Wocester Combi Boiler - Hot Water fluctuates

[Lennie]

I have a problem with my combi boiler. When you run the hot water, the boiler will turn off for a few seconds before igniting again which means you have about 30 secs of hot water then about 10 secs of cold and so on which does not make for a nice shower or a hot bath. The pressure is OK and it works fine for the central heating. I have had a water softener installed recently, could that have anything to with it? Any ideas of what the cause could be would be much appreciated.

 

[DarkInferno]

sounds like you have crud in your DHW heat exchanger, pop it off and give it a few knocks whilst running cold water through it that should dislodge anything stuck in there...

 

[Lennie]

Thanks for that. I have a gas to water heat exchanger and also a water to water heat exchanger which one should I clean (or both)?

 

[kevplumb]

the second one

 

[beezer]

I have a Worcester/Bosch Combi boiler that does exactly the same. I have had British Gas and Bosch engineers on it and they came to the same conclusion. Apparantly it was the water inlet flow was too high. They used a flowmeter and said the boiler could not handle the flowrate and checked the spec to the manual. It was too high to cope with the flow so they reduced the water flow coming in to boiler.