RKI Instruments 65-2405RK-05-04 User manual

RKI Instruments, Inc.
www.rkiinstruments.com
65-2405RK-05-04
Combustible Gas Transmitter
Operator’s Manual
Part Number: 71-0547
Revision: P1
Released: 2/1/21

2 • 65-2405RK-05-04 Combustible Gas Transmitter
WARNING
Read and understand this instruction manual before operating detec-
tor. 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 frequen-
cies for most applications are between 3 and 6 months, but can be
required more often or less often based on your usage.

65-2405RK-05-04 Combustible Gas Transmitter • 3
Product Warranty
RKI Instruments, Inc. warrants gas alarm equipment sold by us to be free from defects in materials,
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 repair
procedures not in accordance with the operator’s 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. IN NO
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 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 the replacement of parts or our complete goods.
a) Absorbent cartridges d) Batteries
b) Pump diaphragms and valves e) Filter elements
c) Fuses

4 • 65-2405RK-05-04 Combustible Gas Transmitter
Table of Contents
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Specifications. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Combustible Gas Detector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Amplifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Amplifier Junction Box . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Detector Junction Box . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Installation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Mounting the Combustible Gas Transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Wiring the Detector to the Amplifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Wiring the Amplifier to a Controller . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Startup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Introducing Incoming Power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Setting the Zero Signal. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Preventive Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Replacing Components of the Combustible Gas Transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Calibration Frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Determining Response Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Calibration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Preparing for Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Setting the Zero Reading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Setting the Response Reading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Returning to Normal Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Parts List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

65-2405RK-05-04 Combustible Gas Transmitter • 5
Overview
This manual describes the 65-2405RK-05-04 combustible gas transmitter. This manual also describes
how to install, start up, configure, maintain, and calibrate the transmitter when it is used with a gas
monitoring controller. A parts list at the end of this manual lists replacement parts and accessories for
the combustible gas transmitter.
Specifications
WARNING: Do not use this product in a manner not specified in this manual.
Table 1 lists specifications for the combustible gas transmitter.
NOTE: The following symbol on the detector label is a caution to the user to refer to this
documentation for installation instructions:
WARNING: When using the 65-2405RK-05-04, you must follow the instructions and warnings in
this manual to assure proper and safe operation of the 65-2405RK-05-04 and to
minimize the risk of personal injury. Be sure to maintain and periodically calibrate
the 65-2405RK-05-04 as described in this manual.
Table 1:Specifications
Description Specification
Target Gas Combustible gas, methane calibration standard1
Area Classification Explosionproof for Class I, Groups B, C, and D
Sampling Method Diffusion
Signal Output 4 to 20 mA
Detection Range 0 to 100% LEL
Accuracy ± 5% of reading or ± 2% LEL (whichever is greater)
Response Time 90% in 45 seconds
Operating Temperature -40°F to 167°F (-40°C to 75°C)
1If calibration to a combustible gas other than methane is required, specify the required
calibration gas at time of order.
!

6 • 65-2405RK-05-04 Combustible Gas Transmitter
Description
This section describes the components of the combustible gas transmitter. The transmitter is a 4 - 20
mA type detector head. It consists of the combustible gas detector, amplifier, and junction box.
Figure 1: Combustible Gas Transmitter Component Location
Combustible Gas Detector
The combustible gas detector is a catalytic type detector that produces an electrical output that
corresponds to the detection range. It is packaged in a 1/2 NPT nipple with a sintered metal flame
arrestor on one end allowing ambient air to diffuse into the detector. The flame arrestor also contains
any sparks which may occur within the detector. The 1/2 NPT mounting threads at the top of the
detector allow you to mount it into the bottom conduit hub of the junction box. A flame arrestor guard
is located at the bottom of the detector and is permanently bonded to the detector housing. The flame
arrestor guard protects the flame arrestor from impact damage. Four color-coded leads extend from the
top of the detector. The leads allow you to connect the detector to the amplifier.
S
LEL PWR /SIG
BR W G
Detector
Junction Box
ZERO
Terminal Strip
SPAN
Sensor C urrent
mA
Amplifier
Junction Box
Combustible Gas Detector
Calibration Cup/SplashGuard

