Apex Precision Gas Flow Controller Operating Manual

16 Series

Mass and Volumetric Flow Controllers

Precision Gas Flow Controller

Operating Manual

Notice: The manufacturer reserves the right to make any changes and improvements
to the products described in this manual at any time and without notice. This manual
is copyrighted. This document may not, in whole or in part, be copied, reproduced,
translated, or converted to any electronic medium or machine readable form, for
commercial purposes, without prior written consent from the copyright holder.

Note: Although we provide assistance on our products both personally and through
our literature, it is the complete responsibility of the user to determine the suitability
of any product to their application.

The manufacturer does not warrant or assume responsibility for the use of its
products in life support applications or systems.

Wide-Range Laminar Flow Element Patent:

The wide-range laminar ow element and products using the wide-range laminar
ow element are covered by U.S. Patent Number: 5,511,416. Manufacture or use of
the wide-range laminar ow element in products other than products licensed under

said patent will be deemed an infringement.

Warranty

This product is warranted to the original purchaser for a period of one year from the date

of purchase to be free of defects in material or workmanship. Under this warranty the

product will be repaired or replaced at manufacturer’s option, without charge for parts or
labor when the product is carried or shipped prepaid to the factory together with proof of
purchase. This warranty does not apply to cosmetic items, nor to products that are damaged,

defaced or otherwise misused or subjected to abnormal use. See “Application” under the

Installation section. Where consistent with state law, the manufacturer shall not be liable
for consequential economic, property, or personal injury damages. The manufacturer does
not warrant or assume responsibility for the use of its products in life support applications
or systems.

10/24/06 Rev. 0 DOC-APEXMAN16C

Table of Contents Page

Installation 5
Plumbing 5

Mounting 5
Application 5
Power and Signal Connections 6
Input Signals 7
Analog Input Signal 7
RS-232 Input Signal 7
Output Signals 7
RS-232 Digital Output Signal 8
Standard Voltage (0-5 Vdc) Output Signal 8
Optional 0-10 Vdc Output Signal 8
Optional Current (4-20 mA) Output Signal 8
Optional 2nd Analog Output Signal 8
MC Series Mass Flow Controller Operation 10
Main Mode 10
Set Pt. 10

Gas Absolute Pressure 10
Gas Temperature 11

Volumetric Flow Rate 11
Mass Flow Rate 11
Flashing Error Message 11
Select Menu Mode 11
Control Setup Mode 12

Input 12
Loop 13

Select 13
Gas Select Mode 14
Communication Select Mode 15
Unit ID 15
Baud 15
Data Rate 15
Manufacturer Data Mode 16
VC Series Volumetric Flow Controller Operation 17
Main Mode 17
Volume 17
Set Pt. 17
Flashing Error Message 17
Select Menu Mode 18
Control Setup Mode 18
Input 18
Select 18
Gas Select Mode 20
Communication Select Mode 20

Table of Contents Page

Manufacturer Data Mode 20
RS-232 Output and Input 20
Conguring HyperTerminal® 20
Changing from Streaming to Polling Mode 20
Sending a Set-Point via RS-232 21
To adjust the P & D terms via RS-232 21
Gas Select 23
Collecting Data 24
Data Format 24
Sending a Simple Script File to HyperTerminal® 25
Operating Principle 26
Gas Viscosity 26
Other Gases 27
Volume Flow vs. Mass Flow 27
Volumetric Flow and Mass Flow Conversion 28
Compressibility 28
Standard Gas Data Tables 29
Gas Viscosities and Densities Table 30
Volumetric Flow Meters Under Pressure 31
Troubleshooting 32
Maintenance and Recalibration 33
Technical Specications 34
Dimensional Drawings 38

Additional Information

Option: Totalizing Mode 41
Option: Local Set-Point Module 42
Accessories 43
Flow Conversion Table 43
Calibration Certicate Pocket 44

Figure 1. 8 Pin Mini-DIN Connector 6
Figure 2. Simple method for providing set-point to controllers 7
Figure 3. Mini-DIN to DB-9 Connection for RS-232 Signals 8
Figure 4. Typical Multiple Device (Addressable) Wiring Conguration 9
Figure 5. Optional Industrial Connector 9
Figure 6. Main Mode Display, MC Series Flow Controller 10
Figure 7. Select Menu Display 11
Figure 8. MC Series Control Setup Display 12
Figure 9. Gas Select Display 14
Figure 10. Communication Select Display 15
Figure 11. Manufacturer Data Displays 16
Figure 12. Main Mode Display, VC Series Flow Controller 17
Figure 13. VC Series Control Setup Display 18

