Vokera Syntesi Losing Pressure

[adouglasmathie]

Hi,

We have a Vokera Syntesi 25 combi condensing gas boiler.

The boiler was fitted four years ago: it was moved 2.5 years ago when we built an extension.

The hot water works fine.

The heating generally work fine. However, if we have the heating on then as/after the system cools down the system loses a lot of pressure. Typically we have to top it up twice a day.

The obvious answer is that there is a leak in the central heating pipes. However, before we start rippng up floors (including an expensivenew Karndean floor) I would like to make sure: i) its not the boiler and/or ii) explore other options (Radweld for central heating?).

A couple of plumbers have just assumed its a leak - but they didn't inspire a lot of confidence.

Using Google I found two interesting posts.
One mentioned a bleader valve or similar on the pump.
The other mentioned a possible leak in the expansion tank.

Any suggestions to help diagnose or fix the problems would be gratefully received.



Yours

Douglas

 

[muggles]

I would say almost certainly a blown expansion vessel. Fill your system up again to 1bar when cold, then fire it up and see what the pressure is when it gets hot, if it's risen quite a lot then it's the EV and you'll need a new one, unless of course the present one has lost pressure. See if you can find the schrader valve on it and stick a tyre pressure gauge on there with the system filled. You'll get wet if the EV's blown btw.

 

[nickso]

or the heat exchanger is leaking.

its common for them to need topping up a lot and they generally leak more when they are on.

check the vessel first but if its not that i reckon you need a new heatex, easily spotted by the brown stains on the insulation boards below it.

 

[adouglasmathie]

I should also mention that sometimes, but not always, there is a drip of water from the boiler.

 

[Sloop]

Automatic air vent could be leaking, expansion vessel probally lost its charge. check for water coming out of dishcharge pipe outside, you can easy check to see if system as a leak,fill boiler to 1.5bar then turn heating valves off under boiler left hand side 13mm spanner,leave for an hour or two,then open them if theres a drop on pressure gauge system as a leak.

 

[malkie]

It may be dripping inside the boiler and when the flames are on they eveporate the water so its a long shot but it does happen and why not try some internal leak sealer worth a dry before anything drastic

 

[adouglasmathie]

OK thanks for the info / Suggestions.

Some follow up questions.

Muggles - If I put the Pressure guage on the valve what would indicate the expansion vessel is broken, and what would indicate it is OK?

Sloopster - I understand pressuring the boiler and then closing the pipes to/from the radiators. After that I am a bit confused. Do I fire up the heating for two hours? If I then open up the valves again and the pressure drops does that indicate a problem with the boiler or the radiators? Also the system even when pressurised to say 1.5 Bar does not loose pressure unless and until the heating goes on.

Malkie (are you from Glasgow) - What do you mean by internal leak sealer? Is that like Radweld for plumbing?

 

[muggles]

If it's OK then you'll either get a pressure reading, or more likely a reading of zero. If it's broken then you'll get water coming out at the pressure of the system, hence getting wet. You could push in the pin on the valve initially to test rather than putting the gauge on, but do this when the system's cold otherwise you risk scalding yourself if the EV is broken.

If it's broken you'll get a constant stream of water - if it hisses and sputters this may just be clearing condensation rather than indicating a break.

I wouldn't use leak sealer, it can cause you more problems than it solves - for example it can seal up your pressure relief valve if that starts letting by a bit, causing a dangerous situation in the process. It won't solve the problem anyway, it'll just hide it

 

[nickso]

I wouldn't use leak sealer, it can cause you more problems than it solves - for example it can seal up your pressure relief valve if that starts letting by a bit, causing a dangerous situation in the process. It won't solve the problem anyway, it'll just hide it

i wouldnt use leak sealer if its the h/e at fault anyway, it will only halt the problem for a few weeks before its back even worse than before.