Application Principle
This Variable Air Volume system is a little simplified solution
of the Variable Air Colum Systems with VSD Fan Control.
Instead of having constant static pressure or airflow control of the
return air fan it is tracking the positive pressure by following the
"master" supply fan speed. The idea is to keep the return
airflow equal to the supply airflow, which means that the fans
should have equal capacity. This method may be easier to be
kept stable than the systems with static pressure controls.
This system used for multiple zone air conditioning usually has
thermostat and damper controlled terminal units for each zone. |
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Air conditioning system with variable speed
drives |
The system may be designed so that cooling of the rooms is obtained
by outside air without operating the refrigeration plant. Correct
room temperature can be achieved by:
- Air volume control
- Bypass damper control
- Control of heating or refrigeration capacity
Detailed Description
This variable air volume system brings outside air and return air to
the Air Handling Unit (AHU) (3) where the incoming air (8) temperature
and humidity can be controlled. The main AHU components are supply
air fan (2), heating coil (5), cooling coil (6), filter (7) and humidity
control equipment (not drawn). The three-way valves for heating
and cooling are remotely operated by the control panel (11). The
temperature in the individual rooms is measured by thermostats (15),
which directly control the dampers in the room terminal units. The
supply air fan is speed controlled by an AC drive (4) and it delivers
the air to individual rooms throughout the building by supply air ducts.
The AC drive controls the air volume by keeping the pressure constant.
The pressure is measured by the sensor (13). The return air fan
(1) delivers the exhaust air (9) out of the building or part of the air
(10) is returned back to the AHU. The return fan is controlled by
an AC drive (14), which is following the speed of the supply fan.
Performance in Creating comfort zone
The use of variable speed AC drives improves the controllability
of the whole heating, cooling and air conditioning system, enabling
good possibilities to maintain the Comfort Zone. The use of
variable speed drives usually increases the first cost of investment
but through savings in electrical energy in motors along the
investment in VSD has pay-back time between 0.2-3 years.
In addition to savings in electrical energy, there are several
important customer benefits speaking for VSD: |
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Air conditioning is an important system in
industrial buildings (Guangzhou, China) |
- Fast control to maintain the comfort zone conditions
- Accurate control to keep the desired air quality
- Reduced consumption of heating and cooling energy
- Reduced consumption of electrical energy
- Simple to keep the noise level down
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