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Installation and Operating Instructions
For flow rates between settings, interpolation of position can be used.
Please note that DN25 and DN32 test points measure the differential pressure across the seat,
not overall pressure drop.
Please note for the DN40 and DN50 the test points measure the overall differential pressure drop
across the valve only.
The pump speed should be set to ensure that the required differential pressure is always
available. By setting the differential pressure across the least favoured CFR to the value stated
in the above table, it ensures that minimum pump energy is used, therefore, reducing system
running costs and CO2 emissions:
DN25 & DN32
To set pump speed to achieve this: whilst measuring ΔP (across test points), increase
pump speed until a constant ΔP is achieved, however please note that the typical ΔP
value, as shown in the table above, can differ but in itself is not critical to operation.
DN40 & DN50
To set pump speed to achieve this: whilst measuring ΔP (across test points), increase
pump speed until a value greater than the minimum stated in the above table is achieved.
As the measured ΔP is the total pressure drop across the PICV, the measured value will
continue to rise as pump speed is increased. Any value above the minimum requirement
will increase running costs, therefore, reducing system efficiency.
The optimum setting is achieved when there is sufficient, but not excessive, pump pressure
available.
Flow rate verification should be carried out using separate Flow Measurement Devices (FMD)
where fitted. In line with CIBSE & BSRIA recommendations, we recommend that as a minimum
requirement, FMDs are installed in all branches.
5
Hattersley Constant Flow Regulator
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