RKI Instruments GD-K77D User manual

www.rkiinstruments.com
Model GD-K77D
Operator’s Manual
Part Number: 71-0046RK
Revision: B
Released: 3/1/11

Model GD-K77D Operator’s Manual
WARNING
Read and understand this instruction manual before operating
detector. Improper use of the detector could result in bodily harm
or death.
Periodic calibration and maintenance of the detector is essential
for proper operation and correct readings. Please calibrate and
maintain this detector regularly! Frequency of calibration
depends upon the type of use you have and the sensor types.
Typical calibration frequencies for most applications are between
3 and 6 months, but can be required more often or less often
based on your usage.

Model GD-K77D Operator’s Manual
Warranty
RKI Instruments, Inc. warrants gas alarm equipment sold by us to be free from defects in
materials and workmanship, and performance for a period of one year from date of
shipment from RKI Instruments, Inc. Any parts found defective within that period will be
repaired or replaced, at our option, free of charge. This warranty does not apply to those
items which by their nature are subject to deterioration or consumption in normal service,
and which must be cleaned, repaired, or replaced on a routine basis. Examples of such
items are:
Warranty is voided by abuse including mechanical damage, alteration, rough handling, or
repairs procedures not in accordance with the instruction manual. This warranty indicates
the full extent of our liability, and we are not responsible for removal or replacement costs,
local repair costs, transportation costs, or contingent expenses incurred without our prior
approval.
THIS WARRANTY IS EXPRESSLY IN LIEU OF ANY AND ALL OTHER WARRANTIES
AND REPRESENTATIONS, EXPRESSED OR IMPLIED, AND ALL OTHER OBLIGATIONS
OR LIABILITIES ON THE PART OF RKI INSTRUMENTS, INC. INCLUDING BUT NOT
LIMITED TO THE WARRANTY OF MERCHANTABILITY OR FITNESS FOR A
PARTICULAR PURPOSE. INNO EVENT SHALL RKI INSTRUMENTS, INC. BE LIABLE
FOR INDIRECT, INCIDENTAL, OR CONSEQUENTIAL LOSS OR DAMAGE OF ANY KIND
CONNECTED WITH THE USE OF ITS PRODUCTS OR FAILURE OF ITS PRODUCTS TO
FUNCTION OR OPERATE PROPERLY.
This warranty covers instruments and parts sold to users only by authorized distributors,
dealers, and representatives as appointed by RKI Instruments, Inc.
We do not assume indemnification for any accident or damage caused by the operation of
this gas monitor and our warranty is limited to replacement of parts or our complete goods.
Absorbent cartridges Batteries
Pump diaphragms and valves Filter elements
Fuses

Model GD-K77D Operator’s Manual
Table of Contents
Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1
About this Manual. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Important Safety Precautions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Specifications. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
Case. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Alarm Lights . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Display . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Flowmeter. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Internal and Back Panel Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Block Diagrams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Important Safety Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10
Precautions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Wall Mounting the Model GD-K77D . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Removing the Model GD-K77D . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Electrical Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Tubing Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Tubing Material. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Start-up Preparations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Basic Operation Flow and Operating Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Start Up. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Detection Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Maintenance Mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Alarm Test Mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Turning Off the Model GD-K77D . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Alarms. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .29
Alarm Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Responding to Alarms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Maintenance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Monthly Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Semiannual Maintenance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
Storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
Replacing Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

Model GD-K77D Operator’s Manual
Troubleshooting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
Trouble Alarm: Flickering PW/TR Lamp. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
PW/TR Lamp Off . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
Abnormal Performance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
Unable to Calibrate. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
Slow Response. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
Disconnected Fuse. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
Parts List. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .39

