Valliant Combi VCW Sine 18 T3 boiler - overheating

[carlosg]

Anyone know why my boiler is overheating? when i click the thermostat after about 5 minutes it seems to stay on a high flame and continues on a high flame all the way to 100+ degrees then drops to a low flame. On a low flame the temp drops to around 50 degrees and the whole cycle repeats itself all over again.

Anyone?

 

[dmitch071]

I would say it definatly needs a engineer to look at it as there is a number of tests required to diagnose this boiler, is this on C/H or hot water that this is happening? From what you are saying seems it does modulate eventually just way out of its normal limits I would be suspecting temp sensor on the left of the boiler or a PCB fault. The thermistor should have a resistance between 200 - 300 ohms when the boiler is at temp (around 80 degrees).

 

[carlosg]

Hi thanks for replying. Problem only with the central heating, hot water is fine. ntc resistor has already been swapped from another identical boiler and still have the same symptoms as before.

 

[carlosg]

Anyone?

 

[chrishutt]

carlosg, if you're talking about the same problem on the same boiler you should post on the existing topic and not start a new topic every few days. Otherwise we don't know what points have already been covered.