vaillant combi t3w sine 18 - no CH

[alphamike]

hi guys, this is an old beast that my plumber tells me has given up the ghost.. needles to say ide love a second opinion.

here goes. this old boy has been running for about six months with the issue that the HW will not run unless the CH is also on. ive been told this is a diaphram issue. since it was still working to a point ive shamefully neglected to have it repaired, and so much to my dismay the CH no longer runs, however the HW will with the CH stwitched to on.

With the CH switch to "on" the boiler will attempt to cycle. the pump runs, the boiler fires and continues for about 7-10 seconds where it promtly shuts off again. there is absolutely zero heat on the flow or return. All valves are set to open. Nothing has been changed on the system and we have about 1.8bar pressure.

As stated above the HW will work aslong as the CH is switched to on. I initialy thought it was the pump untill i realized the HW was still working. could this be the divertor?


any ideas would be greatly appreciated.

thanks in advance guys

 

[oldplumber]

could be, ask another plumber to visit and let him quote for a new one as well if need be.

 

[stevetheplumber]

hi guys, this is an old beast that my plumber tells me has given up the ghost.. needles to say ide love a second opinion.

here goes. this old boy has been running for about six months with the issue that the HW will not run unless the CH is also on. ive been told this is a diaphram issue. since it was still working to a point ive shamefully neglected to have it repaired, and so much to my dismay the CH no longer runs, however the HW will with the CH stwitched to on.

With the CH switch to "on" the boiler will attempt to cycle. the pump runs, the boiler fires and continues for about 7-10 seconds where it promtly shuts off again. there is absolutely zero heat on the flow or return. All valves are set to open. Nothing has been changed on the system and we have about 1.8bar pressure.

As stated above the HW will work aslong as the CH is switched to on. I initialy thought it was the pump untill i realized the HW was still working. could this be the divertor?


any ideas would be greatly appreciated.

thanks in advance guys

new diaphram should sort this out

 

[alphamike]

could be, ask another plumber to visit and let him quote for a new one as well if need be.

thanks oldplumber, your probably right on that score however i want to try and avoid calling out another plumber due to a low income. so a few ideas on here first might save me unwanted costs. many thanks

new diaphram should sort this out

thanks steve, i knew it needed a new diaphram anyway, but with this new problem..could the diaphram be responsible for both issues even this new one? aswell as the old?

 

[Puddle]

Well diaghram will sort hot water out if seal not leaked and corroded holding grb screws,if this is the case is a sod to get out or you may get away with adjusting micro switches in control box,there are adjustment screws
hot water should still work on the storage side though
As for heating difficult to say,however if hot water storage mode off and still lighting and going out will probably be the wax cartridge in the change over valve,this is back L/H side of boiler, seperate from the hot water diaghram holder under control box
There is a small possibility of a weak pump
These are great boilers but are getting old and you may have to think about replacement due to cost of repair

 

[alphamike]

Well diaghram will sort hot water out if seal not leaked and corroded holding grb screws,if this is the case is a sod to get out or you may get away with adjusting micro switches in control box,there are adjustment screws
hot water should still work on the storage side though
As for heating difficult to say,however if hot water storage mode off and still lighting and going out will probably be the wax cartridge in the change over valve,this is back L/H side of boiler, seperate from the hot water diaghram holder under control box
There is a small possibility of a weak pump
These are great boilers but are getting old and you may have to think about replacement due to cost of repair

Thanks for the detailed reply there, yes i think this new problem is independant of the hot water diaphram. and assuming the change over valve is the culpret. i would be looking at some costly assumptions if im wrong. Perhaps it would be prudent to fix the diaphram first and then see if the problem is solved. i have noticed the pump is exceptionaly hot, perhaps this is struggling also, however the hot water does run at a good rate :S

many thanks for your help it is greatly appreciated

 

[stevetheplumber]

sorry didnt read the problem properly could be any thing stopping ch working

 

[alphamike]

no to worry. thanks for the reply, much appreciated.

Ive got a number for a plumber who will diagnose without charging (friend recomendation) so will let u know whats the fault with an update...

thanks again

 

[stevetheplumber]

no to worry. thanks for the reply, much appreciated.

Ive got a number for a plumber who will diagnose without charging (friend recomendation) so will let u know whats the fault with an update...

thanks again

ive actually got all the bits for a divertor valve rebuild kicking around in my garage so if your stuck let me know not sure how the availability is on old vailants

 

[alphamike]

Well, ordered the diaphram and fitted by my plumber, as suspected the HW is working perfectly now.

As diagnosed by you guys here (many thanks), the divertor is to blame. seems to be jammed/nonresponsive.

ive actually got all the bits for a divertor valve rebuild kicking around in my garage so if your stuck let me know not sure how the availability is on old vailants

That sounds spot on steve, how can i send you the funds for it and the postage costs?


much appreciated guys!

 

[oldhand]

Hi Alphamike ,

just thought I'd throw in my longtime knowledge of Vaillant boilers etc. Your problem with the diverter is caused by the failed 'Waxstat' and yes it looks and acts just like the one 's fitted in your car radiator, it's located on the left side of your boiler on the top of the diverter ( the one with the little aluminium box on top covering the microswitches) the stat is under this with three retaining screws accessed from underneath.

 

[stevetheplumber]

Well, ordered the diaphram and fitted by my plumber, as suspected the HW is working perfectly now.

As diagnosed by you guys here (many thanks), the divertor is to blame. seems to be jammed/nonresponsive.



That sounds spot on steve, how can i send you the funds for it and the postage costs?


much appreciated guys!

if you want them ill send as soon as you send a post dated a week cheque say £30 cant be more than a tenner to post message me direct on here with a phone number

 

[alphamike]

PM sent. thanks again


Thanks oldplumber..even my plumber cant go wrong with those instructions