1 • Overview Model GD-K77D Operator’s Manual
Overview
The Model GD-K77D has been specially developed for semiconductor gas-leak
monitoring and is one of the most advanced units of its kind. It contains a long-life pump
and electrochemical sensor to detect a wide variety of semiconductor gasses quickly and
reliably. The long-life sensor has a memory so it can be calibrated separately from the
monitor, then installed for quick and easy servicing. The Model GD-K77D’s narrow
footprint and wall mounting bracket permit flexible placement. Built for reliability and ease
of use, the Model GD-K77D includes the latest innovations in gas-leak monitoring
technology:
• Digital LED display for readout of gas concentrations
• Sensor information and calibration stored within sensor memory
• Several transmission options available
• Self-diagnostic functions performed by microcomputer
• Easy replacement of pump and sensor
• Two alarm levels plus trouble alarm
WARNING: The Model GD-K77D detects semiconductor gasses that may be toxic
or combustible. Users of the Model GD-K77D must follow the
instructions and warnings in this manual to assure proper and safe
operation of the Model GD-K77D.
About this Manual
This manual is intended for use with the RKI Instruments®Intelligent Gas Detector, Model
GD-K77D. It describes the Model GD-K77D’s specifications, internal components,
operation, calibration, and maintenance.
Important Safety Precautions
To ensure the consistent performance and reliability of the RKI Instruments Intelligent Gas
Detector, Model GD-K77D, carefully read and follow the instructions in this manual before
using the unit. Keep this manual where you can find it easily. When operating or
performing maintenance on the Model GD-K77D, refer back to this manual as required.
Also keep maintenance records, and use them to plan for future repairs and maintenance
of the Model GD-K77D.
If the Model GD-K77D is not operated according to the instructions in this manual, RKI
Instruments, Inc. cannot assume any responsibility for consequential injury or damage.
Because the Model GD-K77D is considered to be safety equipment designed to detect
semiconductor gases, which can be toxic or explosive, be sure to check the Model GD-
K77D daily. If any problem or malfunction is found, contact your local distributor, or RKI
Instruments, Inc. immediately.
Throughout this manual you will see cautionary labels. Read them carefully and heed their
warnings. Failure to do so may result in injury or damage.

Model GD-K77D Operator’s Manual Overview • 2
DANGER: This label alerts you to the possibility of serious injury or death when
using or servicing the Model GD-K77D improperly in potentially
hazardous environments or conditions. The Model GD-K77D is not
explosion proof. Do not use the Model GD-K77D for gas detection
above the lower explosive limit (LEL).
WARNING: This label alerts you to the potential danger of electrical shock, or
other hazards. When electrical safety is not followed, injury or damage
to the Model GD-K77D may result. Remember that the Model GD-K77D
is an electrically powered device. In some circumstances, the Model
GD-K77D may be affected by electrical noise, static electricity, or
electromagnetic interference. If the environment in which the Model
GD-K77D is to be placed has these electrical hazards, take the
appropriate steps to shield the Model GD-K77D properly.
CAUTION: This label alerts you to the possibility of injury or damage to the Model GD-K77D
when operation and maintenance of the Model GD-K77D are not performed in
accordance with the instructions in this manual. When replacing parts for the Model
GD-K77D, use only RKI replacement parts. Modified or non-RKI replacement parts
can damage the Model GD-K77D. Should such damage occur, RKI Instruments, Inc.
is not responsible, and the warranty may be voided.
NOTE: This label indicates that important advice or operating or maintenance tips follow. Read
the note carefully and follow its instructions.

3 • Specifications Model GD-K77D Operator’s Manual
Specifications
Specifications subject to change without notice.
Accessories: Dust filter
WARNING: When using the GD-K77D, you must follow the instructions and warnings
in this manual to assure proper and safe operation of the GD-K77D and to
minimize the risk of personal injury. Be sure to maintain and periodically
calibrate the GD-K77D as described in this manual.
Table 1: Specifications for the Model KD-K77D
Model GD-K77D GD-K77D-NT
Relay output for remote alarm Electrochemical cell
Relay output for remote alarm Refer to the RKI Instrument, Inc. list of detectable gasses
Target gas and detection range See RKI List of Detectable Gases
Accuracy ± 10% of reading or ± 5% of full scale (whichever is greater)
Signal output (4-20 mA) Two-wire digital signal
Display Digital LED display, 4 digit
Alarms Two alarm levels: alarm 1 (yellow LED),
alarm 2 (red LED), trouble
Relay output for remote alarm Dry contact for each alarm1, alarm2, and trouble alarm
Self-diagnostic functions Trouble, low flow, system failure, communication error
Temperature and humidity ranges 0-40 C, 30-85% relative humidity
Power requirements 24 VDC+/- 10%, approximately 10W
Recommended cable (see also RKI
wiring chart) 18 gage shielded cable Shielded twisted pair cable (18 gage)
Dimensions and weight 2.8"(W) x 6.7"(H) x 6.0"(D), 4.4lb.
Recommended tubing 4 mm x 6 mm PTFE (Teflon tubing, RKI part # 06-1272RK)
Fuse 5.2 mm diameter x 20 mm length; 2A, 250V

