DIFFERENTIAL AIR PRESSURE SWITCH CHECK

Following steps and diagram indicate locations of connection points required to check differential air pressure.

Differential air pressure switch is safety device which prevents boiler from firing if there is air intake, boiler heat exchanger or vent blockage.

Turn off service switch, or lower thermostat setting.

Remove vinyl caps from Tee and 4-way connector.

Install testing lines as shown to inclined manometer or differential pressure gauge with ability to read 0.01” to 3.0” w.c.

Turn on service switch and set thermostat to call for heat.

BOILER

DIFFERENTIAL

PRESSURE

SWITCH

STATUS

PRESSURE (W.C.)

CONNECTS

 

 

 

 

 

Not Running

0”

Normally Open

 

 

 

 

1.00” for Model-100

 

Setpoint

1.60” for Model-75

 

 

2.10” for Model-50

 

Running

Greater Than

 

Without

Closed

Setpoints

Blockage

 

 

 

Running

Less Than or Equal to

 

With

Open

Setpoints

Blockage

 

 

 

If manometer readings do not correspond to chart above, check for possible causes:

- Blockage or moisture in suction lines

- Blockage in air intake or vent pipes

- Undersized air intake or vent pipes

- Loose blower wheel or motor shaft

- Incorrect pressure switch or pressure switch setpoint

When pressure reading is proper and the pressure switch is operating properly, remove testing lines and reinstall vinyl caps to Tee and 4-way connector.

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Lennox International Inc GWB9-100IH-2, GWB9-075IH-2 Differential AIR Pressure Switch Check, Boiler Differential Pressure

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