MGS – Murco Gas Sensor EC / SC model
Gas Detector and Transmitter
Installation & Operation*
Content
Page
1- Installation Instructions
2
2- Location Instructions
2
3- Typical Settings
2
4- Installation and Wiring Diagrams
2
5- Operating Instructions
2
6- Test/Function Instructions
3
7- Remote sensor head installation
3
8- MGS - Annual test
3
9-
4
Agree Selectable functions with end-users
10- Troubleshooting
4
11- Connections to Murco Control Panels
4
12- Mounting Diagrams
4
*Technician use only
This unit must be installed by a suitably qualified technican who will install this unit in accordance with these instructions and the
standards set down in their particular industry/country. Suitably qualified operators of the unit should be aware of the regulations and
standards set down by their industry/country for the operation of this unit. These notes are only intended as a guide and the
manufacturer bears no responsibility for the installation or operation of this unit.
Failure to install and operate the unit in accordance with these instructions and with industry guidelines may cause serious injury
including death and the manufacturer will not be held responsible in this regard.
08 ASH (1)
Murco Ltd.
114a Georges Street Lower, Dun Laoghaire Co Dublin. Ireland,
e-mail: info@murco.ie web: www.murco.ie
1
1- MGS Installation Instructions
• With heavier than air gases such as halocarbon and hydrocarbon
refrigerants such as R404A, propane, and butane sensors should be
located near ground level
• With lighter than air gas e.g. ammonia, the sensor needs to be located
above the equipment to be monitored on a bracket or high on a wall
within 300 mm of, or on the ceiling provided there is no possibility of a
thermal layer trapped under the ceiling preventing gas reaching the
sensor. (NB. At very low temperatures, such as in a refrigerated cold
store, ammonia gas becomes heavier than air).
• With similar density or miscible gases, such as CO or CO2, sensors
should be mounted about head high – say 1.5m.
• Sensors should be positioned a little way back from any high-pressure
parts to allow gas clouds to form. Otherwise any leakage of gas is likely
to pass by in a high-speed jet and not be detected by the sensor.
• Make sure that pits, stairwells and trenches are monitored since they
may fill with stagnant pockets of gas.
• If a pressure relief vent pipe is fitted to the system, it may be a
requirement to mount a sensor to monitor this vent pipe. It should be
positioned about 2 m above the PRV to allow gas clouds to form.
• With racks or chillers pre-fitted with refrigerant sensors, these should be
mounted so as to monitor the compressors or if extract ducts are fitted
the airflow in the duct may be monitored.
To open the Standard Sensor enclosure: turn the cable gland ½ turn
anticlockwise to loosen the internal gland nut, depress the clip on top of the
enclosure and open. Reverse to close.
Power: 12-24V AC / DC, connect at positions 0V and +V at connector block
CN1. For AC – Jumper A is on, D is off. (See Diagram 1/2)
For DC – Jumper A is off, D is on. (Default Factory Setting is DC)
Use 2 cores of a 4-core cable, low voltage alarm type, typically 7/0.2
mm sq
Output: you can select the V or mA analogue output at JP1 and JP3. (Default
factory setting is mA) Connect the other two cores of the cable to terminal
block CN2 positions 0V and V or I for voltage or current as per jumper
selection. You can common the two zeros and use 3 core cable if preferred.
connect 4-20mA at CN 2 positions 0V and I
connect voltage output at CN 2 positions 0V and V
Relay set point: P1 sets the trip point for the relay and sounder using the 05V scale (measure at test points 0V and REF1, 2.5V would be equivalent to
half the range - (500ppm on a scale of 0-1000ppm) Default factory setting is
50% of the range.
Refrigerated Spaces
In refrigerated spaces sensors should be located in the return airflow to the
evaporators on a sidewall, below head high preferred, or on the ceiling, not
directly in front of an evaporator. In large rooms with multiple evaporators,
sensors should be mounted on the central line between 2 adjacent
evaporators, as turbulence will result in airflows mixing.
Time delay: A time delay for the operation of the relay and sounder can be
selected using jumpers JP5 and JP6. Default factory setting is zero.
Sounder: The sounder can be disabled using jumper JP2. Default factory
setting is enabled.
There is a 5-minute power up delay to allow the sensor to stabilize. This can
be cancelled by momentarily shorting between either of the upper and lower
pads of SW1 or SW2.
Chillers
In the case or small water or air-cooled enclosed chiller units mount the
sensor so as to monitor airflow to the extract fans. With larger models also
place a sensor inside the enclosure under or adjacent to the compressors
2- MGS - Location Instructions
In the case of outdoor units:
Location of Sensors
Sensors must be located within the appropriate wire lengths from the central
control unit (if used).
