Worcester ZWB 7-25 HE combi Specifications Page 1

Service booklet for the Engineerfor Gas Condensing Boilers6 720 610 577-00.10 ZWB 7-29 CC1 GC-Number: 47 108 05 ZB 7-28 CS1 GC-Number: 41 108 02 Z

7 181 465 346 GB (03.02)10Bosch Heatronic board functionsValues that can only be read - only left display digit:Values that can only be read - only ri

7 181 465 346 GB (03.02) Bosch Heatronic board functions112.5.2 Secondary Service LevelOperationIn order to change or check the values of the service

7 181 465 346 GB (03.02)12Bosch Heatronic board functionsValues that can only be read:Description Display Reset Value5.2 Automatic gas igniter status

7 181 465 346 GB (03.02) Failure identification procedure133 Failure identification procedure3.1 Notes on using the fault code tablesThe procedure is

7 181 465 346 GB (03.02)14Failure identification procedure3.2 Summary3.2.1 Appliance faults 3.2.2 Faults that are not displayedAppliance faultsCategor

7 181 465 346 GB (03.02) 15Failure identification procedure3.3 Error codes on the displayA5 flashing.Heat store NTC sensor 2 defective Check ActionB N

7 181 465 346 GB (03.02)16Failure identification procedure5. To return to normal function mode:B Press buttons and simultaneously.B Regulate the t

7 181 465 346 GB (03.02) 17Failure identification procedureA7 flashing.Hot water NTC sensor defectiveCheck ActionB Note the setting of the temperature

7 181 465 346 GB (03.02)18Failure identification procedure4. B Unplug 20-pin connector from PCB.After max. 60 sec.:Does the displayed code change to a

7 181 465 346 GB (03.02) 19Failure identification procedureA8 flashing.No correct electrical connectionCheck Action1. TR 2 connected? yes: A8? ↓2.no:

7 181 465 346 GB (03.02) 2 Table of contents Table of contents Warnings 3 Symbols 3 1 Layout of Appliance 4 1.1 combi 41.2 system 5 2 Bosch Heat

7 181 465 346 GB (03.02)20Failure identification procedureAC flashing.Module not detected.(Constant CH flow temperature according to CH temperature co

7 181 465 346 GB (03.02) 21Failure identification procedure7. Remote control status still 0.? yes: B Power OFF the appliance.Remote control: B Replace

7 181 465 346 GB (03.02)22Failure identification procedureAd flashing.Heat store NTC sensor 1 not detected (ZB...).Check ActionB Note the setting of t

7 181 465 346 GB (03.02) 23Failure identification procedure4. Temperature between 99. and 95. is displayed.B Unplug connector.After max. 60 sec.:Does

7 181 465 346 GB (03.02)24Failure identification procedureb1 flashing.The Heatronic does not recognise the code key.Check Action1. B Power OFF the app

7 181 465 346 GB (03.02) 25Failure identification procedureC1 flashing.Fan speed too lowCheck Action1. Fan lead connector properly con-nected?yes: ↓2.

7 181 465 346 GB (03.02)26Failure identification procedureCC flashing.Outside temperature NTC sensor not detected. (Boiler heating as if outside tempe

7 181 465 346 GB (03.02) 27Failure identification procedured3 flashing.Wrong signal from pin 8-9 (open?).Check Action1. B Turn ON the appliance.B Meas

7 181 465 346 GB (03.02)28Failure identification procedureE2 flashing.The heating outlet NTC sensor is damaged.Check ActionB Note the setting of the t

7 181 465 346 GB (03.02) 29Failure identification procedureTo return to normal function mode:B Press buttons and simultaneously.B Regulate the tem

7 181 465 346 GB (03.02) Warnings 3 Warnings Repairs B Repairs may only be carried out by an approved installer! B Before carrying out any work on t

7 181 465 346 GB (03.02)30Failure identification procedureE9 and flashing.Safety temperature limiter has tripped.Check Action1. Is the heating press

7 181 465 346 GB (03.02) 31Failure identification procedure5. Is lead disconnected from CH flow safety temp. limiter?yes: B Power OFF the appliance.B

7 181 465 346 GB (03.02)32Failure identification procedureEA and flashing.No flame ionisations signalCheck ActionB Note the setting of the temperatu

7 181 465 346 GB (03.02) 33Failure identification procedure5. Natural gas models:does the building have a supply pres-sure regulator?yes: B Check that

