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Adding geyser control to smart home - wiring question


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10 hours ago, JustinSchoeman said:

Hi all, waking up this thread again, as I intend to do something similar, and would appreciate some advice/input.

Firstly, I would like to store as much energy as possible in the geyser, so the first step would be to install a tempering valve, so that I can store much hotter water in the geyser, without a scalding risk from the hot taps.  But how hot can I safely make the geyser?  I can find a lot of info on the safe minimum storage temperatures, and safe maximum outlet temperatures, but virtually nothing on safe maximum storage temperatures.  Any ideas?

Secondly, I need to add a temperature probe to the geyser.  I don't really like the idea of removing the safety of a mechanical thermostat, so I am considering using a geyserwise thermostat. Specs say it has a 90°C mechanical cut-out, and I have found one internet posting which seems to say that the included temperature probe is a DS18B20, which should be perfect.  Has anyone used one of these thermostats in a DIY project and/or can confirm that it really is a DS18B20 probe?

Thanks,

Justin

If you are keeping the original thermostat, then the max you can set it to is probably 70 degrees. It will stop heating once you get to that. The 90 degree is probably a Physical safety cutoff. 
 

If you are using the geyserwise, then the max you can set it to is 65degrees. That’s what mine allows. 
 

im not sure about the geyserwise using the Ds18B but I am using it in the sonoff th16 just for temperature readings. By next winter, I will probably connect the element to the sonoff via a contactor to heat wTer in my solar geyser. For now it still fine with just solar. I have seen many diy of using the ds18b with a Arduino or pi as well. 
 

the only problem with Diy builds is the risk that your controller fails closed circuit and the element does not shut off. You could probably add a further safety in series that shuts down after day 2 hours. 
 

My kwikott 609 dual has been teaching 80 degrees over the past 2 weeks. 

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57 minutes ago, Vassen said:

the only problem with Diy builds is the risk that your controller fails closed circuit and the element does not shut off. You could probably add a further safety in series that shuts down after day 2 hours. 

That is one of the reasons I was contemplating the geyserwise thermostat.  It is basically a thermometer + mechanical safety. If it reaches 90C, then the safety trips, and you need to press a button on the thermostat itself to reset it (if I read the manual correctly).  This should protect against just about any dangerous failure mode.

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24 minutes ago, JustinSchoeman said:

That is one of the reasons I was contemplating the geyserwise thermostat.  It is basically a thermometer + mechanical safety. If it reaches 90C, then the safety trips, and you need to press a button on the thermostat itself to reset it (if I read the manual correctly).  This should protect against just about any dangerous failure mode.

Do you mean you want to use just the geyserwise thermostat without the controller?  
 

As I mentioned, the controller doesn’t allow you to go over 65 degrees. 

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3 minutes ago, JustinSchoeman said:

Correct - just the thermostat (assuming of course the thermometer part is a DS18B20,or some similar probe that can be easily reused).

 

Okay. If I remember correctly, the geyserwise solar probe is a 2 wire probe, so it’s not the DS18B as that’s 3 wire. 

But not sure about the termostat  

 

Edited by Vassen
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3 minutes ago, Bloubul7 said:

I have not tested it as yet, need to go and buy a spare Sonoff TH16 to run the tests with.  Will keep you posted

Thanks - was referring to changing the original sensor.  Even if the original is not a digital one, if it can be easily replaced with a digital one, it is not an issue.

From your photo, it looks like non-polarised wires on the original probe, so very likely just a thermistor.

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1 minute ago, JustinSchoeman said:

Thanks - was referring to changing the original sensor.  Even if the original is not a digital one, if it can be easily replaced with a digital one, it is not an issue.

From your photo, it looks like non-polarised wires on the original probe, so very likely just a thermistor.

Correct, was refering to the testing the DS18B20 and Mechanical cut out as well.  Would like to get the readings from the DS18B20 and see if the mechanical switch still cuts out at 90 degrees.

For testing the original sensor, I'm looking at getting a MAX31865 to convert the signal to digital.  Want to see if I can get the Sonoff & Geyserwise to work in parralel with the Sonoff being the primary driver and the Geyserwise as a backup safety net.

 

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  • 1 month later...

Fantastic thread - thanks everyone! We've put in an offer on a new place and if the bank comes to the party will be moving in early next year. The new place has three geysers (one for the bathrooms, one for kitchen and one for outside flat). I plan to retrofit all three to solar, and since three geyserwise units will be pretty pricey I'm looking at possibly DIY-ing a solution to turn on the geyser element based upon time and temp (i.e. if not warm enough by 5pm). The other nb function of the geyserwise is to turn on the circulation pump when appoaching freezing temp to prevent flat panels from bursting - I plan to only install tubes, so I won't need this function.

I'm not well versed in smart switches etc so please do let me know if you have better suggestions. My current thinking is simply to use a sonoff TH10 to power a relay that'll turn the geyser on and off based on time and temp settings. The circulation pump I'll hook up directly to a 10W panel, so if the sun shines the water will circulate.

Is the solution as simple as this, or am I missing something?

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We've got a solar geyser at our place and I made it quite simple by adding a TDDGT timer in the DB board which turns the geyser on at 5pm and off at 6pm and again from 5am until 6am, but with a low-ish temperature set on the thermostat of 55 degrees. This is simply to ensure that there is warm water in the evenings and in the mornings. If the sun was out in full force and the water temperature is higher than 55 degrees already then the thermostat simply won't switch on the element.

I think that's the most basic of basic and cheap configurations to ensure there's warm water, but you can obviously then start looking at Sonoff's with relays and temperature sensors etc. which a lot of people are doing to feed excess solar into the geyser if the batteries are fully charged etc.

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32 minutes ago, fredhen said:

We've got a solar geyser at our place and I made it quite simple by adding a TDDGT timer in the DB board which turns the geyser on at 5pm and off at 6pm and again from 5am until 6am, but with a low-ish temperature set on the thermostat of 55 degrees. This is simply to ensure that there is warm water in the evenings and in the mornings. If the sun was out in full force and the water temperature is higher than 55 degrees already then the thermostat simply won't switch on the element.

I think that's the most basic of basic and cheap configurations to ensure there's warm water, but you can obviously then start looking at Sonoff's with relays and temperature sensors etc. which a lot of people are doing to feed excess solar into the geyser if the batteries are fully charged etc.

They say simplicity is the ultimate sophistication. This is such an elegent (and easy) solution. Thanks

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