2017-04-29 Evgeny Fomenko

The device and principle of operation of Bosch boilers

The most popular models among the Bosch line of boilers are double-circuit. They are faced with two tasks: the first is to heat the room to a predetermined temperature, the second is to ensure hot water for household needs.

Bosch devices, namely the Bosch Gas 4000 W and Junkers Bosch models, are equipped with two independent heat exchangers, which allows them to perfectly perform two tasks: heating water and providing heat in the room.

In each of the models it is possible to choose the power of the device that suits you from 12 to 35 kW, the area of ​​the room is taken into account when choosing. Regarding heating the liquid for household needs, the productivity is about 8-13 liters per minute.

Advantages of a wall-mounted double-circuit boiler:

The boiler can be built into the kitchen wall

Disadvantages:

• The first 20-40 seconds after you turn on the hot water tap, cold water flows.

Let's take a closer look at how the device works, using the example of the Bosch Gas 4000 W ZWA 24 model. When the boiler is operating in heating mode, use gas burner heat is transferred to the primary heat exchanger, which is a structure made of copper tubes and records.

So that they do not deteriorate from exposure high temperatures and water, their surface is covered protective layer... Its main task is to transfer the heat generated during the combustion of the flame to the heating system. The movement of water in the system is provided by a pump.

Also, the design provides a three-way valve, its task is to prevent water from entering the secondary heat exchanger. A secondary heat exchanger is required to heat domestic water. The heated liquid for the heating circuit leaves the device through the heating supply line, and the cooled liquid enters through the heating return line.

When the boiler is set to heat water for consumption, the 3-way valve closes the heating circuit. The heated liquid flows from the primary heat exchanger to the secondary one, and then flows out of the device.

Bosch boiler three-way valve

The plus when using different heat exchangers is obvious. When heating is often used plain water, but it usually contains impurities. When it heats up, impurities begin to form deposits that negatively affect the heat exchanger, reduce its throughput, prevent water from heating, and shorten its service life.

And when the liquid that flows through the primary heat exchanger, it is in a closed circuit, does not change its chemical properties, minimizes negative consequences.

Fluid that flows through the secondary heat exchanger will build up deposits over time and over time the heat exchanger will need to be replaced or cleaned. If the malfunction occurs on winter period, your boiler will be able to operate smoothly in heating mode using the primary radiator.

Major error codes

Like any device, the Bosch gas boiler also sometimes fails and needs repair, let's take a closer look at its possible malfunctions and ways to eliminate them.

11

Error 11 is possible in the Bosch BWC 42 device, it stands for, in the same way as error E9, signals that the flue gas temperature limiter has been triggered.

Temperature limiter flue gas

You need to do the following:

• check on the subject wire damage flue gas temperature limiter, if ruptured or melted, replace;
• check pressure in the device;
• check temperature limiter;
• check serviceability of the pump when it starts;
• if air has accumulated in the boiler, drain it.

23

Error 23 is not an error, this code appears during settings and indicates the type of used natural gas

50

Error 50 appears on Bosch ZWA 24 models when there is no flame.

Boiler Bosch ZWA 24

How to fix it:

70

Error 70 means a malfunction of the differential relay during ignition.

Reasons and ways to eliminate it:

• differential relay failure, can be determined by measuring its resistance, if it does not correspond to the nominal, the relay will be replaced;
• mechanical breakdown of contacts and wires suitable for the relay, check and connect the wires;
• poor chimney performance, it may become clogged, clean the chimney;
• incorrect setting or breakdown of the fan, adjust the operation of the fan, if it is faulty, replace it.

a2

Error a2 appears when exhaust flue gases exit on the combustion chamber, indicating that the heat exchanger is clogged with soot and fumes. To eliminate, clean the heat exchanger.

Cleaning the heat exchanger with compressed air

e2

Error e2 - the flow temperature sensor is faulty. Call the sensor for availability short circuit or an open, inspect the connecting wires for a broken circuit or oxidation. Strip or connect the wires, in case of sensor failure, replace with a new one.

e9

Error e9 means the temperature limiter has been triggered.

The reasons for the appearance and methods of elimination may be as follows:

ea

Error ea signals the absence of a flame in the on state.

