Cleaning A Combi Boiler

Powerflushing a Combi-boiler —  Internal layout of a combi

flow diagram - combi boiler
« The Primary Heat Exchanger
« Diverter Valve
« The domestic hot water (Plate) Heat Exchanger

It is essential that:

  1. The primary heat exchanger is clean, particulary if it is a condensing boiler. 
    Symptoms:
     noise, long warm up period, boiler locks out
  2. The diverter valve modulates between heating and hot water and will stick in hard water areas or excess sludge. 
    Symptoms:
     erratic hot water, lock out, temperature modulates.
  3. The waterways of the domestic HW plate heat exchanger are extremely small and block easily. 
    Symptoms:
     Reduced flow