Dwyer 1996 User Manual

Series 1996 Gas Pressure Switches are

reliable and convenient switches for gas-fired furnaces
and equipment using natural, manufactured or LP gas.
Both models (Model 1996-5, with a pressure range of 1.4
to 5.5″ w.c.; Model 1996-20, with a pressure range of 4
to 20″ w.c.) feature visible set point and on-off
indicators.

OPERATION

Pressure acting on the power diaphragm rotates the
amplifying lever, which in turn extends the range spring
and rotates the snap switch input lever. When the set
point is reached, the snap switch is actuated and the
electrical contacts make or break. Decreasing pressure
after the switch has been actuated reverses the action,
de-actuating the switch and returning the contacts to
their normal position.

INSTALLATION

1. Select a location free from excessive vibration and
corrosive atmosphere. These switches may be used in
ambient temperatures as low as - 30°F ( - 34°C) and as
high as 110°F (43°C).

2. Mount switch with diaphragm in a horizontal position
and gas pressure connection at bottom. Connect the
switch to the source of gas pressure using either the
NPT (F)8″ or NPT (M) 4″ thread. Gas pressure connec­tion should always be to bottom connection of switch—
see diagram above—which is equipped with a restrictor
orifice. Be sure to hold or turn switch with a wrench on
the hex portion of the bottom connection. This will pre­vent applying excessive torque to the bottom fitting,
which could damage the switch.

The port identified with the letters LO-PR is used as a
vent in fuel gas switches and should be vented to
outside atmosphere or the combustion chamber in
accordance with the furnace manufacturer’s
instructions. The port identified by the letters HI-PR is

not used in fuel gas switches and is neither tapped nor
connected to the diaphragm chamber.

Series 1996 – Natural and L.P. Gas Pressure Switches

Specifications - Installation and Operating Instructions

Bulletin E-58

DWYER INSTRUMENTS, INC.

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

P.O. BOX 373 • MICHIGAN CITY, INDIANA 46361, U.S.A. Fax: [phone] e-mail: [e-mail]

Lit-By Fax: [phone]

Series 1996 Gas Pressure Switches

are designed for use with natural, man­ufactured or LP gas or air.

Note set point adjustment indicator win­dow. For quick adjustment of set point
before/after installation, turn adjustment
screw until red bar is at desired set point.
To adjust for low gas pressure interlock
service, refer to chart (other side).

Connections, dimensions and visible
on-off indicator: Model 1996-20 and

Model 1996-5 Gas Pressure Switches.

PHYSICAL DATA

Temperature limits: 32°F/0°C (- 30°F/- 34.4°C for dry gas or

air) to 110°F/ 43.3°C

Pressure connection:

8″ NPT (F) or 4″ NPT (M)

Vent connection:

8″ NPT

Electrical rating: 15 amps, 120-480 volts, 60 Hz. A.C.
Resistive

8″ H. P. @ 125 volts, 4″ H. P. @ 250 volts, 60 Hz.

A.C.

Wiring connections: 3-screw type, Common, Normally Open
and Normally Closed

Set point adjustment: Screw type with visible indicator,
inside cabinet enclosure

On-off indicator: In window, on exterior of conduit enclosure.
Shows at a glance whether pressure is above or below set
and reset points.

Housing: Aluminum die casting and steel stamping,
zinc-plated for 200 hour salt spray resistance

Diaphragm: Molded Buna-N

Calibration spring: Stainless Steel

Weight: 1 lb, 2 oz

U.L. and C.S.A. listed, F.M. approved

WARNING:

Do not connect fuel gas to LO-PR port.

REMOVABLE CONDUIT
ENCLOSURE COVER

7/8 [22.23] OPENING FOR
1/2 [12.7] CONDUIT CONNECTION

3-1/8

[79.38]

3-1/2

[88.90]

WINDOW AND VISIBLE
ON-OFF INDICATOR

VENT CONNECTION
ON OPPOSITE SIDE

1/4 NPT EXTERNAL THREAD
(ALTERNATE GAS CONNECTION)

1/8 (F) GAS
PRESSURE CONNECTION

3. Remove the snap-on cover from the conduit
enclosure by loosening its retaining screw and pulling
firmly on its set screw held end. Electrical terminals for
all switches are marked Common, Normally Open, and
Normally Closed. The switch is not actuated until
pressure is applied. On rising pressure, the switch actu­ates and Normally Open contacts close. Should gas
pressure fail, the switch (when set for low gas pressure)
will de-actuate and the Normally Open contacts re-open.
When set for high gas pressure (regulator failure) the
switch will actuate (and Normally Closed contacts will
open) when overpressure occurs. Wire switch accord­ingly: make sure load doesn't exceed electrical ratings.
Use flexible or rigid conduit to enclose wires to switch.

4. Adjust the set point following instructions under
adjustment.

5. Check carefully for leaks. Be sure that switch set
point and installation complies with the furnace/burner
manufacturer’s instructions. Watch the On-Off indicator
in window to observe proper operation.

ADJUSTMENT

1. To change the set point, remove the cover from the
conduit enclosure. Turn the slotted Adjustment Screw at
the end of the range spring housing clockwise to raise
the set point pressure and counter-clockwise to lower
the set point. The visible set point indicator shows the
set point from 4 (min) to 20 (max) inches w.c. for Model
1996-20 and 1.5 (min) to 5 (max) inches w.c. for Model
1996-5.

2. (a) For high gas pressure applications, to actuate on
regulator failure, adjust the set point so that desired set­ting (normally 1″ or 12″ above operating pressure)
shows in the window.
(b) For low gas pressure applications, to actuate on gas

DWYER INSTRUMENTS, INC.

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

P.O. BOX 373 • MICHIGAN CITY, INDIANA 46361, U.S.A. Fax: [phone] e-mail: [e-mail]

Lit-By Fax: [phone]

Series 1996 – Natural and L.P. Gas Pressure Switches

Specifications - Installation and Operating Instructions

Bulletin E-58

Page 2

©Copyright 2000 Dwyer Instruments, Inc. Printed in U.S.A. 6/00 FR # 26-440252-00 Rev. 1

Visible on-off
pointer indi­cates actuation
or de-actuation
of switch. This
permits instant
trouble-shoot­ing of electrical
circuit or gas
supply.

Motorized

Gas Valves

Typical Piping Diagram for Gas-Fired Furnaces

(Pilots Not Shown)

Low Pressure

Gas Switch

Vent outside

separately or to

combustion chamer

per manufacturer's

instructions.

Gas

Supply

Main Gas

Shut-Off Valve

Gas Pressure

Regulator

Solenoid

Vent Valve

(Normally Open)

Test

Cock

High Pressure

Gas Switch

Checking

Gas Cock

To Main

Burner

Inches in Water Column

Set Point Approximate Dead Band Reset Point

Model 1996-5

1.5 0.10 1.30

20.12 1.88

30.14 2.86
4 0.17 3.83

50.19 4.81

Model 1996-20

40.15 3.85

50.15 4.85
10 0.24 9.76
15 0.33 14.67
20 0.41 19.59

pressure failure, adjust the set point slightly below
(usually 2″ or 1″ w.c.) the normal gas pressure.
De-actuation will occur at set point pressure minus the
dead band. See chart below.

MAINTENANCE

The moving parts of these switches are sealed in and are
permanently tamper-proof. The single adjustment is that
of the set point. Care should be taken to keep the switch
reasonably dry and free from dust or dirt. No lubrication
or unusual precautions are required for
normal use.