Model GD-K77D Operator’s Manual Description • 4
Description
The Model GD-K77D is designed to measure gas leaks in an industrial setting. Gas leaks
are detected by an internal electrochemical sensor, and the gas concentration is displayed
by a four-digit LED display.
Figure 1: External Component Location
6.05
Cable Bushing
Flow Meter
Window
SKIP LED
ALM2 LED
ALM1 LED
PW/TR LED
GAS DETECTOR MODEL GD-K77D
LED Display
.36
Gas Exhaust, for ø 4 x 6
mm PFTE Tube
Gas Inlet, for ø 4 x 6
mm PTFE Tube
6
.70
ID Card
Holder
8.0 MA
X
2.80
Cover
Retaining
Screw

5 • Description Model GD-K77D Operator’s Manual
Figure 2: Removing the Cover and Detector Unit
Cover
Wall mounting bracket
Detector unit

Model GD-K77D Operator’s Manual Description • 6
The Model GD-K77D provides a three-wire 4-20mA signal output for a controller. The
Model GD-K77D-NT provides a two-wire digital signal which is used by the RM-77NT
accessory and is then converted to either an RS-232C or RS-485 signal. It has two gas
alarm levels, two sets of gas alarm relay contacts, a trouble alarm, and trouble relay
contacts.
The Model GD-K77D is a sample draw gas detection head. The Model GD-K77D draws in
the sample gas from a remote location using an internal pump. The flow system directs
the gas to an internal gas sensor. Various lengths of inlet tubing can be used, and tubing
length is determined by the target gas and the operating environment. When using the
Model GD-K77D in areas containing dust or other particulate contamination, use the
appropriate sample filter. The correct sample filter is dependent on the target gas.
Case
The Model GD-K77D has a rugged metal case. A sturdy wall mounting bracket is supplied
that allows the Model GD-K77D to be securely attached to a wall for convenient operation
and maintenance.
On the front of the case are four LEDs, a LED display, a flowmeter, and a large screw that
is used to open and close the case cover. On the bottom are located a gas inlet, a gas
exhaust, and two cable bushings for external wiring.
Alarm Lights
Four light-emitting diodes (LEDs) provide visual alarms for gas concentrations and
malfunctions, and are part of the detector panel along with the LED display. These LEDs
are located on the front of the unit in the upper left corner for greatest visibility. They
perform the following functions:
PW/TR. Indicates power on or off and warns that the Model GD-K77D is not operating
normally. When PW/TR is lit (green color), the Model GD-K77D is fully powered and is
operating normally. When the PW/TR is off, power to the Model GD-K77D has been shut
off. When the PW/TR is flickering, the Model GD-K77D is not operating normally.
• ALM1. Indicates the first gas alarm (orange color).
• ALM2. Indicates the second gas alarm (red color).
• SKIP. Indicates that the Model GD-K77D is in Maintenance Mode and has temporarily
stopped gas detection.
Display
An LED display shows gas concentration in parts per million (PPM). The LED display is
located on the front of the unit in the upper right corner for easy viewing.
Flowmeter
The flowmeter checks the sample flow rate of the target gas reaching the sensor inside
the Model GD-K77D. The flowmeter is a glass tube on which are marked two red flow
lines. A flow ball indicates whether the flow rate is within, or outside, the red flow lines.
During normal operation, the standard flow rate to the sensor is approximately 0.5 L/min,
and the flow ball should be within the two red flow lines. When the ball drops below the
bottom flow line, the Model GD-K77D cannot accurately detect the target gas. Increase
the flow rate. When the ball rises above the top flow line, reduce the flow rate. For more
information about adjusting the gas flow rate, see “Flow Adjustment Up/Down” under
“Internal and Back Panel Components.”

