Glow Worm Combi Boiler - Recent Drop in DHW Temp

[R6Rich]

Hi All,

I have a Glow Worm Swiftflow 75 (SIT) combi boiler which has operated fairly consistantly for the best part of 10 years. About a month ago I had a flue fan failure - the fan was replaced by an engineer and everything seemed to return to normal... only I have since noticed that although CH is fine I have in general experienced a drop in the DHW temperature.

Now most of the time the DHW temp is little better than warm though there is a temperature spike when a tap is initially switched on (this has always been the case). The problem occurs whether the CH is switched on or off.

I have read through the "Why Is My Hot Water Not Hot Enough?" FAQ but (based on my very limited knowledge) none of the possible causes listed appear to explain my problem. I am unsure as to whether the recent work on the boiler may have lead to this problem or if it is just a coincidence.

I would really appreciate any help or advice you guys can offer!

Many thanks,
Rich

 

[stem]

It could be because of the present cold weather. The incomming mains water will be colder and need more heat that the boiler may be unable to deliver. What happens if you reduce the flow?

 

[R6Rich]

Hi Stem,

Thanks for your quick response. It had crossed my mind that it might be due to the supply being colder but as I haven't ever noticed this before I had my doubts. Having said that I have just run a test with a reduced flow at the tap and indeed the boiler appears to be heating the water much better. As I decrease the flow the water temp improves - It looks like you've hit the nail on the head!

I guess that as it's been quite a few months since the last proper cold snap it's feasible that my heat exchanger could have lost enough efficiency in that time (due to lime scale build-up etc) to make the effect of a drop in supply temperature more apparent???

Thanks very much!
Rich