When this code appears, you should check:

er

Error er (ep) appears in case of incorrect operation of the boiler in the event of malfunctions in any of the device blocks.

c3

Error c3 appears on the Bosch ZWE boiler in the event of the appearance of exhaust gases on the combustion chamber. This problem can be eliminated by cleaning the heat exchanger in accordance with the instructions in the instructions.

c4

When the differential pressure switch is closed and the fan is off, error c4 appears.

Differential relay

When this code appears, you can do the following:

• blow out the tubes coming from the relay, after removing the relay, which is located in the upper part of the boiler. If the relay clicks, the problem is eliminated;
• measure resistance with a multimeter for an open or short circuit, if the parameters are inappropriate, the relay must be changed.

c6

Error c6 means that the differential relay does not turn on when the fan is turned on.

What to do when this code appears:

• check the chimney, eliminate interference, in coaxial chimneys sometimes it can be ice or frost.
• see if there is condensation on the tubes coming from the relay. Dry the tubes with a hair dryer.
• check relay for short circuit or open, replace the relay if necessary.

ce

The ce error is a fairly often repeated code in Bosch gas boilers (bosch gaz) 6000 24 kW and means insufficient pressure in the heating circuit.

Bosch boiler gas 6000 24 kW

The lack of water in the circuit is determined by the pressure gauge:

• if the pressure gauge is in the red zone, it is necessary to add water to the system using the make-up tap, which is located under the device;
• if the pressure gauge is in the green zone, change the pressure sensor. The sensor may have a defective microswitch or diaphragm.

f0

Error f0 means an internal fault. When it appears, you need to check the reliability of the connection of the terminals and wires to the electronic board. If the wires are not oxidized, the connections are not broken, then this is a malfunction of the board itself, it should be replaced.

fd

The fd error appears if the button has been pressed for more than 30 seconds. To reset this code, press and hold the button for less than this time.

se

The se error signals an insufficient filling of the heating system.

Heat exchanger with limescale and after cleaning

What should be done:

• add water:
• the reason why the pressure drops can be a leak or depressurization of the heating pipes. If the pipes are hot, it is difficult to detect a malfunction, as water can evaporate at the leak. To determine, cool the system, seal the joints in the places of leakage:
• the heat exchanger may be clogged with scale, remove and rinse it, the procedure is described in the instructions for the boiler.

Other malfunctions

Above were the most common error codes, let's look at other possible malfunctions.

Sometimes there are such problems:

Errors of Bosch Gaz 6000 boilers

Error A7 - The hot water temperature sensor has a malfunction.

Error Ad - Not Defined temperature sensor boiler.

Check the boiler sensor and connection wires.

Error C1 - The fan rotates at a low frequency.

Check the mains voltage.

Check the flue gas outlet. Clean or repair if required.

Error C4 - The differential pressure switch does not open when the fan is not working.

Check diff. pressure switch.

Error C6 - The differential pressure switch does not close.

Check diff. pressure switch, as well as flue gas pipes.

Error C7 - The fan is not functioning.

Check the fan, wire and plug. Replace if required.

CE error - Low pressure to fill the heating system.

Top up with water.

Error d7 - There is a malfunction of the gas valve wall boiler Bosch 6000.

Check the connection wire.

Error E2 - Malfunction or breakage of the temperature sensor on the supply line.

Check the sensor for a defect, as well as a possible short circuit in its wire. Replace if required.

Error E9 - Activation of the heat exchanger temperature limiter.

Check the temperature limiter of the heat exchanger for a defect, as well as a possible short circuit in its wire. Replace if required.

Verify operating pressure in the heating system.

Check temperature limiter, replace if necessary.

Check pump start. Replace the pump if required.

Check fuse, replace if necessary.

Remove air from gas boiler Bosch 6000.

Check the water circuit of the heat exchanger; if damaged, replace it.

Check the flue gas temperature limiter for a defect, as well as a possible short circuit in its wire. Replace if required.

EA Error - Flame Not Found.

Check the connection of the protection wire.

Check the opening of the gas cock.

Check gas supply pressure. Correct the problem if necessary.

