Flushing agents can help reduce overall energy costs as well as extend the lifespan of air conditioning systems, says John Ormerod.
Following the virgin HCFC use ban, air conditioning end users have had to make a decision about what to do with existing equipment containing these gases. In many cases, they have elected to retrofit the system, either to a replacement or 'drop in' refrigerant that mimics the operating characteristics of the HCFC they are replacing, or to a mainstream 400 series HFC refrigerant.
Carrying out a retrofit is an excellent chance to give the system an overall MOT and clean its internal heat exchange surfaces of logged oil, remove moisture and any particulates that may have gathered over the life of the equipment.

This has led to the introduction within the market of a variety of internal flushing agents designed to achieve this.

A major benefit of internal flushing is that it cleans internal heat exchange surfaces allowing better heat transfer in a system and therefore improves system performance and energy efficiency. It is unlikely that an air conditioning engineer will service a system and leave the condenser coil fouled with debris, so why let the internal surfaces of heat exchanger surfaces become similarly contaminated and less efficient? Internal cleaning of a system also has an added and equally important benefit of removing moisture and acidity which improves the life span of the compressor and helps prevent premature failure.

Internal cleaning is not just a key requirement of retrofits (especially when an oil change is required) it is also key when a compressor has burnt out and contaminated a system or when a system has been contaminated through operational error.

Internal flushing of systems is not a modern phenomenon, historically the benefits were recognised and the most popular flushing agent was CFC 11. Although R11 was by default a good cleaning agent from a perspective of its solvent properties with common contaminants, relatively low boiling point, its non-flammable nature and non-toxicity, it was banned under the Montreal Protocol due to its ozone depletion potential (ODP).

Modern flushing agents

Since the demise of R11 various options have been tried for internal flushing, most have not been ideal due to the potential of leaving a residue in the system that re-contaminates the refrigerant negating the positive effect of the flush.

Modern flushing agents are designed with the environment in mind and do not exhibit ODP, there is also a move to reduce global warming potential (GWP) as the environmental focus in the industry has moved in the direction of climate change.

A range of products are available on the market, some based on solvent blends and some based on water, experience has identified that the solvent blends are far easier to remove from the system after the flush due to their lower boiling points.

At A-Gas, we have adopted a 'cradle to grave' approach with our solvent based cleaning system, AK Flush which is accompanied by an empty 'solvent waste' container, to collect the dirty solvent coming out of the system.

The waste canister along with the empty cylinder can then be returned to us via wholesalers accompanied by a waste transfer note for responsible destruction.
Using a refrigerant grade carbon dioxide (R744) as a propellant takes advantage of its low GWP and reduces the carbon footprint normally associated with such products.
Using a solvent cylinder with a propellant also means that an expensive pump is not required to introduce the cleaning agent to the system. One 5kg pack can service a system up to 50kW in size keeping costs to a minimum, dependant on the length of the existing pipe runs.

Internal flushing of air conditioning kit fits well with the modern demands of end users which are centred on energy efficiency and lowering carbon footprint.

With energy prices continuing to rise and the introduction of the Carbon Reduction Commitment, measures to improve these such as regular servicing are all the more important. Adding an internal flush to the refrigerant retrofit is recommended to assist in the longevity and energy efficiency of RAC systems.

Heat pumps and the F Gas Regulations

By 4 July 2011 full company certification will be required for those employing personnel working on heat pump (HP) equipment that contains or is designed to contain F gases. Interim personal certificates will no longer be valid; all personnel carrying out relevant work must hold a valid F Gas Certificate.

A split type domestic air to water HP is classed as pre-charged as the entire refrigerant charge is contained in the outdoor section. However the system still needs to be installed on site with refrigerant pipes between indoor and outdoor units to complete the refrigerant pipework circuit. This work comes within scope of the F Gas Regulations.

If the system is a 'monoblock' type and the installing operative is simply placing a unit on site ready to be connected to the electrical supply and the flow and return heating water pipes the installation work would not come within scope of the Regulations. However, all service, maintenance and decommissioning activity on either type of system must be carried out in accordance with the F Gas Regulations.

Heat pumps are defined as heating devices that use a refrigeration system to extract energy from a waste heat source and deliver useful heat. Many organisations use heat pump systems containing HFC refrigerants such as R410A, R134a or R407C which are also known as 'F gases'. F gases are global warming gases which if allowed to leak to atmosphere will damage the environment.

Where such refrigerants are contained, added to or removed from the system, the company carrying out the installation, service or maintenance work must ensure that it meets certain legal requirements. Many of these requirements are also obligations for the operator or owner of the equipment. The regulations that apply are the F Gas Regulation (EC Regulation 842/2006) and the GB Fluorinated Greenhouse Gases Regulations 2009 (Statutory Instrument No 261) which specify penalties for non-compliance. The regulations are designed to improve containment of refrigerant - ie to prevent emissions due to refrigerant leakage.

Potential sources of F Gas emissions

During installation - Poor jointing of pipework, components or insufficient care during charging of systems can lead to leakage.

During plant maintenance - If a component needs to be replaced it may be necessary to remove some or all of the refrigerant from the system. Removed refrigerant must be recovered and contained. It is illegal to vent refrigerant to atmosphere.

Emissions at end of plant life - Waste refrigerant must be recovered during decommissioning, using recovery equipment, recovery cylinders and appropriately certified personnel. Waste refrigerant is classified as hazardous waste and must be returned for recycling or destruction.

For further information on legislation and key obligations see: www.defra.gov.uk/fgas or contact F-Gas Support on 0161 874 3663. This is an edited version of guidance published by the Air Conditioning and Heat Pump Institute, a section of the Institute of Refrigeration.

• John Ormerod is business director of A-Gas