Truma heating problem (1 Viewer)

[Lenny HB]

Remote sensor was fitted to Combi's from June 1997.

 

[tonyidle]

As Tony says it could be a problem with the thermocouple which could mean a boiler out job to change. It won't be the heat sensor thermocouple (the black button thing) as if they go open circuit the heater runs constantly. Neither of you have mentioned if you are getting any error codes (flashing LED's on the controller or PCB).
Another possiblility is a gas flow problem, a faulty regulator.
Have you filled up with LPG in mainland europe and have a percentage of butane in your bottles. As well as butane not gassing off in cold weather, Truma Combi's don't even like butane in summer as butane can't produce sufficent flow rate for the combi's requirerment.

No - l said the thermostat (black button thing). Mine didn't fail open circuit but gave exactly the symptoms being described by the OP. Replacing it cured the fault.

 

[dave newell]

Don't confuse a "thermostat" with a "temperature sensor" they are two completely different things. Many c series heaters have the (room) temperature sensor built in to the control dial (which is the actual "thermostat"). Confused yet? You will be ! Some ( mostly latee) installations will utilise a separate (room) temperature sensor, this is the 1/2" di a black " button".

D.

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[tonyidle]

And the button is a NTC thermister too . It's very similar to the ones used inside phone batteries to sense overheating - I know that because I used one until my replacement button arrived.

 

[Lenny HB]

It's not hard.

A thermostat is a basically a sensor to measure the temperature combined with a switch, it can be fixed or adjustable.
e.g. The temperature of the hot water on your Truma Combi is controlled by a fixed one permanently set to 60° and it turns the boiled on and off to maintain the temperature.
The one on your house central heating is an adjustable one that can be anything fron a basic Bi-Metal strip device to a fully programmable mini computer like the Nest Thermostat.
The TVR's on your radiators are an example of a purely mechanical thermostat. i.e. It measures temperature and turns the water flow on and off.

A Sensor just measures the temperature and does not do anything else, it is connected to the controller, the two together work like a thermostat.

Clear as mud?

 

[tonyidle]

It's a ntc thermister. And there are many different types. I tried a few I had in my junk box and the nearest I found was the one from a mobile phone battery. Is there one on the control board? I haven't delved into that circuitry - the one l changed was inside the 'button' room sensor.

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