Rinnai code 57: burner overheat switch

A bi-metal switch is a simple safety device that opens when it gets too hot. Rinnai puts two of them on the back of the burner assembly. Code 57 means at least one has opened.

The meaning and service steps below come from Rinnai's own diagnostic code guide for its tankless water heaters.

Rinnai lists this code for its non-SENSEI series.

Why a normal reset may not clear it

Rinnai explains that this code stays on even when the heater is idle. It clears only after the cause is fixed and the power to the unit is switched off and back on, which Rinnai calls a hard reset.

What Rinnai tells technicians to check

• The switch wiring back to the control board
• That the heater is connected to the gas type it was built for
• That low and high fire manifold pressures are set correctly for the altitude
• That any conversion from one gas type to another was done exactly per the manufacturer's instructions

What homeowners can do

Very little on this code. It points to how the burner is being fueled, which is qualified gas technician work. Leave the unit off, and mention if it was ever converted between natural gas and propane.

Before you call

Have the model and serial number from the rating label ready, along with the exact code and when it appears: at startup, during use, or only at high demand. Mention any recent work on the gas, water or electrical supply and when the heater was last descaled. This helps the technician bring the right parts and often saves a second visit.

See every code on our Rinnai error codes page.