Suspect Pipe-Contact Thermostat

[teamboxer]

Hi there

Our underfloor heating system has a Tiemme thermostat strapped to the pipes near the manifold which I assume is there as a safety ‘stat.
Has been working fine until recently….and now it seems to only allow the heating to come on when I turn it down to the temperature that the pipe is at….at which point it clicks on, which to me sounds completely wrong. In other words it’s coming on when it reaches the directed temperature, not going off!
Surely it should be set to, say, 35 degrees, the heating come on and then go off when the pipe reaches 35??
Thoughts please…it seems that the stat is faulty, right, or has been wired in backwards!!????!!

 

[Johntheo5]

What make of stat??, it should switch off on rising temperature, if not switching on, then turning it UP shoud make it close sooner, normally you will have a live connected to the common terminal, the other wire should be connected to terminal 1 (not 2), the terminals may be marked 1,2&3 so live to 1 and other (switched) wire to 2 (not 3).

 

[teamboxer]

What make of stat??, it should switch off on rising temperature, if not switching on, then turning it UP shoud make it close sooner, normally you will have a live connected to the common terminal, the other wire should be connected to terminal 1 (not 2), the terminals may be marked 1,2&3 so live to 1 and other (switched) wire to 2 (not 3).

Hi
Thanks for the swift reply
It’s a Tiemme 2075, pdf attached.

I appreciate it should switch off on rising temperatures, but it only gives a demand for heat when the dial is set to match the current temperature of the pipe….ie it click on at the set temperature, not off!
We’ve just had a Nest installed on this zone, which is working fine itself, ie calling for heat when you crank it up, but this safety stat seems to be stopping the boiler firing up.
I have managed to work around but setting the Tiemme to 0degrees, ie always on, but that’s clearly not right.

 

[Johntheo5]

Probably wired wrongly, easy to check, see below. Switched wire should be from terminal 1.

After checking/testing, it should be set at least 5C higher than the manifold temperature.

 

[teamboxer]

Probably wired wrongly, easy to check, see below. Switched wire should be from terminal 1.

After checking/testing, it should be set at least 5C higher than the manifold temperature.

View attachment 289314

Thanks again

I don’t understand how, though.
It’s only seemingly happening since the Nest went in…..?

 

[Johntheo5]

A bit strange allright but the above is the easiest to check out, anf if stat not faulty should switch/click with a differential of ~ 6C to 8C.

 

[oldbutnotdead]

Thanks again

I don’t understand how, though.
It’s only seemingly happening since the Nest went in…..?

Well your first job is to restore the system to as it was before the Nest went in and check function.
Is that the only thermostat on the ufh or are there room thermostat(s)?
Just wondering whether that stat is there for frost protection.....