Installation Manual

H-Series Demand Duo™ 2 Installation and Operation Manual 28

When filling the system with water, follow these guidelines:

• To prevent damage to the water heater, all air must be relieved from the system and a hot

water fixture must be flowing water before the water heater is plugged in and turned on.

DO NOT OPERATE THE WATER HEATER UNLESS IT IS COMPLETELY

FULL OF WATER.

NOTICE

To fill the system with water:

1. Ensure the drain valve located at the bottom of the tank is closed (see A below).

2. Open the nearest hot water fixture.

3. Open the cold water supply valve to the water heater (see B).

4. Keep the hot water fixture open until the tank is filled and constant flow is obtained at the fixture.

5. Close the hot water fixture.

6. Check water heater connections and plumbing system for damage or leaks. Repair if needed.

7. Connect a hose (such as a standard garden hose) to the cold drain valve on one of the tankless water

heaters and open the valve to allow water out; this ensures no air is trapped inside the pump (see C).