Check the connection to the electrical network.

Check electrodes and wires. Repair if necessary.

Check the flue gas outlet. Clean or repair if required.

Adjust the gas. Repair if necessary.

For natural gas: check the gas flow monitor. Correct the problem if necessary.

When using the combustion air intake from a room, check the air draft into the room and the ventilation openings.

Clean the heat exchanger.

Inspect the gas fittings. Replace if required.

Error codes for gas boilers Bosch ZSC / ZWC 24 MFA

A7 - Hot water temperature sensor defective.

Check for damage or short circuit of the temperature sensor and its wire, replace if necessary.

A8 - BUS connection interrupted.

Verify connection cable and regulators.

A9 - The hot water temperature sensor is incorrectly installed.

Check the installation area, if necessary, dismantle the sensor and reinstall it using heat-conducting paste.

Ad - No boiler sensor detected.

Check boiler sensor and connecting cable.

b1 - Coding plug not found.

Insert the coding plug correctly, measure and replace if necessary.

C1 - During the operation of the device, the differential pressure switch has opened.

Check differential pressure switch, exhaust device and connecting pipes.

C4 - Differential pressure switch in non-operating position does not open.

Check differential pressure switch.

C6 - Differential pressure switch does not close.
Check differential pressure switch and flue pipes.

d3 - No jumper detected on ST8 161

If there is a jumper, insert the plug correctly, check the external stop. Otherwise: is there a jumper?

d4 - Too large temperature difference.

Check pump, bypass hose and system pressure.

E2 - The flow temperature sensor does not work.

Check temperature sensor and connecting cable.

E9 - The limiter in the flow line has worked.

Check the pressure in the system, temperature sensors, check the operation of the pumps and the fuse on the electronic board, remove air from the device.

EA - Bosch ZSC / ZWC boiler does not detect a flame.

Is the gas cock open? Check gas supply pressure, mains connection, starter electrode with cable and ionisation electrode with cable.

F0 - Internal fault.

Check that the electrical plug contacts and start lines are properly connected, replace the electronic board if necessary.

F7 - Although the boiler is off, a flame is detected.

Check electrodes and cable. If the flue gas outlet works, check the electronic board for moisture.

FA - Flame detected after gas supply cut off.

Check the ionisation electrode. Verify gas fittings.

Fd - The button was mistakenly pressed for too long (more than 30 seconds).

Press the button again in less than 30 seconds.

CC - Sensor outside temperature Not found.

Check outside temperature sensor and connecting cable for damage.

Malfunctions of gas boilers Bosch

The burner does not start

Check the operation of the emergency switch of the heating system - If necessary, switch it on.

Check operation of the control system start switch - If necessary, switch on.

Inspect the safety breakers - Check their functionality, if necessary, replace the faulty breaker.

Inspect the boiler water temperature regulator - Check and replace the defective part if necessary.

High limit safety cut-out defective - Check, replace if necessary.

An error signal appears from external safety devices (e.g. water quantity safety monitor) - Check heating system, eliminate the errors, replace the faulty device if necessary.

The flue gas relay trips - AW 10: unlock the flue gas relay. AW 50: wait a maximum of 15 minutes.

The Bosch boiler will turn on automatically if there is a request for heat. In the event of repeated tripping, check the flue gas path and the function of the flue gas monitor. Replace relay if defective.

The burner ignites and shuts down due to a fault. No ignition spark

An ignition spark is heard when the ignition cable is removed - If not: replace the ignition transformer.

If yes: replace ignition electrode or ignition burner.

The burner ignites and shuts down due to a fault

Is it open gas cock? - Open the gas cock.

The natural gas supply pressure is higher than 8 mbar - If not: Investigate the cause and rectify the fault.

Is the air removed from the gas pipeline? - Remove air until gas ignition is possible.

The burner ignites and shuts down due to a fault. No ionization current

The N and L connections may be reversed - Eliminate the error.

Check voltage between L and PE - If not: carry out PE grounding, if necessary install an isolation transformer.

Poor ionization wire contact - Correct the error, replace the defective part if necessary.

Ionisation electrode shorted to ground - Burner control defective.

