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Worcester Greenstar 24i Junior - Nest Thermostat - only works if external stat is in place

Discussion in 'Plumbing and Central Heating' started by hcanning, 30 Apr 2020.

  1. hcanning

    hcanning

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    Hi all,

    I have the above mentioned boiler. The Nest thermostat has been fitted and working perfectly for many months, but I noticed at the time the boiler would only operate if the original wireless thermostat was also operational.

    At the time I just left it but now I'd like to sort it, for completeness. I've done a bit of research and the general consensus is removing the timer panel from the boiler and fitting a blanking plate should fix it, but nobody is able to confirm for sure.

    Could anybody confirm for sure whether that's all I need to do - simply disconnect and remove the timer panel?

    For reference the front panel looks like this (although mine has a second knob for DHW temp):

    [​IMG]

    And the old room stat looks like this:

    [​IMG]


    Thanks!
     
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  3. CBW

    CBW

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    To remove that timer, would mean removing the cover which forms part of the combustion circuit, so not just as simple as that. Is there no way you can leave it set to constant and use the Nest? Also your pressure is quite low.
     
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  4. hcanning

    hcanning

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    If the cover were to be removed, would it be "as simple as that"? It doesn't matter whether or not I set the HW to Timed or On, it will ignore the Nest's call for heat if the wireless stat is not calling for heat, for example if the batteries are dead, or you simply set it to a really low temperature. For that reason I've had to keep the old stat in a cupboard, set to about 30 degrees. It's just seems a bit annoyingly unnecessary to me.

    Also that's not my boiler, just a photo I found online :)
     
  5. CBW

    CBW

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    That would depend on any wiring, however I should have made it slightly clearer: if the cover is removed, then critical safety checks need to be carried out. Also you’d probably need a blanking plate.
     
  6. Madrab

    Madrab

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    You have a Worcester DT20 RF Wireless programmer (Drayton LP20 RF) and you need to remove that and blank it or replace it with a manual clock and set to always on. The Drayton wireless thermostat is paired to the boiler therefore when the timer is calling for CH then it looks to the stat if it's paired, if the stat is calling for heat too then it will then run the CH. If the thermostat isn't calling but the NEST is then it still won't fire up as the programmer has priority over the NEST.

    That being said, I'm sure that programmer's RF system can be turned off in it's paring section, so it won't look for the stat and will default to the programmer alone, have a look through programmer's MI. Never had to do it before so can't be sure, another engineer (@ianmcd) may be able to confirm.

    As suggested though, removing the case off that boiler is for a GSR engineer as they will have the equipment to ensure the boiler is working correctly after.
     
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  7. ianmcd

    ianmcd

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    You need a gas safe engineer as you have to remove the boiler cover and disconnect the ribbon between the DT20RF and the boiler PCB, when left plugged in the boiler will keep communicating with it, no links required just pull the ribbon out, you can get a blanking plate if you want to remove the unit but most just leave them in, when the ribbon is disconnected it is just an ornament it doesnt do anything
     
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  8. hcanning

    hcanning

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    Thank you. I've checked the user manual and it only mentions a "temporary override":

    "While the RF link is lost, the Central Heating can be switched ON by pressing the OK button once and switched OFF by pressing the OK button again. In this mode the room temperature will not be controlled"

    I'm guessing this isn't really suitable as a permanent solution?
     
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  10. Madrab

    Madrab

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    Nope, only permanent solution to bypass the stat is to disconnect the programmer.
     
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  11. hcanning

    hcanning

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    Gotcha. As I suspected. Thanks for your help :)
     
  12. ianmcd

    ianmcd

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    And you also need to top up your system boiler pressure :rolleyes:
     
  13. hcanning

    hcanning

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    How many times do I need to state that isn't not my boiler, just a photo I found online? :D
     
  14. ianmcd

    ianmcd

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    That is the reason for the emoji , I was winding you up :LOL:
     
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  15. hcanning

    hcanning

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    :mad:
    ;)
     
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