Sierra Monitor 20X User Manual

The Model 20X Series are all-weather,
solid-state, fixed-installation single­alarm monitors designed for continuous
area monitoring of Combustible Gas,
Hydrogen Sulfide or Carbon Monoxide.

The Model 20X Series consists of 3 gas sensor mod­ules, Model 201 for Combustible Gas, Model 203 for
Hydrogen Sulfide and Model 206 for Carbon Monoxide.
The monitors provide 0.5 Amp dry contract relay that is
activated when the concentration of gas exceeds the
factory-set (and user-adjustable) level. A TTL signal can
be user configurable to interface with Sierra Monitor's
alarm panels. This signal may be used to activate a
remote alarm, fan or process controller.

The standard configuration has a normally operating open
relay but a fail-safe normally operating closed relay is
field selectable. A durable, cast aluminum explosion­proof enclosure houses the sensor electronics. The en­closure provides sealing for hazardous areas - Class I,
Division 1, Groups C, D. The sensor with porous metal
cover is assembled in an aluminum housing that screws
directly into the electronics enclosure. The cover both
protects the sensor and acts as a flame-arrestor. The
monitor can be installed up to 500 feet from the power
source.

Semiconductor-T ype Sensor

Model 20X Series

Gas Sensor Monitors

Model 201 - Combustible Gas
Model 203 - Hydrogen Sulfide

Model 206 - Carbon Monoxide

Remote Alarm Available

If a remote alarm is desired (required for 20X-00), the
Model 2102 Dual Channel Alarm Panel can be connected
up to 500 feet away from the monitors.

A solid-state semiconductor-type sensor and associated
electronic circuitry ensure trouble-free, long-term opera­tion. There are no pumps, filters, or chemical cells to
replace or maintain. Except periodic calibration to verify
the alarm setting, no attention is required after installa­tion. The user may adjust the alarm level by using cali­bration gas with concentration equal to the alarm level.

Features Benefits

 Explosion-proof enclosure Can operate continuously in work areas where

 No chemical cells to replace, no periodic Maintenance free operation

maintenance required other than routine
calibration

 All the electronic circuitry needed to operate Quick easy installation and connection to alarm

panel the monitor contained in a compact unit

Sierra Monitor Corporation 1991 Tarob Court Milpitas, California 95035 [phone] [phone] Fax: [phone]

Model 201 - Combustible Gas

The Model 201 can detect a wide range of combustibles.
Typical applications include combustible gas monitor­ing in manholes, tanks, natural gas fields, parking ga­rages and vehicle maintenance facilities, sewage treat­ment plants, laboratories, chemical plants, and more.

hazardous gases could be present

Model 203 - Hydrogen Sulfide

The Model 203 can be used in such typical applica­tions as wastewater treatment plants, laboratories and
chemical plants.

Model 206 - Carbon Monoxide

The Model 206 Carbon Monoxide Gas Sensor Module
can be used to provide an early warning of Carbon
Monoxide accumulation in tanks, laboratories, chemi­cal plants, parking garages, vehicle test facilities and
more.

SPECIFICATIONS

SENSOR TYPE: Solid-State Metal Oxide Semiconductor
RANGE: (at 50% relative humidity)

Model 201 300 - 2,000 ppm Hydrogen

500 - 10,000 ppm Methane
Model 203 10-50 ppm Hydrogen Sulfide (H2S)
Model 206 50 - 500 ppm Carbon Monoxide (CO)

RESPONSE TIME:
Model 201 Less than 30 seconds

Model 203 Less than 60 seconds
Model 206 Less than 30 seconds

PERIODIC
MAINTENANCE: None, other than routine calibration

OPERATING
TEMPERATURE
RANGE: -4°F TO 158°F

(-20°C TO 70°C)
INPUT: 9 - 24 VDC (+ 1V), 250 mA
OUTPUT : 0.5 amp dry contact, 100 VDC, 130 VAC

Nominal 5 volts DC (TTL), source 25mA.

SAFE and ALARM signals.
INDICAT ORS: Internal LED for calibration
ENCLOSURE: Class I, Division 1, Groups C, D
ENCLOSURE Cast aluminum for protection against

MATERIAL: galvanic corrosion
SIZE: 6.75 x 4.0 x 3.5 in

(17.1 x 10.2 x 6.0 cm)
WEIGHT: 24 o z (678 g)
APPROVAL : UL 61010-1:2004

CSA-C22.2

ORDERING INFORMA TION

Combustible Gas 201-00
Hydrogen Sulfide 203-00
Carbon Monoxide 206-00

© 2008 by Sierra Monitor Corporation Printed in U.S.A.

Sierra Monitor Corporation 1991 Tarob Ct. Milpitas, CA 95035 (408) 262-661 1 800-727-4377 FAX: [phone]

Visit our Web site at: www .sierramonitor .com E-Mail: sierra@sierramonitor .com

Rev. B 4/13/1 1