return air fan

return air fan

A fan which withdraws air from an air-conditioned space and returns it (or part of it) to the central air-conditioning system.
References in periodicals archive ?
The test AHU has both a supply air fan and return air fan, and both fans are equipped with variable-frequency drives (VFDs).
The unit was equipped with both a supply and a return air fan, at fixed speeds, which combined could deliver 3817 cfm (1,801 l/s) at 2" (50 mm) wc external static pressure - this arrangement was changed part way through the monitoring period to reduce total airflow and overall electrical energy consumption.
3]/s (cfm) R = relief air damper control signal for BPP and BPA damper controls S = path resistance factor [omega] = relative fan speed based on design speed [theta] = damper blade position (1 for fully open and 0 for fully closed) Subscripts d = design EF = exhaust air fan ex = exhaust air (path) inf = envelope infiltration (path) MA = mixed air plenum (node) oa = outdoor air (path) OAD = outdoor air damper ra = return air (path) RCD = recirculating air damper RE = relief or return air plenum (node) rec = recirculating air (path) rel = relief air (path) RF = return air fan RLD = relief air damper RM = room air or space (node) sa = supply air (path) SF = supply air fan TB = terminal box
generally described as complete removal of the existing air handling unit (AH-1) and return air fan (F-9) and replacement with new similar units.
The unit was equipped with both a supply and a return air fan, at fixed speeds, which combined could deliver 3817 cfm (1,801 l/s) at 2" (50 mm) wc external static pressure--this arrangement was changed part way through the monitoring period to reduce total airflow and overall electrical energy consumption.
Space was found in the return air section for a new return air fan, and new return duct installation was found to be feasible.
The return air fan is assumed to be reduced by the ratio of the System Four 350,694 cfm (165 492 L/s) to the base system 400,000 cfm (188 760 L/s).
Return air fans are controlled to maintain required airflow through all zone return dampers with minimized pressure drop.
equipment to be controlled/monitored: air handling units, return air fans, exhaust and supply fans, chilled water system including pumps, chillers, and cooling towers, boilers including hot water pumps, split system dx units, packaged rooftop hydronic units, packaged rooftop dx unitsm, interlock to building fire alarm systems for required equipment shutdown, variable volume and constant volume box control, utility metering, power wiring to ddc devices, smoke control dampers and bas panels it is the intent of the district to have all specifications for the services and project materials for each project.
If your AHUs have return air fans, ensure that they don't pull too much air during low demand.
We used Allen Bradley energy evaluation software to study the performance of the supply and return air fans on the World Trade Center, and found that using high-efficiency motors and variable-frequency drives would improve their electrical efficiency," said Gene Kirkendoll, an electrical engineer and senior drives applications engineer at CED in Portland, which is also the local distributor of Baldor motors.