Bosch C 1050 Manual

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Problem solving51
Exhaust  temperature  sensor  -  the 
appliance will close the burner and 
lock  if  it  gets  over  194°F;  (only 
applied for condensing unit). 1. Clean and check heat exchanger.
2. Clean and check condensing heat exchanger. 
3. Reduce maximum power (
chapter 3.14, page 35).
4. Reduce water temperature.
Backflow  temperature  sensor  over 
309°F. 
The appliance will close the burner 
and lock (non-volatile). 1. Check inlet/outlet vent pipes.
2. Check if secondary fan connections are disconnec
ted.
3.  Check  if  venting  specifications  are  met.  Long  ve nt  lengths,
venting with more than three elbows, blocked vent o r combination
venting may cause this failure. See 
chapter 3.3, page 10.
4. Call Bosch Water Heating for further instruction s.
Overheat  sensor  (ECO)  open
circuit  (resets  when  cooler
temperatures are detected 220
°F/
104
°C). 1. Disconnect power supply cord and check wire conn
ections on
the overheat  sensor  (
Fig.  77, page  57)  and  the  two connectors
on the control board. 
2.  Check  white  wire  connections  at  the  overheat  sen sor.  Clean
terminals  with  an  eraser.  If  badly  corroded,  replac e  sensor  and
wire harness.
3.  Check  that  venting  specifications  are  met.  Long  vent  lengths,
venting with more than three elbows, blocked vent o r combination
venting may cause this failure.
4.  In  areas  where  water  has  a  high  mineral  content,   periodic
descaling may necessary, see 
chapter 6.3, page 42.
5.  Unplug  power  supply  cord  to  the  water  heater.  Op en  a  hot
water tap for several minutes  to allow cold water t o pass through
heat exchanger. Close hot water tap and disconnect  lead wires to
overheat  sensor.  Using  a  multimeter,  check  continui ty  through
overheat sensor contacts. Replace sensor if open.
No  flame  ionization  detected  with 
water flow. 1. Verify that all manual gas shut off valves are o
pen.
2. Check gas type. See 
Fig. 2, page 6.
3. Reset error code and open a water tap to cycle th e heater in an
effort to purge air. Cycling hot water tap on and o ff multiple times
may  be  necessary.  If  heater  still  faults  with  EA  er ror  code,  have  a
licensed  gas  technician  properly  purge  air  out  of  t he  gas  line
leading to the water heater.
4.  Check  three  wire  connections  on  the  lower  front  of  the  heat
exchanger are secure.
5. Check gas pressure. See 
chapter 3.14, page 35.
6.  Check  venting  specifications  are  met.  Improper  v enting  may
cause premature failure of the flame sensor rod. See  
chapter 3.3,
page 10.
7.  Check that the minimum power fan speed has been  adjusted to
the proper value.  See 
page 20.
8. Observe inside the viewing window of the heat ex changer when
a  hot  water  tap  is  opened.  Sparking  should  be  follow ed  by  a
steady  blue  flame.  If  flame  is  unstable/yellow  with   proper  gas
pressure, confirm CO2 readings per 
chapter 6.5, page 43.
DisplayCauseSolution
Table 29 * By installer or service technician only. 
						

