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Nest heating control causing oil boiler to activate every 5 mins

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  • 07-05-2024 2:00pm
    #1
    fletch
    Registered Users Posts: 7,405 ✭✭✭


    I have two (3rd gen) Nest heating controllers. One controls downstairs and the hot water, the other just upstairs. They are connected to an oil boiler. Both are plugged into a wall socket as opposed to hard-wired. I've noticed that every 5 mins or so (regardless of whether heat is set or not), my boiler fires up and runs for about 30 seconds and then switches off. The energy usage shows no usage in the app. Any ideas what might be causing this? The pipes leaving the boiler are hot so it is using oil but I haven't been able to determine which zone is calling for heat (as i don't think there's enough time for the heating to reach the house/radiators in the 30 seconds or so that the boiler is on)



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    #2
    emaherx
    Registered Users Posts: 6,138 ✭✭✭emaherx


    Has this setup worked properly before or is there something new?

    It sounds like no zones are calling for heat but the boiler is dry cycling. if it worked before I'd say there is a relay is stuck at the boiler. If a zone was calling for heat that zone would get hot as the valve would be open.



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    #3
    fletch
    Registered Users Posts: 7,405 ✭✭✭fletch


    I'm not 100% sure if the setup worked before or not. The boiler is out in the garage and I noticed it happening the other day as I was out in the garage and heard the boiler firing but knew the house should have been too warm for the heating to be kicking in. How would I diagnose the problem or would it be better to call a plumber/electrician?



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    #4
    emaherx
    Registered Users Posts: 6,138 ✭✭✭emaherx


    https://www.boards.ie/discussion/comment/122110903#Comment_122110903

    When were they installed? Is contacting the person who installed them an option?

    I don't know Nest products particularly but there are a few ways a boiler could be called for heat.

    some possibilities are:

    • System was installed wrong to start with and boiler is just left permanently on wasting fuel.
    • Some form of manual switch / timer in place is overriding the stats.
    • Zone valves have some integrated dry contact relays that can simply switch the live to the boiler.
    • A wireless switch for the boiler is not working or no longer paired (not sure if this is an option with Nest)
    • Some form of wired communications protocol (if boiler and stats support it)

    It was common for plumbers to install boilers with basic time clocks controlling the boiler completely and zone valves controlled by thermostats and completely ignoring the relays built into the valves which leads to this situation where the house is nice and warm come April/May and the boiler has no way of knowing it so stays cycling.

    Ideally the thermostats should control the zones, which in turn call for heat as needed and any scheduling should just turn up/down or on/off the stats.



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