Thermistor 240 combi rsf? Hi what does the thermistor do does it control the temperature...
Hi what does the thermistor do does it control the temperature of the gas to marine heat exchanger and control the gas, When the important heating is on the boiler will cut the gas after going on for 5 minutes the boiler is still asking for demand and the spark electrode is trying to street lamp the pilot light after after about another 5 minutes you can hear a click from the gas spout and then the boiler will muted. on the hot water side it starts making a groaning clatter it sounds like it could be getting overheated
The thermistor checks the warmth of the water, and relays the message to the pcb, check the pump speed, and remove the silver screw at the front so you can see the impellor is physically turning. Then, beside your devotee will be 2 tubes, turn off power, give somebody a lift 1 tube off at the conflicting end to the devotee, blow down it, then do equal with the other tube, power up again and see if this make a difference, sometimes you have to check the electrical resistances to find the problem.
my advice administer someone a call it won't embezzle to long for them to find the problem as it could be numerous things generally if the thermistor is at scorn the boiler should cut out on overheat stat you could have prob next to fan/pressure switch or even the pressure tubes these are great boilers when running but they are getting old very soon and you would be able to receive more heating for your money near a new one.
hasty check= that the flue way is verbs and clear from dirt and debry
Annual service when was the ultimate service these are important but combi boilers hold lots of safety devices and they are at hand for a reason.
Answers: a thermistor is a roast enabled resistor,it regulates the gas rate from the gasvalve modulator via the potentialometer on the pcb,the hotter it gets the more resistance is created which reduce the flow of current.if you are getting a spark at the electrode then i dont regard as there is a problem next to the fan/pressure switch,could be a problem with the gasvalve or relay within the pcb.change the thermistors as they are the cheapest components on the boiler,if its still had it after that i suggest you call out an scheme.what you describe sounds like in attendance is more than one fault on the boiler.annomilies can throw even the most experienced gas cook up, so best of luck