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Problem solving
Ionization failure during operation. 1. Check gas ty
pe, Fig. 2, page 6.
2.  Check  three  wire  connections  to  ignition  group  o n  the  lower
front of the heat exchanger are secure. 
3. Verify that venting specifications are met. Impr oper venting may
cause premature failure of the flame sensor rod. See  
chapter 3.3,
page 10.
4. Check gas pressure. See 
chapter 3.14, page 35.
5. Check and adjust CO2 readings. See chapter 6.5, page 43.
6.  Check that the minimum power fan speed has been  adjusted to
the proper value.  See 
page 20.
Internal hardware/software failure. 1.  Disconnect  po wer  supply  cord  and  check  the  two  wire  and
ground connections on control board as well as grou nd connection
on heater chassis. 
2.  Pressing  the  wrong  combination  of  buttons  on  the   control  unit
can  create  confusion  among  the  microprocessors  insi de.  In  this
case, the error code should not happen more than on ce or twice.
Turn  off  the  water  heater.  Turn  water  heater  back  o n  and  try
resetting error code. Use the reset button ( ) to re set any error
codes.
3.  Possible  defective  control  unit  call  Bosch  Water   Heating  for
further instructions.
Ionization error at standby. 1.  Loose  connection  to  the  flame  ionization  rod.  Verify  that  the
thinner wire leading from the control unit is secur ely connected to
the  set  of  electrodes  located  on  the  lower  front  of   the  heat
exchanger. 
2.  Flame  ionization  rod  or  control  unit  may  be  dama ged.  Contact
Bosch Water Heating for further instruction.
Gas leakage error, gas valve circuit 
not closing properly. 1. Disconnect power supply cord and check wire conn
ections on
gas valve and the two connectors on the control boa rd.
2. Flow water out of a hot water tap above the mini mum activation
point  of  0.5  GPM.  Measure  voltage  at  the  gas  valve  wire  plug
connection. The voltage should measure 24VDC betwee n the left
pair of wires and 24VDC between the right pair of w ires when the
unit  is  operating.  If  voltage  is  not  proper,  contac t  Bosch  Water
Heating for further instruction.
3.  Gas  valve  may  be  defective,  contact  Bosch  Water  Heating  for
further instrucation.
DisplayCauseSolution
Table 29 * By installer or service technician only. 
						

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Electrical diagram53
9 Electrical diagram
Fig. 72 Electrical scheme
1Intlet water temperature sensor
2 Outlet water temperature sensor
3 Backflow temperature sensor
4 Cascading output connection
5 Cascading input connection
6 Ionization sensor
7 Water flow sensor
8 Flue gas limiter
9 Heat exchanger overheat sensor (ECO)
10 Gas valve
11 Exhaust temperature sensor
12 Water valve
13 Primary fan
14 ON/OFF switch
15 Secondary fan
16 AC plug
17 Main connection
18 Ignition electrodes
19 Ground post
20 Antifreeze kit connection
21 Fuse
22 Fuse
20...116...1
JP5JP6
JP7 JP8
JP2
MPSMME
FS
T=104°C 
T=220°F
T=90°C 
T=194°F
Casc.
inputCasc.
output
2
1
4
5
6
7
9
10
11
12
13
15
16
20
19 18
2122
17
148
Backflow3
6720608158-01.1ALT=110°C 
T=230°F 
						

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Sensor resistance charts
10 Sensor resistance charts
Fig. 73 
Fig. 74
Outlet NTC characteristics
3 2
3 7
4 2 4 7
5 2 5 7
6 2 6 7
7 2
7 7
8 2 8 7
9 2 9 7
10 2 10 7
112117
12 2 12 7
13 2 13 7
14 2 14 7
15 2
15 7
16 2 16 7
17 2 17 7
18 2 18 7
19 2 19 7
2 0 2 2 0 7
2 122 17
2 2 2
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 2 0 2 1 2 2 2 3 2 4 2 5 2 6 2 7 2 8 2 9 3 0 3 1 3 2 3 3 3 4 3 5 3 6 3 7
Re sista nce  (Kohm)
Temp ºF
0
5
10
15
2 0
2 5
3 0
3 5
4 0
4 5
5 0
5 5
6 0
6 5
7 0
7 5
8 0
8 5
9 0
9 5
10 0
10 5
110
Temp ºC
Inlet NTC characteristics
3 2
3 7
4 2 4 7
5 2 5 7
6 2 6 7
7 2 7 7
8 2 8 7
9 2
9 7
10 2 10 7
112117
12 2 12 7
13 2 13 7
14 2 14 7
15 2
15 7
16 2 16 7
17 2
17 7
18 2 18 7
19 2
19 7
2 0 2
2 0 72 12
2 17
2 2 2
2 2 7
2 3 2
2 3 7
2 4 2 2 4 7
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 2 0 2 1 2 2 2 3 2 4
Re sista nce  (Kohm)
Temp ºF
0
5
10
15
2 0
2 5
3 0
3 5
4 0
4 5
5 0
5 5
6 0
6 5
7 0
7 5
8 0
8 5
9 0
9 5
10 0
10 5
110
115
12 0
Temp ºC 
						

