Rinnai RUC80i Training Program page 14

Overheat Protection and Safeties
1. The thermal fuse wraps around the copper
portion of the heat exchanger assembly. This
device's primary function is to monitor for high
temperatures in the water heater cabinet due to
physical damage to the heat exchanger that
would allow hot exhaust gasses to escape.
➢
The thermal fuse will open at 264⁰F.
➢
If the thermal fuse opens the water heater will
shut down with a code 14.
➢ The thermal fuse is a "one-time-use" component
and must be replaced once open. It will not reset.
Replacement will require removal of the heat
exchanger. This allows the service provider to
inspect the entire heat exchanger assembly for
damage.
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The thermal fuse and overheat bimetal switch
are wired in series and are replaced as one
component.
An open thermal fuse or bi-metal switch is a symptom of an underlying issue such as a failed/damaged heat
exchanger, scale buildup inside the copper tubing, dirty or clogged heat exchanger, improperly set gas
pressures, incorrect gas type or an improper gas type conversion. The cause of this symptom should be
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PROPRIETARY and CONFIDENTIAL
investigated to prevent further problems.
Enhancing Lives By Changing The Way Water Is Heated
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5/4/2018