Hi
Help please from someone in the know.
10year old Worcester 240 Combi for DCH is working fine. With heating off and drawing hot water, boiler has recently become noisy (kettling?) and hot water at all hot taps is excessively hot (certainly hotter then 60degrees). Hot water flow rate is great - lots of really hot water delivered, but I am worried about someone getting scalded Something must be wrong.. The boiler is not cutting out (so not registering over temperature). I have checked resistance of both Hot Water sensor and Central Heating sensor (thermistors) - and both are between 1.5kohms and 25kohms per the Installation/Servicing manual (they register different resistances of 6kohm and 10kohm, but both within accepted limits..?). I have tried swapping over the two sensors/thermistors just in case the DHW one has gone faulty, no difference there. Increasing and decreasing hot water demand does not result in any voltage variation at Modureg (stable at about 21volts until boiler cuts out after hot tap switched off.)
Diverter valve diaphragm changed 18months ago, but the system has worked perfectly since then.
The first couple of times this happened (hot water over temp) a small amount of grit/sludge accompanied hot water out of the taps, but none since that time. I assume this was just muck dislodged from the water/water heat exchanger the fist few times it was exposed to increased temperature.
Hot water flow from taps makes me think that secondary side of heat exchanger can not be chalked up (we have a salt-based water softener fitted).
Any ideas? Change the DHW sensor/thermistor anyway? Control board gone west? I hope board not gone faulty - expensive component?
Thanks for any advice.
Graham
Help please from someone in the know.
10year old Worcester 240 Combi for DCH is working fine. With heating off and drawing hot water, boiler has recently become noisy (kettling?) and hot water at all hot taps is excessively hot (certainly hotter then 60degrees). Hot water flow rate is great - lots of really hot water delivered, but I am worried about someone getting scalded Something must be wrong.. The boiler is not cutting out (so not registering over temperature). I have checked resistance of both Hot Water sensor and Central Heating sensor (thermistors) - and both are between 1.5kohms and 25kohms per the Installation/Servicing manual (they register different resistances of 6kohm and 10kohm, but both within accepted limits..?). I have tried swapping over the two sensors/thermistors just in case the DHW one has gone faulty, no difference there. Increasing and decreasing hot water demand does not result in any voltage variation at Modureg (stable at about 21volts until boiler cuts out after hot tap switched off.)
Diverter valve diaphragm changed 18months ago, but the system has worked perfectly since then.
The first couple of times this happened (hot water over temp) a small amount of grit/sludge accompanied hot water out of the taps, but none since that time. I assume this was just muck dislodged from the water/water heat exchanger the fist few times it was exposed to increased temperature.
Hot water flow from taps makes me think that secondary side of heat exchanger can not be chalked up (we have a salt-based water softener fitted).
Any ideas? Change the DHW sensor/thermistor anyway? Control board gone west? I hope board not gone faulty - expensive component?
Thanks for any advice.
Graham
