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Replacing my thermastat (honeywell CM737 - OpenTherm)

timgiles
timgiles ✭
in General Questions & Topics

Hi.

I currently have 14 of the Tado smart TRVs running very well here in Sweden. My house is connected to shared hot water supply (district heating) which the boiler like appliance uses for both hot water heating and central heating to the radiators.

The current thermostat is a Honeywell CM737, the heat exchanger appliance is Alfa Laval Cetetherm Mini, which uses a 3 port Honeywell M6410C2031 3 port actuator which I assume does the splitting for HW and Central Heating.

The thermostat has just a 2 wire connection, measures 48V so I assume it is using OpenTherm to talk to the heating appliance.

So, when I change over the termostat, using what I believe are the right connections, the 3 port valve inside the heating appliance goes crazy. It sounds like it is just continuously going around and around. Heating stops (when it is -30oC - not the best time to try the installation :-) ).

Any chance someone here can help?

Answers

  • Exizter
    Exizter
    Hi

    Did you get this working?
    I have the same setup and can not make it work.
  • timgiles
    timgiles ✭

    Unfortunately not. It is so disappointing that there is no real contactable support for tado. I suspect its a config or something really simple to fix. If I ever manage to make contact and get an answer, i will post back here.

  • Exizter
    Exizter
    Thats a bummer. I tried to contact the support two years ago with no answer and finally tried to do it myself. Ended with no heat in the winter…and a professional recommended that I use the cm737.

    Thanks for your reply.

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