Bosch Appliances GWH 260 PN/HN2, GWH 425 PN/HN4GWH 4254 manual Descaling procedure

4 4 Applications manual

6 Maintenance Drawings

Bosch appliances are designed to last for many years. In order to keep the heater operating properly, periodic maintenance is required. Please consult the installation manual for maintenance intervals. A descaling procedure drawing is included to assist in clearing the water heater of mineral deposits that may build up over time.

6.1 Descaling procedure

This procedure should only be done if there is evidence of scale build-up such as a reduced hot water flow rate or if the water is known to have high levels of minerals such as calcium.

1.Disconnect electrical supply from the water heater.

2.Shut off the water supply to the water heater using (installer supplied) isolation valve.

3.Open hot water taps to drain and relieve pressure from the plumbing system.

4.Drain water from the unit’s heat exchanger by disconnecting inlet and outlet water connections.

5.Connect the line (A) from the outlet of the circulating pump (installer supplied) to the inlet water fitting on the water heater.

6. Using another line (B), connect to the water outlet fitting on the water heater. Route the other end of this line into a descaling reser- voir.

7.Using a 3rd line (C) from the descaling reservoir, connect to the inlet side of circulating pump. Verify there is a filter on the end of the line in the descaling reservoir.

8.Make sure all connections are “hand tight.”

9.Fill tank with descaling solution so lines inside are submersed. We recommend a straight white vinegar. If using a commercial descalant, refer to manufacturer’s instructions for proper dilution ratio.

11.Operate the circulating pump.

12.Make sure there are no leaks and the solution is flowing from the descaling reservoir through the heat exchanger and returning to the reservoir.

13.Run solution through the heat exchanger until the solution returning to the descaling reservoir comes out clear. (Changing to a fresh solution may be necessary during this process)

14.Disconnect all lines and drain all solution from heat exchanger. Properly discard of solution.

15.Position a container below the hot water outlet and connect cold water supply. Open cold water supply isolation valve and flush heat exchanger with clean water.

16.Shut cold water isolation valve and reconnect hot water supply to the water heater.

17.Reconnect electrical supply to unit, open water isolation valves, and return the unit to service.

Application manual 11.2007 Bosch Water Heating