal Fuse Assembly online today.
