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Immersion heater not working in Economy 7 mode

Discussion in 'Electrics UK' started by WL187, 10 Jul 2010.

  1. WL187

    WL187

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    Hi,

    I have an Economy 7 immersion heater setup with a Horstmann Economy 7 Quartz control unit. One morning I woke up to find there was no hot water and since then the Economy 7 mode has not worked.

    I have checked the fuse, seems ok. The Boost mode still works. Initially I thought the bottom (Economy 7) thermostat had gone but this wasn't the case. I swapped the top and bottom thermostats around, Boost mode immediately worked, proving my initial thoughts were wrong. I left the top thermostat in the bottom overnight just to see if that worked - it didn't.

    I have opened up the Horstmann unit just to have a quick check. All looks fine. All wires still in place. I do wonder, how do these control units work in Economy 7 mode - is there an internal clock? Curious how it knows what time it is. All there are are some cogs.... I'm thinking whether it's lost it's time?

    What else can I try before calling out someone?

    Thanks in advance.

    WL.
     
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  3. oharaf

    oharaf

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    Sounds shot to me!! Buy a replacement and see if that works
     
  4. WL187

    WL187

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    Before buying a replacement, any advice on what and where to buy? Also how can I check or even set the time on these units?
     
  5. crystal ball

    crystal ball

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    If you have the mechanical clock type, the E7 switching is done by plastic tabs in the clock mechanism, these wear out and sometimes snap off, but are adjustable by fiddling round with a terminal driver

    The electronic version allows you to programme in off peak times
     
  6. flameport

    flameport

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    You can get the same unit to replace the old:
    http://www.screwfix.com/prods/44419/

    The time is set on the clock dial on the front.

    Note that this unit is only for systems where the whole house changes over to E7 at night. It is NOT suitable for systems which have a switched E7 supply via the meter or separate contactor.
     
  7. Taylortwocities

    Taylortwocities

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    RTFM

    http://www.screwfix.com/sfd/i/cat/pdfs/39/p3133739.pdf

    The off peak time period is not adjusted by the front panel. The installer has to take the panel off and mess around with the cams. Anyway, that won't be the problem.

    There is only one feed, from the fuseboard. Check there is power there,
    Next, turn the time dial round slowly and at about 11pm the off peak light should come on and you'll get power to the bottom immersion.



    If it does not do this the unit is knackered if it worked and it doesnt now. They are pretty reliable but I've had a few go pop over the years.
     
  8. WL187

    WL187

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    I'm just about to buy a new unit. I've got one of these old style looking ones -
    [​IMG]

    Can I just do a straight swap with one of these newer style ones
    [​IMG]
     
  9. nozspark

    nozspark

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    It's more than likely to be the immersion element at fault and not the "Horstmann" timer.... don't buy one until you know for certain that this is the case!
     
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  11. ban-all-sheds

    ban-all-sheds

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    Have you checked the actual element?


    Check the bottom element.

    [EDIT]That'll teach me to start a reply and then leave it for a while before posting.[/EDIT]


    [DOH!]Actually it probably won't...[/DOH!]
     
  12. WL187

    WL187

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    Yes, swapped the immersion elements round. This confirmed both elements are still working. I'm still in the position where only boost mode works.
     
  13. ban-all-sheds

    ban-all-sheds

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    You only mentioned swapping the thermostats.

    Draining the tank and swapping the two elements around would have been a hugely disruptive and time consuming task, and a ludicrous way to check that they both worked - why on earth didn't you just check that power was getting to both and measure their resistances?
     
  14. shadyspark

    shadyspark

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    could be either the timer, circuit, fused spur, off peak supply or the actual element. if the stat is fine its most likely the timer but i would check the element first. resistance between the lives should be 20 ohms and both clear to earth. often the timer works on boost ok but the off peak switch can pop individually.
     
  15. Taylortwocities

    Taylortwocities

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    Are you sure that is what you did? or did you just swop the thermostats? (Thats the long rod thing that just slides out)?

    If you swopped the elements then you would need to have drained the tank and used a very big spanner! As BAS said, that's not the way to find this problem.
     
  16. mmcsadler

    mmcsadler

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    Hi I've got exactly the same thing with my Horstman ECONOMY 7 unit. Did you manage to find out what was wrong???
     
  17. EFLImpudence

    EFLImpudence

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    The answer may not be relevant to your situation.
    Your fault could still be any of the above.
     
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