Pressure independent control valves
Test Method for PICVs and DPCVs (BTS 1/2019), published by BSRIA in November 2019, defines a pressure independent control valve (PICV) as: ‘A valve that operates to maintain a controlled flow rate that is, within limits, independent of the supplied differential pressure. The valve may operate mechanically or electronically.’
The Illustrated Guide to Mechanical Building Services, Third Edition (BG 31/2017), by David Bleicher, published by BSRIA in 2017, suggests that pressure independent control valves (PICVs) are: ‘…used in variable flow heating or cooling systems to control the output of devices such as air handling units, fan coil units or chilled beams. They regulate flow constantly during varying pressure conditions and can be placed on either the flow or the return pipe.’
Test Method for Heat Interface Units (BTS 2/2015), written by Colin Judd, and published by BSRIA in December 2015 and amended in June 2016, states: ‘A pressure independent control valve (PICV) operates to maintain a controlled flow rate that is, within limits, independent of the supplied differential pressure. A PICV combines the functions of a DPCV, regulating valve and control valve.’
Energy Efficient Pumping Systems, a design guide (BG 12/2011), written by Chris Parsloe and published by BSRIA in 2011, states: ‘Sometimes referred to as a combination valve, a PICV combines the functions of a double regulating valve, differential pressure control valve and two-port control valve within a single valve body. Because the integral differential pressure control valve holds the pressure differential constant across the integral two-port control valve, the flow rate through the valve always returns to its set value whenever the control valve is fully open (since a constant pressure differential across a fixed resistance results in a constant flow rate). The opening through the two-port control valve can be varied manually, and can therefore be used to regulate the flow rate through the valve to the required design value. The flow rate can be set using an integral mechanism within the valve. Once set, the valve will perform the function of a constant flow regulator whenever the two-port control valve is fully open. Only when the control valve begins to close will the flow rate change from its set value.’
Selection of Control Valves in Variable Flow Systems (BG 51/2014) written by Chris Parsloe and published by BSRIA in June 2014, defines a pressure independent control valve (PICV) as: ‘A combination of an actuated two port control valve that varies the flow through a terminal device, and a differential pressure regulator that maintains a constant pressure differential across the control valve thereby ensuring that the set maximum design flow rate cannot be exceeded… Note 4: Although the majority of PICVs are of the type described above, the same objective of pressure independent control can be achieved by a combined two-port control valve and electronic flow measurement device. For products based on this approach, the control valve is fitted with an intelligent motorised actuator that enables the measured flow to be maintained at its required value regardless of pressure variations in the system. This type of valve is sometimes referred to as an “electronic PICV” and does not require an integral differential pressure controller.’
It suggests that typical applications include; modulating control of heating or cooling outputs from air handling units, fan coil units or chilled beams in variable flow systems. (Used without an actuator, PICVs hold flow rate constant at a fixed value regardless of changes in system pressures.)
For more information see: What makes a good PICV?
--BSRIA
[edit] Related articles on Designing Buildings
Featured articles and news
Key takeaways from the BSRIA Briefing 2024
Not just waiting for Net Zero, but driving it.
The ISO answer to what is a digital twin
Talking about digital twins in a more consistent manner.
Top tips and risks to look out for.
New Code of Practice for fire and escape door hardware
Published by GAI and DHF.
Retrofit of Buildings, a CIOB Technical Publication
Pertinent technical issues, retrofit measures and the roles involved.
New alliance will tackle skills shortage in greater Manchester
The pioneering Electrotechnical Training and Careers Alliance.
Drone data at the edge: three steps to better AI insights
Offering greater accuracy and quicker access to insights.
From fit-out to higher-risk buildings.
Heritage conservation in Calgary
The triple bottom line.
College of West Anglia apprentice wins SkillELECTRIC gold.
Scottish government launch delivery plan
To strengthen planning and tackle the housing emergency.
How people react in ways which tend to restore their comfort.
Comfort is a crucial missing piece of the puzzle.
ECA launches Recharging Electrical Skills Charter in Wales
Best solutions for the industry and electrical skills in Wales.
New homebuilding skills hub launch and industry response
Working with CITB and NHBC to launch fast track training.