• such as enclosed air-cooled chillers or the outdoor unit for VRV/VRF
systems mount the sensor so as to monitor airflow to the extract fan.
With large units also place a sensor inside the enclosure under or
adjacent to the compressors
In all cases the sensor supplied is designed for maximum sensitivity to a
particular gas.
In the case of non-enclosed outdoor units
However, in certain circumstances false alarms may be caused by the
occasional presence of sufficiently high concentrations of other gaseous
impurities. If such a situation is likely to arise installers should check with our
Technical Department so that sensor (s) of suitable cross sensitivity can be
supplied. Examples of situations where such abnormalities may arise include.
• If there is an enclosed machinery section then locate a sensor there.
• In the case of units with enclosed compressors, mount sensors in the
enclosures
• Where you have protective or acoustic panels mount the sensor low
down under the compressors where it is protected by the panels.
• With air-cooled chillers or air-cooled condensers with non-enclosed
condenser sections it is difficult to effectively monitor leaks in the coil
sections. With some designs it will be possible using an airflow sensor
to monitor airflow to the start –up fans in the front or rear sections.
• If there is a possibility of refrigerant leaks into a duct or air-handling unit
install a sensor to monitor the airflow.
• Plant room maintenance activity involving solvent or paint fumes or
refrigerant leaks.
• Plant rooms in fruit ripening/storage facilities because of accidental gas
migration (bananas - ethylene, apples - carbon dioxide)
• Heavy localised exhaust fumes (carbon monoxide, dioxide, propane)
from engine driven forklifts in confined spaces or close to sensors.
A response delay may be selected to minimise any problems that might arise.
Weatherproof sensors should be used for unprotected outdoor applications.
Machinery rooms
There is NO ABSOLUTE RULE in determining the number of sensors and their
location. However a number of simple guidelines will help to make a decision.
Sensors monitor a point as opposed to an area. If the gas leak does not reach the
sensor then no alarm will be raised. Therefore, it is extremely important to
carefully select the sensor location. Also consider ease of access for maintenance.
Air Conditioning – Direct systems URV/URF
EN378 states that at least one detector shall be installed in each occupied
space being considered and the location of detectors shall be chosen in
relation to the refrigerant and they shall be located where the refrigerant from
the leak will collect. In this case refrigerants are heavier than air and detectors
should have their sensors mounted low .e.g. at less than bed height in the
case of an hotel or other similar Category Class A spaces. Ceiling or other
voids if not sealed are part of the occupied space.
The size and nature of the site will help to decide which method is the most
appropriate to use. Locations requiring the most protection in a machinery or
plant room would be around compressors, pressurised storage vessels,
refrigerant cylinders or storage rooms or pipelines. Most vulnerable are valves,
gauges, flanges, joints (brazed or mechanical), filling or draining connections etc
In a hotel room monitoring in ceiling voids would not
strictly comply with EN378
When mechanical or natural ventilation is present mount a sensor in the airflow.
In machinery rooms where there is no discernable or strong airflow then
options are:
Do’s
Don’ts
• mount the in-room sensor at less than the • Do not mount sensors
normal heights of the occupants e.g in a
– under mirrors
hotel room this is less than bed height – at vanity units
between 200-500mm off the floor.
– in or near bathrooms
• away from draughts and heat sources like
radiators etc.
• avoid sources of steam
• Point Detection, where sensors are located as near as possible to the
most likely sources of leakage, such as the compressor, expansion
valves, mechanical joints or cable duct trenches, and,
• Perimeter Detection, where sensors completely surround the area or
equipment.
2
Diagram 1
Electrochemical Sensor
SW2
Diagram 2
Semiconductor Sensor
SW1
Short to Cancel
Warm up Delay
Sounder & Relay Set
Point Voltage
SW1 SW2
0V
Sounder & Relay Set
Point Voltage
Adjust Span
Sensor Voltage
Short to Cancel
Warm up Delay
Adjust Span
Adjust Zero
0V
Adjust Zero
Adjust Sounder
and Relay set point
(P1)
Sensor Voltage
Adjust Sounder
and Relay set point
(P1)
6
5
4
3
2
1
Relay and Sounder Delay – JP5 & JP6 off : no delay
JP5 on only : 1 minute
JP6 on only : 5 minutes
JP5 & JP6 on : 10 minutes
JP4 – on : Not used
JP3 – on : 4-20mA or 2-10 Volt output
off : 0-10Volt output
JP2 – on : Sounder enabled
JP1 – on : Divide Voltage output by 2
(0-5 or 1-5 Volt output
off : full 0-10 or 2-10 volt output
A
D
Power
12 to 24V DC
12 to 24V AC
Jumper for
AC or DC
Relay Output
4-20mA output
0-5/1-5/0-10/2-10 Volt output
0V
6
5
4
3
2
1
Relay and Sounder Delay – JP5 & JP6 off : no delay
JP5 on only : 1 minute
JP6 on only : 5 minutes
JP5 JP6 on : 10 minutes
JP4 – Not Used
JP3 – on : 4-20mA or 2-10Volt output
off : 0-10Volt output
JP2 – on : Sounder enabled
JP1 – on : Divide Voltage output by 2
0-5 or 1-5 Volt output
off : full 0-10 or 2-10 volt output
A
D
AC DC
A
D
Power
12 to 24V DC
12 to 24V AC
Jumper for
AC or DC
AC DC
A
D
Relay Output
4-20mA output
0-5/1-5/0-10/2-10 Volt output
0V
For further detailed Installation tips covering most installations and equipment
types.. chillers, air cooled chillers etc see our web site www.murco.ie.
