Is it worth it? Better central heating control.

Discussion in 'Electricians' Talk' started by MGW, Dec 19, 2021.

  1. MGW

    MGW Screwfix Select

    We see on these pages people fitting Tado, Nest, Hive, EvoHome, Wiser and other central heating controls systems, the idea is less hysteresis, faster response times, and more timed and temperature controlled zones.

    So if we look at basic, a single programmable thermostat and make a comparison to a pair of programmable wall thermostats, placed so wind and sun will not either make one side of house cool, and a programmable TRV in every room, cost of wall thermostats around £35 and TRV heads £15 so three bedroom house around £250 rough ball park figure as houses will vary. So £35 - £250 it it worth it likely yes as more comfort, not looking at simple savings.

    But in some cases it goes silly, Hive for example £100 for wall thermostat seems cheap, until you add the £43 for each TRV head likely need 6 so an extra £100 to install but does include geofencing, and only one wall thermostat required as the TRV heads act as remote sensors as long as the wall thermostat cooler than 22ºC.

    Now keeping the wall thermostat cool enough means need TRV in same room as thermostat, and clearly don't want wall thermostat in main room if that room is going to be near the 22ºC limit.

    Now we start to see the little quarks of each system, my Nest was claimed to link to Energenie, but one it seems the Wall thermostat tells the TRV what to do, in most cases it is the reverse, and only when temperature change was from app, a scheduled change or using wall thermostat it did not work.

    So I for one have installed a system which does not really work. OK good enough not to be worth ripping out and starting again, but not the smart system I thought I was installing. OK lovely Energy history.
    upload_2021-12-19_15-3-33.png But it is flawed, it shows when the thermostat called for heat, not when boiler was running, which would with my boiler be a indication of energy used, but with a gas modulating boiler even run time means nothing.

    It is nearly as bad as the advert showing a Freddy Boswell look alike clapping hands and turning lights off/on claiming being done by the Smart meter.

    I would guess I spend around £400 per year on 28 sec gas oil, so around £2 to £3 a day in winter, already have 9 programmable TRV heads, so no room over heated, and rooms not used turned off, if I know not going to use them.

    I could reduce my fuel bill by opening up the open fire and burning wood, it would also save money as would not need to pay to get the wood removed, but likely cost more in petrol for chain saw to what is saved, and as to dusting.

    But cut the wood, dry the wood, carry the wood into the house, and carry ash out of the house, compared with £3 for fuel oil, I'll pay the £3.

    With all the clever technology maybe I can reduce fuel bill from £3 to £2.50, is it all worth the effort? I think not.
    quasar9 likes this.
  2. ElecCEng

    ElecCEng Screwfix Select

    You say that’s the idea but depends on your objective doesn’t it? If it’s simply to be able to control your heating remotely then that’s different to saving money on heating. In the latter case, money spent on insulation and airtightness is going to make far more difference than a control system.

    The only way the system you have can be smart is if the sensor and control setup is good enough, which it seems yours isn’t. Costly to change a wet system to have a stat in each room and each room a zone controlled via manifold, but actually the cost of the parts (stat and manifold valve) probably less than a ‘smart’ trv. Electric easiest to make smart but more costly per kWh. Can vastly reduce this through insulation, smart control etc as part of a holistic approach to the problem. Eliminating the hydrocarbon heat source reduces the maintenance bill and carbon footprint (if on the right supply plan). Each of those different objectives too.
  3. Jimbo

    Jimbo Screwfix Select

    What I see on forums elsewhere time and time again is people have really poor experience with low carbon heating - ASHP in particular - driven precisely by these smart controls.

    There is an interesting dynamic with ASHP in as much as heating the property less doesn’t necessarily save money. The lowest cost is achieved when the total energy demand is serviced with the lowest possible flow temperature. If heating for less time - the basic aim of smart controls with per-room control etc - then higher flow temperatures are later required because the fabric continues to lose heat to outside even when the room isn't being heated. Hence there is a balance between compressor run-time and flow temperature, all else being equal.

