Critical Environment Technologies cGas Detector Digital Transmitter User Manual

Critical Environment Technologies cGas Detector Digital Transmitter

IMPORTANT INFORMATION

The cGas Ammonia Vent Line Gas Detector is either a CGAS-A (analog) or a CGAS-D (digital) Gas Detector that has been physically modified to mount on a vent line stack. How it operates is the same as its corresponding base model, the CGAS-A or CGAS-D Gas Detector. This document is an addendum and contains specific information for the installation and calibration of the cGas Ammonia Vent Line Detector models. For more information on wiring connections, wire gauge and run length, refer to the CGAS-A Installation Manual or the CGAS-D Installation Manual
Refer to the cGas Detector Operation Manual for information on:

• Policies
• Warranty
• Copyrights
• Basic Operation and Instrument Settings
  • Display Settings
  • Alarm Status and Fault Settings
  • Alarm Setpoints
  • Enable/Disable Channel
  • Relay Operation
  • Test Functions
• Modbus and BACnet Configuration (digital model)

cGas Ammonia Vent Line Detector Part Numbers:

• CGAS-A-VLT-NH3-S
• CGAS-D-VLT-NH3-S

INTRODUCTION

General Description
The cGas Ammonia Vent Line Detector is designed for continuous monitoring of ammonia levels in the vent line of refrigeration systems, including the detection of equipment failure in ammonia plant vent stack applications. Using a a ¾” cast steel coupler, the cGas Ammonia Vent Line Detector is to be mounted indoors on the ammonia vent relief stack above the pressure relief valve.
IMPORTANT: The cGas Ammonia Vent Line Detector is NOT designed to monitor ammonia in applications requiring human health safety levels detection and is not designed to protect people from toxic gas concentrations. The lowest reading the sensor will detect is above the recommended exposure limit to ammonia.

NOTE: CET manufactures other ammonia gas detectors that meet human health safety levels, if that is the required application. If you have any questions, please do not hesitate to contact our service department for technical support. This product must be installed by a qualified electrician or factory- trained technician and according to instructions indicated in this manual. This instrument should be inspected and calibrated regularly by a qualified and trained technician. This instrument has not been designed to be intrinsically safe. For your safety, do not use it in classified hazardous areas (explosion-rated environments). The cGas Ammonia Vent Line Detector is not intended for use in hazardous-rated areas. If after reading through the manual, you have any questions, please do not hesitate to contact our service department for technical support.

Key Features

• Single channel, internal catalytic Ammonia sensor
• 4-20 mA output (CGAS-A-VLT model)
• Field configurable BACnet® MS/TP RS-485 or Modbus® RTU RS-485 digital output signal (CGAS-D-VLT model)
• 24 VDC or VAC power (ground referenced)
• Easy Plug & Play Smart Sensor replacement at end of life, comes pre-calibrated
• Bright LCD display
• USB port for configuration changes and firmware upgrades
• 1 optional 2A SPDT dry contact relay (Option -RLY)
• Optional low temperature operation package (Option -LT)
• Standard water / dust tight, corrosion resistant enclosure (drip proof)
• Thermal resetting fuses
• RoHS compliant circuit board

INSTRUMENT SPECIFICATIONS

Technical Specifications

SENSOR

• Sensor Type Catalytic
• Gas Type Ammonia (NH3)
• Range 0 – 3.00% volume rangeMeasures to 2 decimal places, tolerant to 17% volume
• Response Time T90 < 30 seconds

MECHANICAL

• Enclosure ABS / Polycarbonate, IP54 rating with a splash guard installed. Copper-coated interior to reduce RF interference.
• Weight 825 g / 29 oz
• Size Detector with splash guard: 127 x 127 x 84 mm / 5.0 x 5.0 x 3.3 in Completely assembled product: 127 x 127 x 182.5 mm / 5.0 x 5.0 x 7.18 in
• Coupler 19.5 mm / 3/4 inch NPT, cast steel
• Sensor Assembly Length (including coupler) 98.5 mm / 3.875 inches
• Conduit Entry Points 12.7 mm / 1/2 in diameter
• Mounting Holes 4.47 mm / 0.175 in diameter maximum head diameter 8 mm / 0.32 in, #8 or 4 mm screw

