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Honeywell wiring centre

Discussion in 'Electrics UK' started by blup, 24 Mar 2019.

  1. blup

    blup

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  3. AndyPRK

    AndyPRK

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    If u have an existing junction box use it if confident.
     
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  4. ericmark

    ericmark

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    Look at the instructions it does seem the pump is powered independently to boiler, it also gives wiring for a number of the Honeywell plans.
     
  5. stem

    stem

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    If the wiring is presently correctly installed, and the system has been working as it should, then there should be no need to alter or add a wiring centre / junction box to change programmers. Apart from having a 230V mains supply to power them, both programmers just contain a pair of switches, one for the heating and one for the hot water. The connections at the ST7100 are as below.....

    ST7100.JPG

    .....the existing wires are simply transferred from the ST7100 to the wires at the ST9400C that have exactly the same function....

    ST9400C.JPG

    .....the only difference is that the ST9400C doesn't have accessible 'common' terminals. You can see from the diagram above that the 'commons' are already linked to the 'live' internally, rather than being brought out to external terminals for the installer to connect to the 'live' as is the case with the ST7100.
     
  6. blup

    blup

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    @stem thanks, yes the wiring is as you describe, and all is working fine, except the HW on programmer button is not responding so the plan is to put in a new programmer in anticipation of the unit's failure.

    The live feed to the programmer is 3 C+E from the CU downstairs, from where it is also connected to the boiler via a flex outlet.

    The switched live of this feed is connected to a freestanding terminal block within the programmer body.

    Connected to this, are the live cores from the cylinder stat, diverter valve and pump (all brown except an orange from the diverter valve). All these are upstairs next to the HW cylinder. The other cores fit into the programmers built in terminal blocks.

    It doesn't seem to be a straight swap because the st9400C doesn't have the built in terminals of the st7100.


    Blup
     
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  8. stem

    stem

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    Sorry don't understand what you mean by that, external wires from the wiring centre etc will be terminated at the ST7100, those wires will go to the new terminals at the ST9400C.

    Have you have removed the cover?

    cover.JPG
     
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  9. blup

    blup

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    IMG_0232.JPG

    There's no existing wiring centre, the programmer appears to act as that.

    Blup
     
  10. stem

    stem

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    Where that's been done, I normally:

    1) Sink a single socket back box into the wall behind the programmer & insert a terminal trip for the connections that are not actually associated with the actual functions of the programmer. [A metal back box will need an earth connection to it]

    2) Fit the new programmer backplate to the screw hole tabs on back box.

    3) For a Y Plan, only the 'N' 'L' 'CH On' 'HW On' and 'HW Off' wires need taking through to the new programmer backplate.

    4) The cables should be secured with clamps / clips / enclosed in trunking / or buried in the wall to prevent strain on the terminals.

    Alternatively you could fit a wiring centre at this location to terminate the wires and then run cables to the programmer at the side of it. If you get one with with cable clamps built in so much the better.
     
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  11. blup

    blup

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    Thanks, that's much clearer.

    Blup
     
    Last edited: 26 Mar 2019
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