Boiling sounds

Is there limescale or scale build-up in the Bosch boiler?

Clean the boiler water circuit according to the manufacturer's recommendations.

In case of constant water loss, find and eliminate the cause.

If necessary, treat the water and install a dirt trap.

Flat main flame

Are the injectors suitable for the gas supplied? - If not: install the correct nozzles.

Match holes supply and exhaust ventilation local regulations and requirements for the installation of gas equipment?

In case of insufficient air flow, the deficiency must be rectified immediately.

Harsh whistle of the burner

Is it installed correct pressure on the injectors? - Check the set value, correct if necessary.

The burner smokes

Is there any noticeable contamination in the crevices or below the slots of the burner rods? - Carry out damp cleaning of the burner as described in this manual.

Find the source of contamination and protect against further contamination.

Are the air inlet and outlet openings permanently functional? - Are there deposits or fibrous contamination on the surface of the heat exchanger?

Inspect through the cleaning holes and combustion chamber. Carry out a dry and, if required, damp cleaning of the boiler as described in this manual.

Are the burner rods damaged or deformed, are there any deformation of individual slots? - Replace burner rods, identify and eliminate the cause of the malfunction.

Information: Damage or deformation is only caused by at least one of the above faults.

Burner ignition is very loud, with strong combustion noises, you can see the flame on the nozzles

Are the correct nozzles installed? - Switch off the burner, fit a new burner rod and correct the incorrect setting for the type of gas.

Are the nozzles set to the correct pressure? - Smell of flue gases in the room where the boiler is installed.

Is the flue gas coming out of the draft breaker? - Determine the cause of the incorrect flue gas discharge and rectify the fault.

If the elimination of the cause is not immediately possible, then the burner must be turned off.

Vacuum in chimney more than 3 Pa? Blockage in the flue gas path?

Are the dimensions of the chimney correct?

Do they work in the boiler room exhaust fans removing air from the room?

Problem: “On a new BOSCH WBN 6000-24c boiler, an EA error appears - no flame was detected. The more degrees are set, the less frequent the error. But at low temperatures, it gives an error almost every day. The flame icon disappears before the error occurs. What to do?"

• Check if the protective conductor is connected;
• Make sure the gas cock is open;
• Check gas pressure, correct if necessary;
• Make sure that the connection to the mains is working properly;
• Check electrodes with wires, replace if necessary;
• Check the flue gas outlet system, clean or repair if necessary;
• Check the gas regulation, correct if necessary;
• For natural gas: check the gas flow monitor. Replace if necessary;
• When working with combustion air intake from a room, check the air supply to the room and ventilation openings;
• Clean the heat exchanger;
• Check gas valve, replace if necessary.

In 90% of cases, the problem is in the board. The best thing is to contact the service center right away. There they will be able to provide quality assistance: make diagnostics and repair the boiler.

Hopefully the article " Gas boiler WBN BOSCH 6000-24c EA error"Was useful to you.

Automation and malfunctions of Bosch Gaz 6000 W boilers

Control automation for gas boilers Bosch Gaz 6000 W

The control panel for gas convection boilers Bosch 6000 W with Cotronic 3 data bus allows the heating system to be controlled depending on the room temperature.

For these wall-mounted convection gas boilers, two types of Bosch regulators are recommended.

OpenThermTM CR12005 Programmable Room Temperature Controller

Rice. 7. Combination of an OpenThermTM CR12005 programmable room temperature controller with a Bosch 6000 gas convection boiler control panel

Purpose and functions:

OpenThermTM programmable thermostat for controlling boilers with Cotronic data bus 3.

Data exchange with the regulator via a two-wire bus.

Two-wire bus technology, reverse polarity protection.

Simple, intuitive settings for temperature control and DHW control.

Preset weekly programs with six switching points. The ability to manually change the program for each day of the week.

LCD display with digital and graphical display of work status.

Display of the current heating and DHW temperature, outside temperature (only in the case of a temperature sensor), indication of the boiler burner operation status and error codes.

Possibility of remote reset of boiler error.

Using the OpenThermTM protocol.

The setting range of the air temperature in the control room is 7 ... 39 ° С with a setting step of 0.5 ° С.

