Boiler pressure loss

[Keith Melnyk]

Hi I have a 10yr old Alpha cd28c boiler that has given faultless service until last week.No hot water.Engineer diagnosed faulty diverter valve and motor.This was replaced and all was well for a day!Then the boiler would lose pressure over the 24hr period and would not start up until water was added via the loop.Engineer came again and diagnosed leaking Pressure Relief Valve.This was replaced and now boiler will lose all pressure when off within 3hrs.Also to note it looks as though water is still leaking out of PRV external pipe.Any guidance would be much appreciated as I will have to call engineer again and it,s all getting rather expensive.

 

[ianmcd]

sounds like your engineer used the PRV to drain the boiler and the valve didnt reseat properly,replacing the valve should have sorted it, set the pressure at 1.5 Bar cold then put the heating on and check the pressure 20 mins later if it is up near 3 Bar then you have an expansion problem and that is why the PRV is operating, that is why it is there

 

[Keith Melnyk]

Thanks Ian yes when boiler is running it is close to 3 bar.Does this mean expansion tank has an internal leak or that it needs repressurising? Regards Keith

 

[terryplumb]

The EV isn't functioning as it should. Needs Investigation ,may just need to be re charged.

 

[Keith Melnyk]

Thanks for all info guys,will get engineer(hopefully)to invedtigate tomorrow and will report back.

 

[Keith Melnyk]

Well! Now here,s a thing boiler held pressure overnight,fired up this morning no bother.It has a running pressure of 2.2 bar does this sound about right?Also would I be right in assuming that because of this:A)there is no leak in the CH system B) the Epansion Vessel doesn,t leak.The only other factor since the PRV was fitted on Friday is that it didn,t freeze overnight,although this hasn,t been a problem in previous winters.So upshot is I,m holding off calling engineer unless it loses pressure again and if it doesn,t I,ll call him soon to top up inhibitor.

 

[ianmcd]

Get the EV sorted or a good chance you will need another new PRV

 

[Keith Melnyk]

Thanks Ian for prompt reply.I will contact engineer asap.

 

[Keith Melnyk]

Engineer came this morning,drained boiler and checked EV pressure it was just under a 1 bar so all ok.Drained towel rail and put in 1 cartidge of inhibitor.Recharged system and fired up boiler,running at about 2 bar.Can,t see any leaks in boiler or from PRV so hopefully it will hold pressure overnight and fire up in the morning.Thanks for everyones input.One thing I did learn was to surf the 'net for replacement parts i.e Diverter valve £120, on 'net new internal spindle c/w all seals etc £20 new DV motor £80,on 'net £20 new PRV £30,on 'net £7:80.So a lesson learned all round.

 

[Keith Melnyk]

Spoke too soon just checked and there,s water under boiler!!! It was leaking after engineer finished but he traced it to some "valve" that is only open on commisioning so he closed that and it stopped.Cant see now where its coming from as cover is back in place.Oh well have to call him back again!

 

[Keith Melnyk]

Looking at a diagram on line its the automatic air vent,any thoughts?

 

[ianmcd]

if it is the AAV they are very common to leak, not just on your boiler but on ,most they tend to pass

 

[Keith Melnyk]

There was a leak from this and the engineer turned it off,all was ok for a few hours,now its dripping with heating on.Is it a fix for a competent DIYer? as they,re pennies to buy

 

[dilalio]

That's engineering... Replace one thing... Then it's neighbour fails

 

[Keith Melnyk]

Update on this epic saga.AAV didn,t leak a molecule of water overnight but didn,t fire up this morning,recharged system and it fired up.Water leaked straight away,approx quarter cupful,and then stopped.I took front off and checked on top of AAV,water all over it.Dried it off and it,s now been running for 2 hours without leaking.Engineer coming this morning to fit new AAV.What next?