Is there not a hidden menu. Even on my Evohome it's in the service menu,
What smart themostart are using?
- Thread starter tsobo
- Start date
Unless there's some kind of gesture to reveal it, then no. Even the "Tado for professionals" app doesn't offer much more than a "status check".
I understand the logic behind TPI, but I just wish there was a toggle! There'd likely be less of an issue if I was able to run extra wires through the house to get OpenTherm on Tado, but I can't/don't want to right now, so TPI is the only offering when Tado is set as a relay.
Ideal's own Halo system supports OpenTherm and would let me essentially "drop in" the controls right next to the boiler without having to run a single extra wire anywhere, but it'd also be about £400 for parts and to wire in the OpenTherm cable means removing the boiler's front cover which forms part of the room seal so that'd (legally) need a Gas Safe engineer visit too....
OpenTherm is a communication protocol that allows a thermostat to modulate the flow temperature of the heating system dynamically. So whereas now you'll likely just have it fixed to one temperature on the boiler (usually 60-70ºC), an OpenTherm thermostat will tell the boiler to start lowering the flow temperature of the heating system as it gets closer to the temperature you want the house at. This reduces overshoot and improves comfort, as well as burning less gas, though we're talking single digit % saving.
So if you have the thermostat click on requesting 20ºC, but the house is at 15ºC, it'll tell the boiler to run at a high flow temp to really pump the heat into the house. Then as the temperature starts getting above 18ºC, it'll tell the boiler to start rolling back, so when it gets to 20ºC the flow temperature is low enough to just hold the house near enough perfectly at 20ºC for the time period you've selected.
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Gotcha. And things like Hive and Tado don't automatically implement this?
I presume the boiler will be trying to modulate the gas based on the radiators capacity to expel the heat (i.e. return flow)? Or is that not science?
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They do, but it requires different wiring usually, so they get wired in as simple on/off if they've replaced another thermostat.
The boiler modulates its gas output to maintain the flow temperature set point; OpenTherm allows that set point to be altered dynamically (equivalent to you going up to the boiler and reducing the temp).
Is there an easy way to tell how my Hive has been installed? It was literally a rip out and replace everything job (here).
For gas boilers, there are really four types of stats. Also note lower flow temp improves efficiency, more condensing and less heat out of the exhaust:
System design is important, most boilers, especially combis, are oversized and therefore cycle on and off when the home is up to temp, which increases wear and reduces efficiency. This affects whatever type of stat you have.
Heat pumps are different again, require a different system design with much lower flow temps and higher flow rates than gas boilers (lower dT), and also require an always on regime in winter, otherwise you will be always cold.
| No modulation | Modulating | |
| Dumb | Conventional programmable stat. The boiler will still modulate down the power output once the set flow temp is reached, however you would need to manually adjust flow temp to get the best efficiency. | Once the home gets to to the set temp the stat will communicate with the boiler to lower the flow temp, this will improve efficiency. More efficent than a non modulating 'smart' stat. Plus no reliance on internet connection. Example: ideal halo lite |
| Smart | Only advantage over the conventional type is the ability to turn on and off via a phone. Can still do this manually with a conventional stat, but not before you get home. No real efficiency bonus. Example: hive | Efficiency of modulation with smart control, best of all worlds as long as your internet is reliable. Example: google nest |
System design is important, most boilers, especially combis, are oversized and therefore cycle on and off when the home is up to temp, which increases wear and reduces efficiency. This affects whatever type of stat you have.
Heat pumps are different again, require a different system design with much lower flow temps and higher flow rates than gas boilers (lower dT), and also require an always on regime in winter, otherwise you will be always cold.
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Great post above. To hammer home the point about boiler oversizing - my boiler is a 35kW combi, and it can only modulate the heating down to 7kW. My house will never ever be losing 7kW (only a couple of years old with good insulation), perhaps even in the minus temperatures, and only have 10 rads, of which a couple are quite small. It’ll never be expelling 7kW of heat, so the boiler is always cycling the burner.
Even when I manually put the flow temperature to 68C and it was -6C outside, the boiler still cycled the burner. It pains me to know I’m losing a lot of efficiency because of this.
That said, the insulation of the house also means I very rarely need a flow temperature above 60C so at least I know I’m getting the benefit of a condensing boiler (and I can hear the condensate running through the pipe quite often).
Even when I manually put the flow temperature to 68C and it was -6C outside, the boiler still cycled the burner. It pains me to know I’m losing a lot of efficiency because of this.
That said, the insulation of the house also means I very rarely need a flow temperature above 60C so at least I know I’m getting the benefit of a condensing boiler (and I can hear the condensate running through the pipe quite often).
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From earlier links Hive doesn't provide an opentherm interface and TADO only if you have the eu control box - plumbing geek, is it, that list the system suppoorting OT/breakout
if you read earlier linked report too OT doesn't provide that much improvement/ROI, if, you have, anyway, kicked down the outflow temp and the open radiators are providing good temperature drop.
Need those boiler dynamic stats (modulation, out/return temp, flame on/off) to see if OT outlay could help
if you read earlier linked report too OT doesn't provide that much improvement/ROI, if, you have, anyway, kicked down the outflow temp and the open radiators are providing good temperature drop.
Need those boiler dynamic stats (modulation, out/return temp, flame on/off) to see if OT outlay could help
Tado has OpenTherm with wired thermostat (which I have), but can’t use the wired thermostats with multiple heating zones (which I have) as they don’t have a master/slave setup available.
