Central Heating Thermostat "Hack".....is it possible ?

[shaky1105]

Hi all.

As the title suggests. I've recently been gifted a couple of really nice looking full colour screen underfloor heating thermostats (for the wall) and I was wondering if I could connect a fixed resistor across the floor sensor probe terminals to stop the 'stat error messaging through lack of probe being installed and just use the air temperature sensor in the 'stat body itself ?

Also, the normal output is L and N for the heating element so do you think it would be possible to just connect the live out from the 'stat into the CH CCT (to use as a switched Live) or would it be better to connect a relay across the L and N terminals to switch the Live remotely ?

Thanks for any advice

 

[Taylortwocities]

It depends on the stat. Some require a floor temp probe only, in which case it will always be looking for a probe. You could hang a resistor across the probs terminals, but the thermostat will be set on the temperature that the value of the resistor tells the stat.
Typically a floor sensor has a resistance between 8K ohms and 12K ohms, depending on the floor temp.

Some Stats have a temperature sense menu option. Like
Floor probe, room or both. Set the option to room and it will not look for a floor probe.
RTFM, maybe yours has the menu option.

 

[shaky1105]

Thanks TTC. The 'stats are warmup 3ie models. According to the manual, they will work without a floor probe attached but they give an error code. They have got the function to just use the air sensing option hence my question about replacing the probe with a fixed resistor.

All I'm concerned about really is whether or not it would have to be a resistor that could dump some power as I can't seem to find out what voltage the 'stat would use while monitoring the probe values.

Does my idea re: the switched live situation sound OK ?

 

[Taylortwocities]

select set Heating Target in the menu

If no probe installed, you may get an ER1 Error code. You should be able to clear this by doing a reset.

I’ve never used a 3ie without a probe, you could ask Warmup support, they usually pretty good.

If you need to go the resistor route instead of the probe: There’s no appreciable voltage on the probe connections. It’s just monitoring the resistance So any resisTor in the range 8-12kΩ above will be ok.

 

[shaky1105]

Great stuff TTC. Thanks for your help. I've got nothing to lose as I got them given FOC so I'll see what comes of it.

So can you see any problems with how I want to connect the switched live output into my CH system ?

 

[ericmark]

It seems there is not just one NTC sensor I tried to look up the resistor value.

Not very helpful, however 27°C is suppose to be temperature limit of floor.

 

[shaky1105]

The probe that comes with (new boxed) the 'stat is described as a 10KΩ NTC which, with my limited knowledge appears to indicate a 10KΩ value for 25°C. I was gonna fit an 18KΩ resistor (only coz I've got one handy) which gives a temp. reading of approx 10°C but as I'll be setting it up to ignore the floor reading and just using the air temp. setting I didn't think it would matter ? Just want to get rid of the error message.

 

[Taylortwocities]

If that resistor gets rid of the error then you go with that 18K resistor.
The contacts in the 3ie are rated at 16A. The CH system will be less than 3amp, so no worries connecting it up.

 

[shaky1105]

Thanks again TTC. Nice to know that one of my "ideas" will actually work this time

 

[AndyPRK]

some of these new thermostats are too cleaver.

Some have settings for a wet system, others under floor to change hysterics.
It's worth ago, but if you get problems..... being too hot or cold.......

 

[Taylortwocities]

Thanks again TTC. Nice to know that one of my "ideas" will actually work this time

Let us know if it does!

 

[shaky1105]

Let us know if it does!

Will do buddy

 

[shaky1105]

Hi TTC.

Well, it seems like the resistor is not required after all

I'm sure you prolly already know this but in the settings you can set up the floor type to "user defined". Once I did that and then told it to just use air temperature it didn't show an error message so all's good.

It does just switch the L as well without having to link anything.

Thanks for your help anyway it was appreciated.

 

[Taylortwocities]

Glad it’s sorted.