Honeywell F300 Instruction Manual

Air Flow Switch Operation
The air ow switch (AFS) senses differential pressure across its inputs. The AFS signals the air cleaner ON when a vacuum
is present at the unit. Removing the tubing and using a straw to apply a vacuum near the orice will turn the AFS ON.
Also blowing air into the unconnected input will activate the AFS.
This test will bypass the airow switch allowing the power supply to operate. If the indicator light does not turn on with
the airow switch bypassed, then this indicates a problem with the power supply. Note the collector cells should be
removed to insure the output is not being shorted.
Honeywell manufactured two AFS versions. The new version has a smaller circuit board. Zoom in to the photos to
determine your version.
Air Flow Switch Bypass Procedure
1. Bypass the AFS:
• (2012 - Present) Unplug the AFS then connect the two pins marked “bypass AFS” using a jumper wire.
• (Prior - 2012) Short the resistor to ground with a jumper wire, see photo for your model
2. The door interlock switch must be ON
3. Turn ON the On-Off switch
F300 F50 F52 Models ................................................................................................................. 2012 - Present
On the power supply, connect the two pins labeled “Bypass AFS” located on J3 with a jumper. To permanently bypass the
AFS cut the R16 jumper/resistor.
Tech Note ©
October 2013
Honeywell Air Flow Switch (AFS) ElectronicAirCleaners.com
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J3R16

F300 F52F Models .......................................................................................................................... 2006 - 2012
Ground the power supply resistor J8, a paint coating may need to be cleaned.
Permanently disabling the AFS is outlined the Honeywell F300 Product Data Manual, see page 13.
F300 F50F F50E F52 Models .......................................................................................................... 1990 - 2006
Tech Note ©
October 2013
Honeywell Air Flow Switch (AFS) ElectronicAirCleaners.com
ElectronicAirCleaners.com
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Note:
The last bypass procedure (1990 -2006) will light the neon indicator and bring the power supply to full power but it does
not fool the optional W8600F remote indicator. The LCD indicator will remain off itndicating the air cleaner is not running.
Permanently disabling the AFS is outlined the Honeywell F50F Product Data Manual, see page 11.
Air Flow Switch Voltages
We measured these voltages
WIRE OFF ON
Black gnd gnd
Gray 13.7 vdc 13.2 vdc
Orange 0.7 vdc 13.2 vdc
Violet 5 vdc 0 vdc
Dimensions
We measured the 4074ETH:
Four 5/32” dia holes on 2-23/32” center.
Overall size 3-5/16” square. Height 15/16”
Tech Note ©
October 2013
Honeywell Air Flow Switch (AFS) ElectronicAirCleaners.com
ElectronicAirCleaners.com
Bel-Aire ElectronicAirCleaners.com, Inc · 70 Case Avenue Seekonk MA 02771 · Ph: 774.901.4770