
Series 1950G – Integral Explosion-Proof Pressure Switches
Specications - Installation and Operating Instructions
Bulletin E-57G
Set point
adjustment screw
1/2˝ female NPT
electrical conduit
connection
Vent drain
plug
The Series 1950G Explosion-Proof Switch combines the best features of the
popular Series 1900 Pressure Switch with a compact explosion-proof housing.
This unit is UL, CSA, FM listed for use in Class I, Groups A*, B, C, D, Class II, Groups
E, F, & G and Class III atmospheres and Directive 2014/34/EU (ATEX) Compliant for
2813 II 2G Ex db IIB+H2 T6 Gb. IECEx certied Ex db IIB+H2 T6 Gb (-40°C
< Ta < + 60°C) units are available. It is also totally rain-tight for outdoor installations.
Six models allow set-points from 0.07 to 20 in w.c. (1.78 mm to 508.0 mm w.c .).
Easy access to the SPDT relay for electrical hook-up is provided by removing the top
plate of the aluminum housing. A captive screw allows the cover to swing aside while
remaining attached to the unit. Adjustment to the set point of the switch can be made
without disassembly of the housing. The unit is very compact, about half the weight
and bulk of equivalent conventional explosion-proof switches.
Attention: Units with the “NA” sufx are not Directive 2014/34/EU (ATEX) compliant.
These units are not intended for use in potentially explosive atmospheres in the EU.
These units may be CE marked for other Directives of the EU.
External
ground screw
Captive
screw
UL, CSA, FM Listed For
CL, I GR. A*, B, C, D - CL. II GR. E, F, G - CL. III
ATEX Compliant for
2813 II 2G Ex db IIB+H2 T6 Gb
EU-Type Certicate Number: DEMKO 19 ATEX 2216X
ATEX Standards:
EN 60079-0, EN 60079-1
IECEx Certied for:
Ex db IIB+H
IECEx Certicate of Conformity:
IECEx UL 19.0045X
IECEx Standards:
IEC 60079-0, IEC 60079-1
UKCA Ex Compliant for
Ex db IIB+H2 T6 Gb
UKCA Ex Certicate
UL 21UKEX2362X
UKCA Ex Standards
EN 60079-0, EN 60079-1
SPECIFICATIONS
Service: Air and compatible combustible gases.
Wetted Materials: Contact factory.
Temperature Limits: 0 to 140°F (-17 to 60°C). Note: Set point drift may occur with
ambient temperature changes.
Pressure Limits: 45 in w.c. (11.2 kPa) continuous; 10 psig (68.95 kPa) surge.
Enclosure Rating: IP54, NEMA 3, 7 and 9.
Switch Type: 1 Form C relay (SPDT).
Electrical Rating: 10A, 120/240 VAC, 28 VDC. Resistive 50 mA, 125 VDC.
Power Requirements: 24 VDC ±10%. 120 or 240 VAC ±10% optional.
Electrical Connections: Internal terminal block.
Process Connections: 1/8˝ female NPT.
Mounting Orientation: Diaphragm in vertical position. Consult factory for other
position orientations.
Set Point Adjustment: Screw type on top of housing.
Weight: 2 lb 15.7 oz (1.35 kg).
Note: References to ATEX apply to UKCA Ex.
MODEL 1950G SWITCHES:
OPERATING RANGES AND DEADBANDS
To order Specify
Model Number*
1950G-00-B-__
1950G-0-B-__
1950G-1-B-__
1950G-5-B-__
1950G-10-B-__
1950G-20-B-__
*Specify either 24 for 24 VDC, 120 for 120 VAC or 240
for 240 VAC when ordering. Example: 1950G-00-B-120
*Add “NA” sufx for models with UL, CSA and FM
approvals only. Example: 1950G-00-B-120-NA
2 T6 Gb (-40°C < Ta < +60°C)
Approximate Dead
Operating
Range
in w. c.
0.07 to 0.15
0.15 to 0.5
0.4 to 1.6
1.4 to 5.5
3.0 to 11.0
4.0 to 20.0
Band
At Min.
Set Point
0.04
0.06
0.11
0.4
0.9
1.2
At Max.