Thank you for purchasing an Apex MC or VC Series Gas Flow Controller. Please take the time to nd

and read the information contained in this manual. This will help to ensure that you get the best possible
service from your instrument. This manual covers the following Apex instruments:

MC Series 16 Bit Mass Gas Flow Controllers
VC Series 16 Bit Volumetric Gas Flow Controllers

Installation

Plumbing

All MC and VC Series Gas Flow Controllers are equipped with female inlet and outlet port connections.
Because the ow meters set up a laminar ow condition within the ow body, no straight runs of pipe
are required upstream or downstream of the controller. The inlet and outlet ports are equal in size and
symmetric (in-line). The port sizes (process connections) and mechanical dimensions for different ow
ranges are shown on pages 34-37.

Controllers with 10-32 ports have o-ring face seals and require no further sealant or tape. On other

controllers, avoid the use of pipe dopes or sealants on the ports as these compounds can cause

permanent damage to the controller should they get into the ow stream. Use of thread sealing Teon

tape is recommended to prevent leakage around the threads. When applying the tape, avoid wrapping

the rst thread or two to minimize the possibility of getting a piece of shredded tape into the ow stream.
When changing ttings, always clean any tape or debris from the port threads.

It is also recommended that a 20 micron lter be installed upstream of controllers with full scale ranges
of 1(S)LPM or less and a 50 micron lter be installed upstream of controllers with full scale ranges
above 1(S)LPM.

Mounting

All MC and VC Series Gas Flow Controllers have mounting holes for convenient mounting to at panels.
The sizes and dimensions for the mounting holes are shown on pages 38-40. Position sensitivity is not

generally an issue with small valve controllers. Large valve controllers are somewhat position sensitive
because of the fairly massive stem assembly. It is generally recommended that they be mounted so
that the valve cylinder is vertical and upright. The primary concern in mounting a large valve controller
in a position other than the recommended position is the increased risk of leakage when the controller

is given a zero set-point and is being held closed by the spring force.

Application

Maximum operating line pressure is 125 PSIG (862 kPa).

Caution: Exceeding the maximum specied line pressure may cause permanent damage to the

solid-state differential pressure transducer.

If the line pressure is higher than 125 PSIG (862 kPa), a pressure regulator should be used upstream
from the ow meter to reduce the pressure to 125 PSIG (862 kPa) or less if possible. Many of our
controllers are built after extensive consultations with the customer regarding the specic application.
The result is that two controllers with the same ow range and part number may look and act quite
differently depending upon the application the controller was built for. Care should be taken in moving a

controller from one application to another to test for suitability in the new application. Note that volumetric
meters and controllers are not recommended for high pressure or high backpressure applications (see
page 31).

5

Power and Signal Connections

7 8

1

2

3 4 5

AC/DC Adapter Jack

6

Power can be supplied to your MC or VC Series controller through either the power jack or the 8 pin
Mini-DIN connector as shown in Figure 1. An AC to DC adapter which converts line AC power to DC
voltage and current as specied below. The power jack accepts 2.1 mm female power plugs with positive
centers. Cables and AC/DC adaptors may purchased from the manufacturer (see Accessories page 43)

and are commonly available at local electronics suppliers. Alternatively, power can be supplied through

the Mini-DIN connector as shown below:

Small Valve: If your controller utilizes a small valve (about the size of your thumb), a 12-18
Vdc (standard 68ohm valve coil) or 19-28 Vdc (optional 136ohm valve coil) power supply with a 2.1
mm female positive center plug capable of supplying 300 mA is recommended. Note: 4-20mA output
requires at least 15 Vdc.

Large Valve: If your controller utilizes a large valve (about the size of your st), a 24-30 Vdc power
supply with a 2.1 mm female positive center plug capable of supplying at least 750mA is required.

1

3

6

Pin Function

1 Inactive or 4-20mA Primary Output Signal Black

2

3 RS-232 Input Signal Red
4 Analog Input Signal Orange
5 RS-232 Output Signal Yellow
6 0-5 Vdc (or 0-10 Vdc) Output Signal Green

7 Power In (as described above) Blue
8 Ground (common for power, communications and signals) Purple

Note: The above pin-out is applicable to all the ow meters and controllers available with the Mini­DIN connector. The availability of different output signals depends on the ow meter options ordered.

