Tepid water from combi boiler

[deeyewhy]

I have an old (approx 12-15yrs) combi gas boiler.

We used to have a problem that the hot water temperature was very inconsistent, requiring constant fiddling with the taps to get hot water. We've recently had the boiler serviced, and the heat exchange plate de-scaled which has improved matters considerably. Other than the scaled up heat exchange plate, the boiler was given a clean bill of health.

However, despite the recent descaling, we do still have a problem that the water temperature is not totally consistent - the main issue seems to be often if you open the hot-tap immediately to full-flow, then it will tend to only deliver tepidly hot water. If I partially open the tap to mid-flow until the water has heated up fully, then slowly move to full-flow, I can usually get a consistent flow of very hot water, although it sometimes takes a few attempts - very annoying when trying to take your morning shower!

Despite the age of the boiler we are hoping to avoid forking out for a new one unless absolutely necessary as we don't expect to be in the house for more than a few years. Any suggestions as to what the problem might be?

 

[DP]

Make and model would help.

 

[coytech]

yes model etc, also gas supply pipe size?

 

[45yearsagasman]

also gas supply pipe size?[/quote] After 12/15 years its a bit late to worry about pipe sizing

 

[Dan Robinson]

It always amazes me how many people suddenly want to move house when their boiler goes t1ts up

 

[homes]

Sounds like a sensor problem.

 

[deeyewhy]

It's a Ariston Eurocombi - precise model I don't know, will have to wait until I can dig out the manual.

As for gas supply pipe size - I have no idea I don't know how I'd begin to find out! If it's important let me know how I'd find out and I'll report back!

 

[mcmoby69]

it could be that the original installer never bothered to check or change the hot water pipe to the bath from 22mm to 15mm. this is a common mistake made by lazy installers, or they just cant be bothered.

basically the cold water goes thru the DHW heat exchanger too fast, to pick up any heat. you get hotter water by turning the tap down, or, turning the cold water into the boiler down, the latter option will affect the hot water all over the house tho, and cause some noise.
if the pipe sizing is the problem then a repipe of the hot water to the bath is the ideal solution.