Scheduling - Scheduling is the practice
of turning equipment on or off depending on time of day or day of the week.
Improving equipment schedules is one of the most effective measures for saving
energy in commercial buildings. A feature called "Optimum Start," can
increase energy savings by automatically starting a system no earlier than
necessary based on daily variations in the weather.
Resets- HVAC systems typically use
less energy when their operating parameters are adjusted to meet the building
load. Because this load varies with the weather, a BAS can help equipment to
operate at greater efficiency levels by automatically varying these operating
parameters. The simplest approach is to use a proportional reset schedule based
on outdoor temperature. Although that method works reasonably well, a more
effective method is to base resets directly on building loads. Examples of
building control parameters that can be reset include supply-air and
discharge-air temperature for fan systems that use terminal reheat, hot-deck
and cold-deck temperatures for multizone HVAC systems, and heating-water supply
temperature.
Demand limiting- Because
electrical demand charges can comprise 40 percent or more of a utility bill,
many building automation systems can benefit from demand-limiting or
load-shedding functions. For example, when the demand on a building meter or
piece of equipment, such as a chiller, approaches a predetermined setpoint, the
BAS does not allow the equipment to load up any further. In buildings with
electric heat, electrical demand charges can be reduced if the heat is staged
on in the morning over a several-hour period starting with the coldest spaces
first. Other demand-limiting strategies are expected to be developed as
utilities implement time-of-day or real-time electrical pricing in their rate
structures.
Direct digital control (DDC)- Direct digital control is provided by a BAS that
directly controls valves, dampers, and other system components for building
temperature control. The advantage of this approach is that a more advanced
control algorithm called PID can be implemented in the BAS's computer code. If applied properly, PID can both save energy and
provide improved comfort.
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