Fan coil units: operation and function

The key difference between the two systems is that the fan coil uses ‘forced convection’ with the aid of fans, whilst a radiator is based primarily on the transmission of heat by convection. The fan coil will have a copper tube with aluminium fins in a casing and is much smaller than a radiator, which is generally made of sheet metal.

In the past, the housing of the fan coil would be pretty large and not that attractive to look at, but it was designed to heat large open spaces.

• Having fans moving the warm air offers a number of advantages.
  • Quicker heat-up times – the fans contribute to faster heat-up times warming a room up to 3x quicker than a conventional radiator.
  • Low Operating Costs – Fan Coils generally require less water in them, so less energy is needed to heat them and consequently energy costs could be reduced.
  • Perfect on low-temperature systems such as ground or air source heat pumps – with the aid of the fans, radiators do not have to be oversized to compensate for lower operating temperatures.
• One other key advantage of fan coils is the introduction of cooling into a room.
• Fan Coils can either be based on a 2-pipe or 4-pipe system.
• Two pipes work on a single hydraulic circuit passing hot water in the colder months and using the unheated water and fans to lower room temperatures to a more comfortable temperature in the summer.
• A 4-pipe system has dedicated hot and cold water circuits designed for a deeper cooling performance closer to an air conditioning unit when it gets very hot.

• They make ideal additions to energy efficient systems such as ground and air source heat pumps which are working at lower temperatures than conventional heating systems. Besides the fans helping to increase the heat outputs, reversing the heat pump in the summer months offers a cooling function through the same unit.
• They also make perfect heat emitters in larger spaces when wall space is a premium.
• As home insulation is improved, most obviously when developing attic rooms, the heat required for a space will lessen, but the need for cooling may increase and a fan-coil unit allows this to be compacted into a single radiator.

Just like any conventional radiator, fan-coil units can be turned on and off with room thermostats. Unlike standard radiators, most fan-coil units will come with the option of setting varying fan speeds which in turn will increase or decrease the heat you receive.

They only come on for short periods because as soon as the room is heated up or cooled down to the optimum temperature, everything will switch off. And when they are on, they make less noise than a computer fan.