PEMTECH PT920-8FG User manual

MODEL PT920-8FG
8 CHANNEL
GAS MONITOR & CONTROLLER
Operator’s
Manual
Revision 2.0
March 2005
Pem-Tech, Inc.
Houston, Texas
U.S.A.

NOTICE
PEM-TECH INCORPORATED SHALL NOT BE LIABLE FOR
TECHNICAL OR EDITORIAL ERRORS OR OMISSIONS MADE
HEREIN, NOR FOR INCIDENTAL OR CONSEQUENTIAL
DAMAGES RESULTING FROM THE FURNISHING,
PERFORMANCE, OR USE OF THIS MATERIAL.
LIMITED WARRANTY
Pem-Tech, Incorporated warrants all the equipment to be free from defects in
workmanship and material. The products will operate in conformance with the
published specifications when subjected to intended and proper usage for the
period of one (1) year from the date of shipment.
The warranty provides only the benefits specified and does not cover defects
which result from acts beyond the control of PEM-TECH including, but not
limited to: damage by accident, negligence, tampering, or failure to operate in
accordance with the procedures outlined in the Operations Manual. PEM-
TECH’s liability under no circumstances will exceed replacement of the unit
claimed to be defective.
Tampering with the equipment and altering it for uses other than the intended
use or replacement of parts not supplied by the company, shall immediately
void and cancel all the warranties with respect to the affected products.
The warranties specified herein are in lieu of any and all other warranties,
express or implied. In no event, whether as a result of breach of warranty or
alleged negligence, shall PEM-TECH be liable for special or consequential
damages, including, but not limited to, loss of profits or revenue, loss of
equipment or down time costs.
2

SERVICE POLICY
Pem-Tech has service facility at the factory. For all the repairs contact at
our toll free number 1-800-379-3894 or visit our website www.pem-
tech.com
For all repairs call us for a Return Material Authorization number (RMA).
Inform us briefly the nature of the problem and obtain shipping address.
Properly pack the equipment before shipping. Also include your complete
shipping address and contact name and phone number.
For non-warranty repairs you must provide the limit to repair costs. State
if a quote for repair cost is required before you can authorize the repair
cost. For this an additional charge may be applicable.
NOTE:
1. For all the repairs under warranty, serial number must be legible on
the items being repaired.
2. Shipping point is FOB Houston.
3

TABLE OF CONTENTS
Specifications 5
Specifications for PT920-8FG Rack assembly 5
Specifications for Model PT920 Series Control monitor 6
Overview 7
Programmable Relays 7
Figure 1. PT920 Control module Front Panel diagram 8
Installation and Startup 9
Figure 2. PT920-8FG Enclosure dimension 9
Figure 3. System Overview drawing, 10
User termination, control modules in
Rack assembly
AC or DC power Input 11
Connecting sensors to monitor 11
Alarm wiring 11
Figure 4. Sensor and alarm wiring diagram 12
Startup 13
Apply Power 13
Normal Operation and alarms
Normal Operation 14
Alarms 14
Alarm Reset 14
Alarm Bypass 15
Programming Alarms 15
Programming Alarm Levels 16
Setting alarms as Latching or Non-Latching 17
Figure 5. PT920 Control Module diagram 18
Malfunction Condition 19
PartsList 20
4

SPECIFICATIONS
For PT920 Rack Assembly with Power Supply
MOUNTING: Wall or Panel Mount
ENCLOSURE: NEMA 4X Fiberglass Enclosure with clear
window
DIMENSIONS: 14”H x 12”W x 7”D
WEIGHT: 18 Lbs.
OPERATING -40 °F to +170 °F. (-20 °C to +70 °C.)
TEMPERATURE
POWER INPUT: 110-220 VAC or 24 VDC
HUMIDITY: 0 to 100% non condensing
ALARM RELAYS 3 alarm relays. Form “C” type rated 10 Amps
1 relay for Hi-Hi and 1 for Malfunction each
rated 5 Amps
TERMINATIONS Terminal blocks for sensor and alarm
connections for wire size 16-22 AWG
ALARM RESET Master alarm Reset switch to Reset Alarms
SWITCH on all control modules
5