Underlined Items in the above table are optional congurations that are noted on the unit’s
calibration sheet.

Static 5.12 Vdc or Secondary Analog Output (4-20mA, 5Vdc, 10Vdc) or
Basic Alarm

2

4 5

7

8

Mini-DIN

cable color

Brown

Figure 1. 8 Pin Mini-DIN Connector

CAUTION: Do not connect power to pins 1 through 6 as permanent damage can occur!

Note: Upon initial review of the pin out diagram in Figure 1, it is common to mistake Pin 2 (labeled

5.12 Vdc Output) as the standard 0-5 Vdc analog output signal! In fact Pin 2 is normally a constant

5.12 Vdc that reects the system bus voltage and can be used as a source for the set-point signal.

6

Input Signals

7

6

5

4

3

2

1

8

5.12 Vdc

50 KOhm

Potentiometer

0-5 Vdc

Analog Input Signal

Apply analog input to Pin 4 as shown in Figure 1.

Standard 0-5 Vdc: Unless ordered otherwise, 0-5 Vdc is the standard analog input signal. Apply the
0-5 Vdc input signal to pin 4, with common ground on pin 8. The 5.12 Vdc output on pin 2 can be wired
through a 50K ohm potentiometer and back to the analog input on pin 4 to create an adjustable 0-5 Vdc

input signal source as shown below.

Figure 2. Simple method for providing set-point to controllers

Optional 0-10 Vdc: If specied at time of order, a 0-10 Vdc input signal can be applied to pin 4, with

common ground on pin 8.

Optional 4-20 mA: If specied at time of order, a 4-20 mA input signal can be applied to pin 4, with

common ground on pin 8. Note: 4-20mA output requires at least 15 Vdc power input.

RS-232 Digital Input Signal

If you will be using the RS-232 input signal, it is necessary to connect the RS-232 Output Signal (Pin

5), the RS-232 Input Signal (Pin 3), and Ground (Pin 8) to your computer serial port as shown in Figure

3. Adapter cables are available from the manufacturer or they can be constructed in the eld with parts
from an electronics supply house. In Figure 3, note that the diagrams represent the “port” side of the
connections, i.e. the connector on top of the meter and the physical DB-9 serial port on the back of the
computer. The cable ends will be mirror images of the diagram shown in Figure 3. (See page 20 for
details on accessing RS-232 input.)

Output Signals

Note: Upon initial review of the pin out diagram in Figure 1 (page 6), it is common to mistake Pin 2
(labeled 5.12 Vdc Output) as the standard 0-5 Vdc analog output signal! In fact Pin 2 is normally a

constant 5.12 Vdc that reects the system bus voltage and can be used as a source for the input signal.
This allows the user in the eld to run this output through a 50K ohm potentiometer and back into the
analog set-point pin to create a 0-5 Vdc set-point source.

RS-232 Digital Output Signal

If you will be using the RS-232 output signal, it is necessary to connect the RS-232 Output Signal (Pin

5), the RS-232 Input Signal (Pin 3), and Ground (Pin 8) to your computer serial port as shown in Figure

3. Adapter cables are available from the manufacturer or they can be constructed in the eld with parts
from an electronics supply house. In Figure 3, note that the diagrams represent the “port” side of the

7

connections, i.e. the connector on top of the meter and the physical DB-9 serial port on the back of the

7

4

6

21

DB-9 Serial Port

5

5----------Ground--------------------------------------Ground----------8
3----------Transmit------------------------------------Receive---------3
2----------Receive-------------------------------------Transmit--------5

8 Pin Mini-DIN Port

8

1

2 3 4 5

6

7

8 9

3

computer. The cable ends will be mirror images of the diagram shown in Figure 3. (See page 20 for
details on accessing RS-232 output.)

Standard Voltage (0-5 Vdc) Output Signal

All MC and VC Series ow controllers have a 0-5 Vdc (optional 0-10 Vdc) output signal available on
Pin 6. This is generally available in addition to other optionally ordered outputs. This voltage is usually
in the range of 0.010 Vdc for zero ow and 5.0 Vdc for full-scale ow. The output voltage is linear over

the entire range. Ground for this signal is common on Pin 8.