USER INTERFACE

• Display (standard) 2-line by 16-character graphic LCD, user configurable to suppress reading display
• Display (low temp) 2-line by 16-character OLED display for low-temperature applications (with Option -LT)
• USB Port Internal port for USB memory stick connection for field configuration/firmware upgrades
• Push Buttons Initiate calibration and menu options with internal UP, DOWN and ENTER push buttons
• Audible Alarm none

ELECTRICAL

• Power Requirement
  • 16 – 30 VDC, 3 W, Class 2
  • 12 – 27 VAC, 50-60 Hz, 3 VA, Class 2
  • 24V recommended. Refer to Section 6.7 Wiring Connections.
• Wiring CGAS-A-VLT model VDC (or ground referenced AC): 3-conductor 18 AWG (or larger) shielded, stranded within conduit VAC 4-conductor shielded 18 AWG stranded within conduit
• Wiring CGAS-D-VLT model VDC or VAC (ground referenced) 4-conductor shielded 16 AWG stranded within conduit, network wiring (daisy-chain)
• Fuses Automatic resetting thermal

INPUT/OUTPUT

• Analog OutputCGAS-A-VLT model One Linear 4 – 20 mA output, signals gas reading
• RH & Temperature (Option -RHT) User-selectable units (o C or o F) with user selectable display or hide readings
• Digital Output CGAS-D-VLT model User configurable in the field, BACnet® MS/TP (version 1 rev 14) RS-485 or Modbus® RTU (version 1.1b3) RS-485
• Relay (Option -RLY) Optional SPDT dry contact relay, rated 30 volts @ 2 amps

ENVIRONMENTAL

• Operating Temperature 0°C to 40°C / 32°F to 104°F (standard) -40°C to 40°C / -40°F to 104°F (with Option -LT)
• Operating Humidity 15 – 90% RH non-condensing
• Pollution Degree Degree 2
• Altitude below 2,000 m

CERTIFICATION

• Model: CGAS-A-VLT-NH3-S or CGAS-D-VLT-NH3-S S/N: CGASA1807B00010
• Rating: 16-30 VDC, 3W, Class 2 12-27 VAC, 50-60 Hz, 3VA, Class 2
• Conforms to: CSA-C22.2 No. 205-12, UL508 (Edition 18):2018
• Conforms to: EMC Directive 2014/30/EU, EN 50270:2015, Type 1, EN61010
• Conforms to: FCC. This device complies with part 15 of the FCC Rules, Operation is subject to the following two conditions: (1) This device may not cause harmful interference, and (2) this device must accept any interference received, including interference that may cause undesired operation.

Enclosure Dimensions

The area required for enclosure door to be open 90 degrees is 178 mm / 7.0 in or 254 mm / 10.0 in for fully open. With the optional splash guard installed, the enclosure is IP54 rated.

Exterior Enclosure – Front

NUMBER          FEATURE FUNCTION

1.                       Door Hinge                                                Secures door to base and allows easy opening and closing
2.                       Display                                                        LCD display (standard display shown)
3.                       Splash Guard                                               Covers unused sensor vent, protects from water/dust ingress, IP45 rated
4.                       Door Screw                                                Secures door shut
5.                       Lock Slot                                                     For security padlock or tie
6.                       13mm / 1.5 in water tight cable restraint    Water tight conduit entry for shielded 18 awg stranded cable. For outdoor applications,                                                                                                                                         weatherproof and UV-protected cable is suggested.

Exterior Enclosure – Back
The sensor is potted into a 5 cm / 2 in long pipe fitting that protrudes from the back of the enclosure.

