Page 73 - GRIHA Manual Volume III - Introduction to National Rating System
P. 73
66 GRIHA Manual: Volume 3
• Chilled water VAV model: In this type of system, air is distributed from the air handlers,
through ductwork (often medium pressure) to terminal units and then to the space
through a low-pressure distribution system. The terminal units regulate the volume
of air and are equipped with coils that can modify the temperature of the air (if need
be), in response to the requirements of the space to be conditioned. Terminal units
are also equipped with fans to re-circulate room air for energy conservation. The
sizing of the central equipment can take advantage of load diversity. Such systems
make very effective use of air-side economizers.
Components: Mixing plenums (where outdoor air and return air are combined), filters
(these can be medium- or high-efficiency), cooling and/or heating coils, fans, and air
handlers.
Features: Variable speed drives for fan volume control are more cost-effective.
These systems provide a great deal of flexibility for multiple zones and provide
good dehumidification control. They are well suited for proper control of building
pressurization, ventilation air quantities, and opportunity for higher levels of
filtration.
Table 5 Recommended chiller types for different cooling ranges
Range (tonnes) Condenser type Rank Chiller type
1–100 All 1 Scroll
All 2 Screw
All 3 Centrifugal
101–300 All 1 Scroll
All 2 Screw
All 3 Centrifugal
Water 4 Absorption (double effect)
Water 5 Absorption (single effect)
301–1250 All 1 Centrifugal
All 2 Screw
Water 3 Absorption (double effect)
Water 4 Gas engine
Water 5 Absorption (single effect)
Following section provides description of some of the energy-saving equipments
• Energy recovery wheel
Energy recovery wheels are optional enthalpy wheels installed to affect heat exchange
between fresh air and return air. Latent heat and sensible heat are transferred from the hotter
and moist exhaust air to the colder and dry outside air during winter. In summer, latent heat
and sensible heat are transferred from the hotter and moist outside air to the cooler and dry
exhaust air. This acts like pre-cooling or pre-heating of fresh air.
• Economizer
An economizer is a heat exchanger, which is operated to pre-heat/pre-cool the outside air and
to reduce energy consumption.
• Chilled water VAV model: In this type of system, air is distributed from the air handlers,
through ductwork (often medium pressure) to terminal units and then to the space
through a low-pressure distribution system. The terminal units regulate the volume
of air and are equipped with coils that can modify the temperature of the air (if need
be), in response to the requirements of the space to be conditioned. Terminal units
are also equipped with fans to re-circulate room air for energy conservation. The
sizing of the central equipment can take advantage of load diversity. Such systems
make very effective use of air-side economizers.
Components: Mixing plenums (where outdoor air and return air are combined), filters
(these can be medium- or high-efficiency), cooling and/or heating coils, fans, and air
handlers.
Features: Variable speed drives for fan volume control are more cost-effective.
These systems provide a great deal of flexibility for multiple zones and provide
good dehumidification control. They are well suited for proper control of building
pressurization, ventilation air quantities, and opportunity for higher levels of
filtration.
Table 5 Recommended chiller types for different cooling ranges
Range (tonnes) Condenser type Rank Chiller type
1–100 All 1 Scroll
All 2 Screw
All 3 Centrifugal
101–300 All 1 Scroll
All 2 Screw
All 3 Centrifugal
Water 4 Absorption (double effect)
Water 5 Absorption (single effect)
301–1250 All 1 Centrifugal
All 2 Screw
Water 3 Absorption (double effect)
Water 4 Gas engine
Water 5 Absorption (single effect)
Following section provides description of some of the energy-saving equipments
• Energy recovery wheel
Energy recovery wheels are optional enthalpy wheels installed to affect heat exchange
between fresh air and return air. Latent heat and sensible heat are transferred from the hotter
and moist exhaust air to the colder and dry outside air during winter. In summer, latent heat
and sensible heat are transferred from the hotter and moist outside air to the cooler and dry
exhaust air. This acts like pre-cooling or pre-heating of fresh air.
• Economizer
An economizer is a heat exchanger, which is operated to pre-heat/pre-cool the outside air and
to reduce energy consumption.
