Rinnai Tankless Water Heater Installation and Operation Manual
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4.3.5 Freeze Protection
The water heater and its water lines must be protected to prevent freezing. Damage due to freezing is not
covered by the warranty.
When connected to a 120-volt power supply and gas is on, 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 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 water line and
pressure relief valve.
Loss of freeze protection may result in water damage from a burst heat exchanger or water lines that
freeze and break.
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
pressure relief valve is 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. The hot and
cold water pipes should be insulated. To provide additional freeze protection, the pipe cover enclosure
can be filled with insulation materials.
Figure 8: Freeze Protection Piping Diagram
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
Gas Supply
