Rheem 305, 505, 705 Error 16: Over Temperature Warning

Tankless water heater · taken from the manufacturer’s manual, pages cited

Fault code16

Over Temperature Warning occurs when air flow is restricted or there are foreign materials in the combustion chamber or exhaust piping. The manual's first action is: “Check for low water flow in a circulating system causing short-cycling.”

Model
Rheem 305, 505, 705
Display shows
Over Temperature Warning (16)
Type
Fault code
Source
Manual p. 10

What 16 means

Over Temperature Warning p. 10

Common causes

  • Check for restrictions in air flow around unit and vent terminal. p. 10
  • Check for foreign materials in combustion chamber and/or exhaust piping. p. 10

What to do

  1. Check for low water flow in a circulating system causing short-cycling. p. 10
  2. Check for clogged heat exchanger. p. 10

Before you service the product, read the safety instructions in the manual p. 4.

If 16 is still not resolved

  • Immediately call your gas supplier from a neighbor’s phone. p. 1
    “Immediately call your gas supp lier from a neighbor’s phone.”
  • If you cannot reach your gas supplier, call the fire department. p. 1
    “If you cannot reach your gas supplier, call the fire department.”
Open the manual at page 10 All 305, 505, 705 error codes Manual details & download

This page summarises what the manufacturer’s manual says about 16; each statement links to the page it comes from, and quoted lines are copied word for word. It is not a substitute for the manual or for a qualified installer. ManualLib is not affiliated with Rheem. Found a mistake? Report an error.