How to cheat thermostats?
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 last edited by
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.
If you are going to buy Danfoss products I'd add some more money and get the zwave ones
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 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
@executivul Those look interesting valves, though not exactly what I'm looking for
@gohan I don't have zwave controller
You can buy a USB zwave dongle for 45€ and use a raspberry pi with domoticz or other zwave compatible controller