SPECIFICATIONS
For PT920 Control Module
Display Range: 0 to 99 for Toxic and Combustibles
0 to 25.0 % for Oxygen deficiency ( 3 Digit
Display)
Input Signal: 4-20mA
Relay Ratings: 4 each Form C type relay contacts
Rated 5 Amps each
Low, High, High-High, and Malfunction
Field programmable alarm levels, Latching or
non-latching, Normally open or Normally
Closed contact
Visual Indicators: 4 Bright LEDs on the front panel to indicate
alarm status. Amber LED for Low Alarm
Red LEDs for High and High-High and
Malfunction Alarm
Power Input: 24 VDC power input. Power is supplied
to remote sensor & transmitter through a 2
Amp miniature fuse
Power Consumption: < 1 Watt normal operation for each control
module. Max of 2.4 watt with all relays active.
Alarm Reset Pushbutton switch on front panel to Reset
Alarms
Alarm Bypass Toggle Switch to Bypass / Inhibit Alarm relays
6

OVERVIEW
Pem-Tech model PT920 is a microprocessor based single channel monitor
that utilizes the latest digital design techniques in instrumentation. The
monitor uses an 8-bit high speed RISC processor with a highly accurate
analog to digital logic. The controller module receives the signal from
remote gas transmitters and displays the gas concentration. The 24VDC
power to the control module is supplied by the common bus on the back
plane (main connection board). The power to the remote sensor connected
to the module is routed through a miniature fuse on the module.
Standard features are:
•Displays current gas concentration on two (2) Digit Bright LED
display ( 3 digits display for Oxygen deficiency )
•Low, High, & High-High fully programmable alarm relay contacts.
•Alarms programmable via switches on the front panel
•Sensor Malfunction relay contact.
•Visual alarm indicators on the front panel.
•Alarm RESET and BYPASS switch.
•Optional RS485 Serial Communication for Remote data display
•Master Alarm Reset on the main rack assembly to Reset Alarms.
Programmable Relays
Each control module can be programmed for 3 distinct alarm levels. The
alarm levels can be easily programmed using Pushbutton switch provided
on the front panel of the control module. The alarm relays on the main
connection board are configured to have discrete Low level gas alarm for
Toxic (H2S) and combustibles (LEL) gases. Also present on the main
connection board are common High and Hi-Hi alarm relay contacts.
Below each control module there is a 2-pin jumper to select the module for
Toxic or Combustible type. Proper selection of this jumper will enable the
module to properly activate the low level alarm relay.
Also present is a common Sensor Malfunction alarm relay.
All relays are Form “C” type. Low and High alarm relays are rated
10Amps each while Hi-Hi and Malfunction are rated 5 Amps each.
7

Figure 1: PT920 Series Control Module
8
MODEL PT 920
BYPASS
ALARMS
NORMAL
HOUSTON, TX
MALF
RESET
HIGH
HI−HI
LOW
LEDs FOR VISUAL
ALARM INDICATION
DIGITAL DISPLAY
THUMB SCREW
PUSHBUTTON SWITCH
FOR ALARM RESET
TOGGLE SWITCH FOR
ALARM BYPASS
MODULE HANDLE

INSTALLATION AND START UP
PT920 Enclosure must be installed in a safe area. Figure 2 shows the
mounting holes for the fiberglass enclosure.
PT920-8FG rack assembly can house up to eight (8) PT920 series control
modules. On the front panel a captive screw is provided to secure the
control module to the rack. Do not use excessive force to tighten the
screw. Also a handle is provided to facilitate for insertion and removal of
the module from the rack assembly.
Figure 2. PT920 Enclosure. Dimensional drawing.
9

