Simple Wi Fi Heating control

Discussion in 'Home Automation' started by jonm01, 5 Jul 2017.

  1. jonm01

    jonm01

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    I am thinking of getting this:

    http://www.timeguard.com/products/t...pose-timeswitches/wi-fi-controlled-fused-spur

    which is a fused spur unit, but with a wifi control which can be operated from an android phone. I wanted to be able to use it to switch the central heating on, on those few occasions when we may be back late and the programmer has turned it off, or, the thermostat is set low. My thinking is to connect this device so that when the output is 'on' it overides the room stat and programmer and turns heating on. (So, would be connected as would a frost stat.) I don't need to be able to adjust temperature or switch the heating off if its been left on, I just want to be able to switch it on at odd times when it normally may not be. I'd be grateful for any comments on the feasability of this idea. Thanks.
     
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  3. For many reasons that timeguard product is not suitable for your intended scenario.

    Other wifi control systems are available,Tado,Evohome,Hive,Nest and many others.
     
    Last edited by a moderator: 6 Jul 2017
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  4. bernardgreen

    bernardgreen

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    The red bit is not sensible. The heating will run without any limit to the temperature the room reached other than the thermostat on the water leaving the boiler ( typically 60°C or mire ). A cold house would be more confortable ( and safe ) than a house at 50°C
     
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  5. jonm01

    jonm01

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    Thanks Bernard, point taken. There are thermostatic valves on all rads except hall and bathroom, so, temperature is controlled, but, I realise pipework would be heated constantly with no interlock. The intention was just for short periods of use, ( an hour or so ) not long term. I'm not really looking for anything to have full control remotely, rather just a means of switching on at times. Obviously a proprietary system eg hive would do this, but it offers more than required really. Thanks for the replies.
     
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  7. jonm01

    jonm01

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    Thanks - I wondered if you might elaborate on what are the ' many reasons ' ... ?
     
  8. ericmark

    ericmark

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    I would like to do some thing similar, I do see your point, the TRV control the boiler so all that is required is to turn boiler on/off. However in the main today we need to allow boiler to cool down, so we send an off command, but don't actually turn it off, in some cases this is extra low voltage, in others simply low voltage, and with the latter it may be possible to connect the device, it depends on the boiler.

    However point one is you state you are already using a thermostat, this seems to be the flaw in the system, I don't know your system, so I will talk about my mothers system and you can then say how it compares.

    The boiler has a time switch called a programmer, and from that there is a thermostat, also there is a programmable thermostat in parallel with the programmer, this is from a failed attempt at control but has anti-frost so has been left in place just in case the house should ever get below 12°C but in the main now does nothing.

    So the room thermostat is in the hall, it has one function, to turn off the boiler when the day is warm enough not to need it, it work in conjunction with the thermostatic radiator valve, which will start to operate before the room thermostat turns off, so the room in this case the hall, will heat up quickly, until the TRV starts to work, once that happens the heating slows down to allow other rooms to catch up, before on a warm day getting the room warm enough to turn off the boiler.

    The hall TRV and wall thermostat were very carefully set to complement each other. As a result once set the TRV and thermostat are not touched, it took a long time to set up, so anyone touching it needs ear plugs in to stand the comments from me. I actually set the stop in the thermostat to 19°C so if fiddled with easy to return to setting, also a felt pen mark on the TRV. But point is the thermostat does not control the house temperature, the TRV's in each room does that.

    So to turn central heating on/off I use the programmer, the thermostat is always in circuit if the programmer is on. So to override the programmer it simply needs a switch. Some rooms have a set temperature 24/7, I keep bedrooms on the cool side, I have never liked a hot bedroom, the towel rails in bathroom and kitchen do not really heat the rooms that much, and again left on 24/7, however mothers down stairs bedroom and the living room do have programs running which is set in case of living room, 6 am 22°C, 9 am 20°C, 5:30 pm 22°C and 10 pm 12°C it never drops to 12°C but that is the setting, in the morning it never hits 22°C it is set that high so valve is held wide open so room heats up again quickly. Something similar for mothers bedroom.

    So if we want to extend the time room is heated for we would need a wifi connection to the eTRV not the thermostat, the programmer does turn off whole heating at 5 am and back on at 6 am, this is to ensure the boiler is running when the eTRV's try to raise the temperature.

    If it were not for my mother living down stairs where is gets cooler than upstairs as heat raises, then I could use the programmer to turn off heating at an earlier point. Maybe turn off whole heating at 10 pm.

