1. Visiting from the US? Why not try DIYnot.US instead? Click here to continue to DIYnot.US.
    Dismiss Notice

Are my 2-Port Valve wired incorrectly? Kettling problem.

Discussion in 'Plumbing and Central Heating' started by BoutTime, 20 Mar 2021.

  1. BoutTime

    BoutTime

    Joined:
    10 May 2017
    Messages:
    34
    Thanks Received:
    0
    Country:
    United Kingdom
    Greetings all.

    I'm after a bit of advice as we have an issue with our HW kettling and on closer inspection the wiring on our 2-port Valves looks a little suspect to my untrained eye.

    Background:
    The house was built in 2001 and has an 'S' CH/HW System installed. If the HW is on and the CH is not, the HW in the pipes overheats and starts to kettle. We have Drayton ZA6 valves fitted and I know they have an issue where the microswitch can stick and as the original 20 yr old unit was still fitted to the HW side (CH had been replaced at some point) I swapped it out for a new one. I also replaced the Cylinder Stat in case that wasn't switching the pump and boiler off when up to temp.

    Now the problem still occurs. The only workaround is to have the CH and HW on at the same time to enable the additional heat to dissipate in the CH circuit.

    Wiring Issue:
    The cylinder stat does cut power to the valve causing it to close but I've had a closer look at the wiring (still original configuration as the old cables were routed out to make connections to the new cables in a separate junction box). Both HW and CH valves appear to be connected differently to how Drayton instruct.

    upload_2021-3-20_11-4-52.png

    CH Valve - On our system both the Brown and Grey wires are connected together with the Heating Call for Heat from the Nest Thermostat Heatlink. The drawing above shows that the grey wire should be connected to permanent Live. See Terminal 9 in the photo below.

    HW Valve - On our system both the Brown and Grey wires are connected together with the Cylinder Stat. The drawing above again shows that the Grey wire should be connected to permanent Live. See Terminal 6 in the photo below.

    From top to bottom the cables are:

    Pump
    Cylinder Stat
    Nest Thermostat Heatlink (N, L, 1 thru 6)
    Nest Thermostst Heatlink (T1 and T2)
    HW Zone Valve
    CH Zone Valve

    upload_2021-3-20_11-18-55.png

    upload_2021-3-20_11-22-33.png

    The way I see it is wiring the valves this way bypasses the microswitch by using the stats to cut power to the boiler and pump. Am I right or have I got this completely wrong? And could this configuration cause the pump and boiler to actually stay on irrespective of valve position?

    Many thanks in advance.
     
  2. Sponsored Links
  3. DP

    DP

    Joined:
    10 Dec 2003
    Messages:
    14,462
    Thanks Received:
    3,149
    Location:
    Glasgow
    Country:
    United Kingdom
    The wiring unit standard wiring sequence is L, N, ETH, CH IN, CH OUT, HW IN, HW OUT etc with last two/ three positions for pump and boiler. Apart from remote possibility of back feeding, kettling is not caused by miss wiring the ZV
     
    • Thanks Thanks x 1
    • Like Like x 1
  4. flameport

    flameport

    Joined:
    10 Mar 2007
    Messages:
    9,731
    Thanks Received:
    1,931
    Location:
    Poole, Dorset
    Country:
    United Kingdom
    That wiring isn't standard, but won't cause the problem described.
    With brown and grey connected together, it's impossible for a stuck microswitch to cause the system to run continuously as power is only applied to the switch when the controls are on.
    The switched output is still the orange wire, and even with the switch permanently closed, that would only be live with the controls on - unlike a more conventional wiring arrangement where the input to the switch (grey) is permanently live, and if the switch sticks closed, the orange output is also permanently live even with the controls off.

    The problem is likely is a restriction to the flow somewhere, either at the valve or in the cylinder itself.
     
    • Thanks Thanks x 1
    • Like Like x 1
  5. BoutTime

    BoutTime

    Joined:
    10 May 2017
    Messages:
    34
    Thanks Received:
    0
    Country:
    United Kingdom

    Thanks for this. I'm wondering if this is why they've been wired this way because of the issue of these micro switches sticking over time. It's effectively a fail safe as like you say, even if the microswitch is faulty and welded closed, the controls/stat can still cut power to the boiler and pump. Wired conventionally the pump and boiler would still run with the valve closed and the stat triggered open.

    Now I've replaced the valve with a new one it might simply be a matter of the boiler and/or cylinder stat being turned up too high for the system. It has a gate valve for a bypass (not ideal) and possibly the bypass circuit is just to short for adequate heat dissipation when the CH is off.
     
