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hot water temperature problem

Discussion in 'Plumbing and Central Heating' started by miketurner, 26 Jan 2020.

  1. miketurner

    miketurner

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    I have a Glow Worm 24HX Condensing boiler on the ground floor with a pump in the same cupboard, a hot water storage cylinder in the airing cupboard upstairs (Kingspan 1500 x 450 grade 3, 162 Litre. cylinder) in the eaves area I have another pump (both pumps are Salus MP200 domestic circulating pump). Upstairs I have two Drayton 2 port Zone Valves ZA5, one on the hot water supply to the hot water cylinder and one to the central heating supply.

    The hot water and central heating is timed to go on in the afternoon 4pm to 1030pm every day and has been working fine for the last 7 years, I think the whole system is around 11 years old.

    One evening I found that the temperature of the water coming out of the upstairs shower was warm and I couldn't get it to go hot, no matter how much I adjusted the shower control

    I then checked the temperature of the pipe coming out of each ZA5 valve, heating pipework was hot entering the valve and leaving the valve.
    Hot water pipe was hot going into the ZA5 valve but only a little warm going out, towards the hot water cylinder.

    I turned off heating and hot water via the timer and could move the slider switch on both ZA5 valves and they would then return fine by themselves.
    I snapped off the electric head of each and couldn't see anything (although I understand I probably wouldn't see anything unless they were dismantled) and
    snapped them back on.

    Now I seem to find that there is hot water in the evening. I'm assuming that having moved the sliders on each ZA5 valve has maybe freed the hot water ZA5, sticking maybe? but now there does not seem to be any hot water in the morning, whereas their used to be hot water all day long (left over from the night time).

    I'm just wondering if I changed the snap on ZA5 zone valve (actuators) would help and is it worth changing the whole valve including the compression pipework ?
    I have not changed any hot water temp on the hot water cylinder thermostat.

    Is it ok to just change the snap on ZA5 actuator part on the zone valves (£52) and not having to drain the system,
    or for the sake of £12 extra is it better to change the complete value with pipework attached but would mean I have to drain the system down first ?

    Any help or suggestions as to trying to diagnose what is causing the problem and ZA5 actuator or whole unit replacement would be much appreciated.
    There is an A and B labelled slide of some kind on the side of the ZA5 that does not seem to move, not sure if that is important.

    I'm going to keep running the heating / hot water as normal over the few days to see exactly what is happening.
    Apologies for the length of this post.

    Many thanks.
    Mike
     
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  3. ianmcd

    ianmcd

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    Why do you have two pumps ?
     
  4. miketurner

    miketurner

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    Sorry I don’t know why I have two pumps as the system was fitted by the previous owner. Both seem to be working though.
     
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  5. ianmcd

    ianmcd

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    Some systems use two pumps some use motorised valves , you have both which is very unusual, on the ZA5 going to the HW cylinder slide the lever across and lock it into the manually open position and put the heating on, does the pipe going to the HW cyl get hot with the valve latched open ?
     
  6. miketurner

    miketurner

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    We may have two pumps due to there being underfloor water heating in a couple of rooms downstairs.

    I've not been able to get the hot water cylinder inlet pipe hot, just warm and just warm coming through the showers.

    The heating and HW has been on for the last couple of hours now and although yesterday the top inlet pipe going into the hot water cylinder in airing cupboard was hot,
    today it just seems a little warm, as does the bottom one.

    I've turned off HW and heating and I can slide the HW ZA5 open and it then closes, then when I turn the HW on the slider locks into the open position and cannot be moved.

    I have turned the HW off and locked the HW ZA5 to the open position and turned the HW on but still there is no HOT going beyond the ZA5 to the cylinder. The ZA5 is locked into the open position.

    Would it do any good to try swapping both (hot water and heating) ZA5 actuators (the heads) and seeing if the heating then has any problems instead ?

    Can it be swapped without any problem as maybe they are wired in the same ?

    I'm assuming when I click them off and on again it's with the slider in the closed position ?
    Can they be put on incorrectly ?

    Sorry for so many questions.
    Thanks.
    Mike
     
  7. ianmcd

    ianmcd

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    with it locked in position you need to switch the CH on and turn up the room thermostat and see if the HW pipe now gets hot, yes the xtra pump will be for the UFH
     
  8. Alec_t

    Alec_t

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    Perhaps not. Do you have a manual / instruction-leaflet for the valve?
     
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  10. miketurner

    miketurner

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    Hi, Thanks I've done as you said, turned CH and HW off then locked the HW ZA5 to the open position, turned up the room thermostat and put the CH on and waited half an hour.

    All the pipes to the ZA5 valves seem to be cooling down, so no the pipe to the HW cylinder is cooling also. I checked the boiler and has turned itself off, don't know if that is correct ?

    So I've now put both CH and HW set to on and the boiler has started up.

    I don't have a manual for the valve but I guess I can find one online, but unsure if that would help.
     
  11. miketurner

    miketurner

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    Now I've started the CH and HW everything seems fine, the boiler is on and there is HW going through the zone valve to the HW cylinder, not sure if is temporary or may have fixed things. Did the above operation prove or do anything ?
     
    Last edited: 26 Jan 2020
  12. ianmcd

    ianmcd

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    sounds like a faulty actuator on the DHW zone valve
     
  13. miketurner

    miketurner

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    Hi Ianmcd, thanks for the info.

    With your suggestion: "with it locked in position you need to switch the CH on and turn up the room thermostat and see if the HW pipe now gets hot"

    Did that operation prove that it was the HW ZA5 valve?

    I understand I can just snap off the actuator and replace it with a new one, is it worth replacing the whole unit (meaning a drain down) or is there no real benefit ?
    Before I buy a new unit could I change over the snap on actuators to see if the problem moved over to the CH and proving it was the original HW ZA5 ?

    Thanks for your help.
    Mike
     
  14. ianmcd

    ianmcd

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    The actual valve seems to be fine, you can just fit a new actuator, yes they unclip , but you have to rewire the new one into the wiring centre, no need to drain down , there are some actuators that you can remove the actuator and they have a plug but yours dont
     
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  15. miketurner

    miketurner

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    Hi, I have tried just the HW on and both CH and HW and it seems to be working fine now. I will change the actuator head as it's probably indicating that it will stop working again soon. Many thanks for your help.
     
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