10
Figure 3. PT920-8FG Connection board with
8 PT920 Series control modules installed
LEL
H2S
++
AC IN
G
N
L
E
CH−1
−
E
+
CH−2
−
−
CH−5
E
E
+
−
CH−6
+
DC IN
−
PEM−TECH, INC.
HOUSTON, TX
PEM−TECH, INC.
HOUSTON, TX
CH−4
−
+
−
CH−3
E
E
+
C−
CH−8CH−7
−
+
E
E
NC
C
NO
NC
+NO
PEM−TECH, INC.
HOUSTON, TX
PEM−TECH, INC.
HOUSTON, TX
PEM−TECH, INC.
HOUSTON, TX
NO
NC
C
HIGH
C
LOW H2S
HI−HIFAIL
LOW LEL
NC
C
NO
NC
NO
PEM−TECH, INC.
HOUSTON, TX
PEM−TECH, INC.
HOUSTON, TX
PEM−TECH, INC.
HOUSTON, TX
CHANNEL 6
LEL MONITOR
MODEL PT 920
CHANNEL 3
H2S MONITOR
MODEL PT 920
ALARMS
NORMAL
BYPASS
RESET
MALF
HI−HI
HIGH
NORMAL
ALARMS
BYPASS
RESET
HI−HI
MALF
HIGH
CHANNEL 1
PPM H2S
LOW
H2S MONITOR
MODEL PT 920
PPM H2S
LOW
CHANNEL 2
H2S MONITOR
MODEL PT 920
NORMAL
ALARMS
BYPASS
NORMAL
ALARMS
BYPASS
RESET RESET
MALF
HI−HI
HIGH
MALF
HI−HI
HIGH
RESET
NORMAL
ALARMS
BYPASS
HI−HI
MALF
HIGH
CHANNEL 4
H2S MONITOR
MODEL PT 920
LOW
PPM H2S PPM H2S
LOW
% LEL
LOW
CHANNEL 5
LEL MONITOR
MODEL PT 920
POWER
O
1
GAS MONITOR
MODEL PT920−8FG
HOUSTON, TEXAS
NORMAL
ALARMS
BYPASS
RESET
NORMAL
ALARMS
BYPASS
RESET
MALF
HI−HI
HIGH
MALF
HI−HI
HIGH
NORMAL
ALARMS
BYPASS
RESET
MALF
HI−HI
HIGH
CHANNEL 7
LEL MONITOR
MODEL PT 920
LOW
% LEL % LEL
LOW
% LEL
LOW
CHANNEL 8
LEL MONITOR
MODEL PT 920
RESET
ALARM
MASTER ALARM
RESET SWITCH
AC POWER SWITCH
JUMPER SELECTION FOR
H2S / LEL CONTROL MODULE
24 VDC POWER IN
AC POWER IN
RELAY CONTACTS 10A EACH
LOW − H2S
LOW − LEL &
HIGH COMMON
SENSOR INPUTS
CH1 THRU CH8
HIGH−HIGH ALARM &
SENSOR FAIL
RELAY CONTACTS.
RELAY RATINGS 5 AMPS

A black terminal block is provided at the lower left corner inside the
enclosure. The connections on the terminal block are labeled L N G.
Connect the external AC power to this terminal.
If the unit is powered by DC, connect 24 VDC supply to the 2 pin green
terminal labeled DC power input on the termination board.
Refer to figure 3 for the location of AC and DC terminals
Connecting Sensors to the Monitor
Three (3) pin screw type terminals are provided on the termination board
for remote sensor connection. The terminals are labeled as SENSOR and
each pin is identified as +, -, & E for sensor DC supply, ground, and
input signal respectively. The DC is supplied to the sensor by the control
module. The supply is fused through a 2 amp miniature fuse on the
control module.
Each remote sensor should be connected by a 3 conductor shielded cable.
See figure 4 for remote sensor connection.
Alarm Wiring
Figure 4 shows a typical wiring diagram for connecting alarm devices to
relay contacts on the main connection board. Note that contacts are dry or
potential free contacts. Refer to the wiring details provided by the
manufacturer of alarm devices.
Below each control module on the main connection board there is a 2-pin
jumper selection to select the module type as H2S or LEL. Install the
jumper properly as this will enable the control module to activate the Low
alarm relay for either Toxic (H2S) or combustible (LEL)
11

