3. Coordinating Engineering Systems - NM Flashcards
List components of forced-air heating systems
- Gas or oil furnace- needs air combustion and vent, in basement or in attic
- Bonnet or plenum - chamber at the top of furnace connected to main duct
- Leaders- ducts that convey warm air
- Diffusers
What is hydronic heating system?
Heating building by means of water - boiler and circulated by a pump through pipes / radiators or convectors.
Advantage and disadvantage of electric heating?
+compact and versatile electric resistance heaters
- no provision for controlling humidity and air quality
List different types of heating systems:
- Forced air heating
- Hydronic heating system (water)
- Electric resistance heating
- Radiant heating (pipes or conduits in floors or ceiling)
- Solar heating
What does solar heating system require?
- Solar collector panels
- Circulation and distribution system - air, water or other liquid
- Heat exchanger
- Storage facility- tank with liquid or bin of rocks
What can a heating,ventilation and air-conditioning system control?
Simultaneously controls temperature, humidity, purity, distribution, and motion of the air inside a building.
What equipment does HVAC system require?
- Boiler - hot water or steam for heating - connected to a chimney
- Chilled water plant - connected to cooling tower (on roof) to dispose of the heat
- Both connected to an Air handling unit inside fan room - it is connected to fresh air that it filters, and exhausts air
- Heated / cooled air is distributed through air, water or combination
- Return air is brought back to central plant.
Types of all-air systems
- Single duct constant air (CAV) - constant temperature
- Single duct variable air volume (VAV) - uses dampers at the terminal to control the flow according to the room requirements
- Dual duct - uses 1 duct for heated air and 1 duct for cool air, delivered to mixing boxes with thermostatically controlled dampers
- Terminal reheat system - more flexible, terminals have reheat coils that regulate the temperature
Types of all-water systems
- Two-pipe system - 1 pipe to supply and 1 pipe to return the water, fan-coil units circulate room air to the coils
- Four-pipe system - 2 circuits (hot and cold) for simultaneous heating and cooling
Advantages of all-water systems?
Pipes require less space than air ducts
Types of air-water systems?
Use high-velocity ducts to supply air to the room through the fan-coil units which heats it via water system. Primary air draws in room air through a filter and passes through coils.
What are packaged systems?
Self-contained boxes (roof or slab) - fan+filters+compressor+condenser+evaporator coils+heat pump or heating elements.
Up to 4-5 storeys.
What are split-packaged units?
Outdoor unit - compressor + condenser
Indoor unit - cooling & heating coils + circulating fan
What are small units that can retrofit existing buildings?
Small terminal units - below a window through wall
Which HVAC system will minimize the initial cost? (2)
- Simplest all-air system: single duct, CAV
- No ductwork / piping: through the wall and packaged terminal units
Which HVAC system will minimize operating cost and energy consumption? (3)
- Converts fuel to heating with maximum efficiency:
- VAV
- single duct CAV
- hydronic convectors - Using ambient heat from surrounding environment:
- closed-loop heat pump system - Med-size & small bldgs, passive system:
- passive solar heating
- natural ventilation cooling
- thermal mass cooling
- evaporative cooling
Which HVAC system will maximize control of air quality & velocity? (1)
All-air heating systems:
- VAV
- VAV reheat
- VAV induction
- dual-duct VAV
- single duct CAV
- CAV reheat
- multizone
Which HVAC system will maximize individual control over temperature in a number of rooms / zones? (1)
System that can react separately to a number of thermostats:
- VAV
- VAV reheat
- VAV induction
- dual-duct VAV
- CAV reheat
- multizone
- air-water induction
- fan-coil terminals
- through wall and packaged terminal units
Which HVAC system will minimize system noise? (2)
- System that operates at low air velocities and whose moving parts are distant from occupied spaces:
- Any all-air system EXCEPT induction
- hydronic convectors - Med-sized & small bldgs, passive system:
- passive solar heating
- natural ventilation cooling
- thermal mass cooling
- evaporative cooling
What is VAV? Applications, advantages, disadvantages?
Air is conditioned at a central source, supply & return fans circulate conditioned air through ducts to occupied spaces. At EACH zone, a thermostat controls the room temperature.
What is single duct CAV? Applications, advantages, disadvantages?
Air is conditioned at a central source; supply / return ducts circulate air to occupied spaces. A MASTER thermostat controls central heating / cooling for the ENTIRE building.
Applications: large open areas, few windows, uniform loads (lobbies, deptartment stores, theaters, autoriums)
+ High degree of control of air quality
+ Simple & easy to maintain
- No possibility of individual temperature control
What is air-water induction system? Applications, advantages, disadvantages?
Air is conditioned at a central source & circulated in SMALL high-velocity ducts to spaces.
Air discharging (primary air) draws a large amount of room air through the filter. Then the air mixture passes through a coil heated / cooled by secondary water piped from boiler or chilled water plant. LOCAL thermostat controls the water flow. Condensate needs to be drained.
Application: wide range of heating / cooling needs where humidity doesn’t need to be controlled (office)
+ less space required
+ no fans in occupied spaces
- complicated system
- noisy
- energy inefficient
- lack of humidity control
What is fan-coil terminals? Applications, advantages, disadvantages?
Hot/cold water piped to fan-coil terminals. Fan draws mix of indoor & outdoor air through filter & blows it across a coil that is heated /cooled by water. A thermostat controls the flow of water. Condensate must be drained.
Application: Multiple zones located around perimeter (school, hotel, motel, apartments, offices)
+ no mechanical room or ductwork required
+ individual control temp
- humidity control
- a lot of maintenance, within occupied parts of building
What is closed-loop heat pump? Applications, advantages, disadvantages?
A water-to-air heat pump in each space. The water circulates in a closed loop.
Applications: hotels with overheated areas (kitchens, laundry, assembly, restaurants)
+ efficient in extracting heat from overheated spaces or heat cold spaces
- expensive
- a lot of maintenance in occupied spaces
What are hydronic convectors? Applications, advantages, disadvantages?
Hot water circulated through fin tube convectors (horiz pipes with vertical fins) that heat indoor air by convection.
Application: where cooling not required, operational windows or as a supplement system
+ economical
+ individual control
- heating only
- cooling / humidity / ventilation not included
Difference electrical service to local circuits for:
- large buildings
- medium buildings
- small buildings
Large: - exterior transformer - elec room - smaller elec closets
Medium: - exterior transformer - elec room - smaller elec closets or panels
- interior transformer & elec room - smaller elec closets or panels
Small: - transformer from Hydro before meter - elec panel