Room temperature controller TRZ 12-2

Fig. 8. Combination of the TRZ 12-2 room temperature controller (on / off) with the control panel of the gas convection boiler Bosch Gaz 6000 W

Description and functions of the regulator

The TRZ 12-2 room temperature controller is recommended for on / off control of the burner flame and control of the circulation pump of gas wall-hung boilers.

Weekly programming of time intervals.

Three operating modes: "Normal", "Economy", "Automatic".

Vacation function (up to 99 days).

Anti-freeze function.

Date and current time display, automatic summer / winter time change (synchronization with the system).

The room temperature adjustment range is from +5 to +39 ° С.

Malfunctions shown on the display of Bosch 6000 boilers

A7 - Hot water temperature sensor defective.

Check for damage or short circuit of the temperature sensor and its wire, replace if necessary.

Ad - Boiler temperature sensor not recognized.

Check the boiler temperature sensor and the connecting cable

C1 - Low frequency fan rotation.

Check the mains voltage.

C4 - Differential pressure switch does not open when the fan is off.

Check differential pressure switch.

C6 - Differential pressure switch does not close.

Check differential pressure switch and flue pipes.

C7 - The fan does not work.

Check the fan and its cable with a plug, replace if necessary.

CE - Insufficient filling pressure of the heating system.

Add water.

d7 - The gas fittings of the wall-mounted Bosch Gaz 6000 W boiler are faulty.

Check the connecting wire.

E2 - Defective flow temperature sensor (open circuit).

Check for damage or short circuit of the temperature sensor and its wire, replace if necessary.

E9 - The heat exchanger temperature limiter has tripped.

Check the heat exchanger temperature limiter and its connecting wire for damage, replace if necessary.

Check the operating pressure in the heating system.

Check temperature limiter, replace if necessary.

Check pump start-up, replace pump if necessary.

Check fuse, replace if necessary.

Remove air from boiler Bosch 6000 W.

Check the water circuit of the heat exchanger, replace if necessary.

Check the flue gas temperature limiter and its connecting wire for damage, replace if necessary.

EA - No flame detected.

Check the protective conductor connection.

Check if the gas cock is open.

Check supply gas pressure, correct if necessary.

Check the electrical connection.

Check electrodes with wires, replace if necessary.

Check the flue gas system, clean or repair if necessary.

Check gas regulation, correct if necessary.

For natural gas: check the gas flow control switch, replace if necessary.

When working with a combustion air intake from a room, check the room air supply and ventilation openings.

Clean the heat exchanger.

Check gas fittings, replace if necessary.

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OPERATION AND REPAIR OF BOILERS

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This article contains all possible malfunctions and options for their elimination, as well as error codes for Bosch boilers. All information is read in the following order: code - name - possible malfunction. If you have any additional questions, please leave them in the comments to this article.

If you are not 100% sure what the problem is and that you can solve it, immediately contact service center for diagnostics and troubleshooting.

Find out the price and buy heating equipment and related products you can from us. Write, call and come to one of the shops in your city. Delivery throughout the territory of the Russian Federation and the CIS countries.

Errors of Bosch Gaz 6000 boilers

The list below presents malfunctions specifically for Bosch Gaz 6000 series boilers. Determine the error code and eliminate the malfunctions in a timely manner.

Error code A7 - The hot water temperature sensor has a malfunction

Error code Ad - Boiler temperature sensor not detected

Check the boiler sensor and connection wires.

Error code C1 - Fan rotates at low speed

1. Check the mains voltage.
2. Check the flue gas outlet. Clean or repair if required.

Error code C4 - Differential pressure switch does not open when the fan is not working

Check diff. pressure switch.

Error code C6 - Differential pressure switch does not close

1. Check diff. pressure switch, as well as flue gas pipes.

Error code C7 - Fan not functioning

Check the fan, wire and plug. Replace if required.

CE error code - Low pressure to fill the heating system

Top up with water.

Error code d7 - There is a malfunction of the gas fittings of the wall-mounted boiler Bosch 6000

1. Check the connection wire.

Error code E2 - Malfunction or breakage of the temperature sensor on the supply line

Check the sensor for a defect, as well as a possible short circuit in its wire. Replace if required.

