We have following topics to cover for In-room terminal system of HVAC.
- Perimeter Zone Air-Conditioning Loads
- Secondary- Water Distribution
- Induction Units
- Two-Pipe Systems with Central Ventilation
- Fan-Coil Units
- Four-Pipe Systems
- Water Distribution
- Refrigeration Load
- Central Plant Equipment
- Changeover Temperature
- Ventilation
- Performance Under Varying load
- Primary Air Systems
HVAC In-Room Terminal System
In-ROOM terminal systems, condition spaces by distributing air and water sources to terminal models put in in liveable areas all through a constructing. In some techniques, air is distributed to the house instantly, not by the terminal unit. In-room terminals normally situation a single house, however some (e.g. a big fan-coil unit) might serve a number of areas. The air and water are cooled or heated in central equipment rooms. The air provided is named main or ventilation air; the chilled water provided is named main or secondary water. Steam may be used. Typically a separate electrical heating coil is included in lieu of a hot-water coil. This chapter
describes induction models and fan-coil models utilized in in-room terminal unit techniques.
These techniques are used primarily in perimeter areas of buildings with excessive smart loads and the place shut management of humidity is not required, however are generally utilized in inside zones. They work, nicely in workplace buildings, hospitals, lodges, colleges, condominium buildings, and analysis laboratories. In most climates, these techniques are put in in perimeter constructing areas and are designed to supply (1) all required house heating and cooling, (2) outdoors air for air flow, and (3) simultaneous heating and cooling in numerous elements of the constructing throughout intermediate seasons.
What is HVAC Terminal Device?
HVAC terminal device is used for regulation of conditioned volume air between occupied space and central air handler.
In-Room Terminal System Advantages
- Individual room temperature management permits every thermostat to be adjusted for a unique temperature at comparatively low value.
- Separate heating and cooling sources within the main air and secondary water give. occupants a selection of heating or cooling.
- Much less space is required for the distribution system when the air provide is diminished by utilizing secondary water for cooling and excessive velocity primary-air supply. The return air duct is smaller and might generally be eradicated or mixed with the return air system for different areas, comparable to the inside spaces.
- The central air-handling equipment is smaller than that of an all-air system as a result of much less air should be conditioned at that location.
- Dehumidification, filtration, and humidification are carried out in a central location remote from conditioned spaces.
- Ventilation air is positively provided and might accommodate fixed beneficial outdoors air portions.
- Space might be heated with out working the air system, by way of the secondary-water system. Night time fan operation is averted in an unoccupied building. Emergency power for heating, if required, is way decrease than for many all-air techniques.
In-Room Terminal System Disadvantages
- For a lot of buildings, in-room terminals are restricted to perimeter space; separate techniques are required for different areas.
- Extra controls are wanted than for a lot of all-air systems.
- Prima&-air supply normally is fixed with no provision for shut off. It is a drawback in residential purposes, the place tenants or lodge room guests’ might favor to show off the air conditioning, or the place administration might want to take action to cut back operating expense.
- Low primary chilled-water temperature and/or deep chilled-water coils are wanted to regulate space humidity adequately.
- The system is not-appropriate for spaces with excessive exhaust necessities (e.g., analysis laboratories) except supplementary ventilation air is supplied.
- Central dehumidification eliminates condensation on the secondary-water heat switch floor beneath most design latent load, however irregular moisture sources (e.g., open home windows, cooking, or folks congregating) could cause annoying or damaging condensation. Due to this fact, a condensate pan needs to be supplied as for different systems.
- Low primary-air temperatures require closely insulated ducts.
- Energy consumption for induction systems is increased than for many different systems due to the increased energy wanted to ship primary air in opposition to the pressure drop within the terminal units.
- Preliminary value for a four-pipe induction system is larger than for many all-air systems.
This article is based on following document. For more details please read following document
Building Air Distribution System of HVAC | ASHRAE
HVAC SYSTEM ANALYSIS AND SELECTION | ASHRAE