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NEST controlling Pre-heat function on WB 30i

Discussion in 'Plumbing and Central Heating' started by Taser, 8 Jan 2020.

  1. Taser

    Taser

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    Hi all,

    My WB 30i combi obviously provides DHW on demand at all times when a tap is opened.

    It has a preheat function to provide a small amount of pre-heated water to reduce DHW heating times - manual control is via the ECO/PREHEAT button.

    It also has a (usually linked) input to presumably allow the preheat function to be enabled/disabled via external controls.

    Am I correct in saying that if I configure NEST as a 'System' boiler instead of 'Combi', wire a live supply/DHW switch using N/O terminals 5&6 on the NEST Heat Link and remove link on the boiler, that I will then be provided with direct app control (and importantly, schedule) for the preheat function?

    If this is indeed possible, does having the NEST set as 'System' affect any thing else that may be detrimental to my combi boiler?

    Thanks
     
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  3. stem

    stem

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    If you are referring to terminals 'L OUT' and 'LR' (with the tap symbol) as below, those terminals are provided for external time control of the hot water pre-heat function.

    The highlighted link is removed....

    Capture.JPG

    ....and the terminals can then be connected to the Heat link 5 & 6 instead as you figured.

    With some types of boiler it is necessary to open a 'room sealed' compartment to access the boiler's wiring terminals, where this is the case, this is not a DIY job and should only be done by a RGI (Gas Safe Engineer) who can carry out the necessary safety checks to make sure that it is properly sealed up again afterwards. I can't remember if your boiler falls into this category or not.

    Configuring the Nest as a 'System Boiler' enables the hot water control functions, the heating doesn't work any differently. I seem to remember that the boiler switch needs to be left on the Pre-heat selected setting and not Eco.
     
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  4. Taser

    Taser

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    Brilliant, thanks for your rapid and comprehensive reply - very helpful.
     
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