7 181 465 346 GB (03.02)34Failure identification procedure8. Is diaphragm in the mixer unit cor-rectly fitted and functional?B Open mixer unit (29).B

7 181 465 346 GB (03.02) 35Failure identification procedure13.B Press buttons and simulta-neously.B Select service-function 5.1.Continuous ignitio

7 181 465 346 GB (03.02)36Failure identification procedure19. Check if the 20-pin connector lead assembly is damaged.B Power OFF the appliance.B Disco

7 181 465 346 GB (03.02) 37Failure identification procedureF0 (and possibly ) flashing.Internal failureCheck ActionB Note the setting of the temperat

7 181 465 346 GB (03.02)38Failure identification procedureF7 and flashing.Although appliance switches off, flame still detectedCheck Action1. Electr

7 181 465 346 GB (03.02) 39Failure identification procedureFA and flashing.Although appliance switches off, flame still detectedCheck ActionB Note t

7 181 465 346 GB (03.02) 4 Layout of Appliance 1 Layout of Appliance 1.1 combi Fig. 1 4 Heatronic control 6 Heat exchanger safety temperature limite

7 181 465 346 GB (03.02)40Failure identification procedure5. Check if the 20-pin connector lead assembly is damaged.B Power OFF the appliance.B Discon

7 181 465 346 GB (03.02) Failure identification procedure41Fd and flashing.Button pressed without necessityCheck Action1.Button is flashing. B P

7 181 465 346 GB (03.02)42Failure identification procedure3.4 Faults that are not displayed3.4.1 Appliance faultsExcessive burner noise, rumbling nois

7 181 465 346 GB (03.02) Failure identification procedure437. B Press buttons and simulta-neously.B Select service-function 5.9.0 is displayed.B S

7 181 465 346 GB (03.02)44Failure identification procedureIgnition too harsh, ignition poorCheck ActionB Note the setting of the temperature controls

7 181 465 346 GB (03.02) Failure identification procedure456. Does the gas supply type match the specifications on the appliance iden-tification plate

7 181 465 346 GB (03.02)46Failure identification procedureLoose or broken contact on heat store NTC sensor Check Action1. Heat store NTC sensor lead i

7 181 465 346 GB (03.02) Failure identification procedure47Specified CH flow temperature from TA... programmer exceededCheck ActionB Note the setting

7 181 465 346 GB (03.02)48Failure identification procedure3.4.2 Programmer faultsCondensation in the flue pipeCheck Action1. Is diaphragm in mixer uni

7 181 465 346 GB (03.02) Failure identification procedure49Set room temperature not reached (TA 211 E und DT 2)Check Action1. Thermostatic valve(s) se

7 181 465 346 GB (03.02) Layout of Appliance 5 1.2 system Fig. 2 4 Heatronic control 6 Heat exchanger safety temperature limiter 7 Testing point for

7 181 465 346 GB (03.02)50Failure identification procedureSet room temperature exceeded by large amountCheck Action1. Do radiators get too hot? yes: T

7 181 465 346 GB (03.02) Failure identification procedure51Temperature rises instead of fallingCheck ActionTimer clock (DT 2) incorrectly set B Check

7 181 465 346 GB (03.02)52Appendix4 Appendix4.1 NTC values4.1.1 Outside temperature sensor4.1.2 CH flow NTC sensor, heat store NTC sen-sor, constant h

7 181 465 346 GB (03.02) Appendix534.2 Electronic schemes4.1 Ignition transformer6 Heat exchanger overheat cut-out6.1 Flue gas NTC sensor6.3 Hot wat

7 181 465 346 GB (03.02)54Appendix4.3 List of most important replacement parts Component Order no. RemarksSwitchboxPCB control board 8 748 300 385Tran

7 181 465 346 GB (03.02) Appendix554.4 Approved corrosion inhibitors and anti-freeze fluids for central heating waterIf any system water treatment is

7 181 465 346 GB (03.02) 6 Bosch Heatronic board functions 2 Bosch Heatronic board func-tions 2.1 Initialisation When it is switched on, the applianc

7 181 465 346 GB (03.02) Bosch Heatronic board functions 7The next time the central heating or heat store calls for heat, the appliance is held at a

7 181 465 346 GB (03.02)8Bosch Heatronic board functions2.5 Boiler service functions2.5.1 First Service LevelOperatingIn order to change or check the

7 181 465 346 GB (03.02) Bosch Heatronic board functions9Values that can only be read:Description Display Reset Value.1 Heating outlet temperature. 0