Controlling TRV (Thermostatic Radiator Valve) from 18M2+

[DamonHD]

Hi,

I thought that people here might be interested to know about my little breakthrough tonight in using a PICAXE as part of a central heating soft-zoning system (project OpenTRV). Tonight's success was talking to a wireless TRV from a 18M2+ via an RFM22 (or RFM23) radio, and regulating room temperature with the help of a DS18B20 temperature sensor.

https://sourceforge.net/p/opentrv/wiki/DHD201302L0/

See the code library which may be of use to others (eg the SPI and RFM22 stufff, still under active development) and the start of a unit-testing harness.

Rgds

Damon

 

[geoff07]

Interesting. What does the wireless bit do? Over-ride the thermostat in the valve? Do you imitate the remote control?

 

[DamonHD]

The FHT8V wireless TRV is fairly dumb: over wireless you tell it how far to open the valve from shut to fully open. The FHT8V has no temperature sensor or schedule.

Usually the wireless TRV is paired with a thermostat/schedule unit that tells the TRV what to do: my PICAXE stuff is doing that instead, using a DS18B20 to sense room temperature and thus regulate it.

Rgds

Damon

 

[premelec]

Damon; I wonder who manufactures these valves? I use Taco Sentry zone valves on a hydronic system and they are either all on or all off... sometimes I think partial control would be better... thanks...

 

[DamonHD]

I don't know: possibly a German company called ELV which seems to make other rebadgeable products in this area, and the actual manufacturing may well be in China or thereabouts of course.

Rgds

Damon

 

[DamonHD]

BTW, for the record, I'd like to make it crystal clear that most of this would not have been possible without Mike Stirling's decoding of the on-the-air protocol:

http://mikestirling.co.uk/2012/10/hacking-wireless-radiator-valves-with-gnuradio/

So lots of kudos to him!

Rgds

Damon