65-2405RK-05-04 Combustible Gas Transmitter • 7
Amplifier
The amplifier converts the electrical output from the detector to a 4 to 20 mA signal that corresponds
to the detection range and transmits the signal to a gas monitoring controller. A foam gasket that
orients the amplifier and keeps it from rotating is installed on the bottom of the amplifier. A label on
the amplifier indicates the detector drive current. This drive current is factory set and is dictated by the
combustible gas to which the detector is calibrated. Consult RKI Instruments, Inc. if you plan to
change the calibration gas for the transmitter, for example from a methane calibration to a hexane
calibration. The amplifier includes the detector terminal strip, controller terminal strip, span pot, zero
pot, and test points.
Figure 2: Amplifier Component Location
Controller Terminal Strip
The controller terminal strip is a three position plug-in style terminal strip located near the top of the
amplifier. Use the controller terminal strip to wire the transmitter to a controller.
Detector Terminal Strip
The detector terminal strip is a four position plug-in style terminal strip located below the controller
terminal strip. Use the detector terminal strip to connect the detector to the amplifier.
NOTE: See “Wiring the Amplifier to a Controller” on page 12 for all wiring procedures related to the
transmitter.
Zero Pot
The zero pot is located in the upper left corner of the amplifier (see Figure 2). Use a small flat blade
screwdriver to turn the zero pot’s adjustment screw and adjust the amplifier’s zero (fresh air) output
during the start-up and calibration procedures.
Span Pot
The span pot is located to the right of the zero pot (see Figure 2). Use a small flat blade screwdriver to
turn the span pot’s adjustment screw and adjust the amplifier’s gas response output during the
calibration procedure.
PWR / SIG
S
Controller Terminal Strip
Detector Terminal Strip
G B
ZERO
SPAN
Span Pot
Zero Pot
RLEL
W
- Test Point
Factory Adjust Pot, x2
+ Test Point

8 • 65-2405RK-05-04 Combustible Gas Transmitter
CAUTION: The amplifier includes two additional potentiometers. They are factory-set. Do not adjust
them.
Test Points
The test points are on the left side of the amplifier (see Figure 2). The test points produce a 100 mV to
500 mV output that corresponds to the transmitter’s 4 to 20 mA output. Use the test points and a
voltmeter to measure the amplifier’s output during the start-up and calibration procedures. The black
test point in the lower left corner is the negative (-) test point and the red test point below the zero pot
is the positive (+) test point.
Amplifier Junction Box
The amplifier junction box protects the amplifier and wiring connections made to the amplifier. Use
the top 3/4 NPT conduit hub to connect wiring from the amplifier to the controller. Use the bottom
3/4 NPT conduit hub to wire the remotely installed combustible gas detector. Use the cover on the
front of the junction box to access the interior of the junction box. The amplifier is factory installed in
the junction box. Three spacers installed on the back of the junction box controls the distance of the
junction box from a mounting surface.
Detector Junction Box
The detector junction box is intended to be installed remotely from the amplifier junction box. The
combustible gas detector is factory installed in the bottom 3/4 NPT conduit hub. A terminal strip is
provided for wiring connections and the detector is factory wired to one side of this terminal strip. The
other side of the terminal strip is for user-supplied wiring to the detector terminal strip located in the
amplifier junction box. This wiring should go through the top 3/4 NPT conduit hub. Three spacers
installed on the back of the junction box controls the distance of the junction box from a mounting
surface.
Installation
This section describes procedures to mount the combustible gas transmitter in the monitoring
environment and wire the transmitter to a controller.
Mounting the Combustible Gas Transmitter
1. Select a mounting site that is representative of the monitoring environment. Consider the
following when you select the mounting site.
• For the amplifier junction box, select a site where the junction box is not likely to be bumped
or disturbed. Make sure there is sufficient room to perform start-up, maintenance, and
calibration procedures. The site should be easily accessible.
• For the detector junction box, select a site where the target gas is likely to be found first. For
lighter gases, mount the detector near the ceiling; for heavier gases, mount the detector near
the floor.
• The junction boxes should be mounted no further than 200 feet from each other.

