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HVSH Solar heating design and installation guide (2016)
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HVSH Solar heating design and installation guide (2016)

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CIBSE is the primary stockist of Domestic Building Services Panel publications. Purchases can be made using the relevant buttons above. Members of the Panel wishing to make bulk purchases at their special rates should email [email protected], telephone +44 (0)20 8772 3618 or by mail to Publications Sales (DBSP orders), c/o CIBSE 222 Balham High Road, London SW12 9BS.


To provide guidance to those designing and installing solar heating systems and to support training and certification schemes, the Domestic Building Services Panel of CIBSE has drawn up this Guide to cover the design and installation of solar domestic water heating.

The Guide covers the predominant types of such systems and notes their advantages and disadvantages. The broad range of systems covered will assist those engaged in repair and maintenance work to understand the principles of operation of a great deal of the equipment that has been installed to date. The Guide underwent a process of revision and update for this edition, published in February 2016.



1.0 Introduction

1.1 Objective

1.2 Scope

1.3 Context

1.4 System Safety

2.0 Overview

2.1 System Terminology

2.2 The Preheating of Domestic Hot Water

2.3 Circulator Pumps

2.4 Heat Circulation

2.5 Primary Fluid Expansion

3.0 Systems

3.1 Indirect Systems

3.2 Direct Systems

3.3 Open Vented Primaries

3.4 Fully Filled & Sealed System Primary

3.5 Drainback Primary

4.0 Equipment

4.1 Solar Collectors

4.1.1 Solar Collector Terminology

4.1.2 Flat Plate & Tubular Collectors

4.1.3 Collector Certification

4.1.4 Collector Areas

4.1.5 Collector Data Badge

4.2 Collector Performance

4.2.1 Collector Efficiencies

4.2.2 Standardised Test Data

4.3 Solar Storage

4.3.1 Solar Heat Store Methods

4.3.2 Operation of Solar Storage Systems

4.4 Solar Store Stratification

4.5 Pre Heating of Water Used in Instantaneous DHW Appliances

5.0 Working Principles

5.1 Solar Thermal Power Availability Against Loading

5.1.1 System Efficiencies

5.2 DIrect & Diffuse Irradiation

5.3 Positioning of Collectors

5.4 Protecting from Freeze Damage

5.4.1 Antifreeze

5.4.2 Auto Pump Control

5.4.3 Drain Back

5.4.4 Auto Drain Down

5.4.5 Freeze Tolerant Materials

5.4.6 Insulation

5.5 High Temperature Conditions

5.6 Limescale

5.7 Disinfection of Bacteria

5.8 Orientation of Flow & Return Pipework

5.9 Solar Input & Losses

6.0 Controls

6.1 Circulation & Temperature Control

6.1.1 Safety & Efficiency

6.1.2 Primary Circulation Control

6.1.3 Differential Temperature Control

6.1.4 Circulation Meters

6.1.5 Check Valves

6.1.6 Systems Allowing Full Thermostatic Control

6.1.7 Motorised Valves Suitable for Solar Primary Circuits

6.1.8 Systems Without Full Thermostatic Control

6.2 Expansion & Overpressure Control

6.2.1 Primary Overpressure Control

6.2.2 Safety Valves

6.2.3 Primary Expansion Control

6.2.4 Membrane Expansion Vessels

6.2.5 Drainback Vessel with Air Pocket

6.2.6 Pressure Gauge

6.3 DHW Safety Temperature Control

6.3.1 Secondary Temperature Control

7.0 Designing the System

7.1 Design Overview

7.2 Example System Layouts – Key Design Steps

7.3 Example Schematic Primary Circuit Layouts

7.3.1 Basic Fully Filled Primary Circuit

7.3.2 Basic Drainback Circuit

7.3.3 Multiple Heat Loads

7.3.4 Multiple Collectors

7.4 Example Schematic Safety Control Layout to Comply with Building Regulation G3 (England)

7.5 Overview of System Sizing

7.5.1 Collector Sizing

7.5.2 Storage Sizing

7.5.3 Store Heat Exchanger Sizing

7.5.4 Calculating DHW Loads

7.5.5 Heat Circuit & Storage Losses

7.5.6 Solar Fraction Vs. System Efficiency

7.6 Collector Sizing

7.6.1 Collector Performance

7.6.2 UK Irradiation Map

7.6.3 Collector Sizing Rules of Thumb

7.6.4 Collector Sizing Method 2

7.6.5 Collector Sizing Method 3

7.7 Solar Storage Sizing

7.7.1 Solar Storage Performance

7.7.2 Solar Storage According to Collector Size

7.7.3 The Effect of Undersized Solar Storage

7.8 Solar Heat Exchanger Sizing

7.9 Pipe Sizing & Circulation Rate

7.10 Volume Content

7.11 Safety Valve Sizing

7.12 Pipework – Mechanical Properties

7.13 Dimensioning of Membrane Expansion Vessels

7.14 Dimensioning of Drainback Vessels

7.15 Pump Sizing & Dynamic Pressure Drop

7.16 Attributes of Primary Fluids

7.16.1 Glycol Concentration

7.16.2 Boiling Temperature with Glycol Concentrations

7.16.3 Boiling Points of Plain Water

7.16.4 Freezing Point of Glycol Concentration

7.17 Arrangement of Solar Collector Circuits

8.0 Installation

8.1 Technical Site Survey

8.2 Selecting Specialist Tools

8.3 Initial Testing

8.4 Structural Considerations

8.4.1 Wind & Snow Loads

8.4.2 Fixing

8.4.3 Temperature of Pipes

8.4.4 Weatherproofing

8.4.5 Lightning

9.0 Commissioning

9.1 Introduction

9.2 Commissioning Procedure

9.2.1 Risk of Burns

10.0 User Information

10.1 Introduction

10.2 Explaining the Solar Domestic Hot Water System to the Customer

11.0 Troubleshooting

12.0 Maintenance

13.0 Health & Safety Considerations

13.1 Method Statement / Risk Assessment

Appendix A Regulations, Standards & Other Guidance

A1 Regulations Applicable in England to Non-combusting Water Heating Equipment

A2 Country Variations of Regulations Where Known to Differ from A1

A3 Microgeneration Scheme & Renewable Heat Incentive

A4 UK Regulations Particularly Relevant for Construction

A5 Solar Standards

A6 Other Relevant Standards

A7 Other CIBSE Domestic Building Services Panel Publications

A8 CORGI Direct

A9 B&ES Publications

A10 CIPHE Publications

A11 OFTEC Publications

A12 Further Reading

Appendix B Glossary

Appendix C Features Frequently Found on Solar DTC’s

Appendix D Detailed Calculation of Expansion Vessel Settings

Worked Example – 1

Worked Example – 2

Appendix E Detailed Drainback Vessel Calculations

Appendix F Specimen Commissioning Sheet

F1 For Solar Primary Sealed Systems – Fully-Filled & Drainback

Appendix G Details of Organisations from Whom this Guide is Available

The Domestic Building Services Panel's website can be found here

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