Another Vaillant problem please help!

[seb01]

Please bear with me here I have searched but can't find anything quite like this!
I have a Vaillant VUW GB242 which recently started losing pressure - assumed it was from leaky radiator in kitchen until we noticed occasional loss of HW and the drain below boiler was soaked (sited in garage) - This led me to diverter valve, which seemed to have been leaking for so long two of the screws were corroded to the point of me having to drill them out!!

anyway to the point! I got a diaphram kit from Plumb centre consisting of the diaphram, new plunger replacement screws and O-rings which all went back ok, so I put everything back together. Now I have hot water but the valve is still losing pressure, the water appearing to come out of the area containing the lever to activate micro switch! The rate of loss is quite high at about 1 bar a day!
Could this water be coming from the top of the valve, the part connected to the pump with the upper plunger in as these seals seem to be a little tired?!?!
I have since pulled the diverter apart again and am happy with the condition of new fittings, and the contact area's and can't see the water comming from anywhere else???

Any help greatly appreciated!!!

 

[chrishutt]

Could this water be coming from the top of the valve, the part connected to the pump with the upper plunger in as these seals seem to be a little tired?!?!

Yes. If it was coming from below (mains pressure side) it would not cause a pressure loss in system.

You replaced a little O ring around the spindle to seal from the mains pressure side. I think there is a similar O ring seal from the system water side, which needs replacing.

 

[seb01]

Thanks for quick response chris, I hope am not beeing too much of a burden and this seems like a silly question but that leaves me wandering what I should ask for! 'Upper' diverter kit maybe (as I might as well replace the other seals aswell!) or maybe upper diverter seals, CH side??? Any idea's would really help me here!
Would vaillant give me an exploded diagram or even just help with part nos as they don't have much usefull info on there site in downloads!

 

[chrishutt]

seb, if you check my profile, you will find my email address. Send me an email and I will try to send some Vaillant bumph back to you. Bear in mind that there are 2 versions of this boiler with slightly different diverter valves.

 

[Agile]

I thought the kit contained two shaft seals for either side of the middle where the lever is located.

Did you change both and more important did you ensure the spindle was spotlessly clean?

Tony

 

[seb01]

First to Chris - Thank you for the info that was great and helped me get the second kit, and a fully working, non leaky boiler Thankyou I will drink a pint on your behalf later

Ok Agile the first kit I got contained all parts nescesary for the lower half of the diaphram i.e. Diaphram, the 'spindle' two o rings new screws (to replace corroded ones I had to drill) and a replacement bush. This solved the lack of spontainious hot water, but not the leak

The second kit contained a similar bush and two o rings as above, another o ring for the 'sleeve', 3 replacement screws and the upper plunger bit (with the middle seal and springs)
This kit solved (or appears to have - touch wood ) the leak problem and yes I am surprised it didn't all come as one kit but there you go!

Just out of interest, I tried to get my head round the complete operation of this valve but the vailant diagram Chris sent is not great (sorry if that sounds ungratefull Chris!).
Am I right in thinking the spring assembly I have just replace has some form of thermostatic operation, which regulates the amount of hot water allowed to flow through the heat exchanger as I have noticed water flow rate is reduced when hot and always wandered what controlled this!?

 

[chrishutt]

Seb, you should have received second email with the full instructions for the boiler, which will (I think) explain the operation of the diverter valve, etc.

To answer your main point, the diverter valve is not thermostatic. It is operated solely by the DHW flow around the diaphragm. It's either open to DHW circuit or CH circuit.

the thermostatic control occurs elsewhere. A sensor reacts to the temp. off DHW and (via the PCB) modulates the gas valve to increase or decrease the flame size.

I'm sure if you plough through the instructions, all will be revealed. Enjoy my pint!

 

[ChrisR]

spring assembly I have just replace has some form of thermostatic operation

Er, no.
The main bit of the valve is the diverting bit. Hot water from the main heat exchanger goes in and is sent either to the secondary heat exchanger to heat the HW, or the rads.

There's a flow restrictor which limits the HW to I think 8 litres/min, in one of the tap water ports on the 2ndry h/e. I think its the one with the ribbed nut .

It's limited to give you a decent (about 40c) rise on the h/w so you can have a bath(45c) in winter.

 

[Agile]

I have to say that we do not fiddle about with reconditioning as we believe that our clients deserve a new diverter valve with a good life expectancy. If it was just the diaphragm failed, we would replace just that if the client wanted to keep costs down.

There is a flow restrictor at the inlet to the plate heat exchanger. This has a different colour depending on the 24 or 28 kW rating. This works as a rubber "O" ring in between two plastic bits. Its on the inlet so should not be affected by temperature effects. In many areas with poor water supply pressure its better removed!

Most taps have a temperature effect which varies the flow between hot and cold but thats not intentional. The unwary often confuse that with a boiler effect.

I am not aware of any intentional flow/temp control in the 242. Expansion effects could cause small changes though. Also the viscosity of water will vary slightly with temperature.

Tony Glazier

 

[Agile]

I thought there was a single kit available for the whole valve.

I am now left wondering which of your kits contained the plastic lever for the microswitch ( which sometimes breaks! )

Tony Glazier
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