User’s Guide
TM
omega.com
®
e-mail: [email protected]
DSW490B and DSW790B
Pressure Control Switches
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INSTALLATION AND MAINTENANCE OF THE
DSW490B AND DSW490B SERIES
®
OMEGA SNAP ACTION SWITCHES
FOR DIFFERENTIAL PRESSURE CONTROL
DSW490 series standard – one 3
hole right side.
DSW790 series standard – two 3
holes with one permanent plug. NEMA 7 & 9
enclosures require proper conduit seals and
breathers as per the National Electrical Code.
⁄
4 NPT conduit
INTRODUCTION
The OMEGA differential pressure switch is a
precision built U.L. approved control device
which features a mechanical snap action switch.
Controllers are available for operation on vari-
ous pressure differentials with fixed or variable
switching differentials. The standard electrical
switch is SPDT and is available with various
electrical characteristics.
⁄4 NPT conduit
DSW490 SERIES
SPDT – Wire directly to the switch according to
circuit requirements.
Two SPDT switch elements mounted together
are available. Various wetted material construc-
tions for compatibility with a wide range of
pressure media may be obtained.
2-SPDT – Dual switching elements consist of
two SPDT switches mounted together in a
bracket. Switches are calibrated to have simul-
taneous operation within 1% of range either on
increasing or decreasing pressure but not in
both directions. Wire directly to the front and
rear switch according to circuit requirements.
Leads are provided on rear switch color coded
as follows:
The snap action differential pressure switch is
furnished in the standard NEMA 4/4X and explo-
sion proof NEMA 7 and 9 enclosure styles. Both
enclosures are epoxy coated aluminum castings.
INSTALLATION
Common
Normally Closed
Normally Open
– White
– Red
– Blue
These controls are precision instruments and
should never be left with internal components
exposed. During installation insure that covers
are in place and conduit openings are closed
except when actually working on the control.
When hermetically sealed switch element(s) are
supplied, the lead color coding is as follows:
Common
Normally Closed
Normally Open
– White
– Red
– Blue
MOUNTING DSW490 AND DSW790 SERIES
There are three holes external to the enclosure
for surface mounting. Location of these holes is
shown on the general dimension drawing. They
may also be mounted directly on pressure line
using the pressure connections.
DSW790 SERIES
SPDT – Wire directly to the switch according to
circuit requirements.
ELECTRICAL CONNECTIONS
Remove cover
DSW490 Series – two screws hold cover to
enclosure
2-SPDT – Wire to front switch terminal block
(left) and rear switch terminal block (right) as
marked. Strip insulation 5
⁄16,˝ insert in proper
terminal connector and tighten clamping screw
to secure.
DSW790 Series – cover unscrews
CONDUIT CONNECTIONS
Note – It is recommended that Teflon tape or
other sealant be used on conduit, bushing or
plug threads to ensure integrity of the enclosure.
ADJUSTMENT OF SETPOINT
®
DSW490 & DSW790 Series – A single setpoint
adjustment nut (7
⁄
8˝) is located centrally at the
bottom on the inside of the enclosure.
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For accurate setpoint calibration, mount the
switch on a calibration stand, a pump or catalog
Omega DWT 1305 deadweight gauge tester. A
suitable reference standard such as a Test Gauge
is necessary to observe convenient changes in
pressure.
Note – As indicated above, adjustment of set-
point is made by use of 7
8˝ nut. Precision switch
element mounting screws and bracket adjusting
screw are factory sealed and should not be
tampered with.
⁄
A typical calibration procedure would be
as follows:
TERMINAL BLOCK
FRONT SWITCH
TERMINAL BLOCK
REAR SWITCH
NC
NO
C
NC
NO
C
Static Working Pressure
– 300 psi
Adjustable Differential Range
– 5-200 psid
Differential SetPoint
– 150 psi above static working pressure
Simultaneously raise the high and low side pres-
sure to 300 psi. Maintain the low side pressure at
300 psi. Raise the high side pressure to 450 psi to
obtain 150 psi differential.