7 • Description Model GD-K77D Operator’s Manual
Internal and Back Panel Components
Refer to the diagram below for the location of Model GD-K77D internal and back panel
components, which are described below. After each component name is a number, which
corresponds to the same number in the diagram.
Figure 3: Internal Components
Power Switch (10). Turns power on or off to the Model GD-K77D.
Power Fuse (11). Protects the Model GD-K77D from a power overload.
Mode Switch (12). Toggles the Model GD-K77D’s operating mode between detection and
maintenance. When the Model GD-K77D is being used for gas detection, the Model GD-
K77D is in normal operation; when performing maintenance on the Model GD-K77D, use
this switch to put the unit into Maintenance Mode.
Test/Set Switch (13). This switch has several functions in Maintenance Mode.
FLOW ADJ Switch (▲/▼) (14). Increases or decreases the gas flow rate to the Model
GD-K77D when the unit is in normal operation. Gas flow adjustments are made when the
flow ball is outside the red flow lines. When the flow ball is above the top flow line, press
the FLOW ADJ switch down to reduce the flow rate. When the flow ball is below the
bottom flow line, press the FLOW ADJ switch up to increase the flow rate. This switch is
also used to increase or decrease parameters in Maintenance Mode.
Pump (15). Draws the sample gas by suction to the sensor inside the Model GD-K77D.
Lithium Battery (16). Provides a bias voltage to the Model GD-K77D sensor in the event
of a power outage or a drop in line voltage.
13
10
20
Detector Unit
Side View
11
18
16 14
17
19
15
Wall Mounting
Bracket
Front View
Detector Unit
Front View
12

Model GD-K77D Operator’s Manual Description • 8
CAUTION: When the Model GD-K77D is not used for long periods of time, the lithium battery may lose
power. The lithium battery, under normal operating conditions, has a life expectancy of about
three (3) years from the date of manufacturing. When the lithium battery is replaced, put the unit
into maintenance mode before replacing the battery by pressing the Mode switch for 3 seconds.
Then calibrate the unit as described in the Calibration section. If the Model GD-K77D has been
stored for a long time, calibrate the Model GD-K77D when the unit is put back into service.
Sensor (17). Detects the target gas.
Detector Unit Set Screw (18). Tighten this screw when attaching the wall mounting
bracket to the Model GD-K77D’s case.
Terminals (19). Provides terminations for external wiring.
Flowmeter (20). The flowmeter indicates whether the sample flow rate of the sample
reaching the sensor inside the Model GD-K77D is okay. See “Flowmeter” for more
information.
Block Diagrams
Figure 4: Electrical Block Diagram
Pump
Low flow sensor
GD-K77D 4-20 mA
Transmission
Transmission
Control unit
(MODE) (FLOW ADJ.s t ) TEST/SET)
Pump
Amp unit Sensor
Power source
POWERINPUT(24 VDC)
Alarm con tact control
Display
Gas alarm contact
(ALM 1, ALM2)
Trouble alarm contact
(Trouble)
- Relaysare normally
de-energized(NDE)
- Contactsclose at
alarm condition
(PW/TR) (ALM 1) (ALM2)(SKIP)

9 • Important Safety Procedures Model GD-K77D Operator’s Manual
Figure 5: Flow Diagram
Important Safety Procedures
WARNING: Before installing and operating the Model GD-K77D, please read the
following list of precautions before continuing:
Power Source. Check the power source before turning on the Model GD-K77D. Make
sure the power source voltage is within the specified voltage range.
Ground Wire. Do not cut or remove the ground wire to the Model GD-K77D.
Fault Protection. When an electrical fault has occurred (e.g., the fuse blows), do not
attempt to operate the Model GD-K77D. Before starting up the Model GD-K77D, make
sure an electrical fault has not occurred.
Fuse. When replacing the Model GD-K77D’s fuse, turn off the power to the unit. Use only
replacement fuses that have the correct current and voltage ratings. Do not use any fuse
other than the one specified for the Model GD-K77D. Using a non-specified fuse will
cause a short and damage the Model GD-K77D.
Explosive Gases. Do not operate the Model GD-K77D in environments containing
explosive gases. The Model GD-K77D is not explosion-proof; its internal circuitry may
cause a spark which could ignite combustible gas or vapors.
External Connections. After making sure the Model GD-K77D is properly grounded and
an electrical fault has not occurred, wire all external connections to the Model GD-K77D.
Lithium Battery. When the lithium battery is replaced, turn all power off to the Model GD-
K77D before removing the battery. Do not recharge, burn, mutilate, or expose the lithium
battery to temperatures greater the 212oF (100oC) because it may leak or explode. Do
not immerse the battery in water.
GAS OUT GAS IN
Sensor
Pump
Baffle Flowmeter
Low flow sensor

