Hydronic Systems Design Set of 2

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A BSRIA Guide www.bsria.co.uk

Selection of Control Valves in Variable Flow Systems

By Chris Parsloe

BG 51/2014

1 Acknowledgements

This publication has been written with the help of an industry steering group. BSRIA would like to thank the following people, without whom it would not have been possible:

Simon Barden Arup Peter Clackett Skanska Luke Collier BSRIA Stuart Cruickshank Samson Controls Ltd. Elio Galluzzi SAV Systems Ltd. Ashish Goyal Honeywell Andy Harrop Armstrong Fluid Technology Stephen Hart Frese Andy Lucas Crane Building Services & Utilities Nick Martin Marflow Hydronics Ltd. Martyn Neil Danfoss Ltd. John Middleton Samson Controls Ltd. Justin Pearce Belimo Automation UK Ltd. David Queen Herz Valves UK Ltd. Christian Bo Rasmussen Frese Peter Rees TA Hydronics Mike Smith BSRIA Bob Swayne The Hampden Consultancy Hedley Thomas Belimo Automation UK Ltd. Paul Wightman Danfoss Ltd.

BSRIA acknowledges the very significant contribution made by all the steering group members, and especially the author, Chris Parsloe of Parsloe Consulting. The final editorial responsibility for this publication rested with BSRIA. It was designed and produced by Joanna Smith of BSRIA.

The guidance given in this publication is correct to the best of BSRIA’s knowledge. However BSRIA cannot guarantee that it is free of errors. Material in this publication does not constitute any warranty, endorsement or guarantee by BSRIA. Risk associated with the use of material from this publication is assumed entirely by the user.

All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means electronic or mechanical including photocopying, recording or otherwise without prior written permission of the publisher. © BSRIA June 2014

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CONTENTS

1 INTRODUCTION 1 1.1 Objective 2

2 MATCHING CONTROL VALVE TYPE TO TERMINAL DEVICE 4 2.1 Natural convection/radiation (passive) 4 2.2 Forced convection (active) 4 2.3 Water to water heat exchangers 5

3 ACHIEVING EFFECTIVE MODULATING CONTROL 8 3.1 Flow characteristic 8 3.2 Valve authority 10 3.3 Actuators 12

4 CONTROL VALVE SIZING 13 4.1 Motorised on/off valves 13 4.2 Thermostatic radiator valves (TRVs) 13 4.3 Three-port control valves 14 4.4 Four-port control valves 16 4.5 Two-port control valves 17 4.6 Pressure independent control valves (PICVs) 21

REFERENCES AND BIBLIOGRAPHY 25

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symbols

Isolating valve Pressure independent control IV valve (note this is different from the symbol used in previous BSRIA publications) PICV Drain off cock DOC

Pump LSV Lockshield valve

TP Pressure test point Double regulating valve DRV

Non-return valve Fixed orifice flow measurement NRV device (orifice plate) OP

Differential pressure Three-port control valve control valve DPCV MV MV Four-port control valve Tw o-port control valve

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INTRODUCTION 1

1 INTRODUCTION

This guide has been produced to help designers avoid problems with the selection and application of control valves used in hydronic systems. By way of background, BSRIA has been involved in a number of investigations into the performance of one particular type of device that is widely used in variable flow hydronic systems. These devices are collectively referred to as Pressure Independent Control Valves (PICVs). It became apparent that some issues occurred because there was no common format for presenting the performance of PICVs or independent guidance on their selection.

Working with an enthusiastic steering group of manufactures and others, BSRIA researched and produced both a series of test methodologies and a format for the standardisation of the presentation of results. This is published as BTS 1/2012 Test Method for Pressure Independent Control Valves[1]. Having a test standard is very useful to the industry but it is equally important that, armed with useful performance data, the correct selection processes are followed, so equipment choices are appropriate. Working with many of the same manufacturers and others, BSRIA has produced this guide, which effectively complements BTS 1/2012. As this guide is used by practitioners, and as industry practices change or new products emerge and become more prevalent, it may become necessary to revise this guide. Therefore feedback from users, on any aspect of this guide, would be very much appreciated.

