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Large Retail Store |
VAV FPMB with Central Station Air Handler with Chilled Water |
Fan-Powered Mixing Boxes |
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Fan-powered mixing boxes are variable air volume
(VAV) devices that modulate the amount of air that enters the
space. A damper located in the supply airstream modulates the
amount of conditioned air that enters the space in response to
space thermostat requirements. The difference between a fan-powered
mixing box and a standard VAV box is the addition of a fan inside
the box. This fan induces air from the ceiling plenum and mixes
it with the primary air, hence the name mixing box. By introducing
ceiling plenum air back into the space, the fan box is able to
capture waste heat from the lights to help offset any space heating
demands, thereby saving energy.
On a "series" box, the fan runs continuously
whenever the system is energized to supply a constant quantity
of total supply air to the space. This total air is made up of
a mixture of primary air (from the air handler) and ceiling plenum
air. As the space cooling load becomes satisfied, the primary
air damper begins to close. As this damper closes a proportional
amount of plenum air is induced through a port on the side of
the box such that the total quantity of air entering the space
stays constant.
On a "parallel" box, the fan runs only
when there is a call for heating from the space thermostat. As
the cooling load becomes satisfied the primary air damper closes
to a minimum position. On a call for heat the fan is energized
and pulls air from the ceiling plenum through the box and into
the space. If the space temperature drops further, optional supplemental
heat (either electric resistance or hot water) is energized to
provide additional heat to the space.
The 45S Series Fan-Powered Mixing Box provides variable
volume cooling/heating for large zones. Available in six sizes
from nominal 500 to 3,000 cfm for cooling only, heating only or
cooling & heating. Heat is available in either electric or
hot water.
The 45T Parallel Fan-Powered Mixing Box provides variable volume cooling/heating for large zones. Available in six sizes from nominal 500 to 4,000 cfm for cooling only, heating only or cooling & heating. Heat is available in either electric or hot water. The parallel fan operates in the heating mode only and mixes varying quantities of plenum air with heat from the box to provide precise temperature control over a wide range of operating conditions.
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