Rinnai Tankless Water Heater Installation and Operation Manual
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4.3.5 Freeze Protection
Make sure that in case of freezing weather the water heater and its water lines are protected to
prevent freezing. Damage due to freezing is not covered by the warranty.
When connected to gas and 120-volt power supply, the water heater will not freeze when the outside
air temperature is as cold as -22°F (-30°C) for internal (indoor) models or -4°F (-20°C) for external
(outdoor) models, when protected from direct wind exposure. Because of the “wind-chill” effect, any
wind or circulation of the air on the water heater will reduce its ability to protect itself from freezing.
In the event of a power failure and/or gas interruption at temperatures below freezing, the water
heater should manually be drained of all water to prevent freezing damage. In addition, drain the
condensate trap, drain line and pressure relief valve.
Loss of freeze protection may result in water damage from a burst heat exchanger or water lines.
The water heater may be drained manually. However, it is highly recommended to install the optional
Drain Down Kit accessory that will enable the water heater to immediately drain upon loss of power
(the condensate trap and pressure relief valve are not affected by the Drain Down Kit and must be
manually drained).
The freeze protection features will not prevent the external piping and valves from freezing. It is
recommended that hot and cold water pipes be insulated. Pipe cover enclosures may be packed with
insulation for added freeze protection.
Route Drain Per Local Co
d
e
Cold Water
Supply Line
1/2 in. Normally Open Solenoid Valve
Hot Water
Supply Line
3/4 in. Normally Closed Solenoid Valve
Legend
Vacuum Breaker
Pressure Relief Valve
Union
Check Valve
Ball Valve
Solenoid Valve
Drain Valve
* Position vacuum breaker
above water heater.
Gas Supply
Freeze Protection Piping Diagram
Vacuum Breaker *
Vacuum Breaker
Drain Valve
Pressure Relief Valve
Union
Check Valve
Ball Valve
Solenoid Valve
1/2 in. Normally Open Solenoid Valve
Route Drain Per Local Code
Cold Water Supply Line
Hot Water
Supply
Line
3/4 in. Normally Closed Solenoid Valve
Vacuum Breaker
Freeze Protection Piping Diagram
Figure 7: Freeze Protection Piping Diagram
