Baxi 105e , water hot in the pipes but cool out of taps

[jokerukrs]

have a Baxi Combi Boiler. Shower yesterday suddenly only produces luke warm water no matter how high the thermostat is set, but water arriving in pipes is red hot.
Today the mixer tap in the sink seems to have a similar issue. Hot water comes through red hot then fades to luke warm even with mixer set all the way to hot.

checked kitchen mixer (tap nearest boiler). water is hotter but still not as hot as it was previously (ie i can bear to put my fingers under the stream of water which would have been scalding previously)

as this is now an issue on multiple points i can only assume it is a boiler issue - the hot water not strong enough when mixing with cold?

pressure on boiler is at 1 bar - where it has been for months and issue has only just occured so dont think that is an issue. No other changes been made to the system.

so far i have upped the water temp on the boiler (no difference)
increased pressure on system to 1.5 bar (no difference)
removed shower from wall to check water is hot (originally thought may be limescale build up in shower unit) water hot from the wall.

any ideas on the possible cause? solution?

 

[45yearsagasman]

What do you mean by "water arriving in pipes"? Do you mean the Central heating pipes are getting hot when only the hot water is on? It could be the diverter valve faulty or the plate heat exchanger. Both these are common faults on that boiler, but there is a small chance of other faults. If you are not capable and competent then get a repair and a service booked in.

 

[jokerukrs]

I mean that the boiler is obviously heating the water as when the tap is turned on the pipes feeding the taps are getting hot. Just seems that the cold water is overpowering the volume of hot water resulting in a cool stream of water in shower or basin.

 

[suchafunkymonkey]

So the hot water supply to the mixer tap is red hot, but cold when the water comes out of the tap?

If that's the case then your mixer tap is faulty and only letting the cold water out and thats warming up because the hot water pipes beside them are red hot.

What I suspect is actually happening is the central heating pipes are getting hot rather than the hot water pipes because the diverter valve is duff (it happened to mine). Try replacing the diaphragm in the divertor valve which should cost about £8 to do it yourself and is straightforward.

 

[45yearsagasman]

The diaphragm will not fix a diverter valve that is passing to heating.
Trying a single hot tap, is the water hot? If so the boiler is probably not at fault.
Check that the LH heating pipe remains cold during hot water operation.

 

[jokerukrs]

Sorry about the slow response we have been away for a few days and now am back and really need to sort this out.

We have now noticed that the water coming out of all taps is not as hot. bolier states that it is heating water up to 70/80 degrees on boiler but i can quite easily have my hand under the stream of water at the kitchen tap adjacent to the boiler (where before it was scalding)

i am now wondering if the idea around the diverter valve might be more accurate?

 

[45yearsagasman]

When using hot water, check that the LH pipe under the boiler remains cool like I said before. If you do this it will diagnose a diverter problem.
The diaphragm is a different issue. Do that test and come back.

 

[Agile]

Turn off the CW into the boiler, fourth pipe along.

Then see if anything comes out of any hot tap. Repeat that test moving any mixer taps or valves to all possible combinations of positions.

Tony

 

[McCombi]

Sorry about the slow response we have been away for a few days and now am back and really need to sort this out.

We have now noticed that the water coming out of all taps is not as hot. bolier states that it is heating water up to 70/80 degrees on boiler but i can quite easily have my hand under the stream of water at the kitchen tap adjacent to the boiler (where before it was scalding)

i am now wondering if the idea around the diverter valve might be more accurate?

the 70-80'c refers to the central heating temp in the boiler, not the domestic hot water temperature.
let everything completely cool down
Switch boiler to summer mode (hot water only)
Turn on a hw tap, not a mixer/shared cold tap if possible
Does the boiler fire up? (rule out diaphragm if so) if not then diaphragm faulty usually.
Look under boiler, usually 15mm pipe to dhw tap, this should get hot
Usually 2x 22mm heating flow/return pipes from boiler (possibly another 22mm pipe for gas though) feel these pipes. If heat is travelling along any of these pipes then sounds like diverter is passing.
If you have any single hot water taps that work fine then you can rule out the boiler being at fault.
Most combis give u a heat increase of approx 35'c at a flow rate at tap of approx 10 litres/minute
ie cold temp coming into house is 5'c then hot out your tap approx 40'c at 10 litres a minute flow rate.
This may not be the exact spec for your boiler but won't be far off it.

 

[jokerukrs]

ZThanks all.

Pete: feels like I getting some warmth coming through the left most pipe.

I switched the boiler to summer mode and this still happened. Boiler firing up hence the water pipe getting red hot.

But the heating pipe got warm not hot. Is that what you were expecting??

 

[DP]

Depends how sat the heat is travelling down that pipe. is the flow pipe into radiators getting hot?

The flow pipe can sometimes heat up due to slight 'weep' down that pipe but radiator inlets will remain cold.

I would be inclined to check a hot tap as opposed to a shower mixer to acertaing the problem.

 

[jokerukrs]

DP all taps are running at lower heat not just shower

 

[DP]

Boiler running at 70/80 would suggest it is doing what it is expected of it but not all the heated primary water is not passing through the hot water heat exchanger.

Isolate the two outer fat pipes at the valves under the boiler by turning these a quarter turn. Do NOT run central heating in this mode. Now run a hot tap and check if the water is hotter and LED display shows the same temperature 70/80

 

[jokerukrs]

DP,
done this and had no effect.

boiler is heating but guessing there something off somewhere- there must have been a little bleed into the heating but nothing significant (heating pipes are obviously cold with valves off) certainly not enough to improve the water.

so if it isnt the hot water bleeding into the heating due to a faulty heat exchanger could it be going anywhere else??

The pipe exiting the boiler is red hot (too hot to touch for more than few seconds) but the water at the tap is no where near as hot.

 

[McCombi]

Im puzzled.
Can you feel the pipe just before the hw tap? Is that hot?
Sounds like mixer faulty but strange that more than one has gone faulty at the same time.