65-2405RK-05-04 Combustible Gas Transmitter • 9
Figure 3: Mounting the Combustible Gas Transmitter
2. At the monitoring site you select, hang or mount the junction box with the detector facing down
(see Figure 3).
3. Install 3/16 inch I.D. flexible polyurethane tubing to the fitting at the bottom of the calibration cup/
splash guard and route it to an accessible area that is close to the amplifier junction box. See “Parts
List” on page 21 for available tubing.
.382.70
3/4 NPT Female
Rubber
Spacer,
3X
1.13
5.25
9.80 Max
Ø3.65
Combustible
Gas
Detector
Calibration
Adapter/
Splash
Guard

10 • 65-2405RK-05-04 Combustible Gas Transmitter
Wiring the Detector to the Amplifier
WARNING: Always verify that the power to the controller is off before you make wiring
connections.
1. Confirm that no power is being applied to the amplifier. If the amplifier has already been
connected to a controller, turn off the controller and turn off or unplug power to the controller.
2. Remove the detector junction box’s cover from the junction box.
3. Remove the amplifier junction box’s cover from the junction box.
4. Guide a four-conductor, shielded cable or four wires in conduit through the top conduit hub of the
detector junction box. To make wiring more convenient, use wire colors that correspond to the
detector wire colors: red, white, green, and black.
NOTE: Consult RKI Instruments, Inc. for cable lengths longer than 200 feet.
5. Connect the detector leads to the terminal block in the detector junction box.
6. Secure the detector junction box’s cover to the junction box.
7. Guide the other end of the four-conductor, shielded cable or four wires in conduit through the
bottom conduit hub of the amplifier junction box.
8. To gain access to a plug-in terminal strip for wiring, pull it out of its socket by grasping the
terminal strip and pulling. The detector strip is keyed so that the controller and detector terminal
strips cannot be reversed inadvertently.
9. Pull out the detector terminal strip and connect the four wires to the terminal strip as follows (see
Figure 4).
• Connect the wire corresponding to the detector’s red wire to the LEL “R” terminal.
• Connect the wire corresponding to the detector’s white wire to the LEL “W” terminal.
• Connect the wire corresponding to the detector’s green wire to the LEL “G” terminal.
• Connect the wire corresponding to the detector’s black wire to the LEL “B” terminal.
CAUTION: If shielded cable is used, leave the cable shield’s drain wire disconnected and insulated at
the detector junction box. You will connect the opposite end of the cable’s drain wire to
the amplifier junction box’s chassis (earth) ground.

65-2405RK-05-04 Combustible Gas Transmitter • 11
Figure 4: Wiring the Detector to the Amplifier
10. Reinstall the detector terminal strip into its socket.
11. If shielded cable is used, connect the cable’s drain wire to an available chassis (earth) ground at the
amplifier junction box. The amplifier mounting screw is a convenient grounding location. Install a
lug on the shield drain wire or wrap the shield drain wire around the mounting screw. Do not
connect the shield drain wire at the detector junction box.
GRB
S
PWR /SIG
WLEL
Black
Green
White
Red
Cable
Shield
Detector
Terminal
Strip
Black
Green
White
Red
Amplifier
J-Box
Combustible Gas Detector
Calibration Cup/Splash Guard
Detector J-Box

