Vokera 24, slow pressure loss problem. help appreciated.

[gizmoy2k]

Hi there
Recently moved into a house which has said boiler. unfortunatly i have no manuals so please go slow with any instructions.

Basically system has been fine for 2 months, used heating on friday night, woke up saturday to no hot water. Pressure reading on front was zero( i dont know what it was previously as i had no reason to check).

Anyway refilled system to 1.5bar using filling loop, boiler refired no probs. This morning my partner was up first to run a bath, i had a quick look at the gauge and it was bouncing around between 0.5 and 1 bar while bath was filling. Refilled to 1.5 bar, hot water and heating continued as normal. After use of heating tonight pressure now sits at about 1 bar.

I have had a read around these forums and a common theroy is the PRV is faulty.
Can anyone provide instructions on how to prove this and please remember i have to manual so im not sure on the location of the various parts.
Thanks

 

[Slugbabydotcom]

Hi there
Recently moved into a house which has said boiler. unfortunatly i have no manuals so please go slow with any instructions.

Ok I'll type slower


Water leaking from PRV is indicated by water passing through the pressure relief pipe. Usually this leads outside directly behind the boiler.

Doesn't always mean there's a problem with the PRV though! .... It could be the pressure vessel thats gone causing the excess pressure to be blown out at the PRV. Plus one or two other things, but thats the most likely.

 

[gizmoy2k]

hi there, I am pretty sure im not getting over pressure, at least enough to set off the prv. no evidence of water in the pipe going outside. Home tonight and pressure is sitting at just above 0.5bar, boiler does seem to be working ok and i may put the heating on shortly. I know 0.5 bar is the minimum limit for operation but i would be happy if it would hold a little more, Any other suggestions?

I hope i can rule out a leak because the onlytime i have seen it at 0bar was when original fault developed. if i had a total leak i doubt i would hold 0.5bar for 24hrs or so.

Thanks Again

 

[Slugbabydotcom]

If there is no water coming from the prv pipe outside then it can only be that there is a leak on the system inside.
Re-pressurise to 1.5 bar then switch the boiler on. Watch that prv pipe and note the pressure guage readings till the system is fully warm.
Post back with the info

 

[gizmoy2k]

Hi there followed instructions, pressure rose slightly to about 1.7bar and remained there for the duration i had the heating on, about 2-3 hrs. Switched off again and left overnight, pressure was down to about 0.5bar this morning, Defo no water coming from prv pipe, it has been dry here for the last 2 day and no water in sight. A friend has contacted his plumber mate and he suggested it may be the pressure vessel in the boiler which is the problem.

Im off to search for this now because im sure i read about it somewhere on theses forms too.

Would be great if someone could confirm that this could be the problem,

Thanks Again
Andrew

 

[DarkInferno]

It ain't your pressure vessel.

If it were the pressure would go up far greater then 0.2.. and the PRV would leak.

What you have there is technically known as a leak somewhere.

 

[gizmoy2k]

But why would pressure rise and stay constant with the heating on if i had a leak in a sealed system, I would have thought i would have lost pressure quickly if i had a leak and turned the heating on.
ta

 

[gizmoy2k]

Have just put heating on again now and pressure has risen from 0.75 to 1bar and is sitting there steadily.
Thanks

 

[chrishutt]

Check that automatic air vent in boiler isn't leaking. Common problem. Also check for leaks around system, particularly on rad valves.

 

[gizmoy2k]

Hi there, i dont have a manual so a little help locating the automatic air vent would be great, thanks again

 

[DarkInferno]

Quick runthrough of what happens to the pressure of a heating system.

(Pressures used are just examples and will vary)

No Problems:

• Cold (1 Bar)
  
  Turn the Boiler on, Depending on pump location pressure may drop or rise slightly (1.2 Bar)
  
  Boiler Fires, hot water expands increasing the pressure of the system, Expansion vessal allows water in at the higher pressures as it expands (1.5 Bar)
  
  Boiler Runs, water expands further but as it does it is taken in by the expansion vessal for the most part, keeping pressure stable(ish) (1.5 Bar)
  
  Boiler Turns off, Pump pressure dropped (or regained) (1.3 Bar)
  
  System Cools, Pressure is lost as the water contracts water in the expansion vessel is now put back into the system as the system is at a lower pressure (1 Bar)

Faulty Expansion Vessel:

• Cold (1 Bar)
  
  Turn the Boiler on, Depending on pump location pressure may drop or rise slightly (1.2 Bar)
  
  Boiler Fires, hot water expands increasing the pressure of the system, Expansion vessal is already full of water (2 Bar)
  
  Boiler Runs, water expands further, water has nowhere to go, so the pressure increases (>3 Bar) Water is expelled through the PRV to stop the pressure building to unsafe levels, (2 Bar)
  
  Boiler Turns off, Pump pressure dropped (or regained) (1.8 Bar)
  
  System Cools, Pressure is lost as the water contracts, nothing to replace lost water with. (0.2 Bar)

Leak:

• Cold (1 Bar)
  
  Turn the Boiler on, Depending on pump location pressure may drop or rise slightly - small leak (1.1 Bar)
  
  Boiler Fires, hot water expands increasing the pressure of the system, Expansion vessal allows water in at the higher pressures as it expands. Leak either increases or decrease due to temp/pressure, but the water volume is still higher then it was at cold (1.5 Bar)
  
  Boiler Runs, water expands further but as it does it is taken in by the expansion vessal for the most part, keeping pressure stable(ish), any small loss of water is taken up by the Expansion vessel (1.5 Bar)
  
  Boiler Turns off, Pump pressure dropped (or regained) (1.3 Bar)
  
  System Cools, Pressure is lost as the water contracts water in the expansion vessel is now put back into the system as the system is at a lower pressure, but the system has no way of regaining the water lost to the leak (0.5 Bar)
  
  System continues to leak.... (0 Bar)

 

[DarkInferno]

Tha auto air bleed is a fairly small cylindrical bottle almost always in either brass or black plastic. usually on the top is a car tyre valvelooking opening, which lets air out of the system, unless its faulty in which case it also lets water out.

I can't remember the boiler layout but its usually either on the back of the pump, inside the case above the heat exchanger, or poking out of the top of the case.

If its leaking, drain down (if required, lol) and renew.

 

[annemarie]

hi.. this is very similar to my problem with a glow-wrm boiler....will look out for your replies.

Anne marie

 

[Slugbabydotcom]

hi.. this is very similar to my problem with a glow-wrm boiler....will look out for your replies.

Anne marie

Darkinferno has it mostly sewn up when he said

What you have there is technically known as a leak somewhere.

and followed it up with an essay.

Only thing I would like to add is that the source of leaks such as this tend to be from below the ground floor where wooden floors exist, and proliferate profusely under laminate or tiled [over wood] floors where people cant get access without ripping their expensive floor coverings to bits.

Deep down most of them knew there was a leak there all along yet they carefully look down every other alleyway [and rightly so] before accepting the painful truth

 

[annemarie]

Oh dear. And what happens then? New pipes everywhere? Lots of money to be spent?

AM