Junkers on demand water heater

[Dan Walters]

Got a heating problem with a Junkers wall mounted water heater. The gas part is ok but heating of the water is poor. The pilot is fine and good flame from the burners as soon as the tap is opened. You can hold you hand under the heated water. The heater would be around 25 years old. Does the heat exchanger on these clog up and reduce the heat tranferr to the water? Can they be cleaned out? Are parts still available? Its a model V250 K1/23
Thanks in advance for any help.

[SelgasParticipant]

BrainG
I see you are in Australia to obtain the technical information you require in the first instance you should make contact with Robert Bosch Aust. Pty Limited who are the Junkers importers/manufacturers in Aussie as seek advice from their technical staff.
However, in saying that I can also answer your question based on being a Bosch/Junkers service agent here in New Zealand – Heat exchangers ( the copper part that the water runs through ) can and do lime up with calcium in hard water areas, however this usually takes a fair while to affect the heat output of the heater, once the lime or build up has formed in the copper coils it can on some ocassions be disolved with a product we call “Lime-Away” which is an acid that attacks lime/calcium and disolves it.
You may wish to try this experiment first : try slowing the flow through your taps down during the winter months as this action causes the water to stay in the heating chamber a little longer than full flow allows and will allow the heater to apply more heat to the water as it passes through. In the summer months the warmer inlet cold water temperature usually compensates for the same thing so full flow can be used then.

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Selgas Services Ltd
Craftsman Gasfitters, Plumbers, Electrical Service Technicians

[BriangParticipant]

Thank you Peter. I will try all you suggestions the next time I have access to the heater. I will let you know how I go.

[Author]

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