Condensing combi boiler losing pressure (Saunier Duvall Semia Condens F24E)

Francis63

I have an issue with a Saunier Duvall F24E condensing combi losing pressure. It has gone from needing to be topped up every few weeks, to now every day. I have tightened the valves on the radiators and can't see any visible leaks outside of the boiler or on radiator joints etc.

I have had an engineer around but when he arrived he told me he didn't work on that make even thoughI had told him the make and model in advance!. He made no effort to check for a leak (I didn't tell him I'd tightened the valves already) but stood there with his arms folded and tried to sell me a new boiler. He walked away with his call-out fee having made no checks whatsoever - not even a pretence of care.

I have read that I could possibly attempt to re-pressurise the expansion vessel myself using a bicycle pump.

My questions are:-
a) Is this the correct valve? see photo above (this is looking down from above the boiler - just under the ceiling so not much space to work)
b) Can I do harm? e.g. if I over-pump it?
c) Are all valves the same size? As per any bicycle pump?
d) What precautions should I take? Aside from turning the electrics off?
e) How likely is this to fix anything?

Failing this can anyone recommend a proper heating engineer in the Twickenham/Richmond area that can deal with a Saunier Duvall boiler? (The cowboy I had said no-one will work on them!)

I would be so grateful for any advice .

Ganga

Can you not contact the manufacturers and ask if they have a local installer/ engineer ?

Bendy_House

Hi Francis.

First, get your money back for that call-out charge. He has no excuse - you told him the make of boiler in advance. Informing him you'll report him to any organisation he's tied to, coupled with a frank and honest review of Google should he not do 'the right thing' might help.

Anyhoo, before you start doing stuff to your boiler, you should try and figure out what's wrong with it...

For instance, the amount of topping-up you've had to do, especially recently, discounts it being a leaking radiator valve. Why? Because your floor would be obviously wet - you are probably talking about a cupful of water each time the boiler drops to zero? Possibly more. Ie, obvious.

A discharged or faulty EV is certainly a possibility, but that shows up in other ways that don't require you to wield a tyre pump.

First is the system pressure reading. On most systems you'd have this at around 1bar or slightly above. When the system water then heats up - when your rads are fired up - this reading should not move much, although a small amount is fine. Eg, if it went up to, ooh, around 1.5bar, I'd be perfectly ok with that. (Some boilers are normal going even above 2 bar, but for most that would be not a healthy sign.)

So, repressure to 1 bar, turn on your CH, and observe over the next 30, 40 minutes until your rads are piping. Please report back.

The second check is to rubber-band a plastic bag over the end of the 15mm copper discharge pipe outside your house - it should either be pointing down at the ground, or else curved back to point at the house wall. Monitor that for water - there shouldn't be any.

(We'll introduce you to the mysteries of EV recharging if it's likely to be the cause.)

NSG666

Francis63 said:

a) Is this the correct valve? see photo above (this is looking down from above the boiler - just under the ceiling so not much space to work)
Yes
b) Can I do harm? e.g. if I over-pump it?
Yes, the expansion vessel should be charged to 0.5bar - if you have a tyre pressure gauge use it to check the current reading, if it's 0.5bar then it's correct.
c) Are all valves the same size? As per any bicycle pump?
Yes - Schrader valve (car tyre type)
d) What precautions should I take? Aside from turning the electrics off?
Don't burn yourself or fall off the ladder
e) How likely is this to fix anything?
Depends on existing charge pressure

If you need to pressurise the expansion vessel, the pressure needs taking out of the CH circuit both before and during 'pumping up' as you cannot compress water. Come back if you need to do it and Bendy will give more detail.

Bendy_House

NSG666 said:

Francis63 said:

a) Is this the correct valve? see photo above (this is looking down from above the boiler - just under the ceiling so not much space to work)
Yes
b) Can I do harm? e.g. if I over-pump it?
Yes, the expansion vessel should be charged to 0.5bar - if you have a tyre pressure gauge use it to check the current reading, if it's 0.5bar then it's correct.
c) Are all valves the same size? As per any bicycle pump?
Yes - Schrader valve (car tyre type)
d) What precautions should I take? Aside from turning the electrics off?
Don't burn yourself or fall off the ladder
e) How likely is this to fix anything?
Depends on existing charge pressure

If you need to pressurise the expansion vessel, the pressure needs taking out of the CH circuit both before and during 'pumping up' as you cannot compress water. Come back if you need to do it and Bendy will give more detail.

It's simpler just to release the system pressure via a rad bleed screw, and to keep it open during recharging. But first Francis has some tests to do :-)

Francis63

Thank you all. 

Unfortunately, the system pressure reading does go up when the rads are fired up  And also the ouside pipe has a slow drip...about 2 drips a minute.     What does it mean?

BUFF

probably means that your expansion vessel needs either recharged (pumped up) or replaced (diaphragm gone).

Bendy_House

That means your EV is faulty or needs a recharge. With luck, it'll just be the latter.

Ok, boiler FULLY off at it's power switch and system cool (doesn't have to be stone cold).

First test - unscrew the Schrader valve cap, and press the wee pin as you would do on a car tyre to release air. Does compressed air come out? Does any water come out?!

If water comes out, then you can pretty safely conclude your EV is kaput. You either get it replaced - if you can find one - or else have a remote EV fitted elsewhere - it gets plumbed in to the 'return' pipe from your rads. So, stop all tests now, and either source a boiler EV or ID a location for a remote one (they are big and red and ugly...)

If air only comes out, either lots or little, then take a pressure gauge reading of it. Note down what it says.

Then get ready to recharge:

Find your highest rad, and get an old towel and container - and a helper! Bleed the rad via the screw until no more water comes out - your system is now depressurised. Leave the bleed screw open, and have someone there to catch subsequent water.

Now get your pump - either bike or car type (if you use an electric one, then run it for very short 'pulses' in case you over-pressurise). On that point, with a manual bike or car pump, it'll likely take a few minutes to fully recharge the EV, so you ain't going to overdo it unless you are daft; ie you ain't going to 'blow' it with one stroke!

Start to pump away, and take regular readings - you want to get it up to ~1 bar.

The person at the rad will be collecting squirts of water as you do this.

When you have the EV up to 1bar or close, then shut off the rad bleed screw, and replace the safety cap on the EV. Repressurise your system to 1bar.

Fire up, get the CH going, and see what the pressure reading does.

Keep an eye on the discharge pipe too - there's sadly a very good chance it'll keep on leaking; they tend to do that once opened. It may need replacing.

Francis63

Wow, thanks so much Bendy, I'll give this a go tomorrow! Great advice.

Thanks all. 

Will let you know how I get on. Fingers crossed.

Francis63

I love you guys!

It worked and has held out. Took literally 10 minutes on my own.

Two weeks later and its still going, with no loss of pressure and the outside pipe appears to be no longer dripping (though I have been living elsewhere at the moment so the heating has only been on the timer and no hot water used).

After weeks of worry I am elated and can't thank you enough! 

Bendy_House

Blimey! I'm impressed! I don't actually expect anyone to carry this out, so write in hope rather than expectation :-)

If the drips from the discharge pipe have also stopped, then you are lucky as they very often carry on leaking a bit. You can quite safely rubber-band a clear poly bag over the end to monitor it properly.

If your system has needed lots of topping up over a significant time, then it's likely the inhibitor content will be low, so you may wish to top this up - you can get 'injections' via bleed screws.

What's the medium/long term plan for your boiler?