2 years ago we installed a new boiler Valiant ecoTec plus 438. We have a 5 bedroom detached house with 20 radiators. The problem is that the boiler continually goes into waiting period - fault code S53. Which diagnoses that the VL-RL spread is too large. To solve this I have increased the bore of the pipe system through out the house to reduce any resistance however the problem still occurs. The only way I can get the boiler to work at all is to down-rate the power to 12-14 kW. The same problem also occurs when on HW only. any suggestions on how to resolve this. is this the right type of boiler?
