Noritz NC250-SV-ASME Guide De L'utilisateur page 19

If the water heater will not be used for a long period of time,
Drain the water.
Drain the water as follows:
CAUTION
To avoid burns, wait until the equipment cools down before draining the water.
The appliance will remain hot after it is turned off.
High Temperature
Drain water into a bucket to prevent water damage.
1. Close the gas valve.
2. (1) Turn the power on.
(2) Turn and leave open the hot water fixtures for more than 2 minutes and close.
* If multiple units are being used, drain two minutes for each unit.
* An 11 Error Code may appear on the remote controller.
This is not a malfunction of the unit. Do not turn Power ON/OFF Button OFF.
3. Close the water supply valve, disconnect
the electrical power supplied to the unit.
Do not touch with wet hands.
4. Fully open all hot water fixtures.
5. Open all drain plugs and drain the water out
of the unit.
6. When the water is completely drained, replace all drain
plugs and close the hot water fixtures.
1. Check that all drain plugs are inserted.
2. Check that all hot water fixtures are closed.
3. Follow the procedure on p.11 "Initial operation", steps 1 through 4.
Fixture
Turning the Unit Back On
Fixture
Drain Plugs
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