Viessmann Vitoden Combi Boiler problem - Cooling of water

[1ndyandy]

Hi All. Just thought I would put a post here before I seek help from Viessmann. I've had a new Vitoden 100 boiler fitted about 18 months ago. New pipes, new radiators, new everything. Its worked absolutely fine until last week when I noticed that the hot water output is abit cooler than normal. More noticeable when running a bath. There is no fault code and no other symptom to really report. The central heating appears to be ok and obviously I'm watching this like a hawk especially at this time of year.
When running a bath, the boiler reading might say 60-65 deg C but with my hand under the tap I really do doubt that. What could the problem be?
TIA - Andy

 

[ALEC1]

flow is too fast, throttle back the tap to about 10l/m

cold water out if the main is very cool in winter, especially after the cold snap...

 

[Agile]

If its only the basic 24 kW boiler then it will only give about 8 li/min at a reasonable temperature.

The boiler reads the internal circulating water temperature and not the hot water output temp.

Tony

 

[petertheplumber12]

What alec says is right, you need a slower flow of water, as he said which you may not understand is that the cold water that is coming into the house at this time of the year is much colder than a month ago, so the boiler can't heat it as hot in the same time, It heats at the rate rate of about 13 ltrs/mins raised thro a temp of 35degrees centigrade. The colder the water coming in the colder the hot water out, Golden rule with ALL combi's, the slower the flow the hotter the water.

 

[1ndyandy]

Thanks everyone above. You are right of cause. It did cross my mind but wasn't 100% sure based on 2 reasons. 1. Didn't have this problem last year and 2. I didn't think it was that cold outside. However, on reflection, I realize now that this time last year I had an old bathroom suite which has since been replaced and the current bath taps and associated plumbing provide a much greater flow rate now. That coupled with the recent cold snap has magnified the problem, or limitation of my boiler. Thanks all again. No need anymore to contact Viessmann.