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Thermostat comes on then immediately goes off

Discuss Thermostat comes on then immediately goes off at UK Plumbers Forums; Hi, I'm hoping someone can help. I'm in rented accommodation (house built 2 years ago) that has a combi boiler & underfloor heating in the kitchen and living room. Last ...
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    Default Thermostat comes on then immediately goes off

    Hi, I'm hoping someone can help. I'm in rented accommodation (house built 2 years ago) that has a combi boiler & underfloor heating in the kitchen and living room. Last winter it was working fine, but now the living room thermostat is playing up. When it is set to a high temp, the red light comes on as if to draw heat, but then shuts off - nothing happens with the boiler. The kitchen thermostat is working fine. What could be causing this?


    Here's a video of the thermostat

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    Default Re: Thermostat comes on then immediately goes off

    Hi dan85, If it is a wireless stat then it could simply be a matter of changing the batteries.

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    Default Re: Thermostat comes on then immediately goes off

    Quote Originally Posted by Darren Jackson View Post
    Hi dan85, If it is a wireless stat then it could simply be a matter of changing the batteries.
    Thanks Darren, I wish it were that simple. It's a wired thermostat.

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    Default Re: Thermostat comes on then immediately goes off

    Could you have a faulty actuator on the manifold? When the room thermostat's call for heat, the UFH pump will start and the actuator(s) for the zone in question will open and let water into its circuit's. It takes 3 to 4 minutes until it is fully open. It is
    important that the actuators are fitted tightly onto the return manifold and no loose wires and also check the fuses.
    Last edited by Darren Jackson; 09-10-2016 at 04:17 PM.

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    Default Re: Thermostat comes on then immediately goes off

    have you tried calling the manufactures ?

    number : 01455 555930

    also darren it might not be ufh it could be just normal rads off a manifold
    IMPORTANT:
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    Default Re: Thermostat comes on then immediately goes off

    Quote Originally Posted by ShaunCorbs View Post
    have you tried calling the manufactures ?

    number : 01455 555930

    also darren it might not be ufh it could be just normal rads off a manifold
    The op says he has UFH in the living room and the living room thermostat is playing up.
    ShaunCorbs and Darren Jackson like this.

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    Default Re: Thermostat comes on then immediately goes off

    Quote Originally Posted by leesparkykent View Post
    The op says he has UFH in the living room and the living room thermostat is playing up.
    didnt see that normally they use a prog room stat for ufh my bad
    leesparkykent likes this.
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    Want gas safety or boiler repair advice? :
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    Default Re: Thermostat comes on then immediately goes off

    Need to get your multimeter out and work through the order of sequence of switching to see what's playing up. If the wiring centre has a PCB it could even be a dry/cracked solder joint.
    Last edited by leesparkykent; 09-10-2016 at 04:39 PM.

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    Default Re: Thermostat comes on then immediately goes off

    The short video shows the green light comes on and stays on, so I would assume it is calling for heat. I am assuming that the flashing red light is the RF signal?? but am not familiar to this make so could be wrong. I would still check the actuator to the living room at the manifold.

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    Default Re: Thermostat comes on then immediately goes off

    Quote Originally Posted by Darren Jackson View Post
    The short video shows the green light comes on and stays on, so I would assume it is calling for heat. I am assuming that the flashing red light is the RF signal?? but am not familiar to this make so could be wrong. I would still check the actuator to the living room at the manifold.
    The green light is power to the thermostat, the red light is the call for heat.

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    Default Re: Thermostat comes on then immediately goes off

    Hi dan85,

    what was the ambient room temperature that time? Was it much less than 21 deg C?
    Do you have a timer installed as well which controls the times of the UFH?

    It's a Maincor branded thermostat but it's made by Heatmiser UK, model called DS-SB.

    You can speak to them directly on 01254 669 090 (press No 2 for technical) and they should be able to tell you what's wrong.

    Hope you will get this sorted.

    All the best,

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