Turn the adjustment nut until the switch
changes mode at 150 psi differential. When the
setpoint has been achieved, raise and lower the
high side pressure to ensure that the differential
setpoint is correct.
After installation of the control replace cover to
insure electrical safety and to protect internal
parts from the environment.
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DIFFERENTIAL PRESSURE SWITCH –
INCHES OF WATER
DIFFERENTIAL PRESSURE SWITCH – PSID
A
D
Ø 0.28
(3 Holes)
B
Ø 0.28
(3 Holes)
E
C
A
D
H
1/4 NPT
Female
3/4 NPT
F
C
H
3/4 NPT
G
1/4 NPT
Low Pressure
Inlet
1/4 NPT
High
Pressure
Inlet
1/4 NPT
Female
E
DSW490B
DSW490B
B
G
B
E
E
B
F
F
0.28 THRU
(3 PLACES)
0.28 THRU
(3 PLACES)
H
H
®
D
®
D
A
3/4 NPT
(2 PLACES)
A
1/4 NPT
FEMALE
C
3/4 NPT
(2 PLACES)
C
1/4 NPT
LOW PRESSURE
INLET
1/4 NPT HIGH
PRESSURE
INLET
1/4 NPT
FEMALE
I
G
PSW790B
PSW790B
DIMENSIONS (Inches) – PSID Ranges
STYLE
A
B
C
D
E
F
G
H
DSW490B
4.0
7.78
3.25
5.20
3.31
4.38
2.75
3.88
2.31
3.58
1.19
1.22
2.31
2.31
2.27
.312
DSW790B
DIMENSIONS (Inches) – ˝H2O Differential Ranges
STYLE
A
B
C
D
E
F
G
H
I
DSW490B
5.69
4.0
3.25
3.31
5.13
–
1.43
2.75
–
DSW790B
6.38
5.20
4.38
3.88
3.96
1.22
–
.312
5.13
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WARRANTY/DISCLAIMER
OMEGA ENGINEERING, INC. warrants this unit to be free of defects in materials and workmanship for a
period of 13 months from date of purchase. OMEGA’s Warranty adds an additional one (1) month grace
period to the normal one (1) year product warranty to cover handling and shipping time. This
ensures that OMEGA’s customers receive maximum coverage on each product.
If the unit malfunctions, it must be returned to the factory for evaluation. OMEGA’s Customer Service
Department will issue an Authorized Return (AR) number immediately upon phone or written request.
Upon examination by OMEGA, if the unit is found to be defective, it will be repaired or replaced at no
charge. OMEGA’s WARRANTY does not apply to defects resulting from any action of the purchaser,
including but not limited to mishandling, improper interfacing, operation outside of design limits,
improper repair, or unauthorized modification. This WARRANTY is VOID if the unit shows evidence of
having been tampered with or shows evidence of having been damaged as a result of excessive corrosion;
or current, heat, moisture or vibration; improper specification; misapplication; misuse or other operating
conditions outside of OMEGA’s control. Components which wear are not warranted, including but not
limited to contact points, fuses, and triacs.
OMEGA is pleased to offer suggestions on the use of its various products. However, OMEGA
neither assumes responsibility for any omissions or errors nor assumes liability for any damages
that result from the use of its products in accordance with information provided by OMEGA, either
verbal or written. OMEGA warrants only that the parts manufactured by it will be as specified and
free of defects. OMEGA MAKES NO OTHER WARRANTIES OR REPRESENTATIONS OF ANY KIND
WHATSOEVER, EXPRESS OR IMPLIED, EXCEPT THAT OF TITLE, AND ALL IMPLIED WARRANTIES
INCLUDING ANY WARRANTY OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PUR-
POSE ARE HEREBY DISCLAIMED. LIMITATION OF LIABILITY: The remedies of purchaser set forth
herein are exclusive, and the total liability of OMEGA with respect to this order, whether based on
contract, warranty, negligence, indemnification, strict liability or otherwise, shall not exceed the
purchase price of the component upon which liability is based. In no event shall OMEGA be liable
for consequential, incidental or special damages.
