Home heating automation

Combining an oil/gas boiler with a stove boiler requires a proper plumbing setup, to prevent one boiler pumping into the other, and some level of electrical control. The stove is unlike the boiler, which fires when a stat/timer makes a request for heat. The stove works the opposite way, when its water jacket reaches a certain temperature, it opens valves or switches on pumps to dissipate the heat, and t requires a certain level of permanent open heat sinks, such as unvalved radiators, and its own HW coil in the HW cylinder. Furthermore, these should be convection connected, higher than the stove, so that the heat can be dissipated even if there is no electricity to power a pump.

A common electrical solution for normal powered operation is to have the stove convection circuit plumbed to the HW cylinder, and a branch from this via a pump to CH flow blender. This pump is controlled with a pipe thermostat on the hot flow outlet of the stove. When this rises above a certain threshold, the stat will close, and operate a circulation pump into the CH system. The stove stat will have a normally closed contact which would be live when the stove is cold, and if this live is used as the source live for the boiler call, either through the CH wall stats/timer or from zone valve relays, the boiler will not fire while the stove is supplying hot flow to the plumbed common CH circuit, which should be some kind of manifold or tank blender. This works well for any situation where the normal thermostat control system is on or off. If there are some smart TRVs on the radiators, then some radiators will have to be open in order to have a reasonable chance of sinking the heat from the stove when there is no call for heating from the thermostat or relay controlling the TRVs and the boiler firing.

An electrical relay box know as a lex box is a useful device as it has a number of relays and wiring points which facilitate muting of the boiler firing voltage when a live call comes from the stove relay. The system operates as normally, TRVs opening and closing, thermostats calling for individual zones, all unaware that the stove is on occasion overriding the boiler as the source of hot flow. When the stove flow cools, the stove stat will open, the residual stove heat may convect to the HW cylinder, and the oil boiler will resume firing if there is still a call for heat from the system thermostats. Easy peasy.

Im not lighting the stove 🤣

Pet hate of mine too. Refurb/extension ongoing. Doing all the deep retrofit stuff but as it's an extension you go out to tender to the market. Like, the real world everyday scenario. Only one of the OSS shops would consider us because of the "complexity" of it being an extension too. And they wanted 8k for "project managing", where I would have a contractor I appointed, and architect managing the project. And guess what? The difference in value between deep retrofit OSS grants and individual grants I can get doing it outside of OSS....you guessed it, 8k. Its all a sham. At least this way I'm paying standard prices for materials.

yep moving from a B3 house to a G (don’t ask why)

however I’m looking forward to getting stuck in. Plan would hopefully be to take advantage of the grant and get external insulation done straight away, along with windows. Then would look to upgrade the central heating, the gas boiler is relatively new so probably just need to move and add some radiators etc.

i like how Tado operates so think I’ll stick with that. My current house is gravity hot water and TRVs on rads.

presumably I should stick with the TRVs but put a zone valve on the hot water?

are combi boilers worth installing? I have an electric shower at the moment which we like so I’d probably just stick with that.

Can u explain the bit about operating at max efficiency by having higher flow rate for HW than for CH please? We're putting in a combi, CH is UFH downstairs, rads upstairs. I'm wondering if we should slightly oversize to allow for lower flow temp.

Is the current gas boiler a combi, that is, a boiler with a seperate direct HW heat exchanger? When these are installed there is generally no HW cylinder. Not to be confused with certain system boilers which have a seperate flow and return from the boiler to the HW cylinder, with an internal 3 port valve to divert at higher temperature to the HW cylinder. On the efficiency question, just read again, its the different flow temperatures, not flow rate, that enhances efficiency. Condenser boilers extract the most heat from the firing by cooling the exhaust gases with the return flow, a double heat exchage process. Larger radiators assist this, as coupled with a modulating thermostat (or a digitally coupled stat to a boiler with Opentherm interface), the radiators will keep set room temperature with a more continuous flow at lower temperatures rather than a series of bursts of high temperature flow. This is particularly suitable for UFH, which requires a low temperature flow anyway so as not to burn bare feet. UfH loops are fitted with blending valves, which will mix the loop return with the incoming hot flow to always limit the floor temperature to safe levels. The radiator in a UFH room is effectively the size of the floor, so doesn't need the same flow temperature to bring the room to a comfortable level.

With system boilers heating both HW and CH from the same flow, you have a requirement to heat the cylinder some of the time to above the threshold for the prevention of legionella bacteria, above 50° is adequate, so you might set your boiler to 65° on the flow to achieve a reasonable differential so that heat will transfer in the HW cylinder, and to have a bit of headroom above 50° for the HW temperature.

Setting the boiler to limit at 65° would be a good rule if thumb, the slight inefficiency arises when say TRVs or valves close in some rooms or zones, and the return flow is quite hot still. This hot return will not greatly condense the residual heat from the flue gasses, so a percentage of available heat will leave the boiler as warmer than necessary steam

A combi will run a lower temperature for the flow, assuming the radiators will still heat the rooms in all cases. The open therm boilers or smart stats modulation will always strive to modulate the firing to reduce the flow heat while at the same time transferring sufficient energy for all demand to be met.

I would run my boiler at 67, with my cylinder stat set to about 60. Only in the coldest weather does this cap on flow test the systems ability to heat the house on a continuous run. Check back on this thread, one of the regular posters tested how low he could set his flow before his house failed to heat to thermostat settings. He was testing to see if his existing rads could heat the house with the typically low temperature flows of low 50s achieved by heat pumps. In short, his rads were all too small.

