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Thread: Using Hot Water for Dishwasher

  1. #1
    Automated Home Lurker
    Join Date
    Jan 2018

    Default Using Hot Water for Dishwasher

    Going off topic here but related to the Hot Water which is controlled by Evohome...

    Reading the manual for the dishwasher I see that it can be connected to either cold or hot water. I had not noticed this before, and our previous dishwasher had stated cold feed only.

    The Bosch manual says:
    The dishwasher can be connected to cold or hot water up to max. 60°C. Connection to hot water is recommended if the hot water can be supplied by energetically favourable means and from a suitable installation. This will save energy and time. The “Hot water” setting allows you to adjust your dishwasher optimally to operate with hot water. It is recommended to have a water temperature (temperature of the incoming water) of at least 40 °C and no more than 60 °C. It is not recommended to connect the appliance to hot water if the water is supplied from an electric boiler.

    Thinking aloud my questions are:
    1. What happens if the hot water coming from the storage cylinder is hotter than the program selected on the dishwasher? E.G., water at 60° and dishwasher program of 45°. Do you get a hotter wash ‘for free’, or does the dishwasher get confused and have an error?
    2. What happens if the hot water coming from the storage cylinder is colder than the program selected on the dishwasher? E.G., water at 40° and dishwasher program of 70°. Does the dishwasher still use its heating element to boost the temperature, or does it never bother using its heating element once you have done the “Hot water” setting?
    3. If it copes fine with Q1, and still uses the heating element when needed in Q2, then what actually is the “Hot water” setting changing? The salt?

    It is connected up to cold water currently, but I am now thinking of switching it over. Has anyone tried using a hot water feed?

    The main issue I imagine is not having any hot water circulation. Depending on when there was last a withdrawal from a tap, it sometimes takes a while to remove the cool water from the pipes before the hot water can be withdrawn. The dishwasher will consume between 9-18 litres depending on cycle, and if unlucky, the first bit of that will be the cool water clearing the pipes.

    I know there’s an argument that its best to do the early rinse with cold water to avoid baking on the dirt, but then that’s negated by the initial cool water in the pipes.

    The hot water isn’t drinking water (vented cylinder fed by header tank in the loft), but the cylinder is stored at 60° and so should have killed off legionella already.

    Thoughts anyone?

  2. #2
    Automated Home Legend
    Join Date
    Jul 2014


    Q1 is interesting and I wonder what happens too. Q2 is easy, the dishwasher will top up the heat, the savings is in the saved electricity from raising the temp of the water to whatever is needed for the cycle. I guess this has come about for people who are heating their water for free using excess solar or similar. I instead run my dishwater off the cold tap but run it when the sun is shining, so it uses my solar any way.

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