Flow-Sensors on Gloworm CXI Boilers

[beermatt3]

Hi everyone, has anyone out there had any problems with the flow sensor leaking on Glow Worm cxi Boilers.

I have fitted 5 over the last 3 years and two of them have developed this fault, a leaking flow sensor. One of those O'ring and circlip jobs.

Am I just unlucky is this a fault with this type of boiler.

Matt

 

[HarrogateGas]

Ahhh the old CXI..yeah ive seen the leak you describe a fair bit...........ive always said this boiler would make a nice water feature in the garden with it springing leaks left right and centre.

 

[gasman]

I must be a one off, but i think the CXI is a great condensing boiler. Never had the problems that you describe. But very easy to work on and replace parts if required. I know there have been issues with the condensate traps and the filling loops but tell me a boiler without any problems! The heat exchanger design is fantastic. Because it is made of stainless steel you do not have the build up the sludge of the alloy/silicon type.

I would like other opinions please.

 

[croydoncorgi]

Apart from some awful exceptions (older types, especially Saunier) most boilers using the 'O-ring plus clip' joints seem to hang together surprisingly well, in my experience. Problem WILL happen if the joint is pushed out of alignment. The CXI is (was?) especially affected by a misaligned flue pushing the whole combustion chamber downwards and causing a condensate leak from the seal at the back. I've also got one on my list that had a mystery leak from the bottom but when I got there was completely dry! There was a suspicious 'tide-mark' all the way found the bottom of the casing, from where (I assume) the condensate trap had blocked or the float-thing stuck. Anyway - nothing to fix and no repetition.

It's quite a weird thing: I've actually found condensate running out of the sight-glass on a CXI - there's no overflow sensor so if the condensate disposal blocks it just keeps on filling up until the water shorts the electrodes or finds somewhere to leak out! But a REALLY bargain-price Vokera / Sabre combi I fitted recently has a pressure switch specifically to detect condensate overflow.... Funny what different manufacturers spend their money on, or not.

 

[RatchetHead]

Can anybody advise me the best way to fix the leaking O Ring problem on the flow sensor/manifold connection. I hear this is a common problem, but I've tried replaced the O ring and attempted to reseat it carefully a number of times now and it just doesn't make any difference. The space that the flow sensor fits in seems too big to me, so there is definite outward tension when you fit everything back together. Presumably this is enough to unseat the O Ring; but how to fix it? Anybody got any ideas?
I've spoken to Glow Worm but they deny any knowledge of the problem.

 

[humgas]

Can anybody advise me the best way to fix the leaking O Ring problem on the flow sensor/manifold connection. I hear this is a common problem, but I've tried replaced the O ring and attempted to reseat it carefully a number of times now and it just doesn't make any difference. The space that the flow sensor fits in seems too big to me, so there is definite outward tension when you fit everything back together. Presumably this is enough to unseat the O Ring; but how to fix it? Anybody got any ideas?
I've spoken to Glow Worm but they deny any knowledge of the problem.

Hi I have the very same problem, have changed o'ring and made no difference still leaks between flow sensor and hydroblock. can only think to replace block but dont want to really, pricey ... Did you have any joy

 

[Agile]

Last two posters should have started their own threads.

The hydroblocks have a history of leaking from cracks in the hydroblocks.

If that happens outside the ( short ) warrantee then you have to pay the money to get it replaced. It often takes out PCBs too.

Sometimes wrapping about five turns of PTFE around the sensor "O" ring will seal a genuinely leaking one. A pro would always replace the "O" ring and lubricate with silicone grease.

Tony

 

[humgas]

cheers tony, replaced oring and greased and have tried wrapping a few wraps of ptfe without joy, weird as there doesnt appear to be any obvious crack on either part unless one is for some reason distorted

 

[mickyg]

usually a pinhole in the flow sensor. is it grey or black ?

 

[humgas]

it is grey the flow sensor

 

[mickyg]

definately suspect the flowswitch then, thats the old original one, its been replaced by a vaillant part. The new one should come with a little cable harness to convert the wiring.

 

[Agile]

The problem is that these "pin holes" are usually really cracks but they are so fine that when inspected closely cannot be seen by eye.

I have a suspicion that what actually happens is that under mains water pressure of 2-3 Bar they open up!

Its nice to have someone like Micky who is no longer under an obligation to trot out the makers spin that these common faults dont exist!

Tony

 

[humgas]

Thanks very much Micky & Tony, have also suggested fitting a PRV as they have pretty good pressure which will have compounded the problem, thanks