NUMBER                                FEATURE

1.                             5 cm / 2in pipe with potted sensor, screws into the cast steel mounting plate
2.                             Cast steel sensor mounting plate
3.                             19 mm / 3/4 in cast steel coupler for connecting to mounting pipe
4.                             13 mm / 1/2 in water-tight cable restraint. If using conduit, replace with liquid tight type conduit fitting.

Interior Enclosure
The sensor is potted behind the enclosure and wires pass from the back of the enclosure into the interior of the enclosure and connect to a smart board that is plugged into the main board.

SENSOR SPECIFICATIONS AND CONSIDERATIONS

The cGas Ammonia Vent Line Detector comes with a catalytic ammonia sensor potted inside the 5cm / 2 in long pipe fitting that protrudes from the back of the enclosure. The ammonia sensor has a standard measurement range of 0 – 3.00% vol or 0 – 30,000 ppm. The ammonia sensor has a lifespan of approximately 2 to 3 years in air. Exposure to very high concentrations of ammonia (>17 %vol) should be avoided. A large release of a high concentration of ammonia may burn out the sensor and it will need to be replaced. If you install and power up the cGas Ammonia Vent Line Detector as soon as it arrives, the sensor will require about a 5 minute warm up period. The sensor goes through a burn in period at our factory so it is ready for operation upon arrival. If the device is not installed within two weeks of delivery, the sensor may require a longer warm up time to stabilize and provide accurate readings (approximately 48 hours). During calibration, when flowing span gas on an ammonia sensor, if the reading climbs higher than the calibration point after applying gas for 3 minutes, use that reading as the calibration point. Silicone, lead and chlorinated hydrocarbon vapours can poison catalytic sensors. Temperature affects calibration. It is important to ensure the gas is at the appropriate temperature during calibration. If the sensor is being used in an extreme temperature range, calibration should be done in that same temperature range.

INSTALLATION

The cGas Ammonia Vent Line Detector is intended to be permanently mounted indoors on the ammonia vent relief stack above the pressure relief valve. If the device is not installed within two weeks of delivery, the sensor may require a longer warm-up time to stabilize (approximately 48 hours) and provide accurate readings. The cGas Ammonia Vent Line Detector should be installed on the vent stack pipe using the cast steel coupler, no more than 0.3 to 0.6 m / 1 to 2 ft from the discharge stack. The bottom conduit entry point on the enclosure has been fitted with a 12.7 mm / ½ in water tight cable restraint. If conduit is being used, replace the cable restraint with a liquid-tight type conduit fitting. The clearance from the PCA to the base enclosure is 12.7 mm / ½ in. Do not use a conduit connector that has more than 12.7 mm / ½ in of thread length. If the transmitter must be installed outdoors, it is suggested to use weatherproof and UV protected cable and additional housing to protect it from the elements and low temperatures. The factory installed splash guard that covers the (unused) sensor vent in the front of the enclosure protects the device from water and dust ingress. Any water or physical damage to the transmitter that occurs from the installer drilling installation holes will not be covered under warranty. If using, the conduit fitting at the bottom of the enclosure, it must be the liquid tight type.

FOR MORE INFORMATION ON INSTALLATION INCLUDING WIRING CONNECTIONS, WIRE GAUGE AND RUN LENGTH REFER TO THE CGAS-A INSTALLATION MANUAL OR THE CGAS-D INSTALLATION MANUAL.

• NOTE: CETCI suggests that upon power-up, all sensors be left to warm up for 24 hours prior to considering the gas readings to be accurate.
• NOTE: All sensors are calibrated in the factory before they are shipped and should not require calibration at the time of a routine installation or replacement.
• NOTE: Temperature affects calibration. It is important to ensure the gas is at the appropriate temperature during calibration. If the sensor is being used in an extreme temperature range, calibration should be done in that same temperature range.

CALIBRATION

The cGas Ammonia Vent Line Detector is an equipment protection device, not a life safety device and should be calibrated every 6 months.

