Expansion Vessel

[DustyM]

Got called to a customer today to look at an open vented system that had been converted to sealed a good few years ago. The old guys system has been running at a constant 3bar+ of late, and the PRV is constantly opening as a result. Suspecting that the expansion vessel was the the fault I took my pressure gauge and pump with me in order to test and re-pressurise if required (I had asked him not to switch on the heating or hot water that morning). The expansion vessel is located right next to the boiler and mounted directly to a manifold containing the pressure gauge, PRV and filling loop input. If couldn't find a Schrader valve where I would normally look for one (i.e. the top half of the vessel) and ran my hands all around the exterior of it. There is only a gap of about 15mm between the bottom of the vessel and the floor, and I couldn't see or locate a valve there either. The label on the vessel states it should be charged to 1.5 bar; it's an 18litre capacity vessel with a manufactured stamp showing 1997. I did my Part G a couple of years ago and have never seen an expansion vessel without a Schrader valve - did they at one time come pre-charged and minus a charging valve? If so, how can I best test this? The customer is trusting me on this and says change the vessel if I suspect it is faulty, but I'd rather know that it was faulty before I go ahead and order a new one. Am I being a bit of a muppet with regards to the Schrader valve?:confused5:

 

[Simon F]

was there nothing, not even a cover that needs unwinding from the schrader valve?
vessel may well be pre charged to whatever but what does the boiler manufacturer specify?
and can the boiler even be converted to unvented?
when testing the ex vessel pressure it needs to be isolated from the system anyway

 

[Nostrum]

If a constant 3 bar I would be looking at the filling loop before the vessel.

As above though, sometimes they are under a cap.

 

[SimonG]

Aye filling loops passing by the sound of it.

 

[kay-jay]

Common to find the schrader recessed in a dimple at the top of thwarting vessel. A cap which feels flatish and has a low profile and about 1/12-2 inch diameter needs unwinding round reveal it.

Sent from my GT-I9100 using Tapatalk 2

 

[Simon F]

just noticed this is posted in the solid fuel/oil section.
hope its not solid fuel!!

 

[DustyM]

No, it's an oil fired 'firebird' boiler and despite looking and feeling (unless I can't actually feel a cover under the vessel), there's nothing indicating a hidden valve. Stupid position to mount it anyway if the valve is under a cover on the bottom! The customer has no literature from when the system was converted, so I'll hunt around online for the manufacturer's instructions. The filling loop is were I'd have gone next if I wasn't satisfied with the vessel's pressure.

 

[WHPES]

I would say leaking filling loop. Disconnect the filling loop hose with the valves shut and see if it drips.

Altechnic branded filling loops are pants.

System will of course require inhibitor.

 

[Nostrum]

If the E.V was shot then it would blow off and you'd be left with low pressure when cool, not 3 bar constantly.

 

[DustyM]

Sorry guys - not made it totally clear. When the system is cold it registers a pressure of 1 - 1.5 bar. once switched on the system pressure rapidly increases to 3 bar and only drops once the PRV opens. That's why I suspected the expansion vessel.

 

[WHPES]

3 possibilities -

1, Expansion vessel failed
2, needs pumping up
3, hose and connection between vessel and boiler blocked with debris

 

[DAVE01]

best thing to do there is replace EV and and SV OR F.L . just make shure EV is on negitive side of pump in all cases the main thing is never pump into a EV other wise fouls up Diaghram in EV.puts extra pressure inon heating system and disconnect Loop from Heating use two checks valves on filling point . Same thing if its a gas boiler and safety valve keeps runing water replace SV leave EV in boiler fit external EV ON RETURN job sorted DAVE 01