Combi boiler questions

We have a sixteen year old Potterton Lynx 2 combination boiler. During its life, it has had many new parts, it even arrived from new with the internal unions not very tight. The CH water pressure keeps dropping, I believe that is the pressure relief valve (I have tried to re-seat the valve many times), is it possible to dismantle the valve? The heat exchanger weeps and has nearly always done so, but it is getting worse. Sometimes it really stinks as it 'boils' the water additive. The heat exchanger is a tinned copper part, does this mean I might be able to solder up the leak ? A new part is around £625 to buy and fit myself.

I have been looking at replacing the whole boiler, but all the boilers I have looked at have different pipe connection locations than the current boiler's, and even worse, when I fitted this boiler, I had to move a rafter to fit the flue, and the new boilers have different positions for that too when compared to the existing flue.

So, opinions please: do I replace the boiler, or repair the current one ?

Thanks

David

Reply to
David
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Forgot to add that the DHW expansion vessel needs replacing too.

Reply to
David

Soldering up the leak might be very difficult as the surfaces to be solder will be covered in crud and impossible to clean. Depending on where the leak is, it might be better to fit a copper patch over the area (cannibalise some pipe for material) A new valve should not be too expensive and will possibly be a standard fitting. repair/replace??? A bit like having a car. Better the devil you know up until the point when it starts to cost serious money to get its MOT.

Put some cash aside towards replacement when you can whilst nursing it along with diy repairs.

Bob

Reply to
Bob Minchin

Good idea

Thanks Bob.

Money is not the problem, things like this take me a long time because I am thorough, and a novice. I do not want SHMBO to be without heating and it might take more time for me to complete than she is at work for the day. I also do not really want a newer boiler that I may not be able to fix, this current one is relays and switches rather than software, EEPROMs PLC or whatever they are now.

I will probably nurse it till the heating is no longer required then fix.

Thanks

David

Reply to
David

This may well be the reason the valve leaks.

If it's the failure everyone else gets then it fills with water; the system pressure rises sharply, because there is nowhere for the water to expand to; water leaks out; then when the temperature drops you see the low pressure and top it up...

Fix the EV first.

Andy (smiles at header tank)

Reply to
Andy Champ

Thanks for the reply, Andy.

Can you expand that a bit ?

The Domestic Hot Water expansion valve does indeed let water by the diaphragm, but how does this interfere with the central heating water system which is sealed ?

David

Reply to
David

It doesn't - but your symptoms sound as if there may also be a problem with the CH expansion vessel. If that has lost some or all of its air, there will be a reduced (or none at all) expansion capacity - causing over pressure, and operation of the PRV, when the system heats up - and a subsequent loss of pressure when it cools.

Reply to
Roger Mills

There, easy ;-)

Reply to
John Rumm

I assume this is in the loft. If so you can always use unistrut to take the boiler outwards. Look at an Intergas. Super reliable with only 4 moving parts. It can be fitted with a normal F&E tank as well to eliminate the pressure vessel if needed.

Reply to
Doctor Drivel

No, no, it's the water that expands!

Send three and fourpence...

I'm only relaying what others have said, and I'm not entirely clear on what your system is like. But every time this has come up that's the first place to look. Some kind of tank thing, perhaps a foot across, with a tyre valve on the top? It should have an air bubble in it, separated from the water by a diaphragm. The diaphragms fail, and the valves leak, so no air bubble and thus no expansion space.

The valve side of the diaphragm should be dry.

Just be aware I've only learned about these things because as the sandwiched middle I've got grannys and kids systems to keep an eye on.

A photo might help.

Andy

Reply to
Andy Champ

Never heard that before, what does that mean ?

OK, thanks.

David

Reply to
David

He was going to a dance:-)

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Atkinson used similar in Blackadder Goes Forth.

Reply to
ARWadsworth

Thanks for responding Adam,

David

Reply to
David

A 12 months maintenance contract with Potterton costs £299 including parts. Get all the knackered parts replaced and the following year switch to a cheaper maintenance contract.

Reply to
Martin

Thanks to all whom responded.

Put a new pressure release valve in, and introduced some air into the nearest rad to the boiler to act as a makeshift expansion vessel.

The old one had a very loose red knob at the end (fnaarr).

Before, when system was cold, if the CH system pressure was upped to

0.75 bar or more, and then the CH isolating valves closed, the pressure gauge raplidly dropped but always stopped falling around 0.5 bar.

Now it can hold 2 bar no problem.

That'll do for now till I decide whether to replace or not.

Hoping that flexible flues are available, or making one have an offset maybe.

David

Reply to
David

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