If it's burning the correct quantity of gas the heat energy must go somewhere. Either the DHW flowrate is too high or heat is going to the rads. Feel the pipework at the rads...are they getting hot when the hot water is being drawn.
Vaillant VCW GB 242 EH Boiler - Is it Diverter Valve?
- Thread starter trelo
- Start date
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Funny that cos while i was scratching my head I did check that earlier but no heat is generated in the flow pipe at the boiler going to the rads when the HW is flowing
Well unless your boiler is the only device in the universe to contradict the first law of thermodynamics then you must be mistaken 
If it is burning the quantity of gas you say and no heat is going to the rads then you must have the DHW flowrate too high.
If it is burning the quantity of gas you say and no heat is going to the rads then you must have the DHW flowrate too high.
i completely agree...I still need to change the water section...i'm awaiting a part. I know i should try cleaning it first but to be honest I'm too darn lazy!! I'll come back as soon as I've done that. I'll go back and check everything again... i might even take the HEX off to see if anything may be wrong.. maybe muck in there i dont know its just wierd... thanks so far...i''ll be back!
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You seem very keen to rush into changing instead of letting us identify exactly whats wrong with your boiler.
All you need to do is turn on a hot tap and measure how long it takes to fill a pot, bucket or other container.
Then we can calculate the flow rate and compare it with the boiler's capabilities.
Tony
All you need to do is turn on a hot tap and measure how long it takes to fill a pot, bucket or other container.
Then we can calculate the flow rate and compare it with the boiler's capabilities.
Tony
I understand what your saying but time isn't a luxury in my house... 2 kids and a wife to keep warm and hot watered. I don't like rushing through anything like this but sometimes you just need to press on and change parts that could be causing the problems to get the job done. I know this boiler well, i've had it 15 years. I've changed 4 HEX's on it and Primary HEX plus a load of other stuff but this has really stumped me. I have done the bucket test and the flow is fine. I did that over a week ago when I fitted the HEX.... Thanks for the info...appreciate all advice
I cant change the flow rate anyway because the adjuster knob jammed years ago. Its jammed in the lowest position (slowest flow)- it always has been at that position for 15 years. Now that the water section pin has jammed its maybe time to change this bit anyway.
The thing is, in the time we've been talking on here and the several parts you've fitted, a registered heating engineer (not plumber) may have been able to sort it. Anyways.... check the flow rate as advised, post back results. Just to clarify, you need to measure how many litres of water is passed in a minute.
I appreciate what your saying and yes its true what you say about getting a heating engineer. In my defence, when i took the diverter valve off it showed signs of corrosion underneath where it had leaked through the exit point of the pin that goes to the microswitches. The HEX was full of Muck and debris and the water section pin is well and truly jammed. The total cost of all these parts came to £120.... no where near what an engineer would have charged... The other thing is that judging from all the posts i've been looking at on this forum that the symptoms to my problem point to at least one or all of the parts i've changed. The only part i wasn't aware of was the gas pressure to which you kindly advised me was ok. The only thing left for me to do is the flow rate which i will adjust as soon as i get the new water section in. Fingers crossed its the flow rate thats causing the problem otherwise i'm gona have to start afresh.... Can I just say you guys here are brilliant and really valued...the lesson for me here is maybe not to rush into changing bits quite so fast.... I'm just praying this last part and subsequent flow check is gona do the trick or my missus is gona kill me
You are right in that you could just as easily picked and engineer that wouldn't have had a clue about this boiler, as one that could have fixed it first time. Anyway, post back the results when you put a new water section in. Thanks!
I cannot understand why you cannot spend just five minutes measuring the flow rate.
I am not asking you to adjust it onmly to measure it.
To adjust it all you need to do is to NOT turn your basth tap on full.
You seem fonder of your computer than just doing a five minute check.
Tony
I am not asking you to adjust it onmly to measure it.
To adjust it all you need to do is to NOT turn your basth tap on full.
You seem fonder of your computer than just doing a five minute check.
Tony
Tony, I did the bucket test if you read my earlier post... ok i didn't provide figures but its about 9 litres per minute... and I am aware that reducing the flow at the tap does increase the temperature.... thing is i know enough about this boiler to know that there's a problem. Over a period of 15 years i've changed 4 plate HEX's with no problems to the flow rate but this time it didn't work? Thats why i changed diverter valve (which now works super fine) The only thing i have a problem with is a jammed pin on the water section. The servo seems fine. The other thing i noticed is that the inlet pipe to the HEX from Primary HEX is hot as outlet pipe when in CH mode. But soon as HW demand kicks in this cools down significantly very quickly... and yes, i do love my computer.... sadly
If the ONLY problem was the water section pin then you can simulate that action by rotating the black cam anticlockwise until the microswitch is activated.
The boiler will then be operating in DHW mode and will give about 8 li/min just too hot to keep you hand under IF its working corectly.
Tony
The boiler will then be operating in DHW mode and will give about 8 li/min just too hot to keep you hand under IF its working corectly.
Tony
With all the checks and tests you've done, and the parts you've changed it's hard to see what the problem could be. I can't think of anything that wouldn't be covering old ground.
If i were there i'd check inlet water temp, flow rate and hot water temp. (with thermometer) just so we knew exactly what kinda fault we were dealing with. Have you done these checks? Your boiler should be approximatly a 35C temp rise.
You said your gas rate is ok, and no heat is being passed to the rads. If all this is ok and your tests are accurate, it should work!
I don't think there's much else i can offer you, other that doing all your checks again. Looks like it's time to get an RGI in
If i were there i'd check inlet water temp, flow rate and hot water temp. (with thermometer) just so we knew exactly what kinda fault we were dealing with. Have you done these checks? Your boiler should be approximatly a 35C temp rise.
You said your gas rate is ok, and no heat is being passed to the rads. If all this is ok and your tests are accurate, it should work!
I don't think there's much else i can offer you, other that doing all your checks again. Looks like it's time to get an RGI in
Ok all... Just about to fit water section and wondering if the water section assembly can be removed without touching the servo? Will the water section come out with the pin as one or is the pin part of the support? I can't quite see enough to understand how each part connects. Does the cheese head screw disengage the assembly?
The other concern is the new water valve has a missing feature. Please look at video clip of me attempting to look like i know what i'm doing
here is the http://www.screencast.com/users/And...em/media/fef9ec52-f570-43ec-bd10-e5478bd69365
Please 'FULL SIZE' the video when you get there to get a better view...
and sorry its a bit slow...i'm a bit knackered
The other concern is the new water valve has a missing feature. Please look at video clip of me attempting to look like i know what i'm doing
here is the http://www.screencast.com/users/And...em/media/fef9ec52-f570-43ec-bd10-e5478bd69365
Please 'FULL SIZE' the video when you get there to get a better view...
and sorry its a bit slow...i'm a bit knackered
There is a small slot head screw going through the water section support plate, it pushes tight on the lip on just near where the pin comes out in the centre, it's a little difficult to describe! Back that screw out a few turns till it clears that lip and it should come off. Obviously un-do the pipes aswell. Watch you don't round that screw, sometimes they seize up
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