HVAC Design Considerations
U S Services offers design solutions for energy conservation oriented air conditioning systems that are duly compliant with ASHRAE, National Building Code (NBC) 2005 and Energy Conservation Building Code (ECBC).
Some of the main features requiring close attention are as follows:
Sizing HVAC System
We, at U S, understand that appropriate sizing of HVAC components is critical for the design of energy efficient HVAC system at optimum cost. Hence we adopt a systematic approach towards HVAC sizing, taking into consideration various factors such as climate, building configuration, space usage, system zoning and layouts.
Chilled Water Plants
U S adopts high efficiency water cooled, low IKW/TR chillers on most of the projects. Depending upon their type and capacity, large chillers are specified with variable speed drives. All the chillers are specified with microprocessor based control system along with chiller manager to monitor all the parameters of the plant. The plant generally consists of energy efficient screw chillers/centrifugal chillers/VFD driven chillers, multiple primary chilled water pumps, secondary chilled water pumps with variable frequency drives, condensing water pumps, FRP cooling towers, VFD driven double skin air handling units with thermal break and variable frequency drive, fan coil units, chilled and condensing water piping, air distribution system, insulation, electrical panels, wiring, control wiring and Earthing.
Efficient Chilled Water Distribution
Efficient Chilled Water DA significant amount of energy is used to distribute water for space cooling due to year round cooling loads in most parts of India. An efficient and proper design can result in substantial operating and capital savings, and can thus have a significant impact on a building's total energy consumption. Hence, at U S, the thrust is to use variable speed pumping system, a concept pioneered in India by U S in the early nineties.
Efficient Air Distribution System
While designing the air distribution system, special attention is paid to minimize pressure drops and noise by increasing the duct size, minimizing the bends & elbows and selecting the right type of air outlets. Air distribution design options are closely coordinated with architecture/interior design keeping in view the choice of duct type. Sizing is limited by the availability of the space above false ceilings. At U S, duct sizing is done utilizing a ducting software known as 'Eazy duct'.
Demand Control Ventilation
High occupancy spaces have huge ventilation requirements resulting in wastage of cooling energy, when the spaces are not fully occupied. Demand control ventilation is used to estimate the number of occupants in a space and reset the ventilation rate from the design occupancy to actual occupancy. Carbon Dioxide (CO2) sensors are the only currently accepted method of demand control ventilation. The benefits of demand control ventilation are reduction in energy conservation, reduced wear & tear of the equipment and confirmed/documented indoor air quality.
Variable Air Volume (VAV) Systems
In office buildings, shops and commercial establishments, we recommend the use of VAV's to provide the right quantity of cool air required for a specific building zone and at the same time supply different volumes to different zones. The result is that the total supply of cool air varies over the course of the day, depending on the heat gain level in different parts of the building at different times.
CO Sensors for Car Park Exhaust
Basement car park ventilation is often provided with exhaust fans to operate during normal occupancy hours. In accordance with ASHRAE Application Handbook, with reduction in vehicle emission, lower ventilation rates may be considered while designing the ventilation system for car parks. Accordingly, we recommend fans to be provided with VFD's which are actuated through CO Sensors based on the level of CO concentration, thus resulting in substantial energy savings..