1. Visiting from the US? Why not try DIYnot.US instead? Click here to continue to DIYnot.US.
    Dismiss Notice

Trying to wire smart thermostat to ideal logic combi

Discussion in 'Plumbing and Central Heating' started by Garry Pinkerton, 19 Sep 2020.

  1. Garry Pinkerton

    Garry Pinkerton

    Joined:
    19 Sep 2020
    Messages:
    4
    Thanks Received:
    0
    Country:
    United Kingdom
    Hi there,
    I'm new to the forum and am search of some help. I recently purchased a BHT-3000-GCLW smart thermostat. I own an Ideal Logic Combi 30 boiler and am trying to wire the new thermostat to said boiler. I so far have taken a twin and earth to the back of the thermostat from the spur which feeds the boiler and have wired the dry contact with a separate twin and earth to go direct to the boiler, to, hopefully, be connected to the terminals marked "room stat". Would this work and does it matter which side of the dry contact I connect to the live side of the room stat terminals within the boiler?
     

    Attached Files:

  2. Sponsored Links
  3. muggles

    muggles

    Joined:
    28 Oct 2005
    Messages:
    13,329
    Thanks Received:
    3,071
    Location:
    Daventry
    Country:
    United Kingdom
    STOP
    You should not have removed the casing from your boiler - that is for Gas Safe Registered Engineers only. It forms the safety room seal and your boiler should not be operated again until the Regulation 26.9 checks are carried out to ensure your safety. Your wiring looks OK, if a little scruffy, although it's a shame you're fitting an on/off room thermostat to an OpenTherm compatible boiler - an OT control would have made it more efficient
     
  4. Garry Pinkerton

    Garry Pinkerton

    Joined:
    19 Sep 2020
    Messages:
    4
    Thanks Received:
    0
    Country:
    United Kingdom
    Hi Muggles,
    Thank you for your reply. First of all, I am an industrial/commercial heating engineer and although as I know that is different from a domestic heating engineer I am more than competent at removing the boiler cover and understand wholly the risks that come with it. The wiring you see in the boiler at the moment (the last picture with the white flex), was made by the guys who fitted the boiler initially, the Gas Safe Registered Engineer, and yes I agree, rather scruffy. In this picture is only the original wiring as I did not want to connect until I knew I would be doing it correctly. As for the open therm circuit, there is no connections on the right hand side where they should be, it is just blanked off! Why I don't know but hey ho, i'll just need to go with the room stat connections. What I need to know is does it matter what side of the dry contact I connect to the live?
     
  5. ericmark

    ericmark

    Joined:
    27 Jan 2008
    Messages:
    18,543
    Thanks Received:
    1,742
    Location:
    Llanfair Caereinion, Nr Welshpool
    Country:
    United Kingdom
    Flounders and Swan did a song about that, "And it all makes work for the working man to do." when doing an EICR the electrician has to inspect the electrical connections so clearly the electrical connections must be outside of any sealed systems as he needs to inspect, the manufacturer would need a recall to modify the boiler if that was the case. I am not Gas Safe but I have worked with flame proof equipment throughout my career and you do not use stuffing glands and standard PVC cables for flame proof enclosures, any electrician would flick to page 32 of instructions to see how wired, main point is what type of RCD is required, there is nothing to say on the instructions that it needs to be connected up by a multi-skilled tradesman.
    An earth loop impedance meter is expensive and its use can result in dangerous voltages being on the system, a competent person should have C&G 2391 for inspection and testing. Yes I know many people DIY and do electrical work without test equipment and do not follow the guidance in BS7671 on how to test it, but to be frank if everyone followed the rules, you may as well get rid of the electrical section of this forum.

    I would agree if fitting a room thermostat may as well use OpenTherm if the boiler can use them. The instructions say
    Clearly rather old instructions as it has not been IEE for around 14 years, BS7671 is a joint IET/BSi document, but a fused connection unit is considered as an isolator, so is a plug and socket. Things have moved on, using for example a Nest Gen 3 it is common to have multi power supplies, where the thermostat is supplied from separate supply to heat link, often using a USB plug and socket arrangement which is powered often from a different supply to boiler. But we would try to power the heat link from boiler supply.

    The worry is that the system is not fully isolated when some one works on it, and in some cases we need labels
    But this [​IMG] is not permitted, and has not been allowed for any installation since 1966. That earth wire needs connecting even if the thermostat is class II, for an installation (not including portable appliances) an earth must be taken to the unit even if not used by the unit, yes I know plumbers and heating guys do flout the rules and I have even seen them use the earth wire as a live wire with tank thermostats, but that is still wrong, in the future some one may change the thermostat for one which needs and earth, and with people trying to persuade people not to inspect the wiring connections in the boiler, and a loop impedance meter is expensive so many DIY people don't have one, plus rules say earth must be provided, it is possible some one will just connect the earth wire without testing. Although 2 core cable would be wrong, at least no one would think it was earthed or bonded. The wire is there, so use it.

    Yes it will work, but it will not comply with regulations or work in the most economic way.
     
  6. Garry Pinkerton

    Garry Pinkerton

    Joined:
    19 Sep 2020
    Messages:
    4
    Thanks Received:
    0
    Country:
    United Kingdom
    Hi EricMark,
    As you will see in the reply above to Muggles, these were the original connections left by the guys who fitted the boiler, and yes I di agree, rather scruffy indeed. As I have asked before, does it matter what side of the dry contact I wire to the live end of the room stat connections. The reason I'm not using the open therm connections is because they are blanked off and I have no other choice but to go through the room stat
     
  7. ericmark

    ericmark

    Joined:
    27 Jan 2008
    Messages:
    18,543
    Thanks Received:
    1,742
    Location:
    Llanfair Caereinion, Nr Welshpool
    Country:
    United Kingdom
    No it does not matter, with a MCB yes there is a flash arrestor, but simple relay either way around.
     
  8. Garry Pinkerton

    Garry Pinkerton

    Joined:
    19 Sep 2020
    Messages:
    4
    Thanks Received:
    0
    Country:
    United Kingdom
    Thank you EricMark
     
  9. DIYnot Local

    DIYnot Local

    Joined:
    3 Sep 2019
    Country:
    United Kingdom

    If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

    Select the supplier or trade you require, enter your location to begin your search.


    Are you a trade or supplier? You can create your listing free at DIYnot Local

     
  10. Sponsored Links
Loading...

Share This Page