Hot water starts warm then runs cold

[scottb]

I have a combi boiler which is a couple of years old.

My heating works fine but when I turn the hot water on it starts of warm and then runs cold.

The only way I can get round this is by having my heating on 24x7 to ensure I have hot water when I need it...

I thought it might have been the hot water heating sensor but that would not explain why I get hot water when the heating is on permanetly.

Any ideas??

 

[gas4you]

Well it would help if we knew the make and model of your combi

Chances are it is a diaphragm or diverter valve gone.

 

[scottb]

I will advise of the make and model this evening.

Why would the hot water only be warm if the heatings on though? residual heat??

 

[corgiman]

we cant say untill we know what boiler it is?

 

[bengasman]

sounds like diverer not working

 

[scottb]

its a Ravenheat rfs84e

 

[scottb]

I now have no heating as well. Could I change the diaphragm or do I nee to change the whole diverter.

I am doing this tomorrow.

Thanks

 

[gasmick2]

you have 2 choices if you can get a repair kit the diaphram can be changed, but i have always changed the whole valve as there is more than the diaphram part that goes wrong, you should use a genuine ravenheat one because the lookalike ones , have been known not to work properly especialy on a washing machine they are all giannani make but they are made specially for ravenheat, i know because i used to be an out of warrenty service engineer for Ravenheat and had to change a few non ravenheat valves when problems occured you will also need all new washers for the valve do not try to relce with out als make sure you replace the filter on the hot outet on the valve whatch it because it tends to drop in the bowl you will need under the boiler when taking the old one out best of luck if you do get one none ravenheat ones you will have to swival round the connections to be opposite of each other but its a simple job to do

there is a lot of difference in price genuine around £130 lookalike £35-£40

mick

 

[richw]

When you open your hot tap, does the microswitch in the boiler click, and the boiler fire-up? Does the water get hot? Does the boiler start to switch off and on, resulting in water going hot/cold/hot/cold/...?

 

[scottb]

This is what happened when I replaced the diverter.

Took the value off.
Opened the top of the value and detailed how the diaphram mechanism went together.
Cleaned out the valve with clean water.
Replaced the diaphram and the push rod.
Put it all back together an connected it back to the boiler.

The value worked great 3 times and then the pushrod stopped moving.

If I made the microswitch manually the heating works but the pushrod will not move when called automatically.

I am able to move the push rod with long nose pliers and it moves smoothly.

Have I missed something??

I will be buying the whole original valve tomorrow.

Can someone confirm that I am doing the right thing.

Thanks for the help.

 

[Bobbo 85.]

was the diapraghm split or holes in it,if the diapraghm is ok and its worked 3 times,i would be looking at water pressure before youchange the valve

 

[Bobbo 85.]

If the diapraghm is split,then swap it,£3 or £150.and easier to fit

 

[Bobbo 85.]

I have a diverter valve that is along with 12 other's in perfect condition and wasnt even 6 months old when the complete boilers were swapped and i got them for spares,as i could buy a part and take the ones i had back and swap them for brand newie's.If you need one i will get it to you.free and donation to a childrens hospital in liverpool

 

[scottb]

Hi Bobbo is the diveter for a ravenheat 84e?

The old diaphram what cracked and had little splits.

The system pressure was held at 1.5 bar - should I need to look at cold feed pressure into the valve?? also the regulator screw is fully open on the valve and I have not adjusted this.

Could the shaft inside have sized up as I only washed it out with clean water??

 

[scottb]

Fitted new ravenheat diverter value and that has cured the problem - also came with a new micro-switch which I did not expect.

One thing though, when you turn the hw tap 3/4 open it will run cold whereas if you turn it half way it run lovely and hot????