Dwyer Instruments 1950G Operating Manual

Bulletin E-57G

Series 1950G – Integral Explosion-Proof Pressure Switches

Specifications - Installation and Operating Instructions

Set Point

Adjustment

Screw

1/2˝ female

NPT

Electrical

Conduit

Connection

Vent Drain

Plug

The Model 1950G Explosion-Proof Switch combines the best features
of the popular Series 1900 Pressure Switch with a compact explosion­proof 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
94/9/EC (ATEX) Compliant for II 2G Ex d IIB + H2T6 Gb. IECEx
and KC certified Ex d 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 inches 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” suffix are not Directive 94/9/EC (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

*GR. A is Only.

UL, CSA, FM Listed For

CL, I GR. A*, B, C, D - CL. II GR. E, F, G - CL. III

Directive 94/9/EC (ATEX) Compliant For

0518 II 2G Ex d IIB + H2T6 Gb

EC-Type Certificate Number: KEMA 03ATEX2402 X

ATEX Standards:

EN60079-0: 2009
EN60079-1: 2007

IECEx Certified for:

Ex d IIB + H2 T6 Gb (-40°C < Ta < +60°C)

IECEx Certificate of Conformity:

IECEx DEK 11.0092X

IECEx Standards:

IEC 60079-0: 2007
IEC 60079-1: 2007

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” suffix for models with UL, CSA and FM approvals

only. Example: 1950G-00-B-120-NA

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˝ 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 50mA, 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).

Operating

Range

Inches, 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

Approximate

Dead 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

DWYER INSTRUMENTS, INC.

Phone: [phone] www.dwyer-inst.com

P.O. Box 373 • Michigan City, IN 46360, U.S.A. Fax: [phone]

e-mail:

[e-mail]

1-11/16
[42.86]

1/8˝ NPT LOW

PRESSURE PORT

5

-7/16

[

138.1]

4

-7/8

[

123.8]

1

/8˝ NPT HIGH

P

RESSURE PORT

1/2˝ NPT

ELECTRICAL

CONDUIT

CONNECTION

RANGE

ADJUSTMENT

SCREW

1

7/64˝ DIA. MTG. HOLES (2)

EXTERNAL GROUND

3-1/2

[88.90]

C

APTIVE

S

CREW

1

3/32

[

10.312]

VENT DRAIN

PLUG

1-17/32

[38.89]

Fig. A

LOCKWASHER

SCREW

CONDUCTOR

CLAMP PLATE

CLAMP

FRONT VIEW DETAIL

SIDE VIEW DETAIL

Bulletin E-57G

-

+

Page 2

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 specific types of
hazardous service.

For units supplied with both internal and external bonding terminals, the
ground screw inside the housing must be used to ground the control. The
enternal 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.

Fig. B

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 flow 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.

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
B. Pressure only (above atmospheric pressure) - connect tube from
source of pressure to high pressure port. The low pressure port is left

counter-clockwise to lower the setpoint. After calibration, replace the

plastic cap and re-check the setpoint.
open to atmosphere.

B. The recommended procedure for calibrating or checking
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.

calibration is to use a “T” assembly with three rubber tubing leads, all

as short as possible and the entire assembly offering minimum flow

restriction. Run one lead to the pressure switch, another to a

manometer of known accuracy and appropriate range, and apply

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 Fig.
A). Electrical connections to the standard single pole, double throw relay

pressure through the third tube. Make final 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, fluid 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.

and DC supply voltage connections to the unit, are provided by means of
terminals marked “COM”, “NO”, “NC”, “+” and “-” (See Fig. 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 specified current ratings as
stated on page 1. For ATEX, IECEx compliance, cables and cable glands
suitable for temperature of at least 95°C shall be used. The cable entry
device shall be of certified flameproof type, suitable for the conditions of
use and be correctly installed. Refer to Certificate No.: IECEx DEK

11.0092X for conditions of safe use for IECEx Compliant units. Switch
capabilities decrease with an increase in ambient temperature, load
inductance, or cycling rate.

©Copyright 2014 Dwyer Instruments, Inc. Printed in U.S.A. 9/14 FR# 28-440332-10 Rev.10

DWYER INSTRUMENTS, INC.

P.O. Box 373 • Michigan City, IN 46360, U.S.A. Fax: [phone] e-mail: [e-mail]

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 there is excessive
condensation within the switch. Repairs to be conducted by Dwyer
Instruments, Inc. Cover bolts are Class 10.9 35 mm long.

Phone: [phone] www.dwyer-inst.com