Economy 7 immersion timer (Horstmann Electronic 7)

Discussion in 'Electricians' Talk' started by cd27idw, Jun 3, 2020.

  1. cd27idw

    cd27idw New Member

    I'm hoping someone can advise on this one. I want to replace my existing timer-free immersion heater with one with a timer; I'm on Economy 7 electric, with a two cable mains input. Unfortunately the above Horstmann Electronic 7 "requires" (it says on the box) a single input. Assuming the switch from day to night rate occurs upstream, would it be sensible just to put the two mains inputs into the single set of posts? I'm guessing the two circuits are never live at the same time. The existing timer, Horstmann E7BX (God knows how old) accepts the two mains inputs.

    Appreciate any comments, irrespective of the tone.
     
  2. Comlec

    Comlec Screwfix Select

    Economy 7 changes the rate you pay for all the electricity you use during the reduced rate period. When not on reduced rate all electricity use is charged at the full day rate. So to control the night storage heaters and ensure they only use off peak rate electricity they are connected to the incoming mains supply via a control switch and often a separate consumer unit.
    The immersion heater is usually connected to a circuit within the main consumer unit and can be used at anytime. However to benefit from of the off peak rate the immersion can be fitted with a simple time switch. To allow use at other times the timer is fitted with an override switch (boost) and some even have a separate boost timer.
    Water heaters that use two elements tanks (Top and Bottom) are a little more complex but work on similar principles.

    I assume you have a single immersion.
     
  3. cd27idw

    cd27idw New Member

    I know how economy 7 works. There are two elements in my tank, and two mains inputs from the commercial unit, but the new timer that I want to install only has a single set of input posts (live, neutral and obviously earth, the latter not a problem) I'm just looking for any comments on the sensibility, or lack of, of doubling the inputs, as I'm assuming the two circuits are never live at the same time.
     
  4. Banallsheds

    Banallsheds Well-Known Member

    What is the "commercial unit?"

    It appears you want to connect both the off peak and on peak supplies together. This will back feed the on peak power to your storage heaters so don't do it.
     
  5. cd27idw

    cd27idw New Member

    "Commercial Unit" is the distribution box with the circuit breakers. As I understand it, the storage heaters and immersion heater should both be on dedicated spurs, and as such independent of each other. I stand to be corrected.
     
  6. Banallsheds

    Banallsheds Well-Known Member

    Consumer unit. The storage heaters and main immersion heater element should be on an off peak supply that is on for 7 hours overnight. The other immersion heater element should be on the normal 24 hour supply.

    You cannot join the two supplies together at the input of the timer for the reason I stated in post 4.
     
  7. cd27idw

    cd27idw New Member

    Yeah, right, "Consumer Unit". My Storage heaters have their dedicate unit with their own breakers, and shouldn't be connected to the immersion heater, as I stated. They're always switched off anyway.
     
  8. Banallsheds

    Banallsheds Well-Known Member

    As I have said the storage heater supply and main immersion heater supply will both be the dedicated off peak supply whether they are on separate breakers or not. The secondary immersion heater will be on the 24 hour supply. DO NOT CONNECT THEM TOGETHER.
     
  9. cd27idw

    cd27idw New Member

    My concern is safety. From what you're saying, the only issue I've got is potentially burning a lot of expensive electric on the storage heaters, which won't happen if they're switched off. I'm not going to overload any circuit, and only the primary immersion heater will be active when the timer is active.
     
  10. Bogle Crag

    Bogle Crag Screwfix Select

    You will have to leave the off peak feed disconnected ( terminate in a JB) the 24 hour feed will be adequate for the new timer, it will supply the bottom heater through the timer and the top heater through the boost button
     
    cd27idw likes this.
  11. cd27idw

    cd27idw New Member

    OK. Off Peak now disconnected and terminated, running on 24 hour supply only. Many thanks both of you for your input (and hopefully I won't give Banallsheds any sleepless nights, I think i'm going to cringe for a while)
     
  12. JP7

    JP7 New Member

    By doing that you are not getting the benefits of economy 7?
     
  13. Lectrician

    Lectrician Screwfix Select

    If it’s true economy 7, the whole supply is cheap at night, so you just use your own timer.
     
    Bogle Crag likes this.
  14. JP7

    JP7 New Member

    He has 2 feeds though, standard rate and E7
     
  15. cd27idw

    cd27idw New Member

    As Lectrician says, all the electric switches to cheap rate after midnight (in my case). I've been monitoring it just to make sure. The two inputs scenario seems perverse; perhaps it's historic (place was built in '88). Obviously lighting , power points, cooker etc are all on the standard rate circuit but they're charge at off-peak rate at off-peak times. There's a radio switch which turns on the low rate.
     
  16. Lectrician

    Lectrician Screwfix Select

    Yes, and he's chosen to control the time himself. Both feeds will still go to cheap rate at midnight, one will switch automatically while the other remains live 24/7.

    It would be VERY rare to find an old "white meter" system where you have two meters, one for heating and one for power.
     
  17. Bogle Crag

    Bogle Crag Screwfix Select

    My in laws have the old two meter tariff with afternoon boost, I rather naughtily wired the immersion to the off peak board
     
  18. pilchardo

    pilchardo New Member

    I hope no-one objects to me piggy-backing on this thread but.....
    I need to replace a 20+ year-old Horstmann Economy 7 Quartz Maxistore timer. The one-hour boost switch sticks, which means it's constantly heating water at peak rate if it gets left on.
    I need it to be a fuss-free like-for-like replacement in which the cables can remain where they are and just neatly slip into an identically positioned terminal block... because the new timer must sit exactly where the old one is, and there'll be no slack on the cables.
    So.... the currently available timer... will it go on as a straight swap with no (or minimal) issues.
     
  19. nigel willson

    nigel willson Screwfix Select

    White meters as they where know where in fact 2 rate meters not separate meters. When they first cam out they where physically white in colour
     
  20. sinewave

    sinewave Screwfix Select

    You and Lectrician are both correct!
    It depends on which is your local DNO!

    Some Landis Gwr 2 rate meters were indeed white, they also came in black.
    'White' Meters was often a generic term used by Meter operators to define a 2 Meter set up, one for 24Hr use charged at X and another Meter which was controlled by standalone DNO Timeclock, which was often White in Colour too, to confuse matters more, this was charged at Y (Off peak)
    It was quite often an 8Hr off peak supply too. Mostly these days E7 E10 (Split over 2 time zones 7 + 3)
    This is the reason why old Immersion setups had 2 incoming supplies so the smaller element could heat the Tank over 7-8 Hrs.
    The bigger element was for Peak Time boost.

    All Off peak tariffs around today will switch the whole house so no need for a dedicated supply if reliable local switching is at the point of utilisation.

    OP, just use the 24Hr supply and terminate the Off peak in a JB or disconnect at the DB
     

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