Bosch C950ES Reference manual

Technical Service Bulletin:
Replacing & Servicing The Condensing
Heat Exchanger
Models: C950ES, C1050ES
Introduction
If replacing the copper heat exchanger (below the condensing
heat exchanger), refer to Technical Service Bulletin: Replacing
the Copper Heat Exchanger once the condensing exchanger has
been removed.
Tools needed:
Phillips head screwdriver
8mm nut driver with 6" extension
4mm allen wrench
Clean rag
Preparation
1. Unplug water heater and turn off gas to heater using installer
supplied manual shut off valve.
2. Remove front cover and combustion cover using instructions in
the installation manual.
3. Close installer supplied inlet isolation or shut off valve and open
a hot water tap to release pressure and drain. If water flows
continuously from the tap, a plumbing crossover is present and
must be corrected.
4. Disconnect inlet and outlet piping from the water heater to
facilitate draining. Have a bucket ready to catch water.
5. Place a clean rag over the water heater‘s control unit to catch any
residual water when removing pipe connections.
Removing the condensing heat exchanger
1. Remove Phillips head screw, gasket and exhaust temperature
sensor from center of condensing exchanger. (Fig. 1, pos. 1).
2. Remove overheat sensor/ECO wires from sensor on heat
exchanger. (Fig. 1, pos. 2). Ensure that wires are out of the way
for heat exchanger removal and reinstallation.
3. Remove clip from black condensate drain pipe connection and
pull drain pipe free. (Fig. 1, pos. 3).
Figure 1
4. Remove clips on copper pipe connecting upper and lower heat
exchanger and remove pipe (Fig. 2, pos. 1). Dripping water is
likely.
5. Remove clips from top and bottom of cold water pipe and
remove pipe from heater (Fig. 2, pos. 2). Dripping water is likely.
6. Remove the two Phillips screws and two 4mm hex head screws
from the top left and right of the exchanger (Fig. 2, pos. 3).
7. Remove the four 8mm nuts from the bottom front and top rear of
condensing exchanger. (Fig. 2, pos. 4). Note: two left nuts are
not visible in Figure 2.
8. Remove the condensing heat exchanger by pulling it forward and
out of the heater.

Data subject to change without notice | Printed in the USA | BTC 740002314 B | 06.2011 Bosch Thermotechnology Corp.
Technical Service Bulletin
18 | Replacing & Servicing the Condensing Heat Exchanger - C950ES, C1050ES
Bosch Thermotechnology Corp.
50 Wentworth Avenue
Londonderry, NH 03053
Tel: [phone]
Fax: [phone]
www.bosch-climate.us
5
5
Figure 2
Inspecting condensing heat exchanger
Note: If removing the lower copper heat exchanger, refer to
Technical Service Bulletin: Replacing the Heat Exchanger now. If
installing a new condensing heat exchanger, skip the next
section.
1. Using a flashlight, look through the rear inlet slot of the heat
exchanger so that the fin coils inside are visible.
2. If there are any signs of soot, combustion byproducts or
corrosion, the condensing exchanger must be disassembled to
clean the fin coils.
Disassembling condensing heat exchanger
1. Remove clips from copper "U" bend pipe (Fig. 2, pos. 5) and
"offset" pipe (Fig. 2, pos. 6). Remove pipes from heat exchanger.
2. Remove the four 4mm hex head screws from one side of the heat
exchanger. (Fig. 3, pos. 1)
3. Carefully separate one side of heat exchanger from main body by
prying evenly. Use caution to prevent damage to the aluminum
and gasket.
4 Please note o-ring positions when dissassembling. Smaller
o-rings (Fig. 3, pos. 2) fit on fin coil pipe ends. Larger o-rings are
placed on the outside of the heat exchanger sides
(Fig. 3, pos. 3).
5. Gently pull both fin coil tubes (Fig. 3, pos. 4) free from the
exchanger body. If necessary, the other side of the heat
exchanger can be removed to ease removal of fin coils.
6. With fin coils exposed, vacuum them clean with a soft bristle
vacuum brush. Then spray clean with water. Ensure drain hole
in bottom right of exchanger is clear of debris or corrosion.
Reassembling and installing condensing heat exchanger
1. Reinsert fin coils (without o-rings) into exchanger body. (Fig. 3,
pos. 4).
Figure 3
2. Place side with gasket (Fig. 3, pos. 5) on to main exchanger body
and push firmly on sides to properly seat fincoils.
3. Install four 4mm hex head screws with washers to secure each
heat exchanger side (Fig. 3, pos. 1)
4. Place four small o-rings (Fig. 3, pos. 2) on fin coil ends and four
large o-rings (Fig. 3, pos. 3) where "U" bend, "offset", and cold
water pipes connect. Use dish washing liquid to lubricate large
o-rings and seat them with connecting pipes.
5. Reinstall "U" bend pipe on right side of exchanger (Fig. 2, pos.
5) and “offset” pipe on to left side rear of heat exchanger (Fig.2,
pos. 6). Secure both pipe connections with clips.
6. If lower heat exchanger was removed, reinstall before
proceeding.
7. Place condensing heat exchanger back into heater. Ensure that
gaskets between upper and lower heat exchanger and between
condensing exchanger and flue gas collector are correctly in
place.
8. Tighten the four 8mm nuts at the bottom front and top rear of
condensing exchanger. (Fig. 2, pos. 4). Note: two left nuts are
not visible in Figure 2.
9. Install the two Phillips screws and two 4mm hex head screws
from the top left and right of the exchanger (Fig. 2, pos. 3).
10. Reinstall upper cold water pipe (Fig. 2, pos. 2) and connecting
pipe (Fig. 2, pos 1) with o-rings to left side of exchanger. Secure
with clips.
11. Reinstall condensate drain pipe to connector with o-ring and
clip. (Fig. 1, pos.3).
12. Reinstall exhaust temperature sensor with washer and screw
(Fig. 1, pos. 1).
13. Reconnect wire leads to overheat sensor/ECO (Fig. 1, pos. 2).
14. Turn on water supply and check for leaks.
15. Replace combustion and front covers.
16. Plug in power cord and return heater to service.