    In other words, smart control don’t play well with ASHP and usually cause owners dissatisfaction with the systems. Add in the impact of short cycling caused by TPI algorithms and dumb 'thermostat' style integration and we are left with ASHP industry already being damaged by user perception of entirely avoidable problems.
  4. Sparkielev

    Sparkielev Screwfix Select

    I fitted a nest e on my combi, I hate it keeps turning itself on even when I'm out, was on 4 hours the other day whilst I was at work, have tried everything now I unplug it until I get home, I'm going to rip it out and buy simple mechanical stat
    Muzungu likes this.
  5. WillyEckerslike

    WillyEckerslike Screwfix Select

    Not only is there a considerable capital outlay converting your house to a smart home but there is another hidden cost.
    Whilst home automation is invaluable to people with mobility and other health related conditions it is making people lazy. "Oh let me use this latest gizmo on my £700+ iPhone to control my bathroom towel warmer". Really?
    Have a watch of the animated film WALL-E to see where this is heading.
    ElecCEng and Muzungu like this.
  6. The Happy Builder

    The Happy Builder Screwfix Select

    Many people still have programmers that use the same time settings for both heating and hot water, this is very wasteful as they will fire a cold boiler to top up the heat in a hot water cylinder late in the evening when no hot water may be required until the following morning and the boiler will fire again anyway first thing in the morning.

    Also many people still have their room thermostat in a hallway, not in the room where they sit for most of the time, so they are trying to maintain a level of heating that is comfortable with a thermostat that isn’t even in the same room.

    So for many people simply replacing their programmer with one that has separate timings for heating and hot water as well as replacing their existing wall mounted room thermostat with a portable wireless thermostat that can be used in their living room when relaxing, home office if working or bedroom if ill will save them a significant amount of money, without all the hassle and cost that can go with creating more complicated systems.
    ramseyman likes this.
  7. Peter208

    Peter208 Active Member

    For me, adding a smart control for the heating and hot water tank was a good move. So I would say, it’s all depends on what you did have and what you now need. I have no need for smart Trv’s but wanted better control of heating and hot water. My old system did not have a frost stat and the hot water control was dated. The electro mechanical heating and hot water timer was poor with limited options. The smart system gives a better control of both along with remote actions if needed. So for me, updating to a smart thermostat was and is a worthwhile investment.
  8. MGW

    MGW Screwfix Select

    Now that is to me a problem, but can't really see a way around it, boiler runs (C Plan) for whatever and DHW heated, impossible to turn off the DHW.

    But if DHW set to heat ½ hour 4 days of the week so around 20 minutes every other day in summer, as boil shuts down after 20 minutes, which is enough to give us hot water at taps, I want this to auto stop if the central heating has been running that day. What I would like is a wireless tank thermostat, bought one for parents house, but they seem to have dried up. At least at a reasonable price. Been looking at zigbee etc, sonoff or other way to transfer info three floors without running wires.

    I have reverse problem with Nest Gen 3, if I sit in bedroom on the PC so not walking past it, then it turns off with the geofencing, it was OK when on Nest, it was when google took over, the thermostat does seem sensitive, so would think a cat or dog would trigger it, do you have a cat or dog so it thinks some one at home?

    I would not think so, my TRV head bluetooth £15 each, not sure if these upload_2021-12-20_13-49-51.png will fit a TRV? They are designed for under floor heating, but at £12.90 without the programmable wall thermostat which is likely another £35 plus getting low voltage to power them likely looking at £48+ per radiator and the expensive energenie TRV heads were £47 each. And with Drayton Wiser upload_2021-12-20_13-56-26.png it claims clever algorithms to remove the problem I had with Energenie, in that the anti hysteresis software is OTT, so change from 16ºC overnight to 20ºC 7 am and it was 11 am before the room had reached temperature, so I would set to 22ºC for an hour then back down to 20ºC which completely messes up any idea of geofencing.

    Personally I have one major problem, hall cools down too slow. What I need to do is monitor multi-rooms and if any below set point boiler must run, the device is made upload_2021-12-20_14-9-6.png for the US market, £136.80 for three.
    but can't find out if it works with Nest Gen 3? It says works with Nest E, but Nest US is very different to Nest UK. upload_2021-12-20_14-17-58.png It seems it will work with Nest Gen 3 so it seems now I can at last get Nest working as it should. Only found UK advert today, up to now seemed only for US version.

    However even for three £136.80 is expensive, at £45.60 each the sensor is nearly the same price as a linked TRV.
  9. The Happy Builder

    The Happy Builder Screwfix Select

    But if the boiler keeps cycling on and off to keep itself, the heating system pipework and the hot water cylinder up to temperature when there isn’t any demand you are wasting money and creating unnecessary pollution.

    Controlling a heating system with thermostatic radiator valves rather than turning the boiler off is very inefficient utter regardless of how sophisticated the TRVs are, particularly if there isn’t any controls on the hot water cylinder.
  10. Bazza-spark

    Bazza-spark Screwfix Select

    Non of that smart nonsense for me.

    Combi boiler with a simple EPH room stat.