To test the siren and or relay function, check the delay is set at zero using the
header as shown on the installation diagram and expose to gas as above. You
can mute the siren by removing the jumper JP2.
3- MGS - Typical settings
After the gas has cleared the red led, siren and relay will automatically reset.
Gas: Refrigerant R404A
Range: 0-1000ppm
Alarm Set Point: 500ppm
Before testing the sensors on site the MGS must have been powered up and
allowed to stabilize.
For a particular unit please refer to the gas settings shown on the rating plate.
7- MGS Sensor - Remote sensor head installation
If you do not wish to surface mount the MGS or need to match room decor,
we can supply a remote sensor with a decorative faceplate (standard:
brushed stainless steel). The remote sensor is mounted in an electrical back
box 44mm deep to which the vented face plate is fitted.
4- MGS- Installation and Wiring Diagram
See diagrams 1 and 2.
5- MGS - Operating Instructions
1.
1- On powering up it will sense for the presence of gas after an initial warmup delay of 5 minutes, the green LED will flash at 1 second intervals during
the warm-up.
2.
2- In alarm condition:
• the green LED stays on
• the red LED will be on
• the siren operates (if it has not been disabled and after a delay if this
option has been selected)
• the relay output activates (after a delay if this option has been selected)
• the voltage or current output changes proportional to gas concentration
Remove the connector from the sensor PCB to feed the cable through the
trunking.
Immediately refit the connector to the sensor board in the backbox. The
MGS and remote sensor must be kept together as they are calibrated
together and are a matched pair.
Do not remove the sensor boards from a number of units at
the same time in case they get mixed up. If doing so, label
them, or, ensure you check the serial number on the main
PCB and the remote sensor PCB are the same when reinstalling.
3- Fault condition:
• the green LED will be off
• the red LED will be on
• a voltage or current fault output will activate
2mA on the 4-20mA output
0.5V on the 1-5V output
1.0V on the 2-10V output
3.
If construction / decoration is still going on, fit a standard plastic blanking
plate immediately you install the sensor in the back box to avoid dust or
damage to the in-room sensor. You can fit the SS vented plate when
decoration is completed.
4.
Cleaning: the decorative face plate should be lightly dusted – it should
not be sprayed with cleaning/polishing aerosols.
6- MGS – Test / Function Instructions
8- MGS Sensor - Annual Test
The MGS is calibrated in the factory and does not require to be calibrated on
installation. After installation the units should be bump tested. Expose the
sensors to test gas using a Murco ampoule (NH3 or CO2 etc) or test cylinder
(appropriate to the installation) or crack open the valve of a cigarette lighter
(only for Semiconductor units) without igniting it and hold it over the vent holes
on the upper right side of the MGS. The gas is heavier than air and should fall
into the MGS. This will put the system into alarm. The red LED will light
showing the system is in alarm. The delay will prevent the siren sounding or
relay switching for the preset delay, if delay is set.
To comply with the requirements of EN378 and the F GAS regulation sensors
must be tested annually. However local regulations may specify the nature and
frequency of this test. If not the Murco recommended procedure should be
followed. Contact us for details.
Check local regulations on calibration or testing
requirements.
With a bump test you can see the functions of the sensor - the red led will
light, the relay and sounder will function, the output selected, say 0-10V- will
show the gas level.
After exposure to a substantial gas leak, sensor should be checked and
replaced if necessary.
3
Agree Selectable functions with end-users:
MGS to MGD Controller wiring diagram
You should agree these important functions with the customer so that
the system will operate as he/she requires:
Time Delay Response: available on the sounder and relay to avoid
false alarms. This is set with jumpers. The default delay is 0
minutes. You may wish to set to 15 minutes during start up and
construction if you may have VOC (volatile organic compounds)
fumes, paint etc in the rooms. They should be reset as required.
Connectivity: Decide how the outputs are to be used.
