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Honeywell V4073 midpoint valve

Discussion in 'Plumbing and Central Heating' started by btb23, 17 Oct 2012.

  1. btb23

    btb23

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    This midpoint valve was making a fairly load clicking/ticking noise whenever the central heating was used and continued even when the CH was later turned off. It seemed likely the motor wearing out, as the noise was becoming more obvious, so I got a replacement head. I fitted it and was testing all was working OK with the top off and noticed the motor was being constantly driven when open, and it was getting very hot, really very hot. Thinking there was a fault I did some research and found this explanation.

    As you probably all know it's designed to work this way, the motor is constantly driven as per the explanation...

    I understand its made to operate this way, though that would be why the motor was worn out and noisy and needed replacement. I wasn't so bothered about the constant power consumption, (6 watts, but lets keep a sense of perspective), it was more that it was being driven when not needed and was unnecessary. I had a look at the Y plan wiring from our boiler manual and saw a nice elegant solution was possible.


    The reason the motor stays live and driven is due to the line from 'HW-OFF'. (I've attached a scan to show this). What I've done is modified the wiring slightly and interrupted this line with a small 240v relay that switches with the room stat. Now when CH is ON, and room stat is OFF this line is interrupted and the motor returns to rest, when the room stat calls for heat this line is switched through and the motor opens normally.

    CH and HW are operating normally, except now the motor can only be driven open if CH is ON and room sat calls for heat. I'm sure this mod won't meet with everyone's approval, after all the motor was designed to work constantly, but there isn't any need for it to. Also we tend to have the CH time switch on constant, and control the CH with a remote room stat, so you can see the motor would have been mostly driven all day and night in this scenario, now its only driven when needed.
     
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  3. D_Hailsham

    D_Hailsham

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    It will also stay live if HW is ON and the HW stat is off (satisfied).

    See bottom diagram

     
  4. matt1e

    matt1e

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    Isn't that what the op just said Dave ? I think he has inserted the relay on the valve grey, if so he will have that covered

    Matt
     
  5. btb23

    btb23

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    Its my understanding that for HW, (either HW stat condition), the valve is at B. It's only A+B or A that the motor is driven. B is the rest position, the motor is not powered and pulled back to that position by the spring.

    I just had a look at the valve, put HW ON and the valve is at rest in B position, I adjusted to tank stat up and down and the valve stayed at rest. In addition I can double check this is the case as the motor is cold with any HW ON and tank stat combination.

    In your diagram its the line from HW OFF that I've interrupted, it doesn't matter what position the tank stat is in with HW OFF.

    Until yesterday I'd never taken the top off a midpoint valve or looked at the circuits, so I'm happy to be corrected, though my mod works for all conditions, and doesn't effect HW working.
     
  6. D_Hailsham

    D_Hailsham

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    No; he said:
    No mention of the alternative scenario where HW timer ON and HW stat is OFF/SAT.

    I don't think so.
    So he has not considered the HW timer ON, HW stat OFF/SAT case. In fact he hasn't understood what I was saying.
     
  7. matt1e

    matt1e

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    but that will have no impact on the functioning of his system, and when he refers to "line" he may be referring to "live" as in voltage as that's what it's called these days, and in that respect he has made a correct statement

    What don't you think? as above It will will have no impact and the valve will work as the op intends

    as stated it will work as he intends if he has interupted the HW off line just upstream of the valve grey

    Matt
     
  8. D_Hailsham

    D_Hailsham

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    I agree, but you are assuming he is interrupting the grey where as he seems to be saying that he is interrupting only the HW OFF.

    BTB23

    Please confirm which of the three wires is being interrupted.
     
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