Differential Pressure Requirements
Each valve size DN15 at each % setting option requires a specific constant ΔP
(Differential Pressure) to ensure the PICV is within its working range.
For flow rates in between settings, extrapolation of position can be used.
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
PICV to the value stated in the above table, it ensures that minimum pump energy
is used, therefore, reducing system running costs and CO2emissions.
To set pump speed to achieve this; whilst measuring ΔP, increase pump speed
until ΔP is at, or just above, the minimum shown in the table above. 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.
Where flow rate verification is required at terminals, FMDs may also be installed
at each terminal. Terminal flow rates can also be confirmed by measuring branch
flow rates and closing individual terminal PICVs one at a time and measuring the
reduction in flow at the branch. Care should be taken to ensure that reduced flow
rates are still within the measuring range of the branch FMD, i.e. that the measured
‘signal’ doesn’t drop below 1kPa.
DN15 LF DN15 SF DN15 HF
POS Typical
ΔP FLOW POS Typical
ΔP FLOW POS Typical
ΔP FLOW
2 15 0.008 2 20 0.060 2 25 0.085
3 15 0.015 3 20 0.085 3 30 0.130
4 15 0.028 4 20 0.115 4 35 0.175
5 15 0.038 5 20 0.130 5 35 0.210
6 20 0.050 6 20 0.150 6 35 0.250
7 20 0.060 7 20 0.170 7 40 0.280
8 20 0.070 8 25 0.180 8 45 0.300
9 20 0.075 9 25 0.190 9 45 0.320
10 20 0.080 10 25 0.200 10 50 0.340
Installation and Operating Instructions
Hattersley – Pressure Independent Control Valve – Fig. 1934