For the purposes of this guide, a control valve is a valve which (governed by an automatic control system) varies the flow of water through the pipe or branch in which it is installed. The main valve types discussed in this guide are summarised in Table 1.

This guide explains the selection and sizing of valves for the control of heating or cooling outputs from terminal devices. The term terminal device is used to denote any heating or cooling output device connected to a heating or chilled water pipework system. Examples include radiators, fan coil units, air handling units, chilled beams, trench heaters, plate heat exchangers and calorifiers.

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MATCHING CONTROL VALVE TYPE TO TERMINAL DEVICE 2

Figure 1: Relationship between heat transfer and flow rate for forced convection heating and sensible cooling terminal devices.

120

110

100

60 Heating ∆T = 10oC 50 Heating ∆T = 20oC Heat transfer (%) 40 Heating ∆T = 30oC ∆ o 30 Cooling T = 6 C

0 5040302010 60 70 80 90 100 110 120 Design flow rate (%)

For this type of terminal device (if recommended by the manufacturer) some form of “modulating” control valve can be effective i.e. a valve that varies the flow of water in order to vary the heating or cooling output of the emitter. This might typically include a two-port valve, three-port valve, four-port valve or pressure independent control valve (PICV). However, to be effective, the valve must have the appropriate type of flow characteristic and be sized with sufficientauthority for the circuit in which it is located. These concepts are explained in the following sections.

2.3 Water to Terminal devices that transfer heat from one flow of water to a different water heat flow of water separated by a thin metal wall do so principally by means of exchangers conduction of heat through the separating wall. For this type of terminal device the relationship between flow rate and heat transfer is close to proportional i.e. for each change in flow rate on the input side of the heat exchanger, there is a proportional change in heat transfer.

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A BSRIA Guide www.bsria.co.uk

Energy Efficient Pumping Systems

A design guide

By Chris Parsloe

Supported by

BG 12/2011

ACKNOWLEDGEMENTS

This document has been prepared with the support of BRE Trust. The project was undertaken by BSRIA with the assistance of a project steering group drawn from the following companies who provided BSRIA staff with technical assistance and supported the publication of this guide:

Andrew Reid and Partners LLP Belimo Automation UK Ltd Crane Fluid Systems Ltd Danfoss Randall UK Frese Ltd Grundfos Ltd Herz Valves UK Ltd SAV UK Ltd.

The research project was led by Dr Arnold Teekaram of BSRIA, with support from Dr Fiona Lowrie of BSRIA and Chris Parsloe of Parsloe Consulting. The guidance was written by Chris Parsloe with the assistance of a project steering group who were:

Andy Lucas David Considine David Queen Howard Hall Jan Hansen Lars Fabricius Luke Collier Paul Wightman Robert Fowler Stephen Hart.

The document has also been reviewed by Mike Campbell of AECOM and members of the BSRIA Publications Panel:

Jim Mellish and Peter Clackett, Skanska Mitch Layng, Prupim.

This publication has been designed and produced by Alex Goddard and Ruth Radburn.

Every opportunity has been taken to incorporate the views of the contributors, but final editorial control of this document rests with BSRIA.

This publication has been printed on Nine Lives Silk recycled paper.

ENERGY EFFICIENT PUMPING SYSTEMS

CONTENTS

1 INTRODUCTION 1 1.1 Scope 1 1.2 Guide structure 1 2 SUMMARY OF RECOMMENDATIONS 2 2.1 Variable or constant flow 2 3 PUMP ENERGY FUNDAMENTALS 4 3.1 Calculating pump energy 4 3.2 Pump affinity laws 6 3.3 Pump speed control 8 4 PIPE SIZING 11 5 PIPE LAYOUT 13 6 SYSTEM CONTROL ISSUES 17 6.1 Remote sensor control 17 6.2 Temperature differentials 18 6.3 Constant and variable temperature circuits 19 6.4 Effect of flow on temperature differential 20 6.5 System by-passes 21 6.6 Pump minimum flow-rate 23 6.7 Flow control at terminals 25 6.8 Secondary hot water circuits 26 6.9 Primary circuits 29 6.10 Low emission heat sources 33 APPENDIX A: VALVE TERMINOLOGY 34 APPENDIX B: SYSTEM LIFE CYCLE ENERGY CALCULATIONS 35 APPENDIX C: COMMISSIONING ISSUES 39 REFERENCES 40