12 • 65-2405RK-05-04 Combustible Gas Transmitter
Wiring the Amplifier to a Controller
WARNING: Always verify that the power to the controller is off before you make wiring
connections.
1. Turn off the controller.
2. Turn off or unplug power to the controller.
3. Remove the amplifier junction box’s cover.
4. To gain access to a plug-in terminal strip for wiring, pull it out of its socket by grasping the
terminal strip and pulling. The detector strip is keyed so that the controller and detector terminal
strips cannot be reversed inadvertently.
WARNING: To maintain the explosion proof classification of the detector/junction box
combination, a conduit seal must be used within 18 inches of the junction box conduit
hub used for wiring to the controller.
5. Guide a three-conductor, shielded cable or three wires in conduit through the top conduit hub of
the junction box.
6. Pull out the controller terminal strip, and connect the three wires to the terminal strip as follows
(see Figure 5).
• Connect the positive wire to the PW R/SI G “+” terminal.
• Connect the signal wire to the PWR/SI G “S” terminal.
• Connect the negative wire to the PW R/SI G “-” terminal.
CAUTION: If shielded cable is used, leave the cable shield’s drain wire disconnected and insulated at
the transmitter. You will connect the opposite end of the cable’s drain wire to the
controller’s chassis (earth) ground.
7. Reinstall the controller terminal strip into its socket.
8. Secure the junction box cover to the junction box.
9. Route the cable or wires leading from the combustible gas transmitter through one of the conduit
hubs at the controller housing.
CAUTION: Do not route power and transmitter wiring through the same controller conduit hub. The
power cable may disrupt the transmission of the transmitter signal to the controller.
10. Connect the wires to the applicable detector/transmitter terminal strip at the controller as shown in
Figure 5.

65-2405RK-05-04 Combustible Gas Transmitter • 13
Figure 5: Wiring the Combustible Gas Transmitter to a Controller
11. If shielded cable is used, connect the cable’s drain wire to an available chassis (earth) ground at the
controller. RKI controllers typically have a ground stud that can be used to ground the cable’s
drain wire.
Start Up
This section describes procedures to start up the combustible gas transmitter and place the transmitter
into normal operation.
Introducing Incoming Power
1. Complete the installation procedures described earlier in this manual.
2. Verify that the power wiring to the controller is correct and secure. Refer to the controller
operator’s manual.
3. Turn on power to the controller.
4. Turn on the controller.
5. Verify that the controller is on and operating properly. Refer to the controller operator’s manual.
Detector Wires
Green
White
Red
Amplifier (Transmitter)
Cable Shield
- (DC Ground)
+24VDC
4-20mAIn(S)
Controller or
Recording Device
Amplifier
J-Box
B
R W G PW R / SIG
Black
LE L
S

14 • 65-2405RK-05-04 Combustible Gas Transmitter
CAUTION: Allow the detector to warm up for 5 minutes before you continue with the next section,
“Setting the Zero Signal”.
Setting the Zero Signal
WARNING: Do not remove the junction box cover while the circuits are energized unless the area
is determined to be non-hazardous. Keep the junction box cover tightly closed during
operation.
CAUTION: If you suspect the presence of combustible gas in the monitoring environment, use the
calibration kit and the zero air calibration cylinder to introduce “fresh air” to the
detector and verify an accurate zero setting. See “Calibration” on page 19 for
instructions to apply zero air when setting the zero signal.
1. Verify that the transmitter is in a fresh air environment (environment known to be free of
combustible gas).
2. Unscrew and remove the amplifier junction box’s cover from the junction box.
3. Set a voltmeter to measure in the millivolt (mV) range.
4. Plug the voltmeter leads into the test points on the amplifier. Plug the positive lead into the red (+)
test point; plug the negative lead into the black (-) test point.
5. Verify a voltmeter reading of 100 mV (±2 mV).
6. If necessary, use a small flat-blade screwdriver to adjust the zero pot until the voltmeter reading is
100 mV (±2 mV).
7. Remove the voltmeter leads from the test points.
8. Secure the amplifier junction box’s cover to the junction box.
Maintenance
This section describes maintenance procedures. It includes preventive maintenance, troubleshooting,
and component replacement procedures.
Preventive Maintenance
This section describes a preventive maintenance schedule to ensure the optimum performance of the
combustible gas transmitter. It includes daily and quarterly procedures.
Daily
Verify a display reading of 0% LEL at the controller. Investigate significant changes in the display
reading.
Quarterly
Calibrate the combustible gas transmitter as described in “Calibration” on page 19 of this manual. See
the calibration frequency discussion in “Calibration Frequency” on page 18 to determine if a quarterly
calibration schedule fits your needs.

