vokera linea expansion vessel

[joe plumber]

ok got called to a boiler last night (vokera linea 24 non condensing) as itkept losing presure over a 24 hour period, nice and easy i thought, most likely to be the PRV!

however once i got to the boiler and switched the central heating on the pressure gauge climbed steadily to 3bar!! and the obv the prv let by. the pressure would then drop down again only after i switched the boiler off (pump not running)

also when running dhw the pressure drops and even with the gauge reading 0 the boiler still fires.

anyone experienced anything like this before. tech said to check the expansion vessel which seems to make sense

any help would be greatly appreciated

 

[Billy Bob Bob]

it is the expansion vessel but check filling loop is not letting by if the prv has opened always a reason for it if replacing ev always change the prv as well

 

[gasmarc]

agree with Gas Man , but the boiler should not fire when the gauge is at zero ,i have had this before and still have not heard back from the customer yet

 

[joe plumber]

nice one. i disconnected the filling loop plus the pressure would only increase when the CH was running. i know you can re inflate vessels?? is this worth bothering with? surely if its deflated in the first place must mean its leaking

 

[gasmarc]

you have to have a sealed system that does not ,leak or drip from PRV and works correctly showing the correct pressure

 

[Nas]

Check the pipe going to the expansion vessel for a blockage (touch it and check its warm). If the pipe is cold then it could be blocked and no water could be entering the expansion vessel hence the increase in pressure.

 

[gasmarc]

spot on Nas that has happened on ones with the braided hose

 

[Billy Bob Bob]

did chaffs also have that problem and the copy BAXI genesis?

 

[SPC]

surely the first port of call is too isolate the boiler from the rest of the system, drain the water off and check the pressure in the expansion vessel is as per manufactorers instructions, if not adjust as necessary. also a handy tip i got told if a PRV is leaking / letting by try opening the filling loop and PRV at the same time incase it has some debris in the PRV seating.

 

[oldplumber]

if boiler fires when pressure gauge at 0 then the feed to pressure sensor is probably blocked and remains pressurised allowing boiler to fire. expn vessel may have lost pressure through shraeder valve which can happen but more likely to have failed. prvs normally need changing as leaks cause the mating surfaces to furrow and constantly leak thereafter. If its a swine to get at the expn vessels, t in another one off the return flow, screwfix ones work out a lot cheaper than the manufacturers expn vessels, and if they ever fail again its a doddle to swap.

 

[Billy Bob Bob]

while your right on that one old plumber there could be another reason why it would fire when the pressures on 0,if it has no LWP switch but has a pump pressure switch it will go very low before the high limit stat kicks in think of the set up in a baxi 105,the weak point being the pump can easily fail

 

[joe plumber]

hey, right problem solved the flex from the pump manifold to the expansion vessel was completely blocked, luckily i thought to check it before putting the new vessel in

thanks guys

 

[Nas]

hey, right problem solved the flex from the pump manifold to the expansion vessel was completely blocked, luckily i thought to check it before putting the new vessel in
thanks guys

Just as I said. Must be a common problem with the flex hoses. Glad you got it sorted