ENVIRO-TEC
22
FORM ET115.24-NOM11 (118)
DIFFERENTIAL AIR PRESSURE SWITCH
General information
This accessory is a differential pressure switch with
a normally-open (NO) dry contact that is factory
calibrated to close at a differential pressure of 0.15
inches of water or greater. The switch measures the
pressure differential between the unit’s fan section and
the environmental pressure outside the unit. When the
filter is sufficiently clogged or dirty, differential pressure
will rise and the switch will close.
Technical specifications
Electrical
Initial resistance
<500m
W
Rating
3.15ma @ 125VAC
10-20ma @ 5-24VDC
Adjustable set point ranges in H
2
O
Ranges
In H
2
O
Min.
Max.
Proof
0.10
0.50
5.0
Functional
Operating positing Diaphragm vertical, barbed
fittings horizontal
Operating temp.
-40 °F to 140 °F
(-40 °C to 60 °C)
General measurements: Pressure Switch
Figure 11
Installation
Assembly
The differential air pressure switch is mounted inside
the unit with double sided tape behind the filter retention
tab. (See figure 12a). Instructions for commissioning or
replacing the differential air pressure switch:
a. Disconnect main power on the unit.
b. Secure differential air pressure switch on the filter
retention tab using double sided tape. Position
the pressure port (marked with “+”) outside the
chassis exposed to the environment. The vacuum
port should extend inside the chassis and be open
to the unit’s fan section. (See figure 12b.)
c. Wire the NO relay using .187 quick connectors.
d. Verify all connections before reconnecting main
power.
Figure 12a
Figure 12b