65-2405RK-05-04 Combustible Gas Transmitter • 15
Troubleshooting
The troubleshooting guide describes symptoms, probable causes, and recommended action for
problems you may encounter with the combustible gas transmitter.
NOTE: This troubleshooting guide describes transmitter problems only. See the controller operator’s
manual for problems you may encounter with the controller.
Table 2:Troubleshooting the Combustible Gas Transmitter
Condition Symptom(s) Probable Causes Recommended Action
Fail
Condition
• Controller
indicates a fail
condition.
• The transmitter
wiring is
disconnected or
misconnected.
• The transmitter’s
zero reading is low
enough to cause a
fail condition.
• The transmitter is
malfunctioning.
1. Verify that the transmitter wiring
is correct and secure.
2. Calibrate the transmitter.
3. If the fail condition continues,
replace the detector.
4. If the fail condition continues,
contact RKI for further
instruction.
Slow or No
Response/
Difficult or
Unable to
Calibrate
• Unable to
accurately set the
zero or response
reading during
calibration.
•Transmitter
requires frequent
calibration.
Note: Under
“normal”
circumstances, the
transmitter requires
calibration once
every 3 months.
Some applications
may require a more
frequent calibration
schedule.
• The calibration
cylinder is low, out-
dated, or defective.
• The calibration gas
flow rate is too low.
• The calibration gas
is not an appropriate
concentration.
• The transmitter is
malfunctioning.
• The flexible tubing
to the calibration
cup/splash guard has
become kinked,
blocked, or
disconnected.
1. Verify that the calibration cylinder
contains an adequate supply of a
fresh test sample.
2. Verify that the regulator used for
calibration is a 0.5 LPM regulator.
3. Verify that the calibration gas
concentration is appropriate for
the transmitter. The concentration
should be in the detection range,
preferably about half of the
detection range.
4. Verify that the flexible tubing to
the calibration cup/splash guard is
clear and connected to the
calibration cup/splash guard.
5. If the calibration/response
difficulties continue, replace the
detector.
6. If the calibration/response
difficulties continue, contact RKI
for further instruction.

16 • 65-2405RK-05-04 Combustible Gas Transmitter
Replacing Components of the Combustible Gas Transmitter
This section includes procedures to replace the combustible gas detector and amplifier.
Replacing the Combustible Gas Detector
NOTE: The combustible gas detector is installed on the junction box that does not house the
amplifier. This junction box was likely installed somewhere difficult to access.
1. Turn off the controller.
2. Turn off or unplug power to the controller.
3. Unscrew the calibration cup/splash guard from the detector.
4. Remove the detector junction box’s cover.
5. Disconnect the detector leads from the terminal block in the detector junction box. Note the
position of the color-coded leads as you remove them.
6. Unscrew the detector from the detector junction box.
7. Guide the detector leads of the replacement detector through the bottom conduit hub of the
detector junction box, then screw the mounting threads of the detector into the conduit hub. If
necessary for environmental conditions, apply thread sealant or Teflon tape to the hub and/or
detector threads to seal them.
8. Connect the detector leads to the terminal block the same way the old detector was wired (see
Figure 4 on page 11).
9. Screw the calibration cup/splash guard onto the new detector.
10. Reinstall the detector junction box’s cover.
11. Turn on or plug in power to the controller.
12. Turn on the controller and place it into normal operation.
CAUTION: Allow the replacement detector to warm up for 5 minutes before you continue with the
next step.
13. Calibrate the transmitter as described in “Calibration” on page 19 of this manual.
Replacing the Amplifier
1. Turn off the controller.
2. Turn off or unplug power to the controller.
3. Remove the amplifier junction box’s cover.
4. Unplug the detector terminal strip and controller terminal strip from their sockets. You may leave
the wires connected to the terminal strips.
5. Unscrew and remove the screw with the flat and lock washers that secures the amplifier to the
junction box.
6. Remove the old amplifier.
7. Place the new amplifier in the same position as the old amplifier. A foam gasket that orients the
amplifier and keeps it from rotating is installed on the bottom of the amplifier. Make sure the
amplifier is seated flat in the junction box.