Model GD-K77D Operator’s Manual Installation • 10
Sensor. Use caution when handling the sensor. The electrolyte contains a dilute acid that
can damage to clothing or other materials, and it can cause skin burns or blindness should
the acid come in contact with the eyes. If the electrolyte makes contact with the skin or
eyes, wash the affected area very thoroughly with water. With eye contact, seek medical
attention immediately.
High Gas Levels. Should the target gas reach levels greater than the alarm present level,
swift and appropriate action is crucial to avoid a potentially hazardous condition.
Communication Devices. Do not use portable telephones or two-way radios near the
Model GD-K77D. The electrical emissions or radio waves of such devices may affect the
Model GD-K77D’s readings.
Power On. When turning the power back on to the Model GD-K77D, wait 25 seconds
before taking readings; otherwise abnormal output may result.
Flowmeter. When the Model GD-K77D is drawing in the sample gas, make sure the flow
ball is between the top and bottom flow lines. When the ball drops below the bottom flow
line, the Model GD-K77D cannot accurately detect the target gas. Increase the flow rate.
Dust Filter. When sampling gas from a dusty environment, use the recommend filter to
avoid drawing dust into the Model GD-K77D. Place the external dust filter on the end of
the hose used to draw in the sample gas. When changing the dust filter, turn off the Model
GD-K77D.
Installation
Precautions
Professional installation of the Model GD-K77D by a licensed contractor is highly
recommend for the best and safest results. The following is a list of precautions that will
ensure the operating performance of the Model GD-K77D:
•Dusty Environments. When extracting gas from a dusty environment, the
recommend filter should be used to avoid drawing dust into the Model GD-K77D.
Place the external dust filter on the end of the hose used to draw in the sample gas.
When changing the dust filter, turn off the Model GD-K77D.
•Sun Light. Do not install the Model GD-K77D in direct sun light, which may affect the
operation and performance of the Model GD-K77D.
•Vibration. Do not install the Model GD-K77D in areas affected by shock and vibration,
which may damage the Model GD-K77D’s electronics.
•Electronic Emissions. Do not install the Model GD-K77D in areas with high levels of
radio interference or electronic noise. This electronic interference may cause
abnormal readings. And do not place the Model GD-K77D near electrical wiring or
other electrical devices, such as industrial motors.
•Target Gas. Do not place the Model GD-K77D where the target gas is to be detected.
Use the sampling hose to place the Model GD-K77D at a safe distance from the gas
source.
•Dangerous or Inconvenient Locations. The Model GD-K77D requires regular
maintenance. Do not place it in environments that are potentially hazardous (e.g.,
near high voltage cables), or in locations in which maintenance is very inconvenient
(e.g., near objects that prevent easy access to the controls inside the Model GD-
K77D).

11 • Installation Model GD-K77D Operator’s Manual
•Grounding. Make sure to ground the Model GD-K77D properly during installation.
Wall Mounting the Model GD-K77D
CAUTION: When installing the wall mounting bracket, make sure to attach it securely to the wall.
If not securely attached, the Model GD-K77D may fall causing damage to the unit.
Find a suitable location for the Model GD-K77D. Allow enough room around the wall
mounting bracket for the Model GD-K77D to be mounted easily. See “Precautions” on the
previous page for installation warnings.
1. Attach the wall mounting bracket to the wall using #10 screws.
2. Mount the Model GD-K77D to the wall mounting bracket.
3. Fasten the screw on the front bottom of the Model GD-K77D.
Figure 4: Outline & Mounting Dimensions
.36
8.0 MAX
1.38 1.9
7
1.5
7
.59
6.05
1.5
4
1.57
3.15 Minimum
1.54
1.97
Flow Meter
Window
Display
Area
ID Card
Holder
Cable Bushing
Gas Inlet, For ø 4 x 6
mm PTFE Tube
Gas Exhaust, for ø 4 x 6
mm Tube
3 #10 screws recommended
for mounting
GAS DETECTOR MODEL GD-K77D
TYPICAL MULTIPOINT
INSTALLATION
2.80
6
.70

