Pressure loss (Halsted Ace High)

iwishiwasaplumber · 30 Nov 2008

Hi -

I am experiencing pressure loss in my Halsted Ace High Boiler. I have checked my radiators; 95% of the pipe work (the rest is under concrete!) and I have also have put leak sealer into the heating system with no joy.

This has led me to believe that I am losing pressure in my boiler; having read lots of threads here I have isolated the boiler and put the pressure up to about 2bar - over night I'll lose half a bar of pressure in the boiler. I've had the boiler cover off and can't see any leaks. I have also checked the pressure release valve and this isn't leaking either. In truth I am running out of ideas - is there anything else that could cause this loss of pressure without showing?

I have also re-set the expansion chamber (10psi) - and have been told by Halsted that if this was losing air pressure I'd see my pressure go up not down. Is that case?

Any advice would be great fully appreciated.
Thank you.

MANDATE · 30 Nov 2008

Can't understand why you set the pressure to 2 bar.
When cold it should be about 1 to 1.5 bar and when it gets hot it goes up by about 1 bar.
If you set to 2 bar there is every possabilty the pressure increases to the 3.5 bar needed to open the pressure relief valve.
I had same problem on same boiler and I secured a plastic bag on the PRV outlet pipe and sure enough there was a cup full of water there the following morning.
Also it seems once opened these PRVs don't always seal properly and mine does still have a leak so the pressure does drop slightly.
What you was told by Halstead does not make sense. If you lose air from the air side of the expansion vessel, water will take its place so its volume will a little more and its pressure a little less. Just like bleeding a radiator, you let out the air and your pressure gauge drops.
The only other thing besides the PRV is the AAV (Automatic Air Valve).
I gather this has some type of float within it, which allows air to escape but not water, but I would think if this was leaking you would notice it.

iwishiwasaplumber · 30 Nov 2008

Thanks Mandate. I up the pressure in the boiler to 2bar when I isolate the boiler; Halsted said i'd force a leak far more easily. I have changed the pressure release valve and have a bag on the back of that pipe to check for leaks; again no leaks.

Could it be that the expansion chamber is losing pressure - that would cause a loss pressure from what you are saying.

The automatic air valve is bone dry .... all very strange i know.

Thanks again.

MANDATE · 30 Nov 2008

The vessel is supposed to be pre charged to about 1 bar with no pressure on the water side. This means the whole vessel is air filled.(diaphram biased to one side)
Then when the water is applied and with a pressure of say 1 to 1.5 bar, it will flex the diaphram slightly. This still leaves adequate space for the water to take up when it expands due to the rise in temperture.
If there was say a pin hole in the diaphram, then the air side would fill with water. There would be no space for the water to expand and pressure would increase considerabley. So depress valve to make sure there is no water on the air side.
Also If the expansion vessel valve was leaking then the air would escape and the space took up by water. giving a similar problem.
Perhaps it needs checking daily to see if its lowering, although you could just replace the valve.(Halfords).
Out of interest how did you drain your boiler, In my case all water pipes go up and over and there is no drain cock on boiler,other than the PRV

iwishiwasaplumber · 30 Nov 2008

I have re-filled the expansion vessel to 10psi after being told so by Halsted; then I have re-filled the boiler to 1bar. And it still lose pressure.

I take the water out the boiler by either using the pressure release valve as i have had to replace it or recently I changed the isolation valves and the water came out of there.

Is it worth fitting an external expansion vessel?
Thanks again.

MANDATE · 1 Dec 2008

Can't see any advantage of fitting another expansion vessel,unless you can prove the existing one is faulty. ie It leaks water from the valve when depressed, or it leaks air from the valve
Just one other thing!. I think you can isolate the the flow and return pipes with the valves at the back. So with the boiler/heating off and the valves closed. does pressure still reduce? This should indicate if problem is related to boiler, PRV or expansion vessel. Or the heating pipe work.

Regarding the AAV, is it possible for any leak to be dried up and not obvious?. I believe there is a cap which is supposed to be loose, but won't do any harm to tighten it up while you test to see if it makes any difference.
I can't think of anything else, but do let me know how you go on.

iwishiwasaplumber · 1 Dec 2008

Thnaks Mandate. I'll check the valve and see if it is leaking either water or air; I do recall putting 10psi into it last week (with the boiler water pressure at 0) and it then being 4 or 5psi three or four days later with no water pressure in the boiler - which would suggest that there is a leak - unless the air pressure drops when you drain the boiler?

I've isolated the boiler using the flow and return pipes and it still loses pressure - so I know it is the boiler leaking rather than the pipe work. I think it is time to change the valve...

Thanks for the help again.

MANDATE · 1 Dec 2008

I think the air pressure may drop when you drain the boiler. If there is water pressure on the diaphram and it is released then the 'air' would expand pushing the diaphram as far as possible. If the air expands then it's pressure will reduce. I gather that is why there should be no water pressure when applying the air pressure.
On mine ( well daughters) I removed 10 litres of water and applied 1 bar on the air side ie 15 lbs sq in.

Agile · 1 Dec 2008

Have you checked to see if there is air leaking from the EXV ?

Tony

iwishiwasaplumber · 1 Dec 2008

Hi Tony -

I don't know what a EXV is - and subsequently wouldn't know how to check it is leaking air.
Where would I find it on my boiler?
Thank you.

Agile · 1 Dec 2008

iwishiwasaplumber said:
Is it worth fitting an external EXpansion Vessel?
Thanks again.

iwishiwasaplumber · 1 Dec 2008

I am replacing the valve tonight. I spoke with Halsted earlier who send if the water is leaking in the boiler and I can't see it - and it isn't coming out of the pressure release valve it could be the heat exchange plate? Has anyone ever known that happen?

thanks again.

Agile · 2 Dec 2008

Unless your mains pressure were lower than 1.5 Bar static AND the double check valve had totally failed, then they are talking nonsence.

Thats the trouble with calling manufacturer's helplines You can get very stupid advice.

Tony

iwishiwasaplumber · 2 Dec 2008

They did say there is a one in a million chance that it would be the heat exchanger plate ... but have no other advice.

I appreciate that they are loathed to admit there could be a problem with the boiler, even though it is out of warranty! But I really am running out of ideas - I took the valve out of the expansion vessel last night and cleaned it; that isn't leaking - checked the prv again that isn't leaking yet when I isolate the boiler it drops pressure. It is clear that there is a leak in the boiler; yet no visible signs.

This has led me to believe that could it be air pressure leaking rather than water pressure? Could the automatic air vent be the problem ? Forgive me because I am not a technical person but if that was leaking air pressure then the system would show the pressure going down?

It seems I am running out of things to change or check - should I consider buying a new boiler?

Any more advice would be greatfully appreciated.
thanks again.

Agile · 2 Dec 2008

If air is leaking out of the EXV then the p[ressure will fall.

The AAV is solely for letting trapped air out of the heating water. They can leak too! If you close the cap on the AAV then that will remove that possibility from the equation.

There are a lot of water connections inside the boiler. Any one of them could be leaking. This will only show up if the boiler is left cold and over pressurised for several hours.

Tony

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Pressure loss (Halsted Ace High)

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