The unit airflow is typically modulated in some way to match the server fan though a constant volume system
can still be employed.
The consequence is that a very expensive VAV system can have the same operating cost as a constant volume system
The building's constant volume system
was converted to a variable air volume (VAV) system, contributing most significantly to the project's energy and fiscal savings.
This system is loosely termed "constant volume." But what keeps this constant volume system
"Since this is a constant volume system
, and I'm not moving much air to begin with, you don't have constantly varying pressures between spaces like you do with VAV," Mumma said.
Unlike the constant volume system
, there is only one requirement that must be satisfied to make this a successful pass.
The older system operated as a large constant volume system
that staged each 15 ton (53 kW) AC unit to match the loading in each space, which ranges between 20 and 40 tons (70 and 141 kW) throughout the year.
The engineering team's contributions included the design of a dual-duct, dual-fan, variable air volume system (VAV) to replace the existing dual-duct, single-fan, constant volume system
. The renovation also included the upgrade of the chilled water system.
The following calculations assume a 25,000 cfm (11 800 L/s) constant volume system
of 55[degrees]F (13[degrees]C) air at 8 in.
In this case, as indicated previously, the actual design flow for the variable flow system is 360 gpm (23 L/s) compared to 400 gpm (25 L/s) for the constant volume system
with a DSF of 11% and a second system with a DSF of 25% and a flow of450 gpm (28 L/s).
While relatively simple for constant volume systems
, which often includes series fan-powered VAV systems, an air balancer forces a VAV system (or a section of a system) to go to full design airflow, typically by setting zone thermostats to call for full cooling in that zone.
One option for the air-distribution system is to convert dual-duct, multi-zone, or constant volume systems
to a variable volume system.