Data Sheet for Product

SW 251 Pressure Electric Switches Technical Instructions
Document Number 155-057P25
Rev. 1, May, 2000
Siemens Building Technologies, Inc.
Page 3
Operation,
continued
DIFFERENTIAL ADJUSTMENT
(ONLY INCLUDED ON MODELS 251-0001 & 251-0011)
POINT 'A'
SET POINT
ADJUSTMENT
4
1
2
3
5 6
7
SW0092R1
Figure 1. Operational Schematic.
Installation
•
Install instrument firmly in any position with the mounting tabs (included). AII wiring
must conform to the National Electrical Code or local regulations. Electrical loads
exceeding the rating of the switch should be controlled by means of an intermediate
relay or starter.
•
Wiring diagrams are shown in
Figure 6
.
Calibration and
Adjustment
The set point can be changed from the factory setting shown in
Table 1
by using the set
point adjustment screw shown in
Figure 1
. Turn it counterclockwise (as viewed from the
top) to increase the set point. The differential can be changed only on Models 251-0001
and 251-0011, using the differential adjustment screw shown in
Figure 1
. Turn it
clockwise (as viewed from the bottom) to increase the differential.
After any adjustment, check operation with a variable air supply or a Baumanometer.
Corrective
Maintenance
Field repairs are not recommended. Pressure electric switches that are not operating
properly should be replaced.
Discontinued