Run Around Coil (RAC)

Run Around Coil (RAC)
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Air handling units incorporating run around coils are important elements in saving energy in HTM:01 Specialised Ventilation (Hospitals), fume cupboards, drying processes, paint spray booths etc.

Heat Recovery Efficiency

The correct efficiency is a subjective decision and depends on the economic calculation and written guidelines, i.e. Ecodesign Commission Regulation (EU) No 1253/2014, on operating data such as energy prices, useful life, running times, temperatures, maintenance costs, and interest rates. With regard to (EU) No 1253/2014, profitability and environmental protection the heat recovery efficiency should be no less than 63%

Dependent on the right conditions heat recovery efficiencies can reach 70%

Air handling units incorporating run around coils are important elements in saving energy in Hotels, Retail, Corporate, High End Housing, Sports & Leisure, Education, Offices, Industrial, Data Centre, Health, and ATEX.

This investment passes off in several ways:


It is common for the supply and extract air handlers containing the run around coil system to be joined together, either in a side-by-side or a stacked configuration. However if required the units can be separated and up to 15m apart.

A run-around coil system comprises two or more multi-row finned tube coils connected to each other by a pumped pipework circuit. The pipework is charged with a heat exchange fluid, water, which picks up heat from the exhaust air coil and gives up heat to the supply air coil before returning again. Thus heat from the exhaust air stream is transferred through the pipework coil to the circulating fluid, and then from the fluid through the pipework coil to the supply air stream.

From this process the specific heat output capacity depends on the temperature difference between the two air streams. Hence the coil is suitable for heat as well as cool recovery, i.e. for winter and summer operation.

Ancillary Items

Air filtration is always present in order to provide clean dust-free air to the building occupants.

Direct heating, placed directly in the air stream, are direct heat exchangers and include those for gas-fired fuel-burning heaters or electric air heater batteries (EAHB).

Indirect Heating and Cooling coils use hot water or steam for heating, and chilled water for cooling. Heat pumps can be used as well. (Prime energy for heating and cooling is provided by central plant).

Humidification is often necessary in colder climates where continuous heating will make the air drier, resulting in uncomfortable air quality and increased static electricity. Various types of humidification may be used as part of our air handler and include evaporative, vaporizer, spray mist and wetted medium.

If dehumidification is required, then the cooling coil is employed to over-cool so that the dew point is reached and condensation occurs. A heater coil placed after the cooling coil re-heats the air to the desired supply temperature and humidity level. This is often used for chilled beam applications.

Smart Control System

Either our Smart Control System or the clients BMS may monitor the return air quality, energy available to recover or CO2 concentration for optimum energy efficiency whilst maintaining desired fresh air requirements. Additionally, when outside air conditions are such, typically mid-season weather conditions, it may be that ambient temperatures are suitable for free cooling purposes.


Our complete range of AHUs can be tailor made to suit all customer requirements including direct & indrect heating, cooling, heat pumps, controls and refrigeration.

Air volume ranges from 0.4m3/s to 35m3/s.