Hi people
We've got an ANCIENT Vaillant VCW GB 242 EB using LPG.
Everything was fine until just before Christmas when the hot water started to become really dicey! DHW would just not get hot - warm (just) but not hot.
Read loads on here and initially thought might be diaphragm in diverter valve but then came across one post with the op found that the diaphragm pump connectors had split. Tried this first and lo and behold mine were cracked and split too! Replaced whole pump because the diaphragm on the pump seemed a little tired and all seemed dandy until recently...
Now we have NO DHW at all. Central heating is fine. Gets up to about 85 degrees when central heating flow temp dial set to 9. We were turning the tap down and down and down to get hot water but now it is useless and even that no longer works.
I bit the bullet and to save messing around changing one bit at a time I ordered a new servo valve, new diverter valve and a new water section (someone in the past had really chewed it up) and set about replacing all three items this evening. All went swimmingly until I found the rusty grub screw in the water section bracket but thats another story involving pillar drill and tapping new threads I do not want to go into ever again!
Finally got everything reconnected, counldnt get any pipe cleaners to check the control lines were clear of muck but could blow down them easily and all had new 'o' rings.
The result was exactly the same as before!!! No hot water!!!
With the CH on the boiler is just dandy and fires away merrily (although I am not too sure that the green light/diaphragm pump should be on for CH alone - please let me know).
When DHW is drawn its a whole different ball game. Servo moves over and activates the micro-switch (as it did before) and Diverter valve also plays the game but after a few seconds the burners go out and the boiler shuts down then a few seconds later (maybe a bit longer) the burners light again and the whole cycle begins again!
I have tested the DHW overheat thermostat and it reads correctly. Hot water is flowing to the DHW HE but it doesn't do it for long enough to heat the water!
What am I missing?
Could it be a PCB when everything else works OK?
Could it be the NTC Probe in the burner compartment - how can I test it?
Any constructive advice would be very helpful as I am now at a total loss! I don't like to keep popping in to ask questions so did as much research as I could, and most posts mention the things I have changed already but its been no help in my case!
What would you suggest?
Thanks guys (and girls)
Update!
Just had a thought and so carried it out. Went to boiler and disconnected lead from NTC probe from terminal on DHW overheat thermostat and connected lead that piggybacked off of that connector (back to control box) directly to the overheat thermostat. Boiler ran perfectly pumping out loads of REALLY hot water! Touch the lead from the NTC probe to the same terminal on the overheat thermostat and the boiler shuts down instantly so that must be it (I hope) as it seems to work perfectly when that NTC probe is taken out of the equation! I wonder if this is the cause for so many peoples problems when they report that their boilers cycle rapidly on and off and they get no hot water?
Anyway - please give any advice you can give and tell me if Im being daft or should check other things.
Many thanks again ;O)
We've got an ANCIENT Vaillant VCW GB 242 EB using LPG.
Everything was fine until just before Christmas when the hot water started to become really dicey! DHW would just not get hot - warm (just) but not hot.
Read loads on here and initially thought might be diaphragm in diverter valve but then came across one post with the op found that the diaphragm pump connectors had split. Tried this first and lo and behold mine were cracked and split too! Replaced whole pump because the diaphragm on the pump seemed a little tired and all seemed dandy until recently...
Now we have NO DHW at all. Central heating is fine. Gets up to about 85 degrees when central heating flow temp dial set to 9. We were turning the tap down and down and down to get hot water but now it is useless and even that no longer works.
I bit the bullet and to save messing around changing one bit at a time I ordered a new servo valve, new diverter valve and a new water section (someone in the past had really chewed it up) and set about replacing all three items this evening. All went swimmingly until I found the rusty grub screw in the water section bracket but thats another story involving pillar drill and tapping new threads I do not want to go into ever again!
Finally got everything reconnected, counldnt get any pipe cleaners to check the control lines were clear of muck but could blow down them easily and all had new 'o' rings.
The result was exactly the same as before!!! No hot water!!!
With the CH on the boiler is just dandy and fires away merrily (although I am not too sure that the green light/diaphragm pump should be on for CH alone - please let me know).
When DHW is drawn its a whole different ball game. Servo moves over and activates the micro-switch (as it did before) and Diverter valve also plays the game but after a few seconds the burners go out and the boiler shuts down then a few seconds later (maybe a bit longer) the burners light again and the whole cycle begins again!
I have tested the DHW overheat thermostat and it reads correctly. Hot water is flowing to the DHW HE but it doesn't do it for long enough to heat the water!
What am I missing?
Could it be a PCB when everything else works OK?
Could it be the NTC Probe in the burner compartment - how can I test it?
Any constructive advice would be very helpful as I am now at a total loss! I don't like to keep popping in to ask questions so did as much research as I could, and most posts mention the things I have changed already but its been no help in my case!
What would you suggest?
Thanks guys (and girls)
Update!
Just had a thought and so carried it out. Went to boiler and disconnected lead from NTC probe from terminal on DHW overheat thermostat and connected lead that piggybacked off of that connector (back to control box) directly to the overheat thermostat. Boiler ran perfectly pumping out loads of REALLY hot water! Touch the lead from the NTC probe to the same terminal on the overheat thermostat and the boiler shuts down instantly so that must be it (I hope) as it seems to work perfectly when that NTC probe is taken out of the equation! I wonder if this is the cause for so many peoples problems when they report that their boilers cycle rapidly on and off and they get no hot water?
Anyway - please give any advice you can give and tell me if Im being daft or should check other things.
Many thanks again ;O)
