Technical guidance

Ammonia (R717, NH₃) – GWP = 0

Ammonia has a relatively high saturation temperature at atmospheric pressure, is highly toxic, low flammable and has a pungent odour.   It can be smelt at concentrations of just 3 mg/m³, so it is evident at levels much lower than those which are hazardous.   It is the only commonly used refrigerant which is lighter than air which means that dispersion of any leaked refrigerant takes place quickly.

Ammonia also operates with very high discharge temperatures.   Single stage compression can therefore normally be used above -10^OC evaporating temperature.   Below this, two stage compression with interstage cooling is required.  The high toxicity limits the application of ammonia to very low charge systems or industrial systems (i.e. systems in areas which are not accessible by the general public).   This typically includes distribution cold stores and food processing plants, usually using secondary systems where ammonia is the primary refrigerant.

City and Guilds offer a specialist Ammonia handling qualification (2078) search our trainers list for more details

FSDF provide a free guide to the Safe Management of Ammonia Refrigeration Systems

BREEAM (BRE Environmental Assessment Method)

BREEAM is a widely used environmental assessment method for buildings and communities. It covers best practice in sustainable design and is a measure commonly used to describe a building's environmental performance. BREEAM provides clients, developers, designers and others with

• market recognition for low environmental impact buildings
• assurance that best environmental practice is incorporated into a building
• inspiration to find innovative solutions that minimise the environmental impact
• a benchmark that is higher than regulation
• a tool to help reduce running costs, improve working and living environments
• a standard that demonstrates progress towards corporate and organisational environmental objectives

The evaluation method addresses wide ranging environmental and sustainability issues and enables developers and designers to prove the environmental credentials of their buildings to planners and clients using a scoring system that is transparent, easy to understand and supported by evidence-based research.  It is designed to have a positive influence on the design, construction and management of buildings and to set and maintain a robust technical standard with rigorous quality assurance and certification.

Read more about the various BREEAM schemes, case studies and training at www.breeam.com

Carbon dioxide, CO_2, (R744) GWP = 1

R744 has high operating pressures, a low critical temperature (31^OC) and a high triple point.  Its volumetric cooling capacity is between 5 and 8 times that of HFCs, reducing the required compressor displacement and pipe size.   Its properties have an effect on how the system is designed and operates, especially in high ambient temperatures.  It has a high discharge temperature, necessitating two-stage compression for low temperature systems.  Carbon dioxide has been used in the following system types:

• Pumped secondary – where carbon dioxide is the secondary fluid cooled by a primary system. Carbon dioxide is a volatile secondary which, coupled with the high capacity and density, reduces the required pump power compared to other secondary fluids such as glycol. 
• Cascade – where the heat rejected by the condensing carbon dioxide is absorbed by the evaporating refrigerant in a separate high stage system. In these systems the carbon dioxide operates below the critical point and the high side pressure is generally below 40 bar g. The high stage system can be carbon dioxide, or it can be HFC, HC, HFO or Ammonia. 
• Transcritical systems – where the carbon dioxide heat is rejected to ambient air and at ambient temperatures above approximately 21^OC the carbon dioxide will be above the critical point (31^OC) – i.e. it will be transcritical. The carbon dioxide does not condense – it remains a super critical fluid until its pressure is reduced to below the critical pressure (72.8 bar g). The high side pressure is typically 90 bar g when transcritical.

Currently carbon dioxide has been used in many retail systems and in industrial systems in Europe.   It is starting to be used in heat pumps and in integral systems. The application of carbon dioxide has required additional skills for design engineers and service technicians, and design of new components.

BRA Carbon Dioxide Short course providers 

REAL Alternatives e-learning

Guidance on Low GWP Alternatives (Gluckman Consulting)

Hydrocarbons (R290, R1270 and R600a) GWP = 3

R290 (propane), R1270 (propene, propylene) and R600a (isobutane) are all hydrocarbons.   They are highly flammable, so refrigerant charge size is limited on many applications.  This limits the application of HCs mainly to integral systems, chillers and some split air conditioning systems.   Electrical devices on the system will be the non sparking type if a leak can result in a flammable concentration around the electrical device.  

R290 and R1270 have similar performance and operating pressures to R404A and they are used in high, medium and low temperature commercial applications.   R600a has a much higher saturation temperature than other refrigerants and operates at a vacuum on the low side in most applications.  Its use is limited to domestic and very small commercial refrigeration systems with minimal leakage so that ingress of air and moisture due to leakage rarely occurs.

Blends of Hydrocarbons are also available, such as Care 30 (propane and isobutene) and Care 50 (propane and ethane).   They are also highly flammable, and have significant temperature glide.  

