Heatmiser UFH Automation

[John Williamson]

I have a job I will be asking a plumber to do but would like to understand what is involved so I can see if the end result will meet my expectations.

I have fully operational Underfloor heating system which I love but am looking to integrate into my smart home system.

Currently it is controlled by

• Heatmiser UH3 8 Zone Wiring Center
• 4 x Heatmiser Slimline (Digital Thermostat). I think these are
  TM1-N V3. Picture attached
  

While the time programming is great, we are in and out of the house at very irregular intervals meaning we are paying for a lot of heating when we are out of the house for hours because we're too lazy/in a rush to turn each individual thermostat off.

What would be the easiest / cheapest way of converting this system to something which could be controlled by home automation? I'm very techy (a programmer by trade) so happy to dive in to raspberry pi wifi or rs232 solution if that avoids upgrading the whole thing to NeoAir or similar. Or would this be easier to achieve at the boiler side of the spectrum? (Vaillant ecoTec 832)

I won't need to do anything clever, just basically override the timers from the thermostats when a trigger (such as our home alarm being set) to turn the UFH system off.

Any advice gratefully received.

 

[Chalked]

You could replace the thermostats with Heatmiser neostats.

 

[Welder]

There are a number of issues with this 'simple' request.

Underfloor heating is far less controllable than the likes of radiators due to 'lag'. When they start they need to, typically, heat up a larger mass before one feels 'benefit' and similarly, they take longer to cool down due to the same issue. This is called hysteresis and you will have different timings for each of your heating loops. The response of each loop can be measured, but you will have to do some tests vs inside and outside air temps to get yourself a lookup table with three axis.

Re control, your first point is to control the boiler. So, reach a set point, bring on the boilers and get it up to temp and then start the pump to the manifold calling for heat. When the flow temp is correct then open the loop. Shutting it down requires more than simply turning the whole thing off as its far better to put waste heat into the space. What that translates to, controls wise, is to called optimising off. You effectively turn the system off early then use the waste heat to coast those last few yards - in car terms.

To be perfectly honest, this is eminently doable but it will be a labour of love and take you quite a while if you are to do it properly. Perhaps the simplest solution is to simply build into the local stats or the the main time clock some form of form of geo fencing so occupancy is sensed. This of itself, again, requires high level thought as geo fencing then effectively holds off the timed function...

Welcome to the world of controls

 

[John Williamson]

There are a number of issues with this 'simple' request.

.....

To be perfectly honest, this is eminently doable but it will be a labour of love and take you quite a while if you are to do it properly. Perhaps the simplest solution is to simply build into the local stats or the the main time clock some form of form of geo fencing so occupancy is sensed. This of itself, again, requires high level thought as geo fencing then effectively holds off the timed function...

Welcome to the world of controls

Thanks so much, to say you have blinded me with science is an understatement....

Taking in to account the warm up time (which I think I may be able to get around by sending my home automation system an "I'm on my way home" trigger, it says in the product specs:

"The UH3 is designed to work with our 4 channel 230v time clock (TM4) and 230v Set back thermostat (DS-SB) but equally could be used with any 230v room thermostat."

So I'm thinking that by replacing the thermostats with something I can control (I can fire off RF or wifi easily) may be the answer or having a central clock to control all zones. The part I don't understand is that I have 4 thermostats for the individual zones, can I combine these with a central 4 zone thermostat (like the Heatmiser TM4-TS) or will this create a race condition where both are trying to control the UH3 simultaneously?

 

[Welder]

The time clock you refer to will simply 'enable' each of the 4 individual zones.
A setback stat will, instead of turning each zone completely off, turn it down to and maintain it at, a lower temp.
Sounds to me like you need a Nest or similar.
Ideally, you use a setback stat during your 'on' periods so it never goes completely cold. This should be quite simply achieved with smart controls.