There are two cause. One the boiler resistance doesn´t turn of because of snap disc or bimetal thermostat fault or because a coil in the working valve (security valve). But if you can heard a click of opening movement of valve when you push the button it is able to be a thermostat.
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There are two cause. One the boiler resistance doesn´t turn of because of snap disc or bimetal thermostat fault or because a coil in the working valve (security valve). But if you can heard a click of opening movement of valve when you push the button it is able to be a thermostat.