65-2405RK-05-04 Combustible Gas Transmitter • 17
8. Install the amplifier into the junction box with the screw, lock washer, and flat washer you
removed in Step 5 above.
9. Install the detector and controller terminal strips into their sockets on the new amplifier as shown
in Figure 5 on page 13. If controller leads or detector leads were removed during this procedure,
refer to Table 3 and Table 4 below.
NOTE: When a transmitter is first powered up with a new amplifier, the initial output may be either
high or below zero depending on the setting of the zero pot. Be sure to make arrangements so
that this does not cause unwanted alarms.
10. Turn on or plug in power to the controller.
11. Turn on the controller and place it into normal operation.
12. Allow the transmitter to warm-up for 5 minutes.
13. Calibrate the transmitter as described in “Calibration” on page 19 of this manual.
Table 3:Reconnecting the Amplifier
to the Controller
Amplifier Controller
Terminal Strip
Controller
Transmitter Terminal
Strip (typical)
PWR/SIG “-” - (DC -)
PWR/SIG “S” S (4 - 20 mA In)
PWR/SIG “+” + 24V
Table 4:Reconnecting the ppm
Detector to the Amplifier
Amplifier Detector
Terminal Strip Detector Lead
DETECTOR “R” RED
DETECTOR “W” WHT
DETECTOR “G” GREEN
DETECTOR “B” BLK

18 • 65-2405RK-05-04 Combustible Gas Transmitter
Calibration Frequency
Although there is no particular calibration frequency that is correct for all applications, a calibration
frequency of every 3 to 6 months is adequate for most combustible gas transmitter applications. Unless
experience in a particular application dictates otherwise, RKI Instruments, Inc. recommends a
calibration frequency of every 3 months.
If an application is not very demanding, for example detection in a clean, temperature controlled
environment where combustible gas is not normally present and calibration adjustments are minimal at
calibration, then a calibration frequency of every 6 months is adequate.
If an application is very demanding, for example if combustible gas is present often and in significant
concentrations or the environment is not well controlled, then more frequent calibration than every 3
months may be necessary. If potential catalyst poisons are known or likely to be present, more frequent
calibration than every 3 months will be necessary.
Determining Response Time
Since the detector junction box is installed remotely from the amplifier, the response time of the
detector will depend on the length of flexible tubing that is attached to the calibration cup/splash guard.
To determine the response time based on the length of tubing connected:
1. Place the controller into its calibration mode or disable external alarms.
2. Note the current gas reading displayed at the controller.
3. Screw the regulator into the calibration cylinder. Do not use a zero air cylinder for this operation.
4. Use the flexible tubing coming from the calibration cup/splash guard to connect the regulator to
the calibration cup.
5. Turn the regulator’s on/off knob counterclockwise to open the regulator. Gas will begin to flow.
Take note of the time or start a stopwatch.
6. When you first start to notice an increase in the gas reading, note how much time passed between
starting the gas flow and noticing a reading response.
7. Turn the regulator’s on/off knob clockwise to close the regulator.
8. Unscrew the regulator from the calibration cylinder.
9. Disconnect the calibration cup/splash guard’s flexible tubing from the regulator.
NOTE: Do not disconnect the flexible tubing from the calibration cup/splash guard.
10. Add 1 minute to the length of time determined in Step 6. This is the response time for the detector.
When performing a response test, zero adjustment, or span adjustment, gas must be applied for this
length of time.

