Honeywell F300 Operation

Air flow switch (afs)

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Tech Note ©

October 2013

Honeywell Air Flow Switch (AFS)

Air Flow Switch Operation

The air flow 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 orifice will turn the AFS ON.

Also blowing air into the unconnected input will activate the AFS.

This test will bypass the airflow switch allowing the power supply to operate. If the indicator light does not turn on with

the airflow 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.

Bel-Aire ElectronicAirCleaners.com, Inc · 70 Case Avenue Seekonk MA 02771 · Ph: 774.901.4770

R16

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Page 1 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.
Page 2 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...
Page 3 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...

F52 F50f F50 F50e