Error code E9 - Activation of the heat exchanger temperature limiter

1. Check the temperature limiter of the heat exchanger for a defect, as well as a possible short circuit in its wire. Replace if required.
2. Check the operating pressure in the heating system.
3. Check temperature limiter, replace if necessary.
4. Check pump start. Replace the pump if required.
5. Check fuse, replace if necessary.
6. Remove air from the Bosch 6000 gas boiler.
7. Check the water circuit of the heat exchanger; if damaged, replace it.
8. Check the flue gas temperature limiter for a defect, as well as a possible short circuit in its wire. Replace if required.

EA Error Code - Flame Not Found

1. Check the connection of the protection wire.
2. Check the opening of the gas cock.
3. Check gas supply pressure. Correct the problem if necessary.
4. Check the connection to the electrical network.
5. Check electrodes and wires. Repair if necessary.
6. Check the flue gas outlet. Clean or repair if required.
7. Adjust the gas. Repair if necessary.
8. For natural gas: check the gas flow monitor. Correct the problem if necessary.
9. When using the combustion air intake from a room, check the air draft into the room and the ventilation openings.
10. Clean the heat exchanger.
11. Inspect the gas fittings. Replace if required.

Error code F7 - Flame detection when the boiler is off

Although the boiler is off, a flame is detected.

1. Check the electrodes for contamination, replace if necessary.
2. Check the moisture content of the electronic board, dry if necessary.

Error code FA - Flame detection after gas supply cut off

A flame was detected after the gas supply was cut off.

1. Check gas fittings, replace if necessary.
2. Check electrodes and connecting wires, replace if necessary.
3. Check the flue gas system, clean or repair if necessary.

Error code P - Boiler type not defined

Set the boiler type.

Error code Fd - The button was mistakenly pressed for too long (more than 30 seconds)

Error codes for gas boilers Bosch ZSC / ZWC 24 MFA

Below is a list of faults specifically for Bosch boilers of the ZSC / ZWC 24 MFA series. Determine the error code and fix problems in a timely manner.

Error code A7 - Hot water temperature sensor defective

Check for damage or short circuit of the temperature sensor and its wire, replace if necessary.

Error code A8 - BUS connection interrupted

Check connecting cable and regulators.

Error code A9 - Hot water temperature sensor incorrectly installed

Check the installation area, if necessary, dismantle the sensor and reinstall it using heat-conducting paste.

Error code Ad - No boiler sensor detected

Check boiler sensor and connecting cable.

Error code b1 - Coding plug not found

Insert the coding plug correctly, measure and replace if necessary.

Error code C1 - Differential pressure switch opened during instrument operation

Check differential pressure switch, exhaust system and connecting pipes.

Error code C4 - Differential pressure switch in the inoperative position does not open

Check differential pressure switch.

Error code C6 - Differential pressure switch does not close

Check differential pressure switch and flue pipes.

Error code d3 - No jumper detected on ST8 161

If there is a jumper, insert the plug correctly, check the external stop. Otherwise: is there a jumper?

Error code d4 - Temperature difference too large

Check pump, bypass hose and system pressure.

Error code E2 - Flow temperature sensor does not work

Check temperature sensor and connecting cable.

Error code E9 - Flow limiter tripped

Check the pressure in the system, temperature sensors, check the operation of the pumps and the fuse on the electronic board, remove air from the device.

Error code EA - Bosch ZSC / ZWC boiler does not detect a flame

Is the gas cock open? Check gas supply pressure, mains connection, starter electrode with cable and ionisation electrode with cable.

Error code F0 - Internal malfunction

Check that the electrical plug contacts and start lines are properly connected, replace the electronic board if necessary.

Error code F7 - Although the boiler is off, a flame is detected

Check electrodes and cable. If the flue gas outlet works, check the electronic board for moisture.

FA error code - Flame detected after gas cut

Check the ionisation electrode. Check gas valve.

Error code Fd - The button was mistakenly pressed for too long (more than 30 seconds)

Press the button again in less than 30 seconds.

Error code CC - Outside temperature sensor not detected

Check outside temperature sensor and connecting cable for damage.