CONDITIONS: Equipment sold by OMEGA is not intended to be used, nor shall it be used: (1) as a “Basic
Component” under 10 CFR 21 (NRC), used in or with any nuclear installation or activity; or (2) in medical
applications or used on humans. Should any Product(s) be used in or with any nuclear installation or
activity, medical application, used on humans, or misused in any way, OMEGA assumes no responsibility
as set forth in our basic WARRANTY/DISCLAIMER language, and, additionally, purchaser will indemnify
OMEGA and hold OMEGA harmless from any liability or damage whatsoever arising out of the use of the
Product(s) in such a manner.
RETURN REQUESTS / INQUIRIES
Direct all warranty and repair requests/inquiries to the OMEGA Customer Service Department. BEFORE
RETURNING ANY PRODUCT(S)TO OMEGA, PURCHASER MUST OBTAIN AN AUTHORIZED RETURN (AR)
NUMBER FROM OMEGA’S CUSTOMER SERVICE DEPARTMENT (IN ORDER TO AVOID PROCESSING
DELAYS).The assigned AR number should then be marked on the outside of the return package and on
any correspondence.
The purchaser is responsible for shipping charges, freight, insurance and proper packaging to prevent
breakage in transit.
FOR WARRANTY RETURNS, please have the
following information available BEFORE
contacting OMEGA:
FOR NON-WARRANTY REPAIRS, consult OMEGA
for current repair charges. Have the following
information available BEFORE contacting OMEGA:
1. Purchase Order number under which the product
was PURCHASED,
1. Purchase Order number to cover the COST
of the repair,
2. Model and serial number of the product under
warranty, and
3. Repair instructions and/or specific problems
relative to the product.
2. Model and serial number of the product, and
3. Repair instructions and/or specific problems
relative to the product.
OMEGA’s policy is to make running changes, not model changes, whenever an improvement is possible. This affords
our customers the latest in technology and engineering.
OMEGA is a registered trademark of OMEGA ENGINEERING, INC.
© Copyright 1999 OMEGA ENGINEERING, INC. All rights reserved. This document may not be copied, photocopied,
reproduced, translated, or reduced to any electronic medium or machine-readable form, in whole or in part, without the
prior written consent of OMEGA ENGINEERING, INC.
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Where Do I Find Everything I Need for
Process Measurement and Control?
OMEGA…Of Course!
TEMPERATURE
Ⅺ
ߜ Ⅺ
ߜ Ⅺ
ߜ Ⅺ
ߜ Ⅺ
ߜ Thermocouple, RTD & Thermistor Probes, Connectors, Panels & Assemblies
Wire: Thermocouple, RTD & Thermistor
Calibrators & Ice Point References
Recorders, Controllers & Process Monitors
Infrared Pyrometers
PRESSURE, STRAIN AND FORCE
Ⅺ
ߜ Ⅺ
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ߜ Transducers & Strain Gages
Load Cells & Pressure Gages
Displacement Transducers
Instrumentation & Accessories
FLOW/LEVEL
Ⅺ
ߜ Ⅺ
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ߜ Rotameters, Gas Mass Flowmeters & Flow Computers
Air Velocity Indicators
Turbine/Paddlewheel Systems
Totalizers & Batch Controllers
pH/CONDUCTIVITY
Ⅺ
ߜ Ⅺ
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ߜ pH Electrodes, Testers & Accessories
Benchtop/Laboratory Meters
Controllers, Calibrators, Simulators & Pumps
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DATA ACQUISITION
Ⅺ
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Communications-Based Acquisition Systems
Plug-in Cards for Apple, IBM & Compatibles
Datalogging Systems
Recorders, Printers & Plotters
HEATERS
Ⅺ
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ߜ Heating Cable
Cartridge & Strip Heaters
Immersion & Band Heaters
Flexible Heaters
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ENVIRONMENTAL
MONITORING AND CONTROL
Ⅺ
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ߜ Metering & Control Instrumentation
Refractometers
Pumps & Tubing
Air, Soil & Water Monitors
Industrial Water & Wastewater Treatment
pH, Conductivity & Dissolved Oxygen Instruments
XXX0000XX
M3420/0599
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