Calibrating the cGas Ammonia Vent Line Detector has 5 processes:

1.  Remove Detector from Vent Stack
2.  Set Calibration Gas Value
3.  Attach Calibration Adapter and Tubing
4.  Zero (Null) Calibration
5.  Span Calibration

NOTE: A calibration label should be applied after every calibration to confirm work performed and the date it was confirmed. If a controller is involved, the alarm set points should be indicated on a label on the front door of the enclosure so anyone working in the environment can be aware.

Remove Detector from Vent Stack
The cGas Ammonia Vent Line Detector must be removed from the vent stack in order to calibrate the sensor. On the back of the device, a long pipe fitting is connected with a coupler to the mounting pipe on the vent stack to secure the device in place. Unscrew the wide ring portion of the coupler and carefully remove the device from the mounting pipe. Be careful to not handle the device roughly resulting in disconnecting or loosening the wires.
IMPORTANT: The catalytic sensor is very susceptible to shock – when working with the sensor do not hit it. Manually loosen then senso. When replacing the fitting does not have to be pressurized, so minimal tightness is all that is required.

WARNING: When you remove the device, the vent stack will be exposed and ammonia may leak into the air. Vent line systems should always be treated with extreme caution and workers should assume a relief valve could release at any time. Take all necessary safety precautions and follow industry standard practices and local regulations when calibrating the cGas Ammonia Vent Line Detector.

Set Calibration Gas Value
Check to make sure that the calibration gas value set in the transmitter matches the gas concentration of the calibration gas you are using. How much gas the sensor detects is directly related to the Calibration Gas setting and the actual concentration of calibration gas used during calibration. The factory default used to calibrate the cGas Ammonia Vent Line Detector prior to shipping is 0.5 % vol (5000 ppm) air balance.

• From the main display, press ENTER. Enter passcode 3032 using the UP button and ENTER button.
• Press ENTER to access the Calibrate Menu.
• In the Selected Channel menu, confirm the desired channel is showing.
• Press the UP button to accept the displayed calibration gas value if it is correct. Or press ENTER and change the value using the UP or DOWN buttons.
• When finished pressed ENTER and then ENTER again to confirm and ENTER to exit.

Attach Calibration Adapter with Tubing
The ammonia sensor is potted into a 5 cm / 2 in long pipe fitting that protrudes from the back of the enclosure. Press the calibration adapter with an O-ring and two zeroing port plugs into the sensor opening with the tubing attached. Ammonia is a reactive gas and can adhere to surfaces which can reduce the amount of gas that reaches the sensor. When calibrating an ammonia sensor use a length of tubing no longer than 0.6 to 1 m / 2 to 3 ft. If a longer length is necessary, use Teflon lined tubing to ensure the correct concentration of gas reaches the sensor.

Zero (Null) Calibration
Catalytic sensors require oxygen to work and thus the user MUST flow clean air or oxygen to obtain a true zero.

NOTE: To exit the Zero Calibration at any time, press ENTER.

• From the main display, press ENTER. Enter passcode 3032 using the UP button and ENTER button.
• Press ENTER to access the Calibrate Menu.
• In the Selected Channel menu, confirm the desired channel is showing.
• Press the UP button to find Calibrate Zero.
• Press ENTER if using ambient air or attach the regulator to the cylinder of zero air, insert the calibration adapter into the sensor opening on the front of the enclosure door (refer to Section 6.3.1 Calibration Adapter Plug if the adapter will not fit). Press ENTER to start the Zero calibration. The display will show a countdown from 20 seconds.
• When the process has finished and the Zero calibration was accepted, press ENTER and use the UP button navigate to Exit and press ENTER to exit. Remove the cylinder of zero gas. If the Zero Calibration was not successful refer to Section 6.3.2 Zero Fault.

Span Calibration
Span calibration is flowing a known concentration of the target gas over the sensor to adjust the output signal to match the gas concentration. It resets the sensor’s electronic circuit against a known concentration of target gas to correct drift and keep linearity. Catalytic sensors require oxygen to work and thus the span gas must have “air” balance, not N2 balance. The factory default used to calibrate the cGas Ammonia Vent Line Detector prior to shipping is 0.5 % vol (5000 ppm) air balance.

