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Thermo Valve for washer & dishwasher


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Hi, I've just finished my Thermo Valve project.


The objective was to convert a Bosch washing machine & Dishwasher to a solar hot water feed to save my batteries & PV load.


The YouTube link below has all the details, but in essence. If you want to reduce electrical load form heating water, and you have excess solar hot water, this makes a MASSIVE difference to reducing electrical consumption.


FYI, it's not possible to select a totally cold wash on most modern washing machines.  If you disconnect the element on these appliances you tend to fool the microcontroller (waits to get up to temperature forever) it took 6 hours to complete a 15min wash. Dishwasher need around a min of 45Deg to wash & dry plates. 


Hope you find this Video informative 


Total outlay was about R650 for the TP Valve,

R 250 copper fittings. 

Lots of time in the attic, chooses a cold day, or a good way to loose a Kg.



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I'm definitely taking a look at this. I suppose it depends on what dish washer you have. I have a Bosch unit, which it turns out (I didn't buy it for that, draw of the luck) was their eco model at the time. It uses about 1kwh a day. I can live with that :-)


For me, the tumble dryer is a much bigger issue. Of course, the obvious answer is not to use it. Use a clothes line, Einstein! Yes, sure. Two things: 1) small kids, 2) SWAMBO. :-)


Now a conversion on a tumble dryer shouldn't be too hard. I can think of three ways to do it:


1. Solar collector outside, suck hot air in from there.

2. Low-pressure solar geyser outside, cycle hot water through a radiator and use a fan to make hot air. Has the upside that it also works after hours.

3. DC heating elements, PV panels.


Tumble dryer already has a thermostat that will keep the internal element(s) off (my Defy has two, that turns on at different temperatures) if the air is hot enough, so it will continue to work with grid power if you need it to.


Caveat: On mine I noticed that it draws the air from inside the case of the unit. It seems clear to me that they are using this method to draw cold air over the working parts (and control electronics) in this manner. If you feed it with hot air, you will probably have to either add a ventilation fan somewhere, or specifically design it such that a portion of air is still sucked over the electronics. In other words: If you don't know what you are doing here, you might well kill the appliance in a few weeks :-)

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The link also 404'ed for me. I hit reload and it worked. Load-balancer somewhere misbehaving.

BTW, I have the same model dish washer. A little younger, but same basic setup. Takes about 3 hours on the 50-degrees eco setting in the middle, which is what we use mostly. Absolutely amazing that it can do a wash using only 1kwh. For that reason, I've not been too worried about it. Tumble dryer uses 3... that's where I want to focus attention.

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Hi, sorry some of you are experiencing problems with the link, it also returned an error on my first try, then worked every time after.

Try this


jdp I haven't come across this type of valve before, it took a long time to find locally, I have seen similar in Shower mixing taps but this Apex was ideal for my application.

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Is this not a normal temper valve used in retrofit solar water heaters ?

I have one exactly like it on my solar geyser. It's on the output and it is set to 55 degrees, or somewhere thereabouts. Its job is to mix the water down a bit in summer, because in summer the water up there is at boiling point. So its a safety feature.

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