Set Point
0.06
0.11
0.29
0.9
1.8
3.0
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RANGE
17/64˝ DIA. MTG. HOLES [2]
FRONT VIEW DETAIL
SIDE VIEW DETAIL
ADJUSTMENT
SCREW
1/2˝ NPT
ELECTRICAL
CONDUIT
CONNECTION
1/8˝ NPT HIGH
PRESSURE PORT
1-11/16
EXTERNAL GROUND
4-7/8
[123.8]
5-7/16
[138.1]
1/8˝ NPT
LOW PRESSURE
PORT
VENT
DRAIN
PLUG
3-1/2
[88.90]
1-17/32
[38.89]
CAPTIVE
SCREW
13/32
Figure A
1950G switch outline dimensions
INSTALLATION
1. Select a location free from excess vibration and corrosive atmospheres where
temperatures will be within the limits noted under Physical Data on page 1. Switch
may be installed outdoors or in areas where the hazard of explosion exists. See
page 1 for specic types of hazardous service.
2. Mount standard switches with the diaphragm in a vertical plane and with switch
lettering and nameplate in an upright position. Some switches are position sensitive
and may not reset properly unless they are mounted with the diaphragm vertical.
3. Connect switch to source of pressure, vacuum or differential pressure. Metal tubing
with 1/4˝ O.D. is recommended, but any tubing which will not restrict the air ow
can be used. Connect to the two 1/8˝ female NPT pressure ports as noted below.
A. Differential pressures - connect pipes or tubes from source of greater pressure
to high pressure port marked HIGH PRESS, and from source of lower
pressure to low pressure port marked LOW PRESS.
B. Pressure only (above atmospheric pressure) - connect tube from source of
pressure to high pressure port. The low pressure port is left open to
atmosphere.
C. Vacuum only (below atmospheric pressure) - connect tube from source of
vacuum to low pressure port. The high pressure port is left open to
atmosphere.
4. To make electrical connections, remove the three hex head screws from the
cover and after loosening the fourth captive screw, swing the cover aside. Electrical
connections to the standard single pole, double throw relay and AC supply voltage
connections to the unit, are provided by means of terminals marked “COM”, “NO”,
“NC”, “~” and “~” (See Figure A). Electrical connections to the standard single pole,
double throw relay and DC supply voltage connections to the unit, are provided by
means of terminals marked “COM”, “NO”, “NC”, “+” and “-” (See Figure B.). The
normally open contacts close and the normally closed contacts open when
pressure increases beyond the setpoint. Switch loads for standard models should
not exceed the maximum specied current ratings as stated on page 1. For ATEX,
IECEx compliance, cables and cable glands suitable for temperature of at least
105°C shall be used. The cable entry device shall be of certied ameproof type,
suitable for the conditions of use and be correctly installed. Refer to Certicate
No.: IECEx UL 19.0045X for conditions of safe use for IECEx Compliant units.
Switch capabilities decrease with an increase in ambient temperature, load
inductance, or cycling rate.
Figure B
For units supplied with both internal and external bonding terminals, the ground screw
inside the housing must be used to ground the control. The internal bonding screw is
for supplementary bonding when allowed or required by local code. When external
bonding conductor is required, conductor must be wrapped a minimum of 180° about
the external bonding screw. See below.
SCREW
CLAMP PLATE
CLAMP
ADJUSTMENT
To change setpoint:
A. Remove the plastic cap and turn the slotted Adjustment Screw at the top of the
housing clockwise to raise the setpoint pressure and counter-clockwise to lower
the setpoint. After calibration, replace the plastic cap and re-check the setpoint.
B. The recommended procedure for calibrating or checking calibration is to use a
“T” assembly with three rubber tubing leads, all as short as possible and the
entire assembly offering minimum ow restriction. Run one lead to the pressure
switch, another to a manometer of known accuracy and appropriate range, and
apply pressure through the third tube. Make nal approach to the setpoint very
slowly. Note that manometer and pressure switch will have different response
times due to different internal volumes, lengths of tubing, uid drainage, etc. Be
certain the switch is checked in the position it will assume in use, (i.e. with
diaphragm in a vertical plane) and switch lettering and Dwyer nameplate in an
upright position.
C. For highly critical applications check the setpoint adjustment and if necessary,
reset it as noted in step A.
MAINTENANCE
The moving parts of these switches need no maintenance or lubrication. The only
adjustment is that of the setpoint. Care should be taken to keep the switch reasonably
clean. Periodically the vent drain plug should be rotated then returned to its original
position. This will dislodge deposits which could accumulate in applications where
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there is excessive condensation within the switch. Repairs to be conducted by Dwyer
Instruments, LLC. Cover bolts are Class 10.9 35 mm long.