Plumbing Question - Shower not hot

[brianmoooore]

The boilers you list are conventional , not combi rubbish, so it looks like you probably do have a gravity hot water system, fed from a tank in the loft. Hopefully, the cold water supply to the shower is also from the same tank.
The problem is almost certainly that the new shower has a higher minimum pressure requirement than the original.
It is becoming almost impossible to find taps, mixers, showers, etc. with really low minimum pressures since the rise of the combi boiler and a regulation change some years ago that replaced a minimum flow rate with so called water saving specification.
To make this work, I suspect a shower booster pump will have to be fitted.

 

[plugsandsparks]

There is the other think to check and thats the source of the hot and cold. Typically gravity fed shower mixers require that the cold supply also comes from the same header tank as the hot supply. Its possible that the mixer is not suitable for gravity supply and if the cold is coming directly from the mains it may be pushing past the mixer thus diluting the incoming hot even from the mixer is on full hot.
Suggest ask plumber whether mixer is even suitable for the install..

 

[LukeD]

YOu sure there is a Hot water tank in the loft ??

 

[Mark Wright]

Water tank in loft
Hot water tank upstairs
Boiler Kitchen
Shower down stairs.

 

[brianmoooore]

In that case, the 0.4 bar version may have been fitted. Can you determine the exact model?

 

[LukeD]

Here is a "tangent " to the debate ..... !! Ive seen the very reverse . And a child was badly injured .The water came from the shower at full temp causing the child to "throw itself through a shower door . NO matter what .There should be a "master " control that limits showers and taps in homes . I use valves to ensure when taps are open the volume of water entering a basin etc is not to much and sprays all over the place .But also to ensure that people dont get scalded .

 

[Mark Wright]

Thanks guys again for all your input.

Here is a link to the manual. If you can't download let me know
https://tinyurl.com/3p6un49r

Better upload https://tinyurl.com/49rfynrd

 

[mainline]

We still don’t know if this is gravity fed or not as it could be an unvented tank and the header tank could be for central heating.

Run a hot water tap and check if the header tank ball cock starts putting water in.
Then do the same with shower just using cold.

 

[LukeD]

Can you

We still don’t know if this is gravity fed or not as it could be an unvented tank and the header tank could be for central heating.

Run a hot water tap and check if the header tank ball cock starts putting water in.
Then do the same with shower just using cold.

exactly .....And God bless the King !

 

[brianmoooore]

The manual confirms you have the version with a min pressure of 0.4 bar, so it's odds on that this is the problem.
Manual also confirms that there are inlet filters (part #3).
The filter also incorporates check valves, which aren't needed if both hot and cold supplies come from the same header tank. Removing the hot one may solve the problem, to a degree, at least.