Baxi 105E Pressure Loss.

[trixsales]

I have a baxi 105e boiler installed approx 2 years ago and since its installation I have had no end of problems attempting to resolve its gradual low pressure problem - as time has progressed the problem has slowly but surely become worse to the point where if I switch the boiler off over night i'm presented with a 0 pressure gauge reading in the morning. If I isolate the CH side of the boiler when the pressure seems to be normal at around 2 Bar and switch over to HW only and leave overnight, the pressure remains stable but as soon as I open both CH stop valves [return and flow] the pressure immiedietly drops to 0 bar. Rightly or wrongly I assumed that there was a leak on my CH system but having carried out a full inspection of the pipework/joints etc this doesn't seem to be the case. I even tried checking at high temp / switching off and also checking whilst cold to see if expansion and contraction of the pipework had any affect - all to no avail. In my view the water must be going somewhere but there are no obvious signs eg damp patches on the ceilings or walls. In operation if I pressurize via the loop to 1Bar with the CH on the pressure rises to approx 2.5Bar before dropping back to approx 1.5 - 2 Bar which according to the Baxi literature is OK. When the CH is turned off and the water cooled down the pressure drops slowly down to '0' once again. I have noticed a very small amount of water [a few drops] being emitted via the PRV while at the higher operating pressure but not enough to warrant the amount of water that I need to re-pressurize the system. I would appreciate any advice or recommendations. [Hair loss suffering]

 

[nickso]

"having carried out a full inspection of the pipework/joints etc"

everything checked under every floor?

 

[trixsales]

Tnks for a fast reply. Yes all the joints underneath the floor boards have been checked - the floor boards are currently up. Hence the urgency in trying to resolve the problem.

 

[nickso]

so just to be absolutely clear....if you pressurise the system up to say 1.5 bar and isolate the boiler there is no pressure loss over a given time? but if you were to leave the boiler valves open you have pressure loss?

it will most likely leak when cold. if it is as described above then it looks like a leak on the system and you wont have to lose a lot of water volume to lose that pressure. i dont mean to make you sound stupid but the amount of times a customer says he has checked the pipework and i find a leak within 5 minutes would make me a rich man. sometimes the leaks may not be visible and you have to physically touch every pipe/joint/valve to feel for water.

the prv shouldnt leak at all unless it is around 2.5-3.5 bar.

 

[baxpoti]

f I isolate the CH side of the boiler when the pressure seems to be normal at around 2 Bar and switch over to HW only and leave overnight, the pressure remains stable but as soon as I open both CH stop valves [return and flow] the pressure immiedietly drops to 0 bar. Rightly or wrongly I assumed that there was a leak on my CH system

You have proved that there is a leak on the system.
All you have to do now is find it!

 

[trixsales]

nickso
Your understanding is correct - and the conclusion that I arrived at was that there was a leak somewhere - As stated the floor boards have been raised and the joints where checked by the finger test and also by wrapping toilet tissue around each in an attempt to detect leaks. There is no indication of leaks around or inside the boiler.

 

[nickso]

just re-read your original post.

you say you pressurise it to one bar and it will rise to 2.5 when the heating is on?
i would check the expansion vessel pressure and also check/change the prv as that kind of pressure increase isnt brilliant.

 

[Vic Spanner]

Are pipes under floorboards lagged, If so remove all lagging and check every inch
Maybe you might have a external draincock outside letting bye.??May be covered by a bush or plants

 

[trixsales]

nickso -
The pressure of 1 rising to 2.5 bar is according to baxi within the correct operating range but as you indicate it might be worth my while having the expansion vessel checked - but would this explain where the daily additional water added to the system is lost ?
poxi -
The pipes are not lagged - and I have confirmed that there are no external draincocks.

 

[nickso]

2.5 bar is not normal no matter what the instructions say.

if its set to 1bar then i would expect minmal rise if the expansion vessel is big enough for the size of system and is operating correctly.

the drips out of the prv is where your water is going.

 

[trixsales]

Thank's to all members for your contributions especially nickso - I have already ordered a new PRV and will have my expansion vessel checked in the hope that both measures will resolve the problem. I will let you know the outcome.

 

[trixsales]

The problem has now been resolved - it turned out that there was NO air pressure in the Expansion Vessel and this allowed the water to expand increasing the pressure sufficiently to activate the PRV and allow dripping, sufficient when water had cooled to reduce the boiler pressure. The problem was rectified by closing the Flow and Return valves on the boiler - draining the boiler via the drain tap - check the air pressure in the expansion vessel - using a car foot pump insert a pressure of approx 10psi - open the Flow and Return valves and re-pressurize the system to 0.5 - 1 bar - RESULTS. [ When cold pressure indicating 0.7 Bar - when CH running pressure indicates 1.4Bar - CH switched off pressure returns to 0.7Bar.

 

[nickso]

better but still not perfect. did you leave the drain valve open when you repressurised the expansion vessel?

vessel should be 1 bar....cant remember if 10 psi is one bar

water pressure should be one bar cold.

i wouldnt advise the use of the boiler flow and return valves either...they will start to leak.

 

[trixsales]

nickso
Yes I did leave the drain valve open whilst repressurising the expansion vessel - The vessel was pumped up to just over 10 psi where 1 Bar = 14psi and the water pressure was set between 0.7 Bar when cold. There seems to be conflicting information on the forum with regards to pressures - some say that the expansion vessel should be 0.5 Bar while others say 1Bar and the same applies to the cold water pressure. I have gone for the middle ground.

 

[nickso]

fair enough....0.7 bar is a little low for my liking but as long as you are aware of it being at that level then it may be ok.

everyone has their opinions on pressures but 1 bar for each has never done me harm