Sorry for the long answer.

Does any one have a suggestion for smart thermostats to run with underfloor heating? I will have 16 thermostats overall and plumber is pricing for non-smart stats but said if I want to source myself he will fit what I want.

The heatmiser neoStat which are wifi I think seems to be the one that keeps coming up in searches, I am surprised there is such a lack I thought most/all of the main smart devices manufactures would be catering for underfloor also.

Does anyone have any feedback on the heatmiser ones and importantly are they a simple swap for the standard stats* that the plumber would be supplying i.e. will they complicate the install in other ways or require additional equipment?

*when I say standard I mean they are a digital (possibly touch screen) stat not some type of old basic twisty knob one.

Smart stats will 'know' the heating characteristics of the room when the stat closes the relay, rate of heating, rate of cooling, and will use this information to modulate the heating calls so as to minimise the hysteresis or over/undershoot that you will get from a stat that simply turns off when set temperature is achieved, and on when it drops below. Such a basic stat, which would include many electronic ones, will present a temperature graph which oscillates about the mean set temperature, often by several degrees. With UFH , response time is slower, so there is higher likelyhood that the stat will always be playing catchup.

The better smart stats should have finer control of this by using second order calculations, learning, and modulation. Basic on off thermostats for UFH will often have an additional probe sensor which is fitted in the floor substrate to measure the actual floor temperature and assist in the thermostatic function. Tado state their stats are suitable for controlling UFH rooms, they're confident their algorithms can track the heating behaviour of the UFH room.

1. Yes. The Climote is currently wired as a two zone timer, plus a HW timer. The internal thermostat of the climote is not used as it is in a utility room. The two wall thermostats provide the temperature control for the two zones. Two wired Tado stats can be installed in place of these to control timing and temperature of each zone.

2. If you require individual room temperature control, then you can fit TRVs to some or all radiators in a zone. A partial fit is useful to close off selected rooms from zone heating, e.g., you might fit TRVs just to spare bedrooms in the upstairs zone, to keep them off when general upstairs heating is called.

3. With the addition of the Tado Extension kit receiver, you can replace the Climote and control HW timing with the Extension kit HW relay. Alternatively, you can leave the climote to perform HW timing only, and set the two CH zones to always on with the Tado wired thermostats hich will assume full control, time and temperature, of these zones.

Solar iboost+ is a device which detects excess solar PV power and turns on the immersion element in your HW cylinder, reducing dependency on Gas. It is not interconnected with the HW timer for the gas HW zone. You may still require a certain amount of gas powered HW heating, but assuming there is a cylinder stat to cut the HW zone when water is sufficiently hot, it's a matter of trial and error to optimise the times you would expect the solar to deliver sufficient power to justify using the immersion to heat HW, as against using gas.

I would expect it to be the main source of HW during bright summer days. It's not clear if the iboost will only turn on the immersion if the solar power provides all the energy for the immersion element, or if solar provides just a certain percentage,If configurable. This % would need to be in excess of 66%, as otherwise the immersion will consume the additional electricity (approx 42c/kwh) from the meter to heat HW, about 3 times the cost of heating by gas (about 14c/kwh).

You'll need one at each zone wired in, with the two former zone connections at the climote hardwired to live on the extension kit. There is a wireless connection on the extension kit fir one Tado thermostat, this can be used for one of the zones, which gives you the option of relocating that stat in a different location in the zone. The old wired fixed stat there would need to be turned up to always on, or removed and it's thermostat wire pair linked together.

Swapping the old wired stats for two wire Tado, is roughly similar to replacing a single gang wall light switch, two wires. If you don't own a €3 phase testing screwdriver, which is used to indicate a live wire/terminal, and have never looked behind a wall switch, you should ask someone who has the basics at least, and can perform this, or help you.

Replacing the Climote has a few more wires involved, and could quickly become confusing if you removed them all, then weren't sure what each one was, live in, neutral, 3 switched lives out, earth. On the Tado Extension kit you will have to manually add some links from the live in to the common terminal of the HW relay, and the CH relay if you use the wireless facility for one stat, and you'll also have to tie in one or both CH switched lives out to the permanent live, which becomes the live in at the old stats.

So the first is easily diy, the second may be beyond a novice.

You should always worry about electrocution, we all have to go sometime, but being blasted by electrons wouldn't be my choice of exit, and even a brief mains shock is very unpleasant.

It's obviously permissable to diy even in these highly regulated times, else the manufacturers of these various devices wouldn't publish instructions that are aimed at competents rather than qualified electricians.

€180. Good price.

I also currently have a Climote after buying a D2 rated bungalow which came with the house but interested in moving to Tado.

Can the Tado system work with the Climote (single zone plus water heating) or am I better off getting the tado in on its own.

Its a 3 bed bungalow which is east west facing using a Grant condensing boiler.

On sunny mornings the East facing rooms are too warm, and also some rooms not in use so would like to get a handle on the those.

3 bedrooms, large kitchen, sitting room and a cold bathroom, so what do I need to buy? Do I need to get the seperate thermostats to the TRV's for each room or are the thermostats on the TRV's enough? Can I upgrade to the seperate thermostats at a later point either?

Thanks!

Thanks for that, is that the same product as above from the flogas site, or is it specifically "wireless"?

Thanks for your help Deezell, straight on to them...