Replacement thermostat / timer

[atticus999]

Hi. I have very old underfloor heating with thermostats. I'd like to replace the thermostats with timer/thermostats if possible. The current (very old) ones have 2 red cables, 2 black and an earth. One of the red cables is live all the time, the other live when the thermostat kicks in. It appears to be mains voltage. Can anyone suggest a replacement thermosat with a built-in timer please? Many thanks.

 

[Avo Mk8]

I imagine that old Satchwell stat is switching the electric UFH mat directly. I believe its switch contacts are rated at 16A, not that your mat is necessarily taking the full 16A!
I believe many modern UFH timer stats are designed for wet systems, where they switch the boiler or a valve with much lower current. So you would need to get one suitable for the load of your floor.
This sort of thing would do:

Thermostats – Heat Mat

www.heatmat.co.uk

I've used one of these - good but I had one fail!

Programmable Thermostats for Underfloor Heating | Warmup

Warmup’s range of programmable thermostats for underfloor heating, including digital and automatic heating controls. Offering you big savings on your energy bills.

www.warmup.co.uk

There must be others available with 16A contacts!
PS I'm assuming your black wires are actually neutral, I guess that's pretty likely, but worth checking if you have a meter.

 

[atticus999]

I imagine that old Satchwell stat is switching the electric UFH mat directly. I believe its switch contacts are rated at 16A, not that your mat is necessarily taking the full 16A!
I believe many modern UFH timer stats are designed for wet systems, where they switch the boiler or a valve with much lower current. So you would need to get one suitable for the load of your floor.
This sort of thing would do:

Thermostats – Heat Mat

www.heatmat.co.uk

I've used one of these - good but I had one fail!

Programmable Thermostats for Underfloor Heating | Warmup

Warmup’s range of programmable thermostats for underfloor heating, including digital and automatic heating controls. Offering you big savings on your energy bills.

www.warmup.co.uk

There must be others available with 16A contacts!
PS I'm assuming your black wires are actually neutral, I guess that's pretty likely, but worth checking if you have a meter.

Many thanks for your reply which is very helpful. Is there a way to test the Amps needed ? I have a multimeter but limited expertise. Presumably if the Amp rating of the new one is insufficient it will just blow it ?

 

[Taylortwocities]

Match the contact spec of the existing. Quite honestly, just go for 16amp.
The stats may be directly switching the floor element, but many of the old systems used a contactor (aka mains relay). Is there a clunck from the electric cupboard when the heating kicks in?

 

[atticus999]

Match the contact spec of the existing. Quite honestly, just go for 16amp.
The stats may be directly switching the floor element, but many of the old systems used a contactor (aka mains relay). Is there a clunck from the electric cupboard when the heating kicks in?

Do you think this one would do the job ?

https://www.amazon.co.uk/KETOTEK-Underfloor-Thermostats-Programmable-Temperature/dp/B082Y36YTC/ref=sr_1_2_sspa?keywords=16a%2Bprogrammable%2Bthermostat&qid=1668034131&sr=8-2-spons&th=1

 

[Avo Mk8]

Do you think this one would do the job ?

https://www.amazon.co.uk/KETOTEK-Underfloor-Thermostats-Programmable-Temperature/dp/B082Y36YTC/ref=sr_1_2_sspa?keywords=16a%2Bprogrammable%2Bthermostat&qid=1668034131&sr=8-2-spons&th=1

Yes that would do the job - the feedback ratings further down the page, I assume for this model, are not brilliant, but it will do the job. The brand is 'OK', you get what you pay for!

 

[cireland]

I'm not so sure. It looks like the one from Amazon requires an external sensor to control the UFH.
It doesn't look like there is one present from your pics.

My mistake. Seems to have built in temp. sensor

 

[Avo Mk8]

I'm not so sure. It looks like the one from Amazon requires an external sensor to control the UFH.
It doesn't look like there is one present from your pics.

I'm pretty sure it has both an internal sensor (because of the slot in the front), and terminals for the external (underfloor) probe. And you select which you want in the setup menu (which would be the internal one in this case)
PS yes it does say built in air sensor in the features list.
PPS Sorry - I see you saw that yourself!