Figure 4. Remote Sensor connection and typical Alarm wiring
12
E
E
LEL
H2S
−
+
L
AC IN
N
G
DC IN
NC
E
E
−
CH−2
+
+
CH−1
−
E
E
−
CH−3
+
CH−6
−
+
CH−5
+
−
E
CH−7
E
−
+
C
NC
NO
+
CH−4
−
CH−8
+
−
NO
C
LOW H2S
NC
NO
NO
NC
NC
C
HIGH
FAIL
C
LOW LEL
NO
HI−HI
C
YellowStrobe
Siren
RedStrobe
ReturnorCommon
VoltagePowerSupply foralarmdevices
AsAppropriate
Jumper select monitor gas type as appropriate
LowH2S
LowLEL
HighAlarm
SENSOR
SIGNAL
−
+
mA
Connection Board − Model 920−8FG
Sensor connection board
Not shown completely
Sensor Connection
Board
Typical Sensor & Alarm Connections
Only one sensor connection is shown
for clarity

Start Up
Follow the instructions below for normal unit operation.
1. Complete the mounting and wiring procedures described in earlier
sections.
2. Follow gas sensor & transmitter operation manual for proper wiring of
sensors with the monitor.
3. Verify all the wiring connections to be correct and secure.
4. Verify that all the control modules are secured with captive screws on
the front panel.
Apply Power
Before connecting the AC power to the AC terminal on the termination
block make sure that POWER Switch on the unit is in OFF or ‘0’ position.
Flip the Power switch to ON or ‘1’ position to turn on the power to the
monitor and verify following conditions.
1. All the installed control modules will display 00 for few seconds.
2. Each control module will then display low, high and High-High alarm
set points. The visual alarm LED indicator will be lit while the unit
displays the alarm set point.
3. The control module goes into normal operation and starts reading
signal from the sensor / transmitter.
Note: If a control module display remains blank upon power up then
remove the control module and reinsert into card guides in order to
properly snap into the card edge connectors on the termination board.
13

NORMAL OPERATION AND ALARMS
During normal operation each control module will display the current gas
concentration on the display. If the sensor reading is below alarm level
then all the alarm relays and the visual alarm LED indicators on the front
panel should be off.
Alarms
Each PT920 control module is equipped with four (4) alarm relays. The
relays are used to activate relays on the main connection board. The
control module activates the alarm relays when the sensor reading
exceeds the programmed alarm set point. Also LEDs on the front panel of
the control module will also light up for visual alarm indication.
Standard alarm set points are programmed at the factory before shipment.
The user must verify the alarm set points and make changes if desired.
Refer to section on Programming Alarm Set points.
Factory Alarm Settings are:
Alarm # Alarm Level Alarm Type
Low Alarm 10 Non-Latching
High Alarm 15 Non-Latching
High-High 20 Non-Latching
Alarm Reset
Once the gas concentration has dropped below the alarm level the relay
will reset itself. However, this is true only if the relay is configured as non-
latching (NL). If the relay is configured latching then it must be reset
manually. To reset the latching alarm press and hold the push button on
the front panel until relays and LED indicators turn off. A master alarm
reset switch on the control module rack assembly can also be used to reset
the alarms. This will reset alarms on all control modules.
Note: If the gas concentration continues to be higher than the programmed alarm
set point the alarm will be activated again.
14

Alarm Bypass
When the control module is in alarm Bypass mode all the relays on the
module are inhibited. The relays will not be activated however, the visual
alarm LED indicators will be function and flash once every seconds if the
gas reading exceeds the alarm level.
To put the alarms in bypass mode move the ALARM toggle switch on the
front panel of the control module to BYPASS position. The digital display
will flash at a slow rate, thus an indication to the operator in the room that
alarms are inhibited.
The toggle switch must be returned to NORMAL position to end alarm
bypass mode and for normal module operation.
Programming Alarms
Alarm levels must be programmed in order to activate the dry relay
contacts on the main control board. Alarm levels can be set anywhere
between 0 and the full scale of the sensor. Alarm relays can also be
selected as Latching or non-latching type. If any alarm level is set to 00
then that relay will not be activated any time during normal operation.
Note
•Non-Latching alarm is self resetting. Alarm relay will be de-activated if gas
concentration falls below the alarm set point.
•Latching alarm on the other hand will not self reset if concentration falls
below alarm set point. The alarm relays must be manually reset by pressing
the RESET switch on the front panel
15