Optional 0-10 Vdc Output Signal

If your controller was ordered with a 0-10 Vdc output signal, it will be available on Pin 6. (See the
Calibration Data Sheet that shipped with your controller to determine which output signals were
ordered.) This voltage is usually in the range of 0.010 Vdc for zero ow and 10.0 Vdc for full-scale ow.

The output voltage is linear over the entire range. Ground for this signal is common on Pin 8.

Optional Current (4-20 mA) Output Signal

If your controller was ordered with a 4-20 mA current output signal, it will be available on Pin 1. (See
the Calibration Data Sheet that shipped with your controller to determine which output signals were
ordered.) The current signal is 4 mA at 0 ow and 20 mA at the controller’s full scale ow. The output
current is linear over the entire range. Ground for this signal is common on Pin 8. (Current output units
require 15-30Vdc power.)

Note: This is a current sourcing device. Do not attempt to connect it to “loop powered” systems.

Optional 2nd Analog Output Signal

You may specify an optional 2nd analog output on Pin 2 at time of order. (See the Calibration Data
Sheet that shipped with your controller to determine which output signals were ordered.) This output
may be a 0-5 Vdc, 0-10 Vdc, or 4-20 mA analog signal that can represent any measured parameter.
With this optional output, a volumetric ow controller could output the volumetric ow rate with a 0-5
Vdc signal (on pin 6) and a 4-20 mA signal (on pin 2), or a mass ow controller could output the mass
ow rate (0-5 Vdc on pin 6) and the absolute pressure (0-5 Vdc on pin 2).

Note: This is a current sourcing device. Do not attempt to connect it to “loop powered” systems.

2

4

6

7

5

8

Figure 3. Mini-DIN to DB-9 Connection for RS-232 Signals

8

Purple (Ground)

Red

Yellow

Unit A

Purple

Red

Yellow

Unit B

Purple

Red

Yellow

Unit C

2

5

3

5

4

3

2

1

9

8

Female Serial Cable Front

Figure 4. Typical Multiple Device (Addressable) Wiring Conguration

An optional industrial connector is also available:

Pin Function Cable Color

1

Power In ( + )

2 RS-232 Output Blue
3 RS-232 Input Signal White
4 Analog Input Signal Green
5 Ground (commom for power,

Black

communications and signals)

6 Signal Out (Voltage or Current as ordered) Brown

Figure 5. Optional Industrial Connector

7

Red

6

6

1

5

2

4

3

Note: The above pin-out is applicable to all the ow meters and controllers ordered with the industrial

connector. The availability of different output signals depends on the ow controller options ordered.

9

MC Series Mass Flow Controller Operation

The MC Series Mass Flow Controller provides a multitude of useful ow data in one simple, rugged
device. The MC Series can have several screen “modes” depending on how the device is ordered.
All MC Series controllers have a default Main Mode, Select Menu Mode, Control Set Up Mode, Gas
Select Mode (the Gas Select Mode may not be available on controllers calibrated for a custom gas or
blend), Communication Select Mode and Manufacturer Data Mode. (In addition, your device may have
been ordered with a Totaliizing Mode, page 41.) The device defaults to Main Mode as soon as power

is applied to the controller.

Main Mode

The main mode screen defaults on power up with the mass ow on the primary display. The following
parameters are displayed in the main mode as shown in Figure 6.

PSIA oC Set Pt.

+13.49 +22.73 0.000

SCCM
Air

+0.000 +0.000

Volume Mass Main

MASS

Figure 6. Main Mode Display, MC Series Flow Controller

The “MODE” button in the lower right hand corner toggles the display between modes.

Set Pt. – The set-point is shown in the upper right corner of the display. The set-point cannot be adjusted

from the main mode screen. For information on changing the set-point, see “Set”, page 13.

Gas Absolute Pressure: The MC Series ow controllers utilize an absolute pressure sensor to measure
the line pressure of the gas ow being monitored. This sensor references hard vacuum and accurately

reads line pressure both above and below local atmospheric pressure. This parameter is located in

the upper left corner of the display under the dynamic label “PSIA”. This parameter can be moved to
the primary display by pushing the button just above the dynamic label (top left). The engineering unit
associated with absolute pressure is pounds per square inch absolute (PSIA). This can be converted
to gage pressure (PSIG = the reading obtained by a pressure gauge that reads zero at atmospheric
pressure) by simply subtracting local atmospheric pressure from the absolute pressure reading:

PSIG = PSIA – (Local Atmospheric Pressure)

The ow meters use the absolute pressure of the gas in the calculation of the mass ow rate. For
working in metric units, note that 1 PSI = 6.89 kPa.

