13
Fitting the Unvented System Kit.
Fit the components as indicated. In the suggested
schematics detailed on previous pages.
All components must be installed in a frost free area.
Ensure that valves and fittings are fitted correctly to
suit the direction of flow.
Set the Pressure reducing valve (PRV) to 3 bar.
Pipe off expansion relief valve via the tundish provided
to a gulley.
Pipe expansion vessel into cold feed. Fit a lock shield
valve and drain between the vessel and the cold feed
line. This will allow the expansion vessel gas charge to
be checked during maintenance. This is shown on the
right.
Installation of the Expansion
Vessel.
Cold
Feed
Fit a lock shield valve and drain
to allow the expansion vessel to
be isolated and drained for
periodic inspection.
Drain Cock
(By the
Installer)
Strainer
Pressure
Reducing
Valve
Double
Check
Valve
Expansion
Vessel
Lock Shield
Valve (By the
Installer)
Maintenance of Unvented System Kit.
Clean out strainer on commissioning and annually.
Check Expansion relief valve setting annually by
twisting the cap on top of the valve.
Check expansion vessel gas charge pressure, isolate
the vessel, drain off any water in the vessel and test the
gas pressure using a tyre gauge.
Fault Finding.
Symptom Possible Cause(s) Remedial Action
(A) Reduction in water flow Blockage in strainer Clean out strainer.
Blockage in PRV Clean out secondary strainer in PRV.
Wrong PRV pressure setting Check PRV pressure setting alter if necessary.
(B)Discharge from expansion Debris on valve seat Twist test knob and replace if necessary.
Relief valve. Wrong incoming pressure Adjust the pressure setting on PRV.
Expansion vessel diaphram Check expansion vessel gas charge.
Failure.
Insufficient Expansion vessel Check expansion vessel size.
volume.
Expansion Vessel Sizing.
Expansion Vessel Volume = System content (l) x C.o.E.
Vessel Efficiency
Vessel Efficiency = Max Pressure (Bar Abs) - Min Pressure (Bar Abs)
Max Pressure (Bar Abs)
Where: Max Pressure is final desired working pressure + 1.
Min Pressure is pressure setting on PRV + 1.
C.o.E. at 60 Deg C is approx 0.02
Unvented Systems
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