4.4.2 HVAC_Building Systems Facts/Rules Flashcards
- combination 4 pipe hydronic w/ forced air
- indiv control
- less quiet / more maintenance than VAV
Fan Coil
- hot/cool water system w/ local air circ.
- removes heat from water/add to air, or visa versa.
Heat Pump
Forced Air Systems:
- constant air volume,
- inexpensive to install/maintain,
- no indiv temp control.
Single Duct
Forced Air Systems:
- localized mixing boxes
- smaller ducts, saving space
Dual Duct (High Velocity)
Forced Air Systems:
- one plant serving all zones,
- separate mixing boxes,
- centralized at the plant for each zone.
- duct space increases as more zones added
Multizone
Forced Air Systems:
- constant temp, varied volume
- ventilation as well, so can’t be totally closed
- max. inidv. control, quiet, min. maintenance.
- conserves fan energy during light loads.
- adaptable changing / adding zones.
Variable Air Volume (single supply duct)
Forced Air Systems:
- combines heating/cooling/fan, 1 assembly
- simplified installation
- meter on each unit (easily separately billed)
Unitary
Forced Air Systems:
- humidity control / occupant comfort
- usually contained w/in VAV system
Reheat (Constant Volume)
Forced Air Systems:
- high velocity (smaller ducts)
- outside air mixed w/ recirc. conditioned air
- best in perimeter of multistory, multi room
Induction
- “Packaged Terminal Units” individual control,
but less quiet / more maintenance than VAV. - simple sys., evaporator direct contact w/ supply air.
- refrigerant vapor expansion/compression cycle.
- placed on exterior walls or roof.
Direct Expansion (DX) System
<60º, ext. air used, reducing refrigeration
Economizer Cycle
various sized chillers, operate best 1 for load.
Dual Condenser Chillers
If elec costs are high,
and low cost heat sources (steam),
higher initial cost, but only pay cooling.
Gas Fired Absorption Chillers
opperation costs can be less than compressive
Solar Powered Absorption Chillers
hot flue running through tank,
heat exch. on combustion chamber,
reclaims heat lost in chamber.
good where hot water is needed constantly.
Direct Contact Water Heaters
- preheats cold water entering boiler,
w/ recovered sensible and latent heat from flue. - heat would normally be discharged to atmosphere.
Recuperative Gas Boilers
cooler supply at low velocities at floor.
Displacement Ventilation
Reduces drafts, lower velocities, so less noisy.
Larger diffusers needed.
Less cooling needed.
Displacement Ventilation
- CO2 sensor to +/- ventilation w/ occupancy.
- not where constant ventilation necessary.
Demand-Controlled Ventilation (DCV)
can take heat from 1 area (cooling),
and add to other (heating)
w/ little added input
Water Loop Heat Pumps
store excess heat/coolness for use in future,
using water, ice or rock beds.
(utilizes º swings + off peak consumption)
Thermal Energy Storage
condition incoming fresh air, w/ energy from exhaust
- efficient in climate w/ high int/ext temp difference
- energy can be reduced 60-70%
Energy Recovery Ventilators
Air to Air Heat Exchangers
2 ducts, in/out, thin heat transfer wall
Flat-Plate Heat Recovery Units
closed loop runs through in/ext ducts.
exhaust vaporizes refrigerant
Heat Pipes
Infiltration Measurement Tools:
fan mounted in door frame,
pressurize + depressurize space.
Blower door
Infiltration Measurement Tools:
over register/diffuser measure output.
Flowhood
Infiltration Measurement Tools:
similar to blower door, but directly to duct.
Duct blower
Infiltration Measurement Tools:
measures pressure dif. between 2 spaces.
Nanometer
Methods for Analyzing Annual Energy Costs:
- compare to baseline building.
- must be followed to obtain LEED credit.
Building Energy Cost Method
Methods for Analyzing Annual Energy Costs:
- complex calcs based on site’s climate.
System Performance Method
Methods for Analyzing Annual Energy Costs:
- tends to be more restrictive
Prescriptive Criteria Method