10

Gas Temperature: The MC Series ow controllers utilize a temperature sensor to measure the line
temperature of the gas ow being monitored. The temperature is displayed in engineering units of
degrees Celsius (°C). The ow controllers use the temperature of the gas in the calculation of the mass
ow rate. This parameter is located in the upper middle portion of the display under “°C”. This parameter
can be moved to the primary display by pushing the top center button above “°C”.

Volumetric Flow Rate: The volumetric ow rate is determined using the Flow Measurement Operating
Principle described on page 26. This parameter is located in the lower left corner of the display over
“Volume”. This parameter can be moved to the primary display by pushing the “Volume” button (lower
left). In order to get an accurate volumetric ow rate, the gas being measured must be selected (see
Gas Select Mode). This is important because the device calculates the ow rate based on the viscosity

of the gas at the measured temperature. If the gas being measured is not what is selected, an incorrect

value for the viscosity of the gas will be used in the calculation of ow, and the resulting output will be

inaccurate in direct proportion to the ratio between the two gases viscosities.

Mass Flow Rate: The mass ow rate is the volumetric ow rate corrected to a standard temperature
and pressure (typically 14.696 psia and 25°C). This parameter is located in the lower middle portion
of the display over “Mass”. This parameter can be moved to the primary display by pushing the button
located below “Mass” (bottom center). The controllers uses the measured temperature and the measured
absolute pressure to calculate what the ow rate would be if the gas pressure was at 1 atmosphere and
the gas temperature was 25°C. This allows a solid reference point for comparing one ow to another.

Flashing Error Message: Our ow meters and controllers display an error message (MOV = mass
overrange, VOV = volumetric overrange, POV = pressure overrange, TOV = temperature overrange)
when a measured parameter exceeds the range of the sensors in the device. When any item ashes
on the display, neither the ashing parameter nor the mass ow measurement is accurate. Reducing
the value of the ashing parameter to within specied limits will return the unit to normal operation and

accuracy.

Select Menu Mode

Pushing “Mode” once will bring up the “Select Menu” display. Push the button nearest your selection
to go to the corresponding screen. Push “Mode” again to return to the Main Mode display. (Note: If

your controller was ordered with Totalizing Mode option (page 41), pushing the “Mode” button once will
bring up the “Totalizing Mode” display. Pushing “Mode” a second time will bring up the “Select Menu”
display.)

Gas Control

Select

SELECT

MENU

Comm. Mfg.

RS-232 Data Menu

Figure 7. Select Menu Display

11

Control Setup Mode

The Control Setup Mode is accessed by pressing the center button above “Control” on the Select Menu
display (Fig.7) This mode allows the user to set up most parameters commonly associated with PID
control. MC Series ow controllers allow the user to select how the set-point is to be conveyed to the
controller, what that set-point is if control is local, and what the Proportional and Differential terms of the
PID control loop will be. The UP and DOWN buttons for adjusting variables can be held down for higher
speed adjustment or pressed repeatedly for ne adjustment.

Input – MC Series Flow Controllers normally ship defaulted to analog control as indicated in Figure 8.

To change how the set-point will be conveyed to the controller push the button in the upper right hand

corner just above the dynamic label “Input” until the arrow is directly in front of the desired option. The

controller will ignore any set-point except that of the selected input and it will remember which input is
selected even if the power is disconnected.

Analog refers to a remote analog set-point applied to Pin 4 of the Mini-DIN connector as described

in the installation section of this manual. To determine what type of analog set-point your controller

was ordered with, refer to the Calibration Data Sheet that was included with your controller. 0-5 Vdc is
standard unless ordered otherwise. Note that if nothing is connected to Pin 4, and the controller is set
for analog control, the set-point will oat. CAUTION! Never leave a CoNtroller with aNy NoN-zero set-

poiNt if No pressure is available to make flow. the CoNtroller will apply full power to the valve iN aN
attempt to reaCh the set-poiNt. wheN there is No flow, this CaN make the valve very hot!

