Bosch 715ES Reference manual

Models: 715ES, C800ES, C920ES, C920ESC, 2400ES, 2700ES
Descaling the heat exchanger
Service Bulletin G3-13
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 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 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)
Figure 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 owing from the
descaling reservoir, through the heater and returning to the
reservoir.

Data subject to change without notice | Printed in the USA | BTC710002307 A | 01.2009 Bosch Thermotechnology Corp.
Service bulletin
18 | G3-13 | 715ES, C800ES, C920ES, C920ESC, 2400ES, 2700ES
Bosch Thermotechnology Corp.
50 Wentworth Avenue
Londonderry, NH 03053
Tel: [phone]
Fax: [phone]
www.boschhotwater.com
14. Run solution through the heater until the solution returning to
the descaling reservoir/bucket comes out clear. Changing to a
fresh solution may be necessary during this process.
15. Properly discard of dirty descaling solution. Disconnect lines A
and C (Fig. 1). Reconnect cold water supply to the water heater.
16. Open cold supply shutoff valve to ush water heater with clean
water. Allow enough water to ow through the heater to
properly ush it. Filling the 5 gallon descaling bucket once
should be sufcient.
17. Close cold water shutoff valve and disconnect line B (Fig. 1).
Reconnect hot water line to the water heater.
18. Plug in power cord and press On/Off button to "On".
19. Open water shutoff valves, and return water heater to service.
Water Quality
Water quality can have an impact on appliance longevity and may
void the manufacturer’s warranty.
 For water analysis data, call your local water department. If on a
well, have the well water analyzed periodically. If water quality
exceeds one or more of the values specied in Figure 2, Bosch
recommends consulting a local plumber about installing a water
conditioner or softener.
 If the tankless water heater is operating in applications where
the outlet temperature exceeds 140°F, a water softening system
is strongly recommended. The higher the set temperature is on
the appliance, the greater the risk for scale/mineral deposits.
Damage from scale/mineral deposits is not covered under
warranty. Refer to manufacturer’s limited warranty.
Figure 2
Description Max. Levels
pH pH 6.5 - 8.5
TDS (total Dissolved
Solids) mg/l or ppm 500
Total hardness gpg or ppm 100
(6 gpg)
Aluminum mg/l or ppm 2.0
Chlorides mg/l or ppm 250
Copper mg/l or ppm 1.0
Iron mg/l or ppm 0.3
Manganese mg/l or ppm 0.05
Zinc mg/l or ppm 5.0