    I did earlier try using a programmable thermostat which was portable room to room, idea was to vary heat through the day, however it was a failure, it is easy in hind sight, but I thought a thermostat in the room would control the main room temperature, however a thermostat switches on/off, it may be possible to design a thermostat which slowly changes a mark/space ratio but the ones I have used, simply switch on or off. The problem is the further the thermostat is from radiator the greater the hysteresis, but put it close to radiator and the radiator would heat the thermostat prematurely, although one can set to a higher temperature to compensate this means come a warm day and the room can get stinking hot.

    In contrast the TRV is gradual in operation, so once set the room will stay at a constant temperature, the TRV also controls how hot the return water is to boiler, so with a modern boiler the flame height is varied to suit the demand from the TRV. So allowing the TRV to do it's job works well.

    However a standard TRV only measures air temperature so is to some extent effected by the hot water in the radiator, however simply changing the head to an electronic one, then they measure both air and water temperature and correct the reading to allow for the heat from the radiator, also they can be programmed as to when to heat the room.

    The eTRV comes in three flavours:-
    1) Stand alone, with no wifi.
    2) With wifi which although it can be set to do automatic functions, it requires "If this then that" (ITTT) to link with other devices in order to control the boiler.
    3) Designed to use a central hub so boiler is in turn controlled from that hub.

    Although mine are the second type, they are never altered so could have been the cheaper first type. It is rather annoying the web page clearly shows current and target temperature and if the current is below target with any eTRV we want boiler to fire up, to get a switch to use this information seems near impossible, relays are made which can be also controlled using ITTT but as far as I can tell you can't write your own programs, you can only select those written by the manufacturers.

    There are to be fair 100's of pre-written programs, however even though you only want a on/off device, it seems you need something like Hive or Nest to be able to set them to follow the eTRV, however once you do have a hive or nest then the simple matching of the wall thermostat and TRV is completely messed up, as to being able to set heating to either be manually set with phone or automaticity sense how far away from home the phone is and so alter the set temperature can be done without having a hive or nest.

    So in real terms to control heating away from home hive and nest are useless, except of course when using hot air heating systems for which they were designed, or with open plan houses.

    So in real terms we have a huge jump in price from type 1 and type 3, with the third type there is no argument it does really control the house, there are a number of makes, look at EvoHome as an example, this does work well, but the price reflects how good it is.

    So I can see how you could use a simple relay to override a simple programmer, however not so sure if you could use it to override a programmable thermostat? I would say you need to return to a separate thermostat and programmer to do what you want.

    I used MiHome the eTRV works reasonable well, but I found the sockets and light switches are limited to three times on/off.
     
  9. cjard

    cjard

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    Are we really suggesting that if the thermostat in the hallway failed the plumbing system would explode? Cmon, the thermostat is a clock and temperature controlled on off switch, and this is an android phone controlled on off switch. If the OP installs it in parallel with the thermostat switched terminals he gets the remote equivalent of being able to turn the dial on the thermostat all the way up to max. This won't cause his house to burn down or the cat to get scalded, as anyone with an elderly relative will attest: thermostats get locked onto max routinely in this day and age

    Jonm01, the one thing you must must must do, is check how this switch works in terms of the output. Some switches will have a live and neutral terminal to power the switch, and then another two terminals that are connected together when the switch is active. This means if you want to switch a load that is not 230v you can, because all you do is treat the switch like any other, using it to interrupt e.g your 12v lighting circuit
    If on the other hand this device has only 3 terminals, a live a neutral and a switched live output then it will only ever behave in one of two ways: "supplying no voltage to the output" and "supplying 230v to the output"
    If your existing thermostat is also of this kind and switches a 230v signal to the boiler and the boiler is happy to receive 230v then there is no problem. If the boiler is expecting a volt free connection (i.e. The kind you need a plain switch for) then banging 230v into it will probably cause you no end of problems. If you aren't certain what you have, call an electrician before you fry your boiler's control circuitry
     
    Last edited: 17 Jul 2017
  10. jonm01

    jonm01

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    Thanks ericmark + cjard for the responses. The Timeguard unit outputs a switched mains 240v. My heating system is a Micron 60FF boiler, fully pumped system with 3 way valve, hot water cylinder and radiator circuit. All rads have thermostatic valves except the hall, landing, and bathroom. There is a mains voltage room stat in the hall which controls the heating, and a tank stat on the cylinder for hot water, and a 7 day dual channel programmer for timing control of everything. My original thinking, when I saw the Timeguard device was to switch live to the call for heat circuit, (as would a frost stat,) for a timed one hour period. ( The Timeguard has the facility to give a one hour 'boost') I imagine that a second room stat could be incorporated in the output if it was intended to be left on longer than an hour, thereby limiting any excessive temperature rise. I realise there are other devices dedicated to this function, this just looked to be a simple solution. An SMS based system would also achieve a similar result, possibly more reliably as not reliant on wi-fi, but, I haven't seen a suitable device to do this easily.
     
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