Ask The HvacMan
Air Grilles
Air Diffusers
Air Quailty
All Air Systems
All Water Systems
Building .Managament Systems ..BMS
Cooling Towers
Cooling Load Calculation
Energy Saving
Duct ,Smacna
Dampers ,Air
Dust Collection
Fire Dampers
Glass Selection
Heat Exchangers,water
Heat Recovery
Heat Tracing Systems
Hepa Filters
Hvac Applications
Humidifiers / Dehumidifiers
Insulation , Duct
Insulation , Pipe
Insulation , Sound
Nano Tech.,In Building
Occupancy Sensors
Pneumatic Conveying
Pool Ventilation
Process Piping
Radiant Heating
Refrigerant Systems
Solar Collectors
Steam Generation
Tables & Charts Gnr.
VAV Sytems
VRV Systems
Solar Collectors
Flat Plate Collectors
Evacuated Tube Collectors
Concentrating Collectors
Transpired Collectors
Solar Control Systems
Standalone Systems
Grid Connected Systems
Hybrid Systems
Back-up Systems
Solar Cells
Solar Arrays
Change Controller
Hybrid Systems
Grid Systems
Water Pumping
Using Wind Energy
Enviromental Aspects
Buyer's Guide
Save Energy
Solar Water Heating
Solar Electric Systems
Wind Turbines
Passive Solar Heating
Passive Solar Cooling
Building Material
Water Conservation
Ground Source Heat-Pumps
Green Hotels

Glass &Windows Selection

Terminal Systems ,Fan coils,Induction Units

IN-ROOM TERMINAL SYSTEMS condition spaces by distri buting air and water sources to terminal units installed in habitable spaces throughout a building. In some systems the air is distributed to the space directly, not through the terminal unit. The air and water are cooled or heated in central equipment rooms. The air supplied is called primary or ventilation air; the water supplied is called
secondary water. Sometimes a separate electric heating coil is included in lieu of a hot water coil. This chapter describes induction units and fan-coil units used in in-room terminal unit systems.

In-room terminal unit systems are applied primarily to exterior spaces of buildings with high sensible loads and where close control of humidity is not required. In some cases they may be applied to interior zones. They work well in office buildings, hospitals, hotels, schools, apartment buildings, and research laboratories. In most climates, these systems are installed in exterior building spaces and are designed to provide (1) all required space heating and cooling, (2) outside air for ventilation, and (3) simultaneous heating and cooling in different parts of the building during intermediate seasons.


Fan-coil unit systems include cooling as well as heating, normally move air by forced convection through the conditioned space,
filter the circulating air, and introduce outside ventilation air. Fan coil units with chilled water coils, heating coils, blowers, replaceable air filters, drain pans for condensate, etc., are designed for these purposes. These units are available in various configurations to fit
under window sills, above furred ceilings, in vertical pilasters built into walls, etc. These units must be properly controlled by thermostats for heating and cooling temperature control, by humidistats for humidity control, by blower control or other means for regulating air quantity, and they must have a method for adding ventilation air. into the building.

In-Room Terminal Systems

Basic elements of fan-coil units are a finned-tube coil, filter, and fan section (Figure 2). The fan recirculates air continuously from the space through the coil, which contains either hot or chilled water. The unit may contain an additional electric resistance, steam,
or hot water heating coil. The electric heater is often sized for fall and spring to avoid changeover problems in two-pipe systems.

A cleanable or replaceable 35% efficiency filter, located upstream of the fan, prevents clogging of the coil with dirt or lint entrained in the recirculated air. It also protects the motor and fan, and reduces the level of airborne contaminants in the conditioned space. The fan-coil unit is equipped with an insulated drain pan. The fan and motor assembly is arranged for quick removal for servicing. Most manufacturers furnish units with cooling performance certified as meeting Air-Conditioning and Refrigeration Institute (ARI) standards. The prototypes of the units have been tested and labeled by Underwriters’ Laboratories (UL), or Engineering Testing Laboratories (ETL), as required by some codes.

Fan-coil units, with a dampered opening for connection to apertures in the outside wall, are available. These units are not suitable for commercial buildings because wind pressure allows no control over the amount of outside air that is admitted. Also, freeze protection may be required in cold climates. However they are often used in residential construction because of simplicity of operation, low first cost, and the operable windows can unbalance
a duct ventilation air system. Fan-coil units for the domestic market are generally available in nominal sizes of 200, 300, 400, 600,
800, and 1200 cfm, often with multispeed, high-efficiency fan motors. Where units do not have individual outside air intakes, means must be provided to introduce retreated outside air through a duct system that engages each room or space.

Types and Location

Fan-coil units are available in many configurations. Low vertical units are available for use under windows with low sills; however, in some cases, the low silhouette is achieved by compromising such features as filter area, motor serviceability, and cabinet style.

Floor-to-ceiling, chase-enclosed units are available in which the water and condensate drain risers are part of the factory-furnished unit. These units are used extensively in hotels and other residential buildings. The supply and return air must be isolated from each other to prevent air and sound interchange between rooms.

Vertical models or chase enclosed models located at the perimeter give better results in climates or buildings with high heating requirements. Heating is enhanced by under-window or exterior wall locations. Vertical units can be operated as convectors with the fans turned off during night setback.

Horizontal overhead units may be fitted with ductwork on the discharge to supply several outlets. A single unit may serve several rooms (e.g., in an apartment house where individual room control is not essential and a common air return is feasible). Units must have larger fan motors designed to handle the higher pressure drops of ductwork.

Horizontal models conserve floor space and usually cost less, but when located in furred ceilings, they create problems such as condensate collection and disposal, mixing of return air from other rooms, leakage of pans causing damage to ceilings, difficulty of access for filter and component removal, and air quality concerns.

When outside air is introduced from a central ventilation system it may be connected directly to the inlet plenums of horizontal units or introduced directly into the space. If introduced directly, provisions should be made to ensure that this air is pretreated and held at a temperature equal to the room temperature so as not to cause
occupant discomfort when the unit is off. One way to prevent air leakage is to provide a spring-loaded motorized damper that closes off the ventilation air whenever the unit’s fan is off. Coil selection must be based on the temperature of the entering mixture of primary
and recirculated air, and the air leaving the coil must satisfy the room sensible and latent cooling and heating requirements. ,

Fan Coil Selection
Fan Coil Wiring
Fan Coil Pipng
Fan Coil Capacity Control
Fan Coil Maintanance
Fan Coil Water Disturbition
Fan Coil Central Plant
Fan Coil Ventilation
Fan Coil Application
Fan Coil Advantages Disadvantages
Primary Air Systems



  Discuss on the Message Board
Legionnare Disease
Energy Saving
Control Software
Hotel Design Books

Hotel Design