Weird heat levels from different taps

[peterb20]

Right, a confusing one!

I have a combi boiler system, hot water to 4 outlets.

The first in the run is the kitchen sink, which gets hotter than holy hell.

The 2nd is the bath, tepid. The cold tap is never turned on when filling a bath.

The 3rd in the run is the basin, which like the kitchen sink is hot enough to burn.

The final one is the shower, which again is tepid.

I presume the boiler can be ruled out due to it being hot in some places and not others. The runs to the furthest outlet is no more than 5 metres from the boiler, and only 1.5m from the basin which is boiling hot.

I thought it might be the thermostatic shower, but if the same is happening in the bath mid-run then maybe this isn't the case.

Suggestions please!!

 

[Newboy]

It's possible/likely that you have a thermostatic mixing valves on both the bath mixer and the shower, the supply to both the kitchen & basin taps will be direct from the boiler.

Might be worth measuring the temperature at bath and shower to check if the TMVs are set to the 'correct' temperature.

 

[peterb20]

The bath isn't a mixer, just two bog standard taps.

 

[Newboy]

OK but still possible that there is a thermostatic mixing valve on the hot bath tap.

How old is the property?

 

[peterb20]

Bath taps the same age as the basin taps and shower valve - 9-10 years? Kitchen is 2years.

I don't understand why the basin and bath are different because they're the same tap. And we're cheap at the time which makes me presume they wouldn't have had tmv?

 

[Newboy]

The TMV is a separate unit (not part of the tap)
Have look under the bath for any fitting on the bath hot supply pipework

 

[peterb20]

Ah right, 100% not then! Definitely no tmv there, or anywhere (apart from in the shower mixer)

 

[Newboy]

If you reduce the flow at the hot bath tap does the water temperature increase?

 

[peterb20]

Yes it does

 

[Newboy]

In that case it's more likely that the flow rate through your hot bath tap (when fully open) is the factor - the boiler can only raise the temperature of the incoming cold water from the main so much. The high flow through the bath tap gives you a lower temperature then the comparatively lower flow through the basin tap.

 

[peterb20]

But regardless of the 3/4 taps, it's still only 15mm feed pipe. And with a similar flow rate (albeit by eye rather than a measurement) the basin is MUCH hotter. Nevertheless I will try a flow restrictor on the bath.

Also it's a 12month old not-cheap boiler so surely it's it's output would be more than adequate....

However this doesn't explain the shower being a dick too, unless its two unrelated problems which have happened at the same time

 

[Newboy]

Measure the flow rate and the temperature at each tap

 

[John D v2.0]

Newboy is of course right, and bear in mind in summer the incoming water is already a lot warmer, so this problem will be more apparent in winter.
Our 24kw Combi can handle two showers in summer but in winter it can only do one shower and a basin on gently.
Even if your boiler is expensive and new it will still only have the power rated on the box.
If your shower really is not warm enough and it's not one of those ridiculous 15+l per minute ones then there must be something wrong even on a relativelysmall Combi.

 

[peterb20]

Well ours is also a 24kw boiler by logic. 12months old. It's a really ****y little shower in relation to what you can get. Just the standard head size and flow, and regular sized taps everywhere.

It wont heat to a comfortable level in the bath or the shower even if they're the only thing running. But like I say the kitchen sink and bathroom basin will scold you!

 

[muggles]

24kW is the lowest power combi you can buy, so it shouldn't be too surprising that it's struggling to keep up with high flow rate fittings. As with your bath, does the shower temperature also improve if you reduce the flow rate?