Murco gas detectors can activate external systems such as fans or
shut down and activate sirens, warning lights, activate dial out
systems, or connect to most BMS, SCADA, or other control
systems using one or more outputs.
D
A
Only use 3 wires to connect the controller to the MGS. If there is a 4th wire
then use this to double up on the 0V
connection between the controller and
the MGS. The 0V for the supply voltage
and the 0V for the 4-20mA output are
common. The wiring is the same for
both the Electrochemical and the Semiconductor and the controller wiring is
the same for both controllers.
4-20mA, 0-10V, 0-5V, 2-10V or 1-5V.
Relay 1Amp at 24VDC or 120V AC.
6
5
4
3
2
1
9 - MGS –Troubleshooting
All MGS units are checked and calibrated before shipment.
1.
Symptom: Green /Red light on sensor is not lit.
Possible Cause: Power supply. Possible wiring fault . Check power
supply, check your wiring
MGS possibly damaged in transit. Check by installing another MGS
to confirm fault.
Symptom: red light on, green led off, indicates a fault
2.
4 3 2 1
4.
4 3 2 1
Output: Agree the output required 4-20mA, or 0-10V etc
4 3 2 1
3.
4 3 2 1
Siren: The units have an internal siren. You can disable this by
jumper but the default setting is “enabled” in compliance with
EN378. The customer may not want local alarms especially if you
are connecting to a remote monitoring system. Check the
customer’s preference.
1 CAL
4 3 2 1
2.
P8
4 3 2 1
1.
Fail Safe
CN11
Off On
+12V
Buzz
OV
P7
Diagram 3
2.1 Sensor element may be disconnected from printed circuit board.
check to see sensor element is properly inserted into board.
10 – Murco Control panels
2.2 If it is then possibly the sensor element has been damaged or has
reached end of life and needs to be exchanged.
Contact us for instructions and support.
3.
The connection diagram for connecting to an MGD panel is shown in
Diagram 3. If connecting to the ST-MON panel refer to the ST-IAM manual.
If you experience spurious alarms in the absence of a leak, contact us for
instructions and support.
During operation record any alarms. Establish the cause or likely
cause if no leak has occurred. Report these occurrences to your
supplier or Murco, and we will advise on corrective measures.
11 – Mounting Instructions
MGS Standard Sensor
Vent pipe indoor 1’’ BSP head 3m cable
5 mm Max
86.0
53
152
122
75
04.5
43.0
7.0
IP55 Low Temp
122
7
14
O
8.0
4.5
0
Mounting Holes
2 x Clearance for M6
25.00
36.00
25.00
4
140
120
120
103.50
09.0
Exd
IP66
147
152
122
O3/4'' UNI ISO 7/1 RC
162
160
180
70
122
75
7
14
Mounting Holes
2 x Clearance for M6
O8
O3/4'' UNI ISO 7/1 RC
114
IP 66
Airflow Duct Mount Outdoor
Remote Exd Sensor Head 5m Cable
Vent Pipe Outdoor 1’’ BSP Head 3m Cable
50mm
Hole in Duct
for Pitot
20mm
7
50mm
130mm
150mm
162
122
Back view of MB5 Enclosure
60mm
Mounting Holes
2 x Clearance for M6
IP 66 enclosure 5m remote IP 65 sensor
IP 66 enclosure 5m remote IP 65 EExd sensor
3.5mm drill
Airflow Duct Mount Outdoor
50mm
Pitot protrudes into duct 195mm
All Dimensions in mm
Mounting Holes
2 x Clearance for M6
14
7
122
21
61
Hole in Duct
for Pitot
20mm
122
Pitot protrudes into duct 195mm
76.5
122
162
14
sor
sensor
22mm
152
122
75
End view of MB
5
30mm
81.50mm
Key Hole
Reset Button
13.00mm
16.00mm
4,6 Sensor Controller Enclosure
Relay Expander Box
1,2 Sensor Controller Enclosure
260.50mm
Screw
5.0
130.25mm
15.5
9.0
Mounting
Holes
O5.10mm
O10.00mm
50.0
240.50mm
224.70mm
10.0
Screw
4.8
242.50mm
260.50mm
12.7
77.2
81.50mm
74.5
12.5 5 plcs
PG 7
35.0
25.0
14.0
17.5
12.8
9.0
74.8
15.5
10.0
25.0
10.0
14.0
63.5
15.0
28.7
17.5
12.8
74.8
12.8
9.0
17.5
12.8
15.5
15.0
28.7
6
67.70mm
15.0
15.0
12.7
77.2
O4.60mm
X
X
12.5 5 plcs
X
X
X
X
X
PG 7
X
X
X
X
X
X
Cable Gland
Holes Diameter
x = 12.7mm, PG7
Cable Gla
Holes Dia
x = 12.7m
y = 19mm