How to cheat thermostats?

[KimmoHop]

I'm planning to add MySensors control to radiators in water circulated central heating. Radiators have Danfoss valves and RA2000 sensors.

Electric (thermal wax) actuators can be had for 20-35€ each and they could be driven with either 230VAC (with simple SSR module) or with 24V, depending on model.
Given the cost (and to some extent, availability) of actuators, another possibility would be to heat cheat sensors by heating them with resistor(s), to make them think that the room is hotter and reduce actual temperature. I can live with "default" setting as max temp + controllable cooling.

Now for the questions part:

• has someone done that? Did it work?
• how to locate resistor(s)? Is below sensor enough, or must the resistor go inside the sensor to be effective?
• how much power would be enough? I think 9-12VDC would be available, so FET can easily drive 1-5W. I'm 150km away from radiators, so I can't test it right now...
• should I just stop tinkering and go with commercial actuators? ;)

[executivul]

I went with something like these. Placed in the distribution box. One for each radiator circuit. Plus some DS18B20 on the inlet and outlet of the radiator, allowing some advanced heating schemes, shutting off some radiators to give more flow to the ones needing more power.

https://www.aliexpress.com/item/Brand-New-1-2-DN15-DC12V-Motorized-Ball-Valve-Brass-Electric-Ball-Valve-CR-05-5/2031958276.html?spm=2114.search0104.3.30.2ccd5d0eu2LwjU&ws_ab_test=searchweb0_0,searchweb201602_2_10152_10065_10151_10344_10068_5722815_10342_10343_10340_10341_5722915_10698_10697_5722615_10696_10084_10083_10618_10304_10307_10301_5722715_5711215_10059_5723015_10534_308_100031_10103_441_10624_10623_10622_5711315_5722515_10621_10620,searchweb201603_25,ppcSwitch_5&algo_expid=651c537c-2bad-4664-999d-765e1fc06a79-4&algo_pvid=651c537c-2bad-4664-999d-765e1fc06a79&priceBeautifyAB=0

[gohan]

If you are going to buy Danfoss products I'd add some more money and get the zwave ones

[KimmoHop]

I did a quick test. 1W seemed good point to start, 25 ohms to 5V. I took 4 100 ohm resistors and wound them parallel, and used 4xAA batteries to power them.
Too much heat :D 0.23A at 5.8V and the resistors were really hot. Burning hot to the skin, and IR thermometer got up to 80 degrees C, although it's measuring from bigger area. I'm afraid that so high temperature could damage bellow inside sensor. Same resistors in 2S2P give some 40 degrees C - closer but a bit too low ;)

[KimmoHop]

@executivul Those look interesting valves, though not exactly what I'm looking for ;)

@gohan I don't have zwave controller :thinking_face:

[gohan]

You can buy a USB zwave dongle for 45€ and use a raspberry pi with domoticz or other zwave compatible controller

[OliverDog]

Hi!
After 1 year, Did this post result in any sketch?

I want to use a similar valve @executivul suggested, with 5 wires as well!

Did you get success using mysensors @KimmoHop ?

Tks

[KimmoHop]

Hi @OliverDog !

No update on valve front, it'll be either DIY or Danfoss wired actuator - there are no z-wave components for twa-k valve. I'm have been coding control possibility to current implementation, but all the time thinking affordable off-the-shelf systems or components. Heating control, while it could be -30degC outside, needs trustworthy system and maybe backup even then.

MySensors has been running quite well for two years now. After there was a fix for "fake" NRF24L01+ tranceivers, electricity blackouts have been #1 cause for no data. WLAN was stuck once and range between WLAN router and ESP wifi shield is poor. MySensors has been stuck once or twice after modding. No other errors as far as I can remember.

So, monitoring still ;) (light blue and rose - heating circulation, bottom - outside, green and blue - inside)

[KimmoHop]

Or was the valve type RA :/ That has z-wave actuator