Serial refers to a remote digital RS-232 set-point applied via a serial connection to a computer or
PLC as described in the Installation and RS-232 sections of this manual. CAUTION! Never leave a

CoNtroller with aNy NoN-zero set-poiNt if No pressure is available to make flow. the CoNtroller will

apply full power to the valve iN aN attempt to reaCh the set-poiNt. wheN there is No flow, this CaN make
the valve very hot!

Local refers to a set-point applied directly at the controller. For more information on changing the set-

point locally refer to the heading “Select” below. Local input must be selected prior to attempting to

change the set-point locally. CAUTION! Never leave a CoNtroller with aNy NoN-zero set-poiNt if No

pressure is available to make flow. the CoNtroller will apply full power to the valve iN aN attempt to
reaCh the set-poiNt. wheN there is No flow, this CaN make the valve very hot!

Select Loop Input

>P 200 >Mass >Analog
D 500 Volume Serial

AUT0on

Set 0.00

Up Down Setup

Press Local

Control

Figure 8. MC Series Control Setup Display

12

Loop—The selection of what variable to close the loop on is a feature unique to these mass ow
controllers. When the mass ow controller is supplied with the control valve upstream of the electronics
portion of the system, the unit can be set to control on outlet pressure (absolute pressures only) or
volumetric ow rate, instead of mass ow rate. Repeatedly pressing the button adjacent to the word
“Loop” on the control setup screen will change what variable is controlled. The change from mass to
volume can usually be accomplished without much, if any, change in the P and D settings. When you
change from controlling ow to controlling pressure, sometimes fairly radical changes must be made

to these variables. Note: Full scale pressure is normally 160PSIA. Consult the factory if you are having
difculties with this procedure.

Select – To avoid accidental changing of the PID loop parameters or the set-point, the Control Setup
mode defaults with the selector on a null position. To change the set-point or the P and D PID loop
parameters, push the button in the upper left corner just above the dynamic label “Select” until the

selection arrow is pointing to the parameter you wish to change. When the parameter you wish to
change is selected, it may be adjusted up or down with the buttons under the display below the dynamic

labels “Up” and “Down”. Press the buttons repeatedly to make slow adjustments or hold them down to

make fast adjustments.

P refers to the Proportional term of the PID loop. Before changing this parameter, it is good practice to

write down the initial value so that it can be returned to the factory settings if necessary.

D refers to the Differential term of the PID loop. Before changing this parameter, it is good practice to

write down the initial value so that it can be returned to the factory settings if necessary.

AUT0on / AUT0off refers to the standard auto-tare or “auto-zero” feature. It is recommended that the
controller be left in the default auto-tare ON mode unless your specic application requires that it be
turned off. The auto-tare feature automatically tares (takes the detected signal as zero) the unit when it
receives a zero set-point for more than two seconds. A zero set-point results in the closing of the valve
and a known “no ow” condition. This feature helps to make the device more accurate by periodically

removing any cumulative errors associated with drift.

Set refers to the Set-Point. This parameter may only be changed if “Local” is selected as the Input. See
above for information on selecting the input. Using the UP and DOWN buttons, the set-point may be
adjusted between zero and the full-scale range of the controller. CAUTION! Never leave a CoNtroller

with aNy NoN-zero set-poiNt if No pressure is available to make flow. the CoNtroller will apply full
power to the valve iN aN attempt to reaCh the set-poiNt. wheN there is No flow, this CaN make the valve
very hot!

13

Gas Select Mode

The gas select mode is accessed by pressing the button above “Gas Select” on the Select Menu
display. The screen will appear as shown in Figure 9.

PgUP PgDWN Main

H2 Hydrogen
He Helium
>N2 Nitrogen
N2O Nitrous Oxide
Ne Neon
O2 Oxygen
UP DOWN Gas

Figure 9. Gas Select Mode

The selected gas is displayed on the default main mode screen as shown in Figure 6, and is indicated
by the arrow in the Gas Select Mode screen in Figure 9. To change the selected gas, use the buttons
under “UP” and “DOWN” or above “PgUP” and “PgDWN” to position the arrow in front of the desired
gas. When the mode is cycled back to the Main Mode, the selected gas will be displayed on the main
screen. (Note: Gas Select Mode may not be available for units ordered for use with a custom gas or

blend.)

14