I believe the wireless setup does as you mention - they did a YouTube vid with the Heat Geek channel and said they’ll sell OpenTherm compatible wireless systems if you buy direct from them.
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Some boilers also allow connecting an external temperature sensor (must be north facing/shielded from sunlight) for weather compensation. You then set a power output curve based on the heat loss of the building (in kW), greater heat loss sets a higher output curve. With this the flow temp and hence power output will be lower when the outside temperature is higher.
The problem with this is that the curve does not adjust for the current state of the building, i.e. it can take a long time to heat up from cold. Works best for always on control, such as offices/businesses. Some controller even allow both weather comp and internal temp, the cost is obviously higher, and more potential for teething problems. Cycling is still a problem for oversized boilers.
If you are living somewhere long term it can be a good idea to work out the heat loss of the home, you could see how much benefit you would get from improving insulation and how well matched your heating system is. There a guide to doing it manually in a spreadsheet here:
https://peter-wurmsdobler.medium.co...of-uk-1930s-semi-detached-houses-6f64c6514565
Or if you don't mind making an account you can use this site for free:
https://app.starsapp.co.uk/dashboard
The problem with this is that the curve does not adjust for the current state of the building, i.e. it can take a long time to heat up from cold. Works best for always on control, such as offices/businesses. Some controller even allow both weather comp and internal temp, the cost is obviously higher, and more potential for teething problems. Cycling is still a problem for oversized boilers.
If you are living somewhere long term it can be a good idea to work out the heat loss of the home, you could see how much benefit you would get from improving insulation and how well matched your heating system is. There a guide to doing it manually in a spreadsheet here:
https://peter-wurmsdobler.medium.co...of-uk-1930s-semi-detached-houses-6f64c6514565
Or if you don't mind making an account you can use this site for free:
https://app.starsapp.co.uk/dashboard
still on my browser tab uk govt review of (il)legitimacy of many manufacturer weather compensation claims
https://assets.publishing.service.g...337/heating-controls-compensation-tpi-bre.pdf
insulation - watched an interesting video on the recurrent oc topic of flir use other day to evaluate insulation,
hadn't appreciated readings can be misleading in the presence of damp or different types of surface
https://assets.publishing.service.g...337/heating-controls-compensation-tpi-bre.pdf
insulation - watched an interesting video on the recurrent oc topic of flir use other day to evaluate insulation,
hadn't appreciated readings can be misleading in the presence of damp or different types of surface
Smart TRVs that control the boiler ... are these likely to cause additional wear and tear on the boiler with it clicking the boiler on and off as each room adjusts in temperature? Or is it nothing to be concerned about?
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They will cause additional cycling yes. Most boilers can’t modulate their burner low enough to cope the demand from only 1 radiator (mine can’t even go low enough for 10!) so you’ll hear the burner clicking in and out a lot more.
This thread isn't so big so you should skim it as is answered as well as ideas on appropriate smart TRV use cases.
wear and tear The, think it was, 8 years warranty folks had on their ideal combi gives them some peace of mind in the migration from 100% reliability of 20 year potterton,
and keep the british gas, your peace of mind from £2/30/m, at bay
however I guess wear and tear can manifest itself as lost efficiency/corrosion on burners, valves, gas flow - need to have an analogue of a car dyno mechanism(even if they don't monitor mpg?)
and keep the british gas, your peace of mind from £2/30/m, at bay
however I guess wear and tear can manifest itself as lost efficiency/corrosion on burners, valves, gas flow - need to have an analogue of a car dyno mechanism(even if they don't monitor mpg?)
I swapped a 30 year old potterton that would have likely gone on forever for a vaillant (made by our boys in Derby). The potterton would suck gas like it was an alcopop.
FWIW I think I have found the best use of Smart TRVs - I was finding the "over engineering" of them trying to hit a temp was causing balance issues, so I now have a pseudo "on-off" setup:
Rear bedroom is indicative of how the other bedroom is setup too; but basically in the morning it allows heat from 0630-0700. The TRV needs 5 minutes to open so the first 15 mins are just a buffer.
Hot water comes on at 0600-0700 and is demanded driven depending on how much water was used the day before.
Heating is scheduled for the morning only - and as the upstairs gets warm first but is then mostly unoccupied, it only allows 15 mins of heat. It then forces the water downstairs which means the rads downstairs warm up faster than if both upstairs and downstairs was open.
The rest of the day if the heating is boosted, it just does the occupied spaces. However I have found an oil filled rad + ceramic heater fan are much more effective as only 2 spaces need heating. Then when the little one comes home, the heating gets boosted and her room heats up and retains the heat pretty well till the next day:
As you can see, it heats up in the evening when I boost the whole house, and then turns off until it is allowed to heat up again at 1630 and the heating is boosted again. It then gets 15 mins of heat in the AM to take the edge off before stopping flow to allow downstairs to heat up quicker in time for breakfast.
Costs:
Edit: This is KWH usage. The boiler is a 22KWH boiler so looks like it is modulating its gas usage:
Do you have ‘Heat on Demand’ turned off on your Smart TRVs so they only heat up if the boiler is on or boosted, rather than them triggering the boiler to turn on?
Yeah that's right. Heat on Demand is off. In the old house (and when gas was dirt cheap), it used to trigger the boiler to keep the nursery at temp. The new house is much better insulated though so her room once it hits 17-18 only loses a degree or two over by 0645.