Installation Guide

Rinnai Tankless Water Heater Installation and Operation Manual 89
If the water heater is not going to be used
during a period of possible freezing weather, it
is recommended that the water inside the
water heater be drained.
To manually drain the water:
1. Shut off cold water supply and gas supply.
2. Turn off the controller.
3. Disconnect the power to the water heater.
4. Close the hot and cold isolation valves.
5. Open the pressure relief valve (PRV)
lever.
6. Open the hot and cold drain valves.
7. Remove the condensate trap drain plug
and allow to drain.
8. Remove the pump drain plug (for CXP
models only).
To resume normal operation:
1. Confirm that the gas supply is turned off,
all taps are closed and PRV lever is
closed.
2. Insert the condensate trap drain plug.
3. Insert the pump drain plug (for CXP
models only).
4. Close the hot and cold drain valves.
5. Open the cold and hot water isolation
valves.
6. Open a tap and confirm that water flows,
and then close.
7. Connect power to the water heater.
8. After confirming that the controller is off,
turn on the gas supply.
9. Turn on the controller.
To avoid burns, wait until the equipment
cools down before draining the water. The
water in the appliance will remain hot after it
is turned off.
WARNING
Running a low volume of water through the
water heater to prevent freezing:
If the temperature exceeds the ability of the
water heater to freeze protect itself, or if power
is lost, the following steps may prevent the
water heater and external piping from freezing.
Units connected with cascade cables should be
drained to prevent freezing if not in use.
1. Turn the water heater off and close the gas
supply valve.
2. Turn on a hot water tap
to flow water about 0.1
gal/min (0.4 L/min) or
where the stream is
about 0.2 in. (5 mm)
thick.
When the water heater or
external piping has frozen:
1. Do not operate the water heater if it or the
external piping is frozen.
2. Close the gas and water valves and turn off
the power.
3. Wait until the water thaws. Check by
opening the water supply valve.
4. Check the water heater and the piping for
leaks.
Figure 100
Condensate
Drain Trap Plug
Hot Drain Valve
Cold
Drain
Valve
Figure 101
Pressure
Relief
Valve
Cold
Isolation
Valve
Hot
Isolation
Valve