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Smart Immersion Timer

Discussion in 'Electrics UK' started by mattyc94, 8 Jun 2020.

  1. mattyc94

    mattyc94

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    I've been trying to find a smart switch/timer to replace our standard double pole switch. So far I've struggled to find a smart double pole switch as a direct replacement. Has anyone any suggestions or examples of what they have used? Our heating/hot water can't be controlled separately so having to remember to turn the immersion on each morning is proving a pain.

    See the current switch in place attached.

    Thanks in advance.
     

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  3. oldbutnotdead

    oldbutnotdead

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    No idea about a direct drop-in replacement but most smart 13A sockets connected to a nice chunky relay would do the job (don't power the immersion thru the 13A socket, it probably wouldn't last long).
     
  4. oceansoul

    oceansoul

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  5. mattyc94

    mattyc94

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    This indeed could be the job for me! Thanks for the quick replies.
     
    Last edited by a moderator: 8 Jun 2020
  6. EFLImpudence

    EFLImpudence

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    You don't replace it; a timer would be in addition to the switch.

    You don't need a double pole one; just a normal immersion timer.

    Why not?

    So - you don't need a smart switch or timer either.
     
  7. oldbutnotdead

    oldbutnotdead

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    Aye, EFLI makes a valid point. If your cylinder is well insulated (foamed all over) it won't cost a lot to just leave it switched on. Even if it only has a jacket the heat loss is still relatively low
     
  8. mattyc94

    mattyc94

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    No insulation or jacket on the tank unfortunately. Another thing to add to my list.

    I always thought that leaving the immersion on 24/7 was expensive but I can see the various for/against debates on the forums.
     
  9. oldbutnotdead

    oldbutnotdead

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    It is expensive if the cylinder isn't insulated. Next time you're at Toolstation or screwfix or wherever, get a jacket. It'll pay for itself in about a month
     
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  11. mattyc94

    mattyc94

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    @EFLImpudence 'Our heating/hot water can't be controlled separately'

    My knowledge is very limited (clearly) but we only had a mechanical timer to turn the heating on/off when we moved in. I have since changed out for a Nest but unable to control the hot water separately if that makes sense?
     
  12. oldbutnotdead

    oldbutnotdead

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    Presumably this is a fairly old system- gravity hot water & pumped heating? Even then the usual setup is you can't have only heating, the options used to be hot water or hot water and heating. Some pics of boiler, controller & pipework might be handy, I'd suggest getting a heating engineer in to service the boiler & advise on control but most will probably tell you to get a new combi (which may not be necessary or cost- effective for you)
     
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  13. EFLImpudence

    EFLImpudence

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    Some systems do not allow the central heating on without also heating the water but the other way round is unusual - and would be very inefficient.
     
  14. oldbutnotdead

    oldbutnotdead

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    Not sure if Nest software is designed to deal with gravity hot water- if you have the 2 channel version (and your heating has a pump...gravity heating would be very unusual) then it could be made to work but with limitations.
     
  15. JohnW2

    JohnW2

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    Those debates have been going on for decades. I've never really been able to make any sense (in terms of the laws pf physics) of the argument that some people try to produce that it can actually be cheaper to leave an immersion on for 24/7 but, as others have been said here the effect (additional cost) of leaving it on for 24/7 get smaller as the amount of insulation increases.

    The first graph below shows what my immersion did a couple of days ago, with the cylinder being 'ridiculously well insulated'. After a period of an hour or so (can be up to 2.5h if we've used a lot of hot water), the thermostat switches it off and it only comes back on (under thermostatic control) for very brief, and very occasional, 'top-ups' thereafter. Since I use E7 electricity, it is only powered for 7 hours each night but, even if I have it powered for 24/7, the 'top-ups' remain very occasional, and very brief, throughout the 24h. (the dotted vertical lines are the start and end of the E7 cheap period)

    The second graph below shows how much difference the insulation makes, since I upgraded it from 'very well insulated' (around 200mm of insulation all around, in addition to it's foam 'coating') to 'ridiculously well insulated (>600m all around, including top and bottom) in May 2018 (the vertical dotted line) - the effect of which was to more-or-less halve the amount of time the (thermostatically-controlled) immersion of was 'on' each day (from around 2 hours/day to around 1 hour/day). It can be seen that, even with that 'ridiculous' amount of insulation, there is still a lot of seasonal variation, with the immersion having to come on for much longer during the coldest times of the year.

    upload_2020-6-9_14-50-53.png

    upload_2020-6-9_14-52-33.png

    Kind Regards, John
     
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  16. ericmark

    ericmark

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    I have Nest Gen 3, and it will independently allow hot water only, but not independently control central heating, however there was no diagram with Nest to say how to do it. I used this idea C-Plan_basic_Nest.jpg
    And it does work. It seems wrong as two inputs and one output, what it means is with heating selected you get pump, heating not selected no pump.
     
  17. mattyc94

    mattyc94

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    Pictures of the oil boiler attached. It's a Grant Euroflame Condensing Boilerhouse 90-120. We replaced the original boiler with this around 3 months ago. I'm all ears if there are any suggestions to control the heathing and hot water separatley but I don't think it's possible from what the engineer said.

    Thanks for all the responses. Interesting to learn about the various components involved in home heating.
     

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