After a lot of requests from the rest of the family I decided it was time to upgrade the thermostat. This week, the Praxis DIY stores had an offer: Amfra Hestia BT with 35% off.
Above, you see the control unit of this thermostat. If you want to see more pictures, please visit http://www.mijnalbum.nl/Album=VOX3E4N8 and browse this list of images. If you click the images there, a new window will open with the full 7 Megapixel image in it. Revealing ALL details.

The new Hestia thermostat has an NTC sensor in the bottom of the enclosure. It is mounted 10 mm above the PCB so that its tip is in the ventilation 'chimney' of the enclosure.

Above and below you see some pictures of the inside of the Hestia. The top image shows the full backside of the controller circuitboard. The orange thingy is the bipolar relay (mechanical!) that allows the use of just about any furnace. The rectangle holds two alkaline AA cells. Enough for 8 WattHours (over 25 kJ) of energy. Cheap and reliable.
Below you see the way the furnace connections are protected. MOV's are the worlds least appreciated devices for cheap and reliable signal conditioning. These MOV's (which can be assisted by high power zener diodes) will filter off all signals with too high amplitudes.

Well done, Amfra!

Pictures of the Amfra Hestia : http://www.mijnalbum.nl/Album=VOX3E4N8

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