  6. fixitflav

    fixitflav

    Joined:
    20 Mar 2018
    Messages:
    1,085
    Thanks Received:
    124
    Location:
    Stoke-on-Trent
    Country:
    United Kingdom
    As others have said, it's not a wiring issue. The system should work without noise with either valve closed. Sounds like reduced flow, due to eg obstruction, or pump problem. Has the problem always been there, or recently started?
     
  7. BoutTime

    BoutTime

    Joined:
    10 May 2017
    Messages:
    34
    Thanks Received:
    0
    Country:
    United Kingdom
    It's been there since we moved in 4 years ago. I may have noticed it only once we had the Nest installed and I turned up the stats and reprogrammed the timings. The work around has been a mixture of turning the cylinder and boiler stats down or programming the water to come on only when the heating is on. I also opened the bypass a little more but in truth that circuit gets extremely hot. This is probably what the previous owner did. I've just turned the cylinder stat down from 60 deg c to 55 deg c.

    The pump is on the mid setting.
     
    Last edited: 20 Mar 2021
  8. fixitflav

    fixitflav

    Joined:
    20 Mar 2018
    Messages:
    1,085
    Thanks Received:
    124
    Location:
    Stoke-on-Trent
    Country:
    United Kingdom
    Might be worth checking the pump. I had a problem of slight kettling, not really bad enough to worry about, but at one point the pump started to vibrate badly. I replaced it and the the noise disappeared. When I dismantled the old pump the impeller (two stainless steel discs with a gap of about 2mm) was completely clogged. So improving the flow made all the difference.
    You should be able to remove the motor and impeller without disturbing the pipework.
     
    • Thanks Thanks x 1
  9. BoutTime

    BoutTime

    Joined:
    10 May 2017
    Messages:
    34
    Thanks Received:
    0
    Country:
    United Kingdom

    The thing is the pump is perfectly quiet with no vibration. The water is the pipes gets so hot it's effectively boiling up before banging and eventually dissipating. I reckon it's turning into steam. This only happens with WH on and CH off so if it's not electrical it's got to be insufficient flow in the bypass circuit. I can get it to do it easily enough with a tank full of hot water. Turn on HW Boost with CH off, wait a few minutes and the settling starts. Pipe work far to hot to touch. I did this earlier and when it started to kettle I backed off the Cylinder stat which closed the valve. I then confirmed the boiler was also now off.
     
    Last edited: 20 Mar 2021
  10. Sponsored Links
  11. ianmcd

    ianmcd

    Joined:
    15 Aug 2010
    Messages:
    22,231
    Thanks Received:
    8,796
    Location:
    Lanarkshire
    Country:
    United Kingdom
    post pics of your valves and by-pass
     
  12. BoutTime

    BoutTime

    Joined:
    10 May 2017
    Messages:
    34
    Thanks Received:
    0
    Country:
    United Kingdom
    upload_2021-3-20_15-43-33.png
    upload_2021-3-20_15-44-26.png
     
  13. DP

    DP

    Joined:
    10 Dec 2003
    Messages:
    14,462
    Thanks Received:
    3,149
    Location:
    Glasgow
    Country:
    United Kingdom
    Assume CH and HW is on, Both aux switches in the ZV are made. CH time comes to an end and relay in the programmer removes the 240 off the CH on tag. 240 that is running the boiler (via HW ZV) will back feed through CH zone valve aux sw to keep the CH valve open till room thermostat is satisfied.
     
    • Like Like x 1
  14. BoutTime

    BoutTime

    Joined:
    10 May 2017
    Messages:
    34
    Thanks Received:
    0
    Country:
    United Kingdom
    Back through Orange > Grey and across to Brown? If temp not satisfied, power to valve, valve opens, microswitch is closed, grey to orange and boiler and pump run?
     
  15. ianmcd

    ianmcd

    Joined:
    15 Aug 2010
    Messages:
    22,231
    Thanks Received:
    8,796
    Location:
    Lanarkshire
    Country:
    United Kingdom
    what boiler make and model do you have ?
     
  16. BoutTime

    BoutTime

    Joined:
    10 May 2017
    Messages:
    34
    Thanks Received:
    0
    Country:
    United Kingdom
    Ideal Classic FF260
     
  17. fixitflav

    fixitflav

    Joined:
    20 Mar 2018
    Messages:
    1,085
    Thanks Received:
    124
    Location:
    Stoke-on-Trent
    Country:
    United Kingdom
    So was mine until the vibration started, but I still had the kettling because of low flow (it turned out). When I took it apart there was a stainless steel ring pressed into the pump casing which had come adrift.
     
Loading...

Share This Page