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Honeywell F&E using Nest

Discussion in 'Plumbing and Central Heating' started by jaber, 7 Apr 2019.

  1. jaber

    jaber

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    Hi all

    I have installed a few radio thermostats into combi boilers in the past. Simple install, simply a glorified switch. However, my new house appears to have an old heating system approx 20 years old.

    I believe it may be a an F&E? It has a boiler in adjoining garage, copper tank and water tank(s) in the loft. The thermostat is a Honeywell, control box by copper tank and remote thermostat on the wall downstairs. pictures attached.

    On closer inspection, it appears both have a mains supply and will fry my nest. I am keen to learn and do the install myself. Do I need a transformer for the Nest control box and remote unit? Is the thermostat on the mains rig or lighting rig?

    Regards... J
     

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  2. jaber

    jaber

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    +Boilet
     

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  3. ianmcd

    ianmcd

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    you have an open vent Y plan system there should be a wiring diagram for Yplan with you nest if not google it there are loads open vent (what you call F&E) and sealed system are wired exactly the same so just look for Y plan
     
  4. jaber

    jaber

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    Thx Ian - knowing the correct system name is a good start
     
  5. MeldrewsMate

    MeldrewsMate

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    The Nest receiver is designed to switch 240vac, and is powered from 240vac. Its T1 and T2 connections supply 12vdc to the user display, allowing the old wiring to the old thermostat to be re-used, and avoiding the need for the Nest optional power supply (unless you want to use the optional desk stand).
    The biggest bugbear with the Nest IMO is the small size of the terminals on the receiver, getting two 0.5mm2 wires into one terminal is a bit of a challenge!
     
  6. jaber

    jaber

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    Ah ok, thanks for the heads up on the power to the display. I did see any feed from the old thermostat, is it possible it’s radio? Only, look a bit old to me.

    The Nest is up and running, love it.
     
  7. ianmcd

    ianmcd

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    you should not be using 0.5mm2 on a heating system, the minimum is 0.75mm2
     
  8. jaber

    jaber

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    How can I tell if the hot water is working? Unlike the CH, it doesn’t appear to make a noise when switched on.

    Or, have I wired it incorrect... even though I triple checked? Thx
     
  9. MeldrewsMate

    MeldrewsMate

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    Evenmore of a challenge with 0.75mm2 then!

    I disagree, a 0.5mm2 flexible cord is very capable of carrying the load expected of a heating system, and suitably protected with a 3A BS1362 fuse...according to my old BS7671 (17th edition!).
     
  10. bernardgreen

    bernardgreen

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    That is fine as long as the fuse is 3 amp and not 13 amp ( or a bent paper clip ) 0.5mm² cable could get hot before a 13 amp fuse melts on overload current.
     
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  11. EFLImpudence

    EFLImpudence

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    What is it, in such a heating system, that can cause such an overload?
     
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  12. ianmcd

    ianmcd

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    Its the BS factor from those that have no clue
     
  13. MeldrewsMate

    MeldrewsMate

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    There are tables in the British (not oooo-row-pee-an) Standard that indicate the disconnection time (blowing the fuse time) for a BS1362 fuse. It can be several hours at the rated current (3A, 13A, etc). Some may cruelly joke that the wrong fuse rating in a 506 years old cottage with a thatched roof could solve a nagging problem....not me though!
     
  14. bernardgreen

    bernardgreen

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    A fault

    So is it BS from the manufacturers who state that the supply to boiler and controls must ( should ) be fused at 3 amps ?
     
  15. EFLImpudence

    EFLImpudence

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    Somewhat vague??? An example?


    Probably, yes - like the same for extractor fans. It's just what they write.

    If their product requires fusing, they should fit integral fuses. Oh, they do.
     
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