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Sensor resistance charts55
Fig. 75
Back Flow and Exhaust NTC characteristics
3 2
3 7
4 2
4 7
5 2
5 7
6 2
6 7
7 2
7 7
8 2
8 7
9 2
9 7
10 2
10 7 112
117
12 2
12 7
13 2
13 7
14 2
14 7
15 2
15 7
16 2
16 7
17 2
17 7
18 2
18 7
19 2
19 7
2 0 2
2 0 7 2 12
2 17
2 2 2
2 2 7
2 3 2
2 3 7
2 4 2
2 4 7
2 5 2
2 5 7
2 6 2
2 6 7
2 7 2
2 7 7
2 8 2
2 8 7
2 9 2
2 9 7
3 0 2
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 3 0 31 32 33 34 35 36 37
Re sista nce  (Kohm)
Temp ºF
0
5
10
15
2 0
2 5
3 0
3 5
4 0
4 5
5 0
5 5
6 0
6 5
7 0
7 5
8 0
8 5
9 0
9 5
10 0
10 5
110
115
12 0
12 5
13 0
13 5
14 0
14 5
15 0
15 5
Temp ºC 
						

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Functional scheme
11 Functional scheme
Fig. 76 Functional scheme
Fanspeed
OK? waiting
timeof10s passed?
watertap
open?Waterflow 0.5gpm
(>1.9l/min)
(seeWFcalc.) >
NO NO NO NO
YES
YES
YES
YES
NO NO NO
NO
YES YES
Startsparking
IDLE
Openthegas
valve
1st
Safetytime
of5spassed?
Ionization
detected?
6720608158-65.2V
NO
NO
NO
NO YES
YES
YES Seeerror
codetable
Postpurgeof fanfor7sec.
Stayblocked tillRESET
closesecond gasvalve
Postpurgeof fanfor7sec.
watertap
closed

						

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Interior components diagram and parts list57
12 Interior components diagram and parts list
12.1 Interior components
Fig. 77 Components
1Exhaust temperature sensor
2 Flue gas collector
3 Heat exchanger
4 Ionization sensor
5 Primary fan (Mixer)
6 Hot water temperature sensor
7 LCD display
8 On/Off button
9 Reset button
10 Program key
11 Flue gas limiter
12 Heat exchanger overheat sensor (ECO) 13
Ignition electrodes
14 Observation window
15 Backflow temperature sensor
16 Secondary air fan
17 Gas valve
18 Condensate trap
19 Water valve with flow sensor and cold water tempera ture 
sensor
20 Control unit
21 Up button
22 Down button
23 LED 
						

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Interior components diagram and parts list 
Fig. 78 Appliance overview 
						

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Interior components diagram and parts list59
12.2 Components diagram
12.2.1 Group 1 
Fig. 79 Components Diagram
9
9
8
5
12
3
6
7
9
10
12
9
14
16
17
11
1315
15
4
6720902973.AB JF
ItemDescriptionReference
1 Front cover 8 705 431 412 
2 Cover shield 8 705 506 906
3 Trade mark badge 8 701 103 140 
4 Cover screw 8 703 401 170 
5 Combustion cover 8 700 506 300
6 Combustion cover gasket 8 704 701 084
7 Observation window 8 705 600 003 
8 Holding bracket 8 708 104 103 
9 Screw 8 703 403 012
Table 30
10 Combustion cover clip 8 701 201 032 
11 Grommet set 8 710 203 039 
12 Exhaust accessory 8 705 504 152 
13 Gasket exhaust 8 700 103 710
14 Inlet air cover 8 708 006 022 
15 Inlet air gasket 8 700 103 166 
16 Inlet air accessory 8 705 504 154
17 Mounting bracket 8 701 309 164
ItemDescriptionReference
Table 30 
						

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Interior components diagram and parts list 
12.2.2 Group 2 
Fig. 80 Components Diagram
1230
25
13
15
20
1
4
5
6
7
32
8
9
10
8
8
11
11
8
1214
21
22
13
18
17
16
16
1319
172324
2728
28
2829
31
32
33
35
26
6720902980.AA JF
34
13