City and Guilds short course 6187 21/31 CPD unit available from training providers (use our search facility)

REAL Alternatives elearning

BRA guidance notes on servicing, manufacturing and design

BRA Code of Practice for Design and Manufacturer of cabinets using hydrocarbon (2014)

Introduction to the vapour compression cycle

SI units and definitions

Glossary of key RACHP terminology

Using refrigerants with temperature glide

The BRA (British Refrigeration Association) has produced this brief guide (Fact Finder 19 issued March 2017) to provide advice for Service technicians considering retrofitting high GWP systems. Some of the information will also be useful in the case of new installations. The guide is intended to cover single condensing unit and evaporator applications. R404A is the most commonly used high GWP refrigerant.

BRA FACT FINDER Number 19 280317.pdf  Free download

HFO Refrigerants eg R1234ze

Several pure substances and blends using these refrigerants are now coming onto the market.  They have lower GWPs than pure HFCs such as R404A and R134a but some are flammable.

R1234ze for example is a low flammable HFC, marketed as an HFO – hydro fluoro olefin.   This is a halocarbon containing hydrogen, fluorine and unsaturated carbon.   Its mild flammability limits the refrigerant charge size, but not to the same extent as the more flammable hydrocarbons.   Electrical devices on the system will be the non sparking type if a leak can result in a flammable concentration around the electrical device.  The saturation temperature at atmospheric pressure is high compared to other refrigerants so it will operate on a vacuum on the low pressure side of the system for low temperature applications.   It is therefore most suitable for medium and high temperature applications such as water chillers.   Its cooling capacity is also low compared to other HFCs which means that different compressors are required, with a larger displacement relative to the motor. R1234ze is available and most commonly used in chillers and integral units.

For more information on properties and use see guides and free e-learning at www.realalternatives.eu

FETA introduction to the use of A2L refrigerants

Table of CO2 equivalent values for common refrigerants (download)

Guidance on calculating CO2 equivalent values

More on why GWP values change and IPCC Assessment Reports

Putting into Use Replacement Refrigerants (PURR) - 15 Sep 2015

This report has been produced by an Action Group made up of members of the British Refrigeration Association (BRA). The purpose of the report is to help people address the task of meeting some of the key implications and requirements of the EU F-Gas regulation which came into force on 1st January 2015.

The document is aimed at all stakeholders involved in the commercial refrigeration market – designers, manufacturers, installers, commissioners and end users – and is designed to highlight the challenges the sector faces in the next few years, and offer guidance and suggestions as to how these issues can be dealt with.

The ban on new installations and servicing with refrigerants with a Global Warming Potential of 2500 or more, together with the cap and phase down of HFC refrigerants, presents the sector with a major challenge. With a very tight timescale in which these factors must be actioned, the need for advice and information will be vital in the decision making process.

Sections 1 to 3 outline the challenge to be faced in more detail, and propose some of the actions that will need to be taken. Sections 4 and 5 contain detailed comments on replacement refrigerant candidates and the components that are relevant to their use. In Section 6, there is a summary of strategic matters that need addressing.

PURR Report

PURR Report precis

BS EN378 “Refrigerating systems and heat pumps - Safety and environmental requirements”

The safety standard was updated and republished in 2016.  BS EN378 is a safety and environmental standard, published by CEN, the European Committee for Standards.  It provides guidance for companies who design, construct, install, operate, maintain and use vapour compression systems for refrigeration, air-conditioning, heat pumps, chillers and other similar systems.  It is published in four parts, which cover definitions, design (including manufacturing), installation (including commissioning) and operation (including maintenance requirements).  In total, the four parts are approximately 180 pages long.

For the refrigeration, air conditioning and heat pump sector BS EN378 provides a means of proving conformity with certain European directives.  Part 2 (Design, construction, testing, marking and documentation) is harmonized with Directive 2014/68/EU (The Pressure Equipment Directive also referred to as PED) and with the European Directive 2006/42/EU (The Machinery Directive referred to as MD). 

BS EN378 is not, however, a legal requirement in its own right.  It is possible to install a system in compliance with all relevant regulations, including PED and MD, without following the requirements of BS EN378.  It is not a complete design guide for systems.  It gives no presumption of conformity with directive 99/92/EC (The ATEX Workplace directive) or directive 2006/95/EC (The Low Voltage directive).   Any system using a “dangerous substance” as defined in the DSEAR (The Dangerous Substances and Explosive Atmospheres Regulation 2002) is required to meet the requirements of those regulations.  BS EN378 in full does not provide a presumption of conformity with regard to flammability.

IOR produces a free guide to the changes in the 2016 version of this standard

The four parts of BS EN378:2016 can be purchased by searching EN378 at http://shop.bsigroup.com/Navigate-by/Standards/