NOTE: To exit the Span Calibration at any time, press ENTER.

• From the main display, press ENTER. Enter passcode 3032 using the UP button and ENTER button.
• Press ENTER to access the Calibrate Menu.
• In the Selected Channel menu, confirm the desired channel is showing.
• Use the UP button to find Calibrate Span. Press ENTER.
• Confirm the span calibration gas level. It is important to make sure that the span gas level value matches the calibration gas concentration you are using to calibrate the sensor. Press ENTER to confirm value is correct. (If the value is not correct, press the UP button to move the cursor to N and press ENTER. Change the cal gas level using the UP and ENTER buttons.)
• Press ENTER to confirm. Attach the regulator to the span gas cylinder and flow the span gas over the sensor. You have 120 seconds to start flowing the gas. If the gas isn’t detected, the display will return to Calibrate Span.
• When the gas is detected the display will show stabilizing for a countdown from 120 seconds and then spanning for a countdown from 60 seconds.
• When the process has finished and the Span calibration was accepted, press ENTER and use the UP button navigate to Exit and press ENTER to exit. Remove the cylinder of span gas. If the Span calibration was not successful, refer to Section 6.3.3 Span Fault.

Trouble Shooting Calibration
This section is intended to aid in correcting issues that may arise during the calibration procedure. If you are unable to correct a problem or you have questions, please contact our Technical Service Department at help@cetci.com or 604-940-8741 (Local) or 1-877-940- 8741 (Toll Free).

Calibration Adapter Plug Doesn’t Fit
Use a slight twisting motion as you gently push the calibration adapter plug (p/n: CET-7000- CAP) into the sensor opening. If it is hard to insert, moisten the O-ring seal slightly then try re-inserting it.

Zero Fault
If the zeroing process fails, the cGas Detector will show a Zero fault. This will happen if the ambient gas readings are at an unacceptable level due to not enough clean air – there is enough residual target gas in the environment or other gases that are interfering with the sensor seeing oxygen.

Span Fault
If the cGas shows a Span fault after trying to calibrate, it is possible that the sensor is dead or the device isn’t seeing the gas (cylinder is empty, regulator or adapter plug is not attached properly, tube is blocked, kinked, etc.).

Check all connections and possible interferences and try a complete calibration procedure from the beginning again to see if this corrects the fault. If a second calibration does not resolve the fault then the sensor needs to be replaced. Over time, a sensor degrades and when it has gone beyond an acceptable level, it has reached its end of life and will no longer pass a calibration. If replacing the sensor does not correct the fault, please contact Technical Service at help@cetci.com.

Zero Override
If the gas level (possible residual gas) is too high, but still within the override range, the display will indicate that an override is required.

To override the value use the UP button to select Y and press ENTER. To keep the original zero value, leave the indicator on N and press ENTER.

Span Override
During the Span calibration, readings are taken and from the results sensitivity is calculated and compared to the original sensitivity of the sensor at the time of installation. If this sensitivity is below the override range, but above the fault limit, the display will indicate that an override is required. To override the value use the UP button to select Y and press ENTER. To keep the original value, leave the indicator on N and press ENTER.

SENSOR REPLACEMENT

The catalytic ammonia sensor has a lifespan of approximately 2 to 3 years under normal air conditions. The sensor may need replacing sooner if is is poisoned by exposure to a very high concentration of ammonia.

NOTE: In order to remove the smart board from the interior of the enclosure, the transmitter needs to be removed from vent stack. For instructions, see Section 5.1 Remove Detector from Vent Stack. Open the enclosure, remove the 3 screws connecting the smart board to the main board and remove the smart board from the main board socket. With the transmitter is free from the vent stack, unscrew the old sensor pipe from the back of the transmitter and feed the old smart sensor board through the hole in the back of the enclosure and remove the old assembly completely. Feed the wires and new smart board through the hole in the back of the enclosure into the interior of the transmitter and screw the new sensor pipe assembly into the back of the transmitter and. Press smart board into the left side