Advice on thermostat options for underfloor heating with Intergas combi

[phil63]

My mum's builder has installed underfloor heating in her ground floor flat, with living room, one bedroom, kitchen-diner and bathroom. The HRE 24/18 Intergas Combi has been installed, but not yet connected to the underfloor piping. Can anyone suggest a typical manifold/thermostat set up that will work with the Opentherm on the boiler, I assume controlling three or four zones? Underfloor heating is completely new to me!
I'd like to use the opentherm capabilities, with an external sensor. I'm guessing it's a no-no to have a single thermostatic control (like the Remeha Isense on my Combi at home) and individually control the zones manually from the manifold?
I think the builder is in a bit of a huff since I asked for an Intergas in preference over their favoured boiler; so I want to be helpful and move things along..
Any advice at all gratefully received.

 

[Wayners]

sonoff heating controls maybe?

Don't know much about it but have seen it installed on older heating

 

[CountryFan]

I’m not sure on other thermostats including standard room thermostats, but have a look at Heatmiser or Honeywell as these claim to support opntherm

 

[ericmark]

EPH do a range thermostats which are set as master and slaves to work with on/off motorised valves. And Drayton Wiser one hub can connect to many thermostats be it either wall or TRV type, but this is wireless linked not hard-wired like EPH. Both have OpenTherm.

Many other thermostats do have OpenTherm but as to using them with UFH not so sure, depends on if the TRV heads will work, with a manifold

all the activators are together so they would not monitor the correct room temperature. The controllers

have the option for many thermostats, but I see no option for OpenTherm, it does seem EPH is the only one.

As to how much OpenTherm helps not sure, I am an electrician not a heating engineer. I know with a condensing boiler the idea is to have analogue control, so that the boiler can adjust output so return water is cool enough. Underfloor heating needs to run far cooler to radiators, and it needs in the main two pumps, one to circulate the UFH water and one to circulate the main CH water, but I simply fail to see how one can control UFH fast enough.

North facing rooms OK, they will not get heat from other sources, south facing rooms the heating needs a fast response time, so when the sun shines through the windows, the heating is reduced fast so stop rooms overheating. Even with simple radiators, I had a problem with my late mother's house. Which was helped by fitting electronic heads to the TRV's, and ensuring the TRV controlled the room temperature, not an on/off thermostat. There was an on/off thermostat to stop heating running on warm days. But room temperature was controlled by the TRV. So on switch on radiators would get hot, but as the room heated up, radiators would be just warm to maintain the room temperature, so sun through the windows would turn off the radiator, which since only warm, cooled down fast.

So UFH can't really work in rooms which catch the sun, as reaction time is too slow. Also, I have only fitted electric type, but the work to remove the floor and fit the insulation was a massive job, so not really something I would want to do on a ground floor, yes the insulation made a huge difference, and look at the energy certificate and that is the first recommendation. But the return on investment is silly. But no option if you want UFH, I know many don't fit the insulation, so when house hunting, unless there was some paperwork of photos to show insulation was fitted, if UFH fitted we just walked away.

 

[Razor900]

You are massively overcomplicating things.

Run the UFH manifold directly from the boiler with no blending valve/pump on the manifold or outside sensor. If you want to zone each area just do it with actuators and ordinary room stats

Then set the boiler flow temp to 40 degrees and lock it so no one can accidentally alter it.

No advantage whatsoever to using OT or WC in this situation

 

[phil63]

Thanks for the very detailed replies guys; I do like the idea of keeping it simple. I’m trying to confirm the precise zoning installed by the builder, who has gone awol, before deciding.

 

[phil63]

Things have moved on without my input at all: They've been in and installed what looks a pretty complex set-up to me! And is that a pump that has been installed on the left? Surely the pump in the boiler is up to the job?? There are three zones (still not sure what areas the zones are covering..). They're now asking my Mum what thermostat she wants.
Does this install look reasonable?? It's certainly got a lot of gauges...

 

[muggles]

This is the problem with having a builder doing your plumbing. That is a second pump and is indeed entirely unnecessary in your setup. I would suggest that a single OpenTherm stat to control the entire home would be the best way to go here

 

[phil63]

Thanks Muggles. Why would they have put an extra pump on?? I don't understand.. is there a conceivable reason?! I want to go back and have words with them, armed with some knowledge. What are the implications of having two pumps? Would it even function properly? I guess they'll have to be on together, or else all sorts of problems come to mind. Jeez.

 

[phil63]

In the meantime: Any suggestions welcomed for a wireless, Opentherm 'stat that would work here.. and would it literally just control the boiler directly, with no messing about with actuators on zones etc? That sounds good to me. I use a Remaha OT stat on my Intergas at home, and that works fine.. but every room has a thermostatically controlled radiator valve. Seems like this underfloor heating is a little retrograde in the control department.

 

[trojanhawrs]

So you have 3 loops, not 3 separate "zones" although they could be changed to zones by fitting actuators to the manifold. However, it's likely better to leave them as manual and just tweak so that the whole house heats up evenly - this keeps it simple and reduces boiler cycling.

The new hive has opentherm as an option. You will still need to set the max flow temperature on your boiler to avoid cooking your floor coverings. Is it laminate the pipes are installed under?

 

[Razor900]

As I have already said Opentherm is a waste of time with an all UFH system.

In addition the pipe configuration you have there will almost certainly cause poor hot water output from the boiler when the underfloor heating is running at the same time as a hot water demand.

All you needed was a flow and return pipe running directly to the manifold. No blending pump or valve

Plus I can't see the scale reducer or shock arrestor in the picture???

 

[trojanhawrs]

As I have already said Opentherm is a waste of time with an all UFH system.

You might be right, I'm not totally clued up on how it talks to the boiler but surely in an ideal scenario the UFH could be running at say 40 in the autumn and 55 in the winter, or anywhere in between.

 

[Razor900]

You might be right, I'm not totally clued up on how it talks to the boiler but surely in an ideal scenario the UFH could be running at say 40 in the autumn and 55 in the winter, or anywhere in between.

Generally the maximum temp you would run UFH at is 45 degrees with a max floor surface temp of 27 degrees.

Most flats need less heat input depending where they are in the building so properly installed UFH should be sized to run at a flow temp of around 40 degrees.

If I had installed this I would have used an OT thermostat but with the boiler output directly to the manifold without the blending valve and pump set but I know how to set it up properly.

The blending valve will not work properly unless the flow temp is around 15 degrees higher than the set point - they just don't blend properly without this differential.

And with this configuration the UFH will definitely scavenge heat from the boiler if both UFH and hot water are called for leading to poor hot water

 

[trojanhawrs]

Generally the maximum temp you would run UFH at is 45 degrees with a max floor surface temp of 27 degrees.

Might be a bit higher with laminate potentially

If I had installed this I would have used an OT thermostat but with the boiler output directly to the manifold without the blending valve and pump set but I know how to set it up properly.

The blending valve will not work properly unless the flow temp is around 15 degrees higher than the set point - they just don't blend properly without this differential.

Makes sense

And with this configuration the UFH will definitely scavenge heat from the boiler if both UFH and hot water are called for leading to poor hot water

Pretty sure it's a combi