65-2405RK-05-04 Combustible Gas Transmitter • 19
Calibration
This section describes how to calibrate the combustible gas transmitter. It includes procedures to
prepare for calibration, set the zero reading, set the response reading, and return to normal operation.
WARNING: The controller is not an active gas monitoring device during the calibration
procedure.
NOTE: The following procedure assumes the use of a calibration kit which includes a calibration gas
cylinder, a 0.5 LPM fixed flow regulator with an on/off knob, a calibration cup for the
detector, and a short piece of sample tubing to connect the regulator to the calibration cup.
Preparing for Calibration
NOTE: Calibrating the combustible gas transmitter may cause alarms. Be sure to put the controller
into its calibration program or disable external alarms before continuing.
WARNING: Do not remove the junction box cover while the circuits are energized unless the area
is determined to be non-hazardous. Keep the junction box cover tightly closed during
operation.
1. Unscrew and remove the junction box cover.
2. Set a voltmeter to measure in the millivolt (mV) range.
3. Plug the voltmeter leads into the test points on the amplifier. Plug the positive lead into the red (+)
test point; plug the negative lead into the black (-) test point.
4. Use the following formula to determine the correct test points output for the calibrating sample.
Output (mV) = (calibrating sample/fullscale) X 400 + 100
For example, with a calibrating sample of 50% LEL and a fullscale setting of 100% LEL, the
correct output is 300 mV.
300(mV) = (50/100) X 400 +100
5. Screw the calibration cup on the detector housing.
Setting the Zero Reading
NOTE: If you can verify that the combustible gas transmitter is in a fresh air environment, you do not
need to apply zero air to the detector before adjusting the zero reading.
1. Screw the regulator into the zero air calibration cylinder.
2. Use the calibration kit sample tubing to connect the regulator to the calibration cup.
3. Turn the regulator’s on/off knob counterclockwise to open the regulator.

20 • 65-2405RK-05-04 Combustible Gas Transmitter
4. Allow the gas to flow for the length of time determined in “Determining Response Time” on
page 18 and verify a reading of 100 mV (±2 mV). If necessary, use the zero pot on the amplifier to
adjust the reading to 100 mV (±2 mV).
5. Turn the regulator’s on/off knob clockwise to close the regulator.
6. Unscrew the regulator from the zero air calibration cylinder.
7. Leave the sample tubing connected to the regulator and the calibration cup.
Setting the Response Reading
1. Screw the regulator into the calibration cylinder. Verify that the calibration gas is representative of
the transmitter’s target gas.
2. Turn the regulator’s on/off knob counterclockwise to open the regulator.
3. Allow the gas to flow for the length of time determined in “Determining Response Time” on
page 18 and verify that the reading matches the response reading (±2 mV) you determined earlier.
If necessary, use the span pot on the amplifier to adjust the reading to match the correct response
reading.
4. Turn the regulator’s on /off knob clockwise to close the regulator.
5. Unscrew the regulator from the calibration cylinder.
Returning to Normal Operation
1. Remove the voltmeter leads from the amplifier test points.
2. Unscrew the calibration cup from the detector.
NOTE: For convenience, leave the regulator and calibration cup connected by the sample tubing.
3. Secure the junction box cover to the junction box.
4. When the controller display reading falls below the alarm setpoints, return the controller to normal
operation.
5. Verify that the controller display reading decreases and stabilizes at 0 %LEL.
6. Store the components of the calibration kit in a safe and convenient place.