Differential Air Pressure Switch Check - Dunkirk 90-50 Installation, Operation & Maintenance Manual

What is system status?
The following steps and diagram indicate the locations of the con-
nection 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.

differenTial air pressure sWiTCH CHeCk

55
BOILER DIFFERENTIAL
STATUS PRESSURE (w.C.)
Not Running
1.00" for Model-100
Setpoint 1.35" for Model-75
1.55" for Model-50
Running
Greater Than Set-
Without
Blockage
Running
Less Than or Equal to
With
Blockage
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 operat-
ing properly, remove testing lines and reinstall vinyl caps to Tee and
4-way connector.
PRESSURE
SwITCH
CONNECTS
0" Normally Open
Closed
points
Open
Setpoints