Combi hot water ebbs and flows

1 Nov 2023
Reaction score
United Kingdom
I have a Potterton Gold Combi 28 HE on a brand new system following full renovation. However I am unable to get a consistant flow of hot water to any outlet. The temperature holds as hot for around a minute before fluctuating between luke warm and warm.

Boiler has previously been sat in dry storage after light use in an office enviroment. House has 1 shower room and one kitchen sink.

Water pressure is around 2.7bar and flow is around 13lpm at boiler point.

During use the DHW temperature is set at 40 degrees but the boiler shows the temperature shooting to 80-90degrees, this happens at what ever temp the DHW is set to.

Please could you recommend steps to allievate this issue?
Sponsored Links
Thanks for the quick response. Is the secondary heat exchanger something i should look at trying to descale or replace entirely?
Sponsored Links
The 80-90 degrees is the boilers temperature, not the HW temperature at the taps. That sudden increase in temperature indicates a blockage in your plate heat exchanger and the boiler is overheating. I wouldn't advise a DIY repair, get someone competent in. For the price replacing it is better than attempting to clean it.
Replaced the heat exchanger over the weekend and had my first consistantly hot shower since moving in! The existing exchanger it was completely gunked up on the DHW side.

Thanks again for the advice on fixing this!

DIYnot Local

Staff member

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.

Are you a trade or supplier? You can create your listing free at DIYnot Local