Dwyer Instruments 1996 Series 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 connec-
tion 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 pre-
vent 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, man-
ufactured or LP gas or air.
Note set point adjustment indicator win-
dow. 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
3-1/8
[79.38]
3-1/2
[88.90]
1/8 (F) GAS
PRESSURE CONNECTION
1/4 NPT EXTERNAL THREAD
(ALTERNATE GAS CONNECTION)
VENT CONNECTION
ON OPPOSITE SIDE
WINDOW AND VISIBLE
ON-OFF INDICATOR
7/8 [22.23] OPENING FOR
1/2 [12.7] CONDUIT CONNECTION
REMOVABLE CONDUIT
ENCLOSURE COVER
WARNING:
Do not connect fuel gas to LO-PR port.
new E-58 REV 1 6/24/02 8:47 AM Page 1

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 actu-
ates 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 accord-
ingly: 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 set-
ting (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 indi-
cates actuation
or de-actuation
of switch. This
permits instant
trouble-shoot-
ing 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.
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