Help - Boiler pressure problem

[Ipsman]

Ok Ok - I know this subject has been covered a bit in the past - I've looked through those posts and they have helped greatly but just wanted to check out my own circumstances.

I have an Ideal Condensing boiler and the pressure seems to drop quite quickly and we keep having to top it up far more frequently than I would like - like at least once a day.

I have checked the expansion vessel - and air comes out so I know its not completely knackered. I did find a very small leak at the boiler and also did a snap turn of the PRV to hopefully clear out any rubbish.

If I start it cold at 1.25 bar - it now does not seem to lose pressure - but on switch on it seems to rise to nearly 3 bar - i didn't actually let it get there before i switched it off and it has returned to 1.25 bar - so I think finding the very small leak seems to have helped - although I suspect if I had let it go on the PRV would have operated and water would have been expelled - meaning the pressure would have returned to lower than 1.25bar - so here is the big question....

Does this suggest the expansion vessel needs charged up ? - someone before described it as a ballon in a tin can - Has the ballon got a little small meaning the expansion is limited - meaning the pressure rises fast towards 3bar - meaning I'd start losing water.

Also - Since we have now been topping up like this for the last 2-3 months - Should i add inhibitor to the systems to help prevent corrosion ? and if so how much ? - Or Can I add as much as I like and it won't do much damagae - only help ?

Many thanks for all the help on the forum that has helped me so far - if anyone could answer the above questions I could hopefully bring this saga to an end.

Thanks...
Maurice

 

[DP]

So you have been cheking if there is air in the pressure vessel by depressing the valve. Air comes out. Have you considered for a tiny moment why the air is there in the first place?

Fresh water into the boiler for nearly three months. Fresh water has air in it. Air is 20% oxygen. Radiators are made of metal. Oxygen and metal do not like each other. I bet the runoff from the vent has marked the wall with brown rust.

Forget the inhibitor. You system will already have plenty rust in it. I fail to see what inhibitor will do to your system now that 3 months of oxygen has played havoc on.

 

[corgiman]

by checking the expansion vessel you have comprimised it, by pressing the inlet you have let air out and it is now no longer allowing for expansion.

What tells me this is the fact that it is rising to 3 bar whilst operating, the pressure relief valve will open to relief the pressure. and once the water in the boiler cools down you will find that the pressure has been reduced. the water expands when it is heating but you dont get anymore water volume hence its empty when cold.

Contact Idea boilers and get an approved contractor out to re charge your expansion vessel and you should be fine...

 

[Ipsman]

I appreciate your comments guys - I'm sure I have made a few mistakes but I suppose I am where I am now and can only try to improve the situation.

I may have over estimated the situation with regard to topping up - I don't have any rust marks yet.

Also previous posts have suggested checking the expansion vessel by checking for air and I didn't let much out at all - just checked to see if water came out really.

Anyway I've just added a bit of air to the expansion vessell and it seems to have stopped it rising quite well - so fingers crossed. Before you ask I did do this with a gauge attached and with the system open (i.e at 0 on the boiler pressure gauge).

Hopefully I haven't made it worse - but time will tell.

So is it worth adding inhibitor ? or is that a complete waste of time now as previously suggested. By the way the system already has inhibitor in it - I suppose I was just thinking about replacing any that I had lost as a result of the topping up.

Thanks..
Maurice

 

[corgiman]

spot on. nice one

DP of course their is air in the xpansion vessel, its supposed to be, it has a membran seperating the air from the water, so as the water expands its compresses the air

no you have not made it worse you have actually sorted the problem

does anyone else know what the air pressure should be on a icos or isar i think its 3/4 bar but am not sure

 

[Ipsman]

Guys,

I thought I had solved this problem - but sadly woke up this morning with the pressure down at 0 again. I had put a plastic bag round the outlet pipe from the PRV and lo and behold it was full of water.

Now what I don't understand is that it is generally bone dry and the CH etc works fine - does not exceed 1.5 bar or so but the problem seems to occur when the CH and hot water goes off. It then very quickly goes down to 0 almost like the expansion vessel is kicking in and expelling the water out the PRV - which I'm beginning to think may be faulty and will have to be replaced.

Anyone agree ?. I suppose the good news is that I don't think I have a leak now I've proved water is coming out the PRV outlet.

 

[meldrew's_mate]

Ipsman,

Open the PRV and keep it open while you top-up the expansion vessel to 1.2 bar (between 1 and 1.5). Water will be expelled from the PRV while you do this.

Snap shut the PRV and refill to 1 bar cold*.
*Assuming a standard 2 storey house.
Heat up the system and allow to cool, problem should be sorted.

 

[Ipsman]

Thanks Meldrew's mate - I'm not sure what I did different but as a result of your instuctions its looking a bit more promising this time.

On heat up it started at 1 bar - dipped slightly and then rose to just under 1.5 bar. It's now in the cooling down phase. I checked the outlet from the PRV and it was dripping a bit - but that might just be as a result of the previous purge when filling the expansion vessel. I have put a plastic bag over it so I should be able to tell soon. It's now at 1.25 bar and has cooled to 61 degrees - so hopefully it will stay at a reasonable pressure now.

I'll have to take back the PRV that I've just bought !!! Doh !

So is worth putting inhibitor in do you think ?

Thanks again - I'll let you know how it progresses

 

[ChrisR]

NB once a prv has passed dirty water it will probably leak forever.
How big is your house? It's possible that you need a pressue vessel a bit bigger than the one which comes with the boiler. (You could add an extra one anywhere)

 

[Ipsman]

ChrisR - Yep - I'm beginning to come to the conclusion that the PRV is leaking as pressure is still dropping - now slightly below 1 bar - but its an ongoing situation.

I'll probaby wait till I get back from football and change it if that's the case. I'll leave the bag in place to check.

It's a fairly big house 4-5 bedrooms but we haven't had any problems so far and have lived in here for nearly 5 years.

You also have more confidence in my abilities than I have - add another your joking - I'm dreading having the drain the thing down to change this PRV - the manual says the cap on the air vent MUST be loose at all times - I thought it always was anyway and I have no idea why it shows a picture of the pump when explaining filling!!

Anyhow - it looks reasonably OK to do - but I'll probably find out I'm missing some vital tool just after I start

 

[Ipsman]

Just an update to all those folks who have helped.

I've now changed the PRV (I took the plunge and did it before football) and it looks like it has worked. No more leak it would appear.

Just need Ipswich to win now to make it a really great day.

Thanks to all...