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Guide Contents

Section 1 Differential Pressure Control Valves
1.1 Differential Pressure Control Valves
1.2 System Design Incorporating DPCVs
1.3 Typical circuits using DPCVs
1.4 System Balancing using DPCVs
1.5 Trouble shooting DPCV circuits
Section 2 Pressure Independent Control Valves
2.1 Design incorporating PICVs
2.2 Typical circuits with PICVs
2.3 System Balancing using PICVs
2.4 Trouble shooting PICV circuits
2.5 Actuators
1 Cavitation
2 Relationship between flow rate and differential pressure
3 Kirchhoff's 2nd Law
4 Heat output from terminals
5 Preferred numbers
6 Characteristics of control valves
7 Equal percentage characteristics

This Guide on the principles of DPCVs (Differential Pressure Control Valves) and PICVs (Pressure Independent Control Valves) is the latest in the series from Hattersley specifically for Building Services engineers.

The author, Andy Lucas, left school at 15 years old with no formal qualifications. He returned to study in his late 20s, working within various manufacturing industries, culminating in the position of Technical Development Manager for Hattersley.

This Guide is written in a ‘practical language’ that is easy to read, being relevant to practicing engineers at all levels of knowledge and experience including fitters, commissioning technicians, contractors, consultants and system designers.


Andy explains, as everyone becomes more aware of the consequences of global warming, system design has changed to ensure energy use is uppermost in the designer’s mind.

This Guide describes, in detail, changes in system design which made it necessary to introduce DPCVs and PICVs into variable volume heating and chilled water systems.

About the Author - Andy Lucas

Andy has held several positions within the Company, beginning in the Technical Support Team, becoming Technical Support Manager before being appointed Technical Development Manager, which is his current position.

His role within Hattersley means that he works closely with the marketing, engineering and sales teams to ensure that the product range reflects the industry’s requirements.

Hattersley, being a CIBSE Patron and member of BSRIA, support Andy with his work on the project steering groups of these organisations. Most recently, Andy has been involved with the steering groups for:

  • CIBSE Commissioning Code W
  • BSRIA Commissioning Water Systems Guide
  • BSRIA Energy Efficient Pumping Systems Guide
  • BSRIA Test Method for PICVs
  • BSRIA Heat Interface Unites (HIU) Guide
  • BSRIA Selection of Control Valve Guide
  • BSRIA Heat Network Guide

He is also invited to peer review other guides before publication.

Andy also sits on the Technical Sub-committee of the CSA, and was involved with the rewriting of the Commissioning Engineers Compendium. Andy has also written several of their Technical Memorandums, in particular ‘The Theory of Balancing Water Systems’, ‘Alternative Pipework Systems and Fixed Orifice Flow Measurement’ and ‘DPCV Fundamentals and Commissioning’.

Andy’s ‘15 minutes of fame’ came when he designed the Building Services industry first single terminal unit manifold system. The concept of a one piece ‘H’ body design incorporating the flushing by-pass changed the industry, with several other companies copying his design concept.

From his original idea came the development of the multi-manifold commissioning systems and more recently the move towards the 40mm centre terminal unit manifold.