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Honeywell ST699 wired incorrectly?

Discussion in 'Plumbing and Central Heating' started by Rob Watt, 14 Oct 2021.

  1. Rob Watt

    Rob Watt

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    Hi, I have a honeywell st699. The controller works fine but in order to get my heating to come on I need to have the hot water going at the same time.

    I suspect its either a valve issue or that the wiring on the controller is wrong. The wiring will be easier to fix if that's what it is. Can anyone in the know take a look and give me their thoughts?

    Thanks in advance, Rob.

     
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  3. RandomGrinch

    RandomGrinch

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  4. Rob Watt

    Rob Watt

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    That does make sense thanks. I'm hoping that's not the case though as if the water is hot already the heating doesn't come on at all. That's not too big a deal right now but will become one soon as the weather gets worse.
     
  5. ianmcd

    ianmcd

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    Nope that is not wired correctly post pics of everything else you have, motorised valves any thermostats and HW cylinder and we will tell you how to change your wiring
     
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  6. RandomGrinch

    RandomGrinch

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    I'm afraid I can't tell if the wiring is correct or incorrect from your image.
    There appears to be a link between the live terminal and terminal 5, is that right?
    If so it looks as if the live is commoned to 5 and 6, and the outputs (switched lives) are on 8 and 3.
    If this is the case, It is not conventionally wired, but should have the same functionality (if relays do the switching!).
    But as ianmcd says, it depends what's connected at the other end! :)
     
    Last edited: 15 Oct 2021
  7. CBW

    CBW

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    Yes, because if they want a 230v common, then they often use a link wire. 5 and 6 are linked, which shouldn’t be. Also a cpc/Earth has been used as a live, which isn’t good practice either.
     
  8. RandomGrinch

    RandomGrinch

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    Hi,
    Genuine question, coming from an electronics viewpoint and just trying to understand!

    5 and 6 shouldn't be connected together, but if the switching was by relay, I don't believe there would be any difference which terminal (6 or 8 ), was switched live and which was live.
    Does the unit use triac switching, or similar?

    ...and yes, the earth should be sleeved to indicate a switched live. :)

    Thanks.
     
  9. ianmcd

    ianmcd

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    You are correct 5&6 should not be linked, by linking them the switching of the HW side has been disabled, reason I asked for a pic of the HW cylinder is I suspect the OP has gravity HW and that has been fitted as a bodge because whoever done that didnt know how to set the programmer up for gravity HW
     
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  11. bernardgreen

    bernardgreen

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    True if it is only a Make contact.

    I personally would put Live on terminal 6 ( NO ) and Switched Live on terminal 8 ( Com ) which avoids the un-used terminal 7 becoming Live when the relay is de-energised.,
     
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  12. ianmcd

    ianmcd

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    and what if it turns out he has a mid position valve, I dont think he does but no one knows as our crystal balls are all down because of covid, the two com terminals are called com for a reason, it is because they are common and need to be linked to whatever supply the other controls are using
     
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  13. bernardgreen

    bernardgreen

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    Each Com is "common" only to the NO and NC contacts in the triplet of contact for that switch.

    Whether or not the Comms of two or more switches need to be connected together depends entirely on the configuration of the system the switches are part of.
     
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  14. RandomGrinch

    RandomGrinch

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    That was my thought, the manual shows an inserted link to join the 'commons', so no fixed 'common' on board.
    Hence my belief that the unit may be wired 'incorrectly' but functioning as intended.
    And, as we have all said, we won't know for sure if anything is incorrectly wired, until we see the connections in the other end! :)

    EDIT:
    The ST699 does use relays, and there is no common 'Common'!
    It should work properly in the current configuration, with connections the other end being:
    Brown - Switched live, Hot Water
    Green/Yellow - Switched live, Heating
    Blue - Neutral
     
    Last edited: 15 Oct 2021
  15. Rob Watt

    Rob Watt

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    Hello all, thanks for the replies. Hopefully the attached pictures help to show what the current setup looks like. IMG_20211015_180502.jpg IMG_20211015_180509.jpg IMG_20211015_180524.jpg IMG_20211015_180533.jpg IMG_20211015_180542.jpg
     
  16. CBW

    CBW

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    You have an S-plan, with what looks like a hive controlling the heating. It’s still been wired wrong. You still need a live from your programmer to the cylinder thermostat to control the zone valve.
     
  17. Rob Watt

    Rob Watt

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    Thanks, just searched for hive receiver and that does seem to be a British Gas supplied hive receiver. No idea where the thermostat control would be though. I do wonder if it got removed before we moved in.
    Our plumber is coming tomorrow to service the boiler so I think we will get him to come in and see what he thinks.
     
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