Bosch C1050ES Reference manual

Technical Service Bulletin:

Replacing The Control Unit

Models: C1050ES, C950ES, 940ES, 940ESO, 830ES

Introduction

Tools needed:

Phillips head screw driver

Small flat head screw driver

Needle-nosed pliers

Note: Avoid touching printed circuit board (PCB) as static discharge

may damage circuitry.

Preparation

Push power button to "OFF" and unplug power cord.

Loosen two Phillips head screws on bottom rear of front cover.

Pull cover bottom outwards then lift cover upwards to remove.

Removing control unit

Remove three Phillips screws on front of control unit. (Fig. 2,

pos. 1)

Turn control unit to expose the rear. (Fig. 2, pos. 2).

Locate and remove 6 Phillips head screws on back of control

unit (Fig. 2, pos. 3).

control unit front

Figure 2

Remove rear cover from control unit to expose circuit board

electrical connections. Slide wire restraints out of control unit.

(Fig. 3, pos. 1).

Remove two large electrical strip connectors by pulling them

away from board. (Fig. 3, pos. 2).

Remove medium sized electrical strip connector by pulling it

outwards. (Fig. 3, pos. 3).

Remove small electrical strip connector by pulling it outwards.

(Fig. 3, pos. 4).

Remove two large ignition wires by pulling them outwards. (Fig.

3, pos. 5).

Remove yellow/green striped ground wire spade connection by

depressing tab on connector and pulling it gently off the board.

(Fig. 3, pos. 6).

Loosen two small flat head screws on terminal block for power

cord. Pull black and white wires free from terminal block and

control unit. (Fig. 3, pos. 7).

Loosen Phillips head screw and remove green ground wire con-

nection for power cord. (Fig. 3, pos. 8).

Figure 3

1 1

Remove control unit from the water heater.

Appliance evaluation for PCB jumper location

Please evaluate the following prior to installation of the replacement

PCB:

|Replacing The Control Unit Technical Service Bulletin

Data subject to change without notice | Printed in the USA | BTC 740002317 C | 06.2012 Bosch Thermotechnology Corp.

Locate rating plate sticker on right side of heater cover.

Determine model number (Fig.1, pos.A) and gas type (Fig.1,

pos.B).

Figure 1

Locate hot water outlet pipe (Fig.2, pos.A). Determine the type

of outlet temperature sensor installed on the hot water outlet

pipe (Fig.3).

Figure 2

Figure 3

Surface mount outlet

temperature sensor

Immersed outlet

temperature sensor

PCB jumper installation

In order for the appliance to work correctly, the proper jumpers

must be installed on the PCB board. (Fig.4)

Backside of control unit

ackside o

control uni

Figure 4

Based on your model, gas type and type of outlet temperature

sensor, jumpers should be installed on the PCB in the following

arrangement:

C 950 ES or 830 ES with surface mount outlet temperature

sensor

Natural

Gas

atura

Gas

Figure 5

Liquid

Propane

C 950 ES or 830 ES with immersed outlet temperature sensor

Figure 6

JUMPER

NEEDED

Natural

Gas

Liquid

Propane

|Replacing The Control Unit Technical Service Bulletin

Data subject to change without notice | Printed in the USA | BTC 740002317 C | 06.2012 Bosch Thermotechnology Corp.

Bosch Thermotechnology Corp.

50 Wentworth Avenue

Londonderry, NH 03053

Tel: 1-800-283-3787

Fax: 1-603-965-7581

www.bosch-climate.us

C 1050 ES or 940 ES/ESO with surface mount outlet

temperature sensor

Figure 7

Natural

Gas

Liquid

Propane

C 1050 ES or 940 ES/ESO with immersed outlet temperature

sensor

Figure 8

Natural

Gas

Liquid

Propane

Replacing control unit

Once the appropriate jumpers have been determined, remove

rear cover of replacement control unit.

Install jumpers in the proper location on PCB.

Connect green ground wire from power cord to replacement

control board with Phillips head screw. (Fig. 3, pos. 8).

Reconnect black and white power cord wires to terminal

block on replacement control unit; Black -L (Load), White - N

(Neutral). Secure to terminal block by tightening flat head

screws. (Fig. 3, pos. 7).5. Reconnect yellow/green striped

ground wire to spade connection on replacement control

board. (Fig. 3, pos. 6).

Reattach large ignition wires to replacement control board (no

polarity). (Fig. 3, pos. 5).

Reconnect small electrical strip connector to replacement

control board. (Fig. 3, pos. 4).

Reconnect medium sized electrical strip connector to

replacement control board. (Fig. 3, pos. 3).

Reconnect two large electrical strip connectors to replacement

control board. (Fig. 3, pos. 2).

Reseat rubber wire restraints in control unit. (Fig. 3, pos. 1).

Replace rear cover on unit using 6 Phillips screws. (Fig. 2, pos.

3).

Place control unit back into water heater and secure with 3

Phillips head screws. (Fig. 2, pos. 1).

Plug water heater power cord back into electrical outlet and

push On/Off button on water heater to "ON".

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