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Andrew Smith
Andrew Smith, HVAC Technician
Category: HVAC
Satisfied Customers: 3768
Experience:  Heating and Controls engineer
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My Worcester heatslave oil boiler keeps switching off when

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My Worcester heatslave oil boiler keeps switching off when the heating is on constant. I have to turn the roomstat off the back on again in order for it to start working again. This has to be done two or three times a day. Any idea what could be the problem? Many thanks Simon

It does not sound like a boiler problem as it starts up straight away again. Do you have a wireless thermostat?

Customer: replied 4 years ago.
Hi Andrew, yes I have a Heatmiser wifi room stat....... I didn't think this was the problem as the original standard room stat was showing similar problems albeit only once every couple of weeks.
Customer: replied 4 years ago.
Hi Andrew, just for clarification, the Heatmiser roomstat is hard wired in to the boiler. The wifi connection is for remote access via a iPhone App. When the heating fails, I have to turn the room temp on the roomstat down below the current room temperature and I can hear the boiler turning off, (relays in the boiler control panel switching). Then when I turn the temp back up the boiler relays turn back on against and the pump switches on immeadatley and all starts to work again for a while. Hope this helps..
Ok, I understand.
Is this an old type system with a boiler and a cylinder?
Customer: replied 4 years ago.
No, it's a combi boiler, probably around 10 year old...

So the stat is wired, but the boiler does not want to restart. Is this only when the room stat has turned off and back on again or when the boiler has turned off but the room stat has been calling constantly?

Customer: replied 4 years ago.
When the stat is turned off then back on. I don't have to reset the boiler.
Perhaps this a sticking relay in the room stat, does it show it is calling but the boiler does not fire unless you turn it down and then back up again?
Customer: replied 4 years ago.
The roomstat is fairly new, around 6 months. It does show that it's calling the boilers or heat in that the flame symbol is showing. The roomstat is set to 21 degrees while the actual room temp is down to 18 or 19 degrees. if the relay was sticking in the roomstat then I assume that I wouldn't hear to boiler turning off when I turn the temp down on the stat... Could it possibly be a dodgy relay contact on the boiler control panel. And cycling it makes contact again. As I previously indicated, this problem has been there for some time but appears to be getting more consistent.
why don't we try and confirm this.

Turn the room stat up to as high as it will go and turn the boiler temperature down to 1/4 and leave it on.
If the fault still appears then it is the boiler stat not resetting, if the fault disappears then it is the room stat.

Does this make sense?
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Customer: replied 4 years ago.
Ok thanks Andrew, I'll give this a try. It will probably take a few hours for it to fail again. Regards Simon
No problem - just let me know.
I will be on and off all day.