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Viessmann 7450156 Backup Battery Replacement

Introduction

The Duomatik Control Unit/HMI is equipped with a built-in industrial-grade 3.6V 2400mAh AA (Mignon) Lithium (LiSOCl2) Battery, used for maintaining clock functionality and preserving timer settings during boiler shutdowns or power outages. Although these robust cells typically offer prolonged lifespan, eventual failure is inevitable.

Should your boiler frequently lose time and settings, it might signal the need for a battery replacement.

This in guide we will walk you through the process of replacing the battery.


Note

If you're replacing the battery as a preventive measure, when you power on the module after the repair, it might initially seem broken to you. The module will enter an error mode due to time loss, locking all functions except for setting the time. Therefore, your first step would be setting the clock before accessing other features.

What you need

  1. Viessmann 7450156 Backup Battery Replacement, Shut off the Boiler: step 1, image 1 of 2 Viessmann 7450156 Backup Battery Replacement, Shut off the Boiler: step 1, image 2 of 2

    • Locate the shutoff switch of your boiler and press it.

    • The switch is usually positioned right next to the flame-resistant door leading to the boiler room and labeled as Boiler Emergency Shutoff.

    Edit

  2. Viessmann 7450156 Backup Battery Replacement, Locate the HMI module: step 2, image 1 of 1

    • Locate the HMI module of the Duomatik, that you want to remove.

    Edit

  3. Viessmann 7450156 Backup Battery Replacement, Loosen the HMI module: step 3, image 1 of 2 Viessmann 7450156 Backup Battery Replacement, Loosen the HMI module: step 3, image 2 of 2
    Tool used on this step:
    Spudger
    $3.99
    Buy

    • Insert a flathead screwdriver or a Spudger into the small notch on top of the module to gently loosen it.

    Edit

  5. Viessmann 7450156 Backup Battery Replacement, Remove the HMI module: step 4, image 1 of 2 Viessmann 7450156 Backup Battery Replacement, Remove the HMI module: step 4, image 2 of 2

    • Pull out the module straight toward yourself.

    Edit

  6. Viessmann 7450156 Backup Battery Replacement, Remove the back: step 5, image 1 of 3 Viessmann 7450156 Backup Battery Replacement, Remove the back: step 5, image 2 of 3 Viessmann 7450156 Backup Battery Replacement, Remove the back: step 5, image 3 of 3
    Tool used on this step:
    Spudger
    $3.99
    Buy

    • Place the module on its front.

    • The back of the module is held in by four clips. Use Spudgers to hold the clips open while you remove the back.

    • You might meet a bit of resistance from the little red connector holding the two PCBs inside together.

    Edit

  7. Viessmann 7450156 Backup Battery Replacement, Remove the encoder knob: step 6, image 1 of 3 Viessmann 7450156 Backup Battery Replacement, Remove the encoder knob: step 6, image 2 of 3 Viessmann 7450156 Backup Battery Replacement, Remove the encoder knob: step 6, image 3 of 3

    • Place the module on its back.

    • Open the flap that covers the buttons for setting the timer.

    • Remove the encoder knob by pulling it off.

    Edit

  8. Viessmann 7450156 Backup Battery Replacement, Remove the PCB: step 7, image 1 of 2 Viessmann 7450156 Backup Battery Replacement, Remove the PCB: step 7, image 2 of 2

    • Release the first two clips holding the PCB inside the housing.

    • Release the last two clips holding the PCB inside the housing.

    • Remove the PCB from the housing.

    • The last two clips might be a bit hard to release, though take care to not use too much force and break them.

    Edit

  9. Viessmann 7450156 Backup Battery Replacement, Desolder the battery: step 8, image 1 of 3 Viessmann 7450156 Backup Battery Replacement, Desolder the battery: step 8, image 2 of 3 Viessmann 7450156 Backup Battery Replacement, Desolder the battery: step 8, image 3 of 3

    • Desolder the negative connection.

    • Desolder the positive connection.

    • See this guide on how to solder and desolder connections.

    Edit
Conclusion

To reassemble your device, follow these instructions in reverse order.

Take your e-waste to an R2 or e-Stewards certified recycler.

One other person completed this guide.

Author

Sebastian

Member since: 08/19/18

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5 Comments

I am in this boat. Replacing the battery is not a problem. The problem is what is the procedure to reinitialise the control unit afterwards? What values need to be put back and what button presses achieve that?

Michael LEE - Reply

The module will enter an error mode due to time loss, locking all functions except for setting the time. Therefore, your first step would be setting the time before accessing other features. I'm not sure for the process, it has been a while for me. You can just download the user manual on the Viessmann Website, though.

Sebastian -

Thanks Sebastian, I can see the clock can be adjusted. At the moment, with the old battery still installed (I did measure it and it seemed ok to me @4.2V but will accept it may be borderline) I can adjust the time but that is all, the temperatures from the thermistors are not there, this is why I believe it may need initialising. I can also enter the options pages where you can set various options like room thermostat fitted or not and hot water cylinder temperature 60 or 70 degrees and I believe there will be a 'secret' code in there somewhere to initialise the control board. It isn't in the manual, at least, not the manual for mere users, it will be a reserved engineering code.

Michael LEE - Reply

Maybe post your problem in the Answers forum. There are a lot of talented people on there who might be able to help you with your problem.

Sebastian -

Already done Sebastian, thanks.

Michael LEE - Reply

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