The systems can be with air-water or all water. They can be further divided into
• Two-pipe: Either hot or cold water
• Three-pipe: Two supplies and one for common return
• Four-pipe: Two for supply and the other two for return.
Auxiliary condensate pan
Fig. 9 Four-Pipe System Room Unit Control
Fan coil unit consists of:0
New fan coils usually have separate coils for heating and cooling that increases first cost compared to the units with a single coil. However, four-pipe system is more flexible than two — pipe system, and does not require “changeover” or zone reheat.
The fan coil unit is flexible, can condition w/o primary air and has better filtration than the induction unit. Primary air is directly supplied to space if the system is air-water.