Vokera Mynute 20E Losing pressure

[itscoldhere]

Hi,

I have a Vokera Mynute 20e boiler which is tripping daily on low system pressure.

During fault finding I have found no actual leaks on the radiator or hot water circuit which I was expecting to find.

On further investigation (putting a bottle on the PRV outlet) I have found that the safety valve is discharging the contents of the boiler loop gradually.

I am losing about a litre of system water a day which invariably results in the boiler tripping out overnight.

I am happy that this is the problem but it's not particularly practical to be filling the boiler up everyday!

My question is, do you think that this is the root cause of the problem or is there something else amiss?

I find it hard to believe that 1 litre of fluid can drop the system pressure by 1 bar (it normally runs at 1.5 bar when hot but trips at 0.5bar. Is there another hidden problem?

Thanks for any help or guidance...

Mark

 

[mr.nozzle]

sounds like a problem i had with my old boiler. i renewed the safety blow off valve around the top of the boiler and all was fine ( for about a year anyway)

 

[itscoldhere]

I've just taken a look around the forum and noticed that it may be an expansion vessel problem - no precharge.

I know its a sin not to look before posting as well - shame on me.

Anyway, do the experts think it may be the expansion vessel also?

Regards

Mark

 

[MANDATE]

It sounds reasonable to me losing a litre a day.
Remember you cannot compress water, so when you are using the filling loop and increasing the pressure the water is pushing against a diaphragm.
The diaphragm however can move but there is an opposing pressure I believe of compressed air. When there are no leaks the water pressure is maintained, but when there is a leak it depends on the amount of leakage how long it takes to reduce to an unacceptable level.
Just like a slow puncture in a tyre, sometimes it needs pumping up daily or it could be monthly.
Obviously your PRV needs attention. ie Is there any dirt on the valve seating. I don't know if you can remove it for examination and cleaning or whether you can clean it in situ.

 

[ChrisR]

Yes, sounds like it's simply the p r valve leaking. If you twist the top knob on it (usually red) it will make heavy clicking noises - the spring lifting and shutting the valve. You may find it seals a bit better, but it prob needs changing anyway.

 

[itscoldhere]

Well, almost a year has past and finally we see a stain appearing on the kitchen ceiling - A LEAK!

The leak was from a section of 15mm pipework from a radiator which had what looked like a seam microleak. It's taken over a year to finally track this down.

Everything was repaired and the system has been repressurised to 1bar (cold). The problem is that the system pressure still drops over a couple of days. I am suspecting another leak somewhere but what worries me is there are no more visible leaks. I'm worried that the leak is under the ground floor in concrete somewhere.

What are my options now? It would be a massive upheaval trying to find a leak in the concreted floor. Will an internal leak sealer like fernox work?

 

[WilliamCoulter]

HI I HAVE A VOKERA MYNUTE 14E

I keep filling up the pressure to 1 bar every 2 days.
when i turn everything off the pressure holds at 1 bar so i know i have not got any leaks, when i turn on the central heating and the heat builds up the pressure gauge goes from 1 bar to 3 bar thus discharging water to outside house and inturn less water in system, within 2 days have to fill water up to 1 bar.

does anyone know what the problem could be

thanks.

 

[MANDATE]

expansion vessel has lost it's 'air' charge, meaning it's most likely half full with water before you put heating on. Pressure will rise much further than normal operation and will open the pressure relief at 3bar. Or diaphragm in vessel could be rupture and will still result in PRV discharging at 3bar.