i think you guys are talking x purpose here,if i read it right you have a emersion heater,this can be fitted with two or one elements that have their own thermostats,this type of system has norm a boost control,i.e.if you come home after a holiday,you can press the boost control that will turn the emerser on for one or two hours,depending on the switch,the other element is fed through the white meter ,it comes on during the night when the elect,is half price,providing you have left the switch on in cupboard,its very common for the elements to burn out,as is with the thermostats,you can check these with a test meter,turn of the power,remove the round covers of the elements,disconnect the live lead to the thermostat,check across the therm,with meter set on ohm scale,you should get continuity,if you do,check across the heater element,you should get a reading of about 19.5 or 20 ohms,if you get less than this,the element is burned out,repeat for the other element,hope this helps.
mm
March 2011