Programming Alarm Levels
1. Move the toggle switch on the front panel to BYPASS position.
2. Press and hold the pushbutton switch (above the toggle switch) until
the Low alarm LED starts flashing. Release the switch.
3. While the LED is flashing the display will show the current alarm
level. To change the level press and hold the pushbutton switch until
the display reads the desired alarm setting. The alarm level can be
adjusted between 0 and the full scale of the sensor. For example, for
H2S or LEL the alarm level can be set between 0 and 99. If the desired
alarm level is below current settings press and hold the switch. The
displayed level rolls over to 00 after 99.
4. Release the switch when alarm level set.
5. About five (5) seconds after the switch has been released the Low
alarm LED will be turned off. Low alarm level is set. Now High alarm
LED starts flashing and the display will show the High alarm level.
The monitor is ready for High alarm level. Repeat steps 3 and 4 to set
High and High-High alarm levels.
6. After setting High-High alarm level the monitor will return to normal
operation.
16

Setting Alarm as Latching or Non-Latching
The alarms can be set as latching or Non-Latching by setting the Dip-
Switch located on lower left corner of the control module. See figure 5.
The dip-switch is labeled as Relays with arrow indicating the switch
selection for latching or non-latching. Position 1 of the Dip-switch is for
Low alarm , position 2 is for High alarm and position 3 for High-High
alarm. Position 4 is not used for standard application and is reserved for
custom application or future use.
To set the alarm as latching move the dip-switch up or move the dip
switch down for non-latching alarms.
The dip-switch positions in the diagram below shows Low and High
alarm configured as non-latching and High-High alarm set as latching
RELAYS
LATCHING
NON−LATHING 123 4
17

Figure 5. PT920 Control Module
PEM−TECH, INC.
K4
K3
K2
SENSOR
FUSE
K1
LATCHING
NON−LATHING
RELAYS
Toggle Switch for
Alarm Bypass
Pushbutton Switch
for Alarm Reset
Thumb Screw
DIP Switch to select
Latching / Non−Latching Alarms
2 Amp Mini Fuse
for Sensor DC Power
Digital Display &
LED Indicator Board Assembly
On Board Alarm Relays
18

Malfunction Condition
The malfunction alarm is activated when the 4-20ma analog output from
the sensor transmitter falls below 2.0mA. This is caused if the sensor
requires calibration. The malfunction also occurs if wires connecting the
sensors are broken. The fault relay is always non-latching and has a
common alarm contacts on the main connection board.
If a fault condition occurs:
1. Make sure the wires on the sensor input terminal of the main
connection board are secure and connected properly.
2. Check if the sensor supply fuse located on the control module is OK.
The fuse can be checked by verifying the DC power on the sensor
terminal using a digital voltmeter. If the + and - pin on the sensor
terminal reads 24VDC then the fuse is OK. See figure 5 for the location
of the fuse on the control module.
3. Refer to the reference manual of the remote sensor for the problems the
sensor transmitter may have.
19

Parts List
Part Number Description
C- 994 117/230VAC to 24 VDC power
C- 480 Replacement card guide
C-127 Mini Sensor Fuse
PT920 Series Control Modules
PT920-H Model PT920 Control Module for H2S sensor
PT920-L Model PT920 Control Module for LEL sensor
PT920-OXY Model PT920 Control Module for oxygen sensor
PT920-SO2 Model PT920 Control Module for SO2 sensor
Call factory for detail list of control modules available for various gas
sensors
20