Low presssure from hot tap

[Dannno]

Hi all,
Parents have a relatively new zanussi ultra combi 30kw - installed about 6 months ago.

Hot taps (all of them, including the shower) have a tiny amount of pressure when turned out. The water is hot but the flow is weak.
Cold pressure is good and the boiler is reading 2.5 bar pressure.

Combi is in the loft.

Any ideas what could be causing such weak flow - or how to try to improve it?

Thanks in advance
Dan

 

[ShaunCorbs]

Is your mains cold a low flow ?

 

[Dannno]

Mains cold is lower flow than my own house but its still pretty good. Cold taps have good flow but hot taps really low.

When the hot tap is first turned on, the flow is quite good, but then dies to a dribble quickly (as water starts to run warm).

Thanks!

 

[king of pipes]

There will be pressure loss through the cold supply pipework because the boiler is in the loft , also the water tempreture in the ground is very cold due to this freak weather it takes alot of kw to heat it to 55 degrees and it cant pass through the plate heat to quick so this could be the problem , not familiar with the zannuissi but I think it's a rebadged IDEAL so could have a pre heat function which will give you more hotwater and quicker . Kop

 

[Dannno]

That's really useful - thank you. I'll check for a preheat function.

Is there anything that could be added/in line to increase the hot pressure. Apparently this has been going on since before this cold weather.

Thanks so much.

 

[Scott_D]

Check the stop taps are fully open and cold isolation under the boiler is fully open

 

[Dannno]

Thank you. Both checked and fully open.

 

[king of pipes]

The litres per minute needs to be measured on the cold supply the boiler will only supply 12 .4 litres of hot water a minute with a 35 degree rise , conditions at the moment probably around 10 litres there is a pump that can be fitted to supply a constant 12 litres of cold water to the boiler but they are not cheap better to get a engineer to measure the inlet pressure and flow and go from there . Cheers kop

 

[Dannno]

That's brilliantly useful, thank you.
I'll measure the litres per minute tomorrow and check out the options.
Thank you!