ENERGY EFFICIENT PUMPING SYSTEMS

FIGURES

Figure 1: Pressure loss diagram for a simple pumped circuit 5 Figure 2: Constant pressure pump speed control 9 Figure 3: Proportional pump speed control 9 Figure 4: Remote sensor pump speed control 10 Figure 5: Notional terminal unit layout 13 Figure 6: Layout 1 - Single branch flow return layout 14 Figure 7: Layout 2 - Split branch flow return layout 14 Figure 8: Layout 3 - Split branch reverse return layout 14 Figure 9: Layout 4 - Looped reverse return layout 14 Figure 10: Layout 5 - Single flow return layout feeding valve modules 14 Figure 11: Alternative valve and pump control design solutions 15 Figure 12: Comparative pump energy consumption for alternative pipe system design solutions 15 Figure 13: Example of potential moving index 17 Figure 14: Secondary pump arrangements for constant and variable temperature circuits 19 Figure 15: Constant flow by-pass at end of radiator circuit 21 Figure 16: By-pass through an end-of-line four port diverting control valve 22 Figure 17: Minimum flow rate for canned rotor pumps 23 Figure 18: Determining pump power values at zero flow under different pump speed control regimes 24 Figure 19: Design resulting in excess flows and pressures across terminal units 25 Figure 20: Typical temperatures across hot water cylinder at 30 K design temperature differential 28 Figure 21: Plate heat exchanger unit for provision of hot water 29 Figure 22: Mixing of flows in low loss headers 30 Figure 23: Variable flow primary circuit using boiler shunt pumps 31 Figure 24: Variable flow primary circuit using single primary pump set 32 Figure 25: Primary circuit integrating low emission heat source alongside back-up boilers 33 Figure 26: Total life cycle energy consumption for a constant flow steel pipe system 36 Figure 27: Total life cycle energy consumption for a variable flow steel pipe system with constant pressure control of pump speed 37 Figure 28: Total life cycle energy consumption for a variable flow steel pipe system with remote sensor control of pump speed 37

ENERGY EFFICIENT PUMPING SYSTEMS

ABBREVIATIONS BMS Building energy management system CFR Constant flow regulator DRV Double regulating valve DPCV Differential pressure control valve OP Orifice plate flow measurement device DRV Double regulating valve PICV Pressure independent control valve TRV Thermostatic radiator valve

For detailed explanation of valve functions, refer to Appendix A.

SYMBOLS

ENERGY EFFICIENT PUMPING SYSTEMS

INTRODUCTION 1

1 INTRODUCTION

1.1 SCOPE This application guide provides recommendations on the design of energy efficient pumping systems.

The potential for reducing pump energy consumption is substantial. The US Department of Energy estimates that pumping accounts for 20% of the world’s energy use by electric motors[1]. Europump (a pan European association of pump manufacturers) estimates that systems could be 30 to 50% more energy efficient by careful consideration of components, design and installation[2]. This guide shows some ways in which this efficiency may be achieved.

The recommendations presented here are based on analyses of alternative pipe sizing methods, pipework layouts, valve selections, pump control options and system control measures. Separate research reports for each recommendation are also available from BSRIA.

In building services applications, heating and cooling systems usually incur the largest pumping loads. This guide therefore focuses mainly on these applications. Cooling systems usually offer the best scope for pump energy savings due to the larger flow rates involved.

Most of the guidance is applicable to both heating and cooling applications. Some sections are written specifically for heating systems, including district heating, because a lack of regard for pump energy may lead to missed energy savings elsewhere. For example, excess flows tend to lower system temperature differentials, thereby reducing the effectiveness of some low carbon emission or renewable energy heat sources.

1.2 GUIDE Section 2 provides an executive summary of the main design STRUCTURE recommendations. The research process, its findings, and conclusions are explained in Sections 3 to 6.

ENERGY EFFICIENT PUMPING SYSTEMS 1