Pressure Independent Control Valves Frequently Asked Questions
It is not recommended to flush through PICVs. The PICV is a control valve with close tolerance flow paths. Flushing through these valves may introduce debris which could block the flow paths.
BSRIA BG29 extract: “…it is recommended…that an additional drain point be located between the two-port valve and coil connection to allow the coil to be flushed directly at full flow without the flow passing through the two-port valve….”
Some manufacturers claim their valve is pressure independent if it controls flow. A truly pressure independent valve controls flow and has a pressure independent control characteristic. The Crane FS PICV is fully pressure independent.
Test points are used to verify the pressure drop across the bonnet to ensure there is sufficient pressure for the valve to operate (typically around 12 – 14 kPa). Please refer to the installation manuals.
Although some manufacturer’s claim that flow readings can be obtain by DP measurements these are not reliable as the reading is based on a theoretical Kv figure.
Crane FS recommend fitting separate Flow Measurement devices. Crane FS FMDs use simple but reliable orifice plates to BS EN ISO 5167-2 with an accuracy of +/- 5%.
This can be verified by measuring the pressure drop across the seat using the test points.
The PICV can be mounted in any orientation. However, consideration should be given to choice of actuator. Thermal actuators can be installed in any orientation, but electro-mechanical actuators should not be installed upside down as this can allow moisture to enter the actuator.
However, a PICV with an electro-mechanical actuator can be orientated anywhere between 0-90º from the vertical.
The PICV can be installed on either flow and return. Please ensure that the valve is installed with the flow direction arrow in the correct direction.
With careful alignment of the setting dial to desired flow rate, a pre-set accuracy of +/- 10% can be achieved.
Control valves are not designed to be isolating valves. However, for routine maintenance purposes, i.e. strainer cleaning, the actuator can be removed, and a manual cap fitted which can be used to close the valve.
BSRIA Guide to Commissioning Water Systems BG2 / 2010 and CIBSE Commissioning Code W: 2010 give details of commissioning procedures using PICVs.
No. Flow rate cannot be measured directly from the PICV. Other means of flow verification such as orifice plates/ flow measurement devices should be installed as part of the system. However, the flow rate can be established from valve set position
The PICV must be installed with the flow direction arrow in the correct direction.