Valliant VCW 242 EH Boiler Problem

[mascia]

hello hope someone can help, i have this boiler and the hot water is not working properly. turn the tap on and water takes a bit to warm up, when it does it isnt that hot then it gets cold. leaving the tap running still she gets hot again then cold (this just repeats). plumber has checked the diverta valve and all seems to be working fine between the water and central heating.

he thinks it could be the diaframme washer not opening fully but not broken hence the water getting a bit hot then cold. the boiler lights and turns off every 15 sec is this normal.

can someone please help its driving me mad

thanks in advance

 

[picasso]

probably blocked dhw heat exchanger or faulty thermistor.

 

[Bunnyman]

Blocked dhw ht exch

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• Bunnyman
• 26 Mar 2010
• 499

 

[mascia]

Blocked dhw ht exch

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• Bunnyman
• 26 Mar 2010
• 499

thanks gent but i only changed the dhw heat exchanger last year how can i check if its gone again ? what about thermistor were would i find this piece on my boiler

 

[Bunnyman]

Forget thermister mate they never fail. It's dhw ht exch u must have a dirty system an it's blocked it up get system powaflushed

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• Bunnyman
• 26 Mar 2010
• 499

 

[Andygasman2010]

Bocked plate heat ex. when did you say you replaced it? They can muck-up again pretty quickly.

 

[mascia]

Bocked plate heat ex. when did you say you replaced it? They can muck-up again pretty quickly.

i change it 1 year ago, i had to because the old dhw heat ex was leaking, there was a modification replacement type a lot smaller one than the original, if it is blocked what can i do to test it.

thanks i seem to be getting some where now.

 

[mascia]

Forget thermister mate they never fail. It's dhw ht exch u must have a dirty system an it's blocked it up get system powaflushed

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• Bunnyman
• 26 Mar 2010
• 499

i changed the dhw heat ex 1 year ago, the old one was leaking and the new one they sent had a modification it was a lot smaller, how can i check if its gone again.

 

[Homesafe]

Did you change it yourself?

 

[mascia]

Did you change it yourself?

no my uncle whos a plumber changed it for me, all working fine until now

 

[Homesafe]

He should have at a minimum chemical cleaned your system for you, ask him to do it for you cos your system sound as if very dirty.

Have you been topping it on aregular basis?

 

[mascia]

He should have at a minimum chemical cleaned your system for you, ask him to do it for you cos your system sound as if very dirty.

Have you been topping it on aregular basis?

if your talking about the boiler pressure, yes i check it every 2 weeks and the pressure seem to be steady, if required i top it up.

 

[Andygasman2010]

I wouldn't worry about testing for this, the best indication of a blocked plate heat ex is the fault you describe. You could maybe check flow/return temp differentials.... an easier test would be to pull the single wire off the thermistor and see if it stays on high gas. If it does, it's blocked.

I wouldn't bother with these tests though, they can be tricky to do and the thermistor is within the combustion chamber so you'd have to get an RGI in.

You just need a thorogh clean doing, or replacement heat ex. More importantly, clean the system so it doesn't happen again.

 

[mascia]

I wouldn't worry about testing for this, the best indication of a blocked plate heat ex is the fault you describe. You could maybe check flow/return temp differentials.... an easier test would be to pull the single wire off the thermistor and see if it stays on high gas. If it does, it's blocked.

I wouldn't bother with these tests though, they can be tricky to do and the thermistor is within the combustion chamber so you'd have to get an RGI in.

You just need a thorogh clean doing, or replacement heat ex. More importantly, clean the system so it doesn't happen again.

many thanks mate ill get me uncle right on it

thanks again