Why is my Combi boiler giving me hot water for a short period & then going cold?

By Steven on

This is a common issue for Combi boilers and it usually boils down to a dirty system, there are a number of other factors that could contribute to this issue including:

A weak pump

A system that doesn't have the right chemicals in to protect it from corrosion will build up a scale within the heating side of the system which causes the pump to have to work a lot harder to circulate the water in the system over time this puts excessive pressure on the pump which in turn makes it weak.

Blocked plate-to-plate heat exchanger

A plate-to-plate heat exchanger is a part inside your boiler that heats your water through heat transfer (here is a link to a more in detail video of what one is https://youtube.com/shorts/yyzpCuSRzlg?feature=share) and as you can see the fins are small and can get blocked really easily with any dirt within the system.

These are the two main components that cause this issue but as with everything there could be various other components at fault that could also be responsible. I recommend you get in touch with your local professional heating engineer and if you're in York get in touch with The Boiler Doctor and I'll be more than happy to assist.

PREVENTION IS BETTER THAN THE CURE

How do you prevent this from happening with your boiler? There are a few things that can be done to prevent this from happening:

Installing a central heating filter: This should be installed on the return pipe to the boiler so it picks everything up before it enters your boiler.
Get a power flush: Having a clean system is essential for a combi boiler to run effectively and efficiently. If you have a fully clean system to begin with there is very little chance of blockages in your new Combi boiler. Installation of power flushes can considerably increase the life of your existing or new boiler and make your heating system as efficient as possible.
Add chemicals: An inhibitor added to your system protects it from corrosion which prevents the build-up of magnetite (the black sludge) now if you have all the above in place as well as regular maintenance / servicing you will increase the life span of your boiler, not to mention the cost of running it and the heat output you will get!