Boiler was fine until annual service-now even if switched to water only the radiators heat up and it fires for a few seconds,turns off and then fires again.Have had to turn power off and just turn on when need hot water.The company who did service claim sludge is blocking the heat exchanger and need a power flush-however the boiler is not noisy and no cold spots in radiators so not sure if this is possible
sorry, ignore that.
if your rads are heating up when you are using your water then it's a problem with the diverter valve. it may be caused by sludge but a powerflush won't remove it from the boiler. as far as the cutting on and off, that may be a probelm with the fan or air pressure switch, or possibly the pcb. get a qualified engineer to find the problem, but a powerflush won't fix that as it sounds like an electrical fault.
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