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All the potential replacements for CFC’s and HCFC’s are already known. It is unlikely that there will be a miracle ‘silver bullet’ refrigerant discovered. Of the known alternatives the one favoured to replace the traditional R22 is R410A – an azeotropic blend of hydroflurocarbons (HFC’s).

Its properties are somewhat different to other common refrigerants in particular because it has a very high refrigeration effect and an operating pressure about 50% greater than R22. Its theoretical cycle efficiency is also better than the refrigerant it replaces, which is why leading manufacturers are now optimising both their Split and Variable Refrigerant Volume systems to operate on it.

However, because of its high operating pressures significant re-design is required for all the major components of the refrigeration cycle. In particular the pipework where connections need to be secured to withstand the new operating pressures.

Many of the leading manufacturers, in accordance with recommendations contained in the European standard – BS EN 378 parts 1-4: 2000 are moving away from hand tightening to adopting the principle of torque control. This, they state not only allows them to comply with European Directives, but to prevent failure due to connections being either under or over tightened.

Indeed, one specialist manufacturer of torque control equipment, MHH Engineering based in Bramley, Guildford, Surrey has seen a significant increase in demand for its products from this industry sector.

'Two years ago we never thought seriously of the air conditioning market for our Torqueleader products, but now it’s an important part of our business,' declared David Jackson, Sales & Marketing Director.

'Many of the air conditioning industry’s biggest manufacturers recognise the importance of correctly tightened pipes, specifically when using R410A refrigerant'.

One major air conditioning supplier has already introduced a range of five ‘Torqueleader’ torque wrenches as part of an innovative customer rewards scheme. Spare Airconditioning plc, distributors of Daikin products, advise,

'The integrity of any installation involving refrigerant gas is of paramount importance; not only in relation to the efficient operation of the equipment but from an environmental responsibility viewpoint. If the correct tooling, as recommended by the manufacturers, is not in use as a matter of routine procedure, then that integrity may be compromised. We felt it was important to take the lead in ensuring that the tools for correctly tightening refrigeration pipe glands were included in the range of equipment we make available through our ‘Tools for Points’ loyalty scheme, and we are very pleased that the torque wrenches have been so popular.

Each torque wrench is fitted with a specially designed open-ended spanner head and is pre-set to the correct torque for the spanner used. The spanner sizes range from 17mm to 36mm and are set at torque values from 16Nm up to 100Nm. This system ensures that the relationship between nut size and torque applied is always correct, eliminating operator error.

Torqueleader torque handles ‘break’ through an angle of 20 degrees when the pre-set torque value has been achieved, signifying correct tightening.

'The European standard puts the onus firmly on the installer to use good practice and for manufacturers to give guidance on torque settings in their instruction manuals. In fact it insists the manufacturer or installer supply instruction manuals or leaflets along with safety instructions written in the languages of the country in which the refrigerating system is to be used'.

'There could also be serious legal and health and safety implications if someone gets hurt as a result of a joint failing, to say nothing of environmental concerns should this lead to refrigerant leakage'. Martin Rogers, Director of Air Improve Ltd., the Winchester based air conditioning installation, service and maintenance company, commented;

'We include the ‘Torqueleader’ torque wrenches as part of a standard list of essential equipment for our site engineers. It really is vital that air conditioning and refrigeration installation engineers are properly equipped to fully comply with the manufacturers’ well documented recommendations and to minimise the possibility of problems at a later date.'

With manufacturers concentrating their future on environmentally friendly advanced VRV R410 operated variable refrigerant volume systems the only accepted ‘best practice’ for engineers will be to adopt torque control for all installations.

Indeed, there will be no choice. The European Standard states:

'The joints should be solid and resistant enough to avoid any danger of the gasses being blown out. Flanges with a groove and tongue or projection and recess are preferred. Dismantling should be possible without forcing the jointed components. Care should be taken not to over stress bolts due to cold operation by applying a defined prestress.

When making flared joints, care should be taken to ensure that the flare is of the correct size and that the torque used to tighten the nut is not excessive.'

To prevent possible legal implications some leading manufacturers are currently training their approved installers to ensure they recognise the importance of correct tightening.

'Under tightening can result in leaks and over tightening can strip threads and crack components due to over stressing,' explained Mr Jackson. 'The potential cost implications to the engineer of ignoring torque control is far greater than the solution.'

This is an important consideration especially as R410A not only operates at a higher pressure, but the specific gravity of its vapour is larger than that of air. So should it leak in an airtight room it may stay at low level and cause an oxygen starvation accident. It may also, should it come in direct contact with fire, cause a poisonous gas to occur.

 Torque Settings Chart

A 'TCS' adjustable torque wrench in use at the training centre at Space-Airconditioning plc, Guildford.

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