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Finding good use for excess solar hot water

With the summer in its full glory, I am starting to see excess hot water generated by my solar water heater. In a sunny day I get up to 85 degrees C ( may even boil if not used up)  temperature in the 220l tank and my normal use is less. On the other side, a large share of the electricity bill still goes to .. heating water. Yes, the washing machine and dishwasher still heat up water despite the abundance of readily available such. This calls for taking measures 🙂 Where I live the washing machines with separate hot water inlet are rare, in fact I only found two models.

The bad news is that my washing machine still works nicely and I am reluctant on ditching it just yet. So I focused on the dishwasher, my model is still with cold water inlet, but I had an idea. I would use a hot water mixer to supply 55 degrees to the inlet. The temperature that the mixer can supply is between 45 and 65 degrees, it takes cold water on one side, hot on the other and the third outlet is mixed water at whaterver temperature is set:

The idea is to supply excess hot water (when available) so that the dishasher doesn’t need to heat it up.

I have a neighbor that does pluming, so here I we go, the picture below is underneath my kitchen sink where the cold water inlet for the dishasher is:

We modified it, attaching the water mixer plus two taps so I can switch the source between hot water mixer or the old way – from the cold water when excess water is not available:

I have measured the power consumption to be around 2.4KWh for a washing cycle before, so I loaded the dishwasher and waited eagerly to measure the effect.

I was totally surprised to see that there is no change in behavior, even though water that is 55 degrees C  is being poured in. Quite a frustration. Seems that my dishwasher uses time-based algorithm and not a thermostat.. can you imagine? I turned up the mixer a bit to supply 65 degrees and repeated the cycle, but same result. Really amazed how silly the dishwasher behaves. Oh well, I am left with the only option to add a mechanical switch on the dishwasher’s heater  to bypass it.

Interesting project overall, full of good intentions but with no results at the end of the day.


3 thoughts on “Finding good use for excess solar hot water

  1. AminfiBerlin

    The concept is valid 🙂
    I suggested the same for the laundries of a hotel with 1200 beds before the machines were bought.
    Looking forward to see your Progress 🙂

  2. estqwerty

    здрасти , пробва ли да изключиш нагревателя ? дали пък ако го прескочиш няма да почне да избиват грешки или ще е достатъчно глупаво направена миялната?
    идеята е много добра , и е наистина странно че много малко и само в най-високия клас се продават такива уреди с вход за топла вода.

    1. admin Post author

      не съм, ядосах се на миялната машина и съм замразил проекта за сега. Мисля, че няма да избиват грешки и ще работи перфектно, но все нямам време да я разглобя и пробвам