Bosch C1210ESC Technical Service Bulletin

Technical Service Bulletin:
Descaling the Heat Exchanger
Models: C1210ESC, C1210ES, C1050ES, C950ES, 940ES, 940ESO, 830ES
Introduction
Periodic descaling may be necessary in areas where the water

supply is highly mineralized. Scale build up in the heat
exchanger may result in reduced fl ow rates, error codes and boil-
ing sounds in the heat exchanger.
Tools needed:
Various plumbing wrenches

5 gallon bucket for descaling solution

Small circulator or pump

3 Hoses for circulating

Filter for descaling solution

Descaling procedure
1. Clear error code (if displayed) by pressing the reset button.
2. Press On/Off button to "Off".
3. Disconnect electrical supply from the water heater.
4. Shut off the water supply to the water heater using (installer
supplied) isolation or shutoff valves.
5. Open hot water taps to drain and relieve pressure from the
plumbing system.
6. Drain water by disconnecting the inlet and outlet water connec-
tions from the heater.
7. Connect a hose (A) from the outlet of the circulating pump
(installer supplied) to the inlet water fi tting on the water heater.
(Fig. 1)
8. Connect another hose (B) to the water outlet fitting on the water
heater. Route the other end of this hose into a descaling reser-
voior or bucket. (Fig. 1)
9. Using a 3rd hose (C) from the descaling reservoir, connect to the
inlet side of the circulator/pump. Install a filter on the end of
the hose in the descaling reservoir. (Fig. 1)
10. Make sure all connections are 'hand tight'.
11. Fill reservoir/bucket with descaling solution so both hoses inside
are submersed. We recommend straight white vinegar. If using
a commercial descalant, refer to manufacturer's instructions for
proper dilution ratio with water.
12. Operate the circulating pump.
13. Make sure there are no leaks and the solution is fl owing from the
descaling reservoir, through the heater and returning to the
reservoir.
Figure 1