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Worcester Bosch 30CDi Regular & DT20 Programmer

Discussion in 'Plumbing and Central Heating' started by Mikesm11, 12 Oct 2011.

  1. Mikesm11

    Mikesm11

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    Hi,

    I want to add a DT20 programmer to a greenstar 30CDI regular boiler previously contolled by an external Horstman programmer through a 10 contact wiring centre. I can not find on WB literature site any instruction of how the wired 3 port valve, room stat and Tank stat should be wired so as to work with the built in DT20. Can anyone help?

    Many thanks in anticipation
     
  2. simond

    simond

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    You can't fit any plug in Worcester controls to a 30CDi conventional. It is external controls only, wired through Ls and Lr.

    To be frank, Worcester's controls aren't up to much anyway, being based on Drayton Invensys stuff; you'd be better off using Honeywell parts.

    3 port valve is undersized from a hydraulic point of view for a 30Kw boiler, by the way.
     
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  4. Mikesm11

    Mikesm11

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    Many thanks simond.

    I contacted the company who supplied the DT20 today and they said the same and apoligised that the salesman gave me bum info, they have refunded me so will get a Honeywell to replace the faultly Horstman.

    Are you able to say what should have been fitted instead of a 3port valve? Should it have been two 2-port valves, one on the water and one on the CH?
    S plan layout?

    best wishes

    MikeSM11
     
  5. simond

    simond

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    Yes, Mike, the 2 port valves give less resistance to flow.

    You must also fit a bypass (such as the Honeywell DU144 or DU145) to allow the boiler pump overrun to work when both valves are closed.
     
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