18 | Replacing & Servicing The Condensing Heat Exchanger - C1210ES, C1210ESC
Inspecting condensing heat exchanger
Note: If removing the lower copper heat exchanger, refer to
Technical Service Bulletin: Replacing Copper Heat Exchanger
now. If installing a new condensing heat exchanger, skip the
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 pipes on left and right side of
heat exchanger (Fig. 2, pos. 5). Remove copper "U" bend pipes.
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
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 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,
Data subject to change without notice | Printed in the USA | BTC 740002318 A | 07.2010
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 small o-rings (Fig. 3, pos. 2) on fin coil ends and large o-
rings (Fig. 3, pos. 3) where "U" bend, and water pipes connect.
Use dish washing liquid to lubricate large o-rings and seat them
with connecting pipes.
5. Reinstall "U" bend pipes on each side of exchanger
(Fig. 2, pos. 5) Secure both pipe connections with clips.
6. If lower heat exchanger was removed, reinstall using bulletin G3-
22 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
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 cold water pipe (Fig. 2, pos. 2) and connecting pipe
(Fig. 2, pos 1) with o-rings on heat 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.
Technical Service Bulletin
Bosch Thermotechnology Corp.
50 Wentworth Avenue
Londonderry, NH 03053
Bosch Thermotechnology Corp.