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DIFFERENTIAL AIR PRESSURE SWITCH CHECK
The following steps and diagram
indicate the locations of the
connection points required to check
the differential air pressure.
The differential air pressure switch is
a safety device which will prevent the
boiler from firing if there is an 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 the ability to
read 0.01 to 2.0 w.c.
Turn on service switch and set
thermostat to call for heat.
58
C.
Boiler Status
Not Running
Setpoint
Running Without
Blockage
Running With
Blockage
Differential Pressure (w.c.)
0
1.00 for Model-100
1.35 for Model-75
1.55 for Model-50
Greater Than Setpoints
Less Than or Equal to
Setpoints
Pressure Switch Connects
Normally Open
Closed
Open
If manometer readings do not correspond to the 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
- Inncorect 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.