    In the evemt of power fail, I can swap to 12v battery and inverter to power the heating. Room temperatures controlled via normal TRV's. No cold rooms, dont have to worry about closing doors between rooms. 3 bed bungalow luvverly!
    Sparkielev likes this.
  11. ElecCEng

    ElecCEng Screwfix Select

    After lugging my tools, ladders, reels of cables etc up and down 6 flights of stairs to a top floor flat, I quite enjoy not having to get off my fat bahookie to turn off the towel rail at the end of the day ;)

    WillyEckerslike likes this.
  12. quasar9

    quasar9 Screwfix Select

    Spot on ! I just balanced the rads and fixed the thermostat in the right place. Keeps the whole house at the right temperatures with TRV almost never coming into use. All driven by a simple Drayton programmer and a Salus RT500.

    If the anecdotal evidence from threads on this forum are anything to go by, the complexity of these smart devices has crossed over into the ridiculous. Only yesterday I was responding to a poster whose smart thermostat had too many parameters , all in the hope of saving a few quids of gas, but simply failing in its prime function, keeping the house warm.
    WillyEckerslike likes this.
  13. Bob Rathbone

    Bob Rathbone Screwfix Select

    'Smart' in all of it's media connotations is simply a marketing ploy. How you control your heating is dependent mainly on how the space is occupied, if the house is occupied then it needs to be kept at a comfortable temperature, if not occupied the the temperature can be reduced or the heating turned off. Their are many ways of achieving this objective without resorting to 'Smart' systems. A good programmer and thermostat set correctly to reflect the occupation patterns of the house will be as good as any exotic device.
    quasar9 and ElecCEng like this.
  14. ElecCEng

    ElecCEng Screwfix Select

    I would argue that no heating system should ever be ‘off’. Minimum heating (12-16 deg) needed to prevent damp etc. Big problem for those living with ‘fuel poverty’ and mouldy homes...
    quasar9 likes this.
  15. ElecCEng

    ElecCEng Screwfix Select

    Whilst I install a lot of ‘smart’ devices at work, at home we have a simple Salus wireless stat and Combi gas boiler. Salus can be 7 day programmed and moved to the location we want the reference temp to be. Wireless stat in every room is cost prohibitive at the moment, as is dividing the system into zones for better control. House is very well insulated so not actually a huge problem. We have ideal conditions for a heat pump but again too costly at this stage.
  16. Jimbo

    Jimbo Screwfix Select

  17. quasar9

    quasar9 Screwfix Select

    Talking of Salus, I recently fitted a Salus RT510, a replacement for the RT500. Even here some ridiculous features have crept in. One being a setting for water rads or electric rads, along with an option to limit the boiler cycle to 6 per hour. Luckily you can defeat these and set it to a simple hysteresis value of 0.5, so behaves like the older model.

    never understood this arbitrary 6 cycle limit as it serves no real purpose ! If your boiler is being switched by your thermostat as often as that, either it’s hysteresis value is very low or all the windows are wide open to the elements !
  18. Bazza-spark

    Bazza-spark Screwfix Select

    Our thermostat is also 7 day programmable, but as we are retired I have the same times and temperatures set for each day.

    Being a combi, there is no programming for hot water, get it when we want it.
  19. Jimbo

    Jimbo Screwfix Select

    The idea is to reduce the radiator surface temperature as the set point is approached to reduce overshoot
  20. Muzungu

    Muzungu Screwfix Select

    I too have the Salus 510 on a single zone system and TRVs on all the rads. We just have the transmitter on overide and switch it on when needed in the location needed. If we are not using a room or bedroom we have the TRVs turned down. Unlike alot of folks we don't actually feel the need to have the central heating on at all for most of the day and then we never have it over 18.5. For example even today It is unlikely we will have it on before 1300, not to save money but just we just don't feel it. Never have it on after 2200 unless it is absolutely freezing, perhaps a handful of times over the year. I am aware that some hold to the theory that it is more economic to have it on all day to heat up the house, in our situation I am not entirely convinced.

    I have looked into ASHP as our Vaillant combi is now 30 years old, although still working perfectly. 2 bathrooms and 11 rads (from memory). However the cost of ripping out every one of our lovely cast column rads and replacing, ripping up the floors to replace the microbore, upstairs and down, redecorating etc. would likely be over 10k before we even got to the point of the ASHP itself.

    I would like to think I am not a Luddite, 25 years as an IT systems manager should militate against that, but I sometimes think these smart system are too smart for their own good, and for the consumer. Some folks appear to spend more time fiddling about with these systems to get them to work than any possible gain in time, money or the environment can justify.

    Just bought a new dishwasher and have found it is bluetooth enabled. What does this enable me to do? I have no idea and don't intend to find out.

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