Bosch C950ES Reference manual

Technical Service Bulletin:
Resetting the Watervalve
Models: 830ES, 940ES-ESO, C950ES, C1050ES, 1210ES-ESC, T9800/T9900 SE(C)
Data subject to change without notice | Printed in the USA | BTC 740002333 A | 05.2018 Bosch Thermotechnology Corp.
A qualified service technician is recommended to perform the work.
Problem
Tankless water heater that doesn’t activate, and doesn’t show an error code.
Possible Cause
The watervalve may be clogged or needs to be reset.
Overview
Sometimes a tankless water heater doesn’t start up when water is turned on (above
activation rate), and also doesn’t give an error code. This can be due to the impeller
in the watervalve being stuck or clogged, the water valve being closed, or even just
a clogged inlet filter. Some of the models have an inlet filter accessible from outside
the machine, which you can inspect for debris first. Other models have it directly
in line with the watervalve, in which you will have to disconnect and remove the
watervalve for access.
Procedure
1. Drain the machine down of any water on both the hot and cold sides.
2. Remove the inlet and outlet water clips and remove watervalve from the
machine. After it is removed, disconnect all wiring to the watervalve.
Inspect the screen for any blockage and clean if necessary.
3. Remove the 2 Phillips head screws that hold the watervalve engine to the
watervalve body (Fig. 1).
Figure 1
4. Remove the 2 Phillips head screws that hold the watervalve engine to the
watervalve body (Fig. 1).
5. Separate the 2 the watervalve body and the watervalve engine.
6. On the valve side, locate the brass gear. Rotate the gear counter clockwise
(towards the “0”) until it stops (Fig. 2).
Figure 2
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Data subject to change without notice | Printed in the USA | BTC 740002333 A | 05.2018 Bosch Thermotechnology Corp.
Technical Service Bulletin
2 | Resetting the Watervalve
Bosch Thermotechnology Corp.
65 Grove Street
Watertown, MA 02472
Tel: [phone]
Fax: [phone]
www.boschheatingandcooling.com
7. On the motor side, slowly rotate the gear clockwise to “0” (Fig. 3). There are
gears inside this motor that cause resistance, do not try to move it fast or
you will damage the gearing.
Figure 3
8. Once that is completed, make sure you can blow through the valve freely
from the bottom where the cross diverter is (Fig. 4). When you forcefully
blow through the valve, you should hear the impeller spinning. If not, use
a small pick or similar device to manually move it. It should move freely
with no resistance. Any resistance could be signs of buildup inside the
valve. Flushing out the valve at this point would be your only way to clear
that obstruction. The impeller is not removable on these valves. If it can’t
spin freely by flushing out the valve or manually rotating it, you may need to
replace the valve.
Figure 4
9. After performing the service, attach the watervalve engine to the watervalve
body with the 2 phillips head screws as shown in Fig. 1.
10. Plug the wiring back in, and reinstall the clips on both the incoming and
outgoing side of the valve.
11. Slowly turn on water supply to check for leaks, before powering up and
returning the tankless unit to service
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