Model GD-K77D Operator’s Manual Installation • 12
Removing the Model GD-K77D Detector Unit
When connecting tubing, making electrical connections, or servicing the Model GD-K77D,
it is more convenient to remove the Model GD-K77D detector unit from its wall mounting
bracket.
Figure 5: Removing the Detector Unit
1. Loosen the large screw on the front of the unit and remove the cover.
2. Loosen the screw on the lower part of the unit.
3. Remove the Model GD-K77D detector unit from the wall mounting bracket.
NOTE: When returning the Model GD-K77D detector unit to the wall mounting bracket,
assemble the unit in reverse order.
Electrical Connections
CAUTION: Unstable power or power with electrical noise may cause the Model GD-K77D to give
false readings or to trigger a false alarm. When connecting the Model GD-K77D to a
power source, carefully follow the instructions in this manual.
During warm up at power on and during a power failure, unwanted alarms may occur
depending on the relay logic and wiring used. Take any steps necessary to address this
situation.
Loosen this
screw

13 • Installation Model GD-K77D Operator’s Manual
Power Requirements
External Alarm
The Model GD-K77D can be used to control an external buzzer or alarm light. The Model
GD-K77D ‘s external alarm contacts are rated for 0.5 A @ 125 VAC, 1A @ 30 VDC, and
0.5 A @ 60 VDC. Use the alarm contacts on the Model GD-K77D to control only low
power devices. If heaver loads or inductive loads need to be controlled, use a slave relay
to accommodate the load. A CR circuit device (or Spark Killer) should be installed to
protect the alarm contacts if there is any question about the load. When driving a slave
relay, use a Spark Killer since the slave relay is an inductive load.
Figure 4: CR circuit for Alarm Relay
Table 2: Power Requirements for the Model GD-K77D
Power Voltage DC-24V +/- 10% (Terminal Voltage)
Power Failure Tolerance (Time) Approximately 10 milliseconds. After a power failure
of 10 milliseconds, the Model GD-K77D re-starts.
To ensure continuous operation, install a standby bat-
tery.
Requirements Do not connect power to the Model GD-K77D con-
taining a high power load or with high frequency
noise.
If noise is present, use a line filter to separate the
power from the noise source.
When rack-mounting the Model GD-K77D in an area
with restricted ventilation, allow for adequate ventila-
tion by mounting fans near the unit.

Model GD-K77D Operator’s Manual Installation • 14
WARNING: The alarm contacts on the Model GD-K77D are designed to take a
resistance load and not an inductive load. (An inductive load can be
created by a patlight, external relay, buzzer, siren, fan, fluorescent
light, motor, etc.)
When an inductive load is present, a very high reverse voltage may be
generated that can melt the alarm contacts on the Model GD-K77D,
damage the external alarm, or damage the CPU if one is connected to
the system. Also note that the intrusion of electrical noise in the alarm
circuit can cause the same problems generated by an inductive load.
To avoid these problems, whether created by an inductive load or by
noise, do not use an inductive load and protect the alarm contacts on
the Model GD-K77D with the appropriate surge protectors.
Grounding
Attach ground wires to the ground terminals on the Model GD-K77D, labeled chassis
(earth) ground bolts in the diagram below, before turning on the power to the Model GD-
K77D.
WARNING: Be sure to ground the Model GD-K77D properly for safe operation. Do
not connect the ground wires to the sample tubing.

15 • Installation Model GD-K77D Operator’s Manual
Figure 5: Grounding the GD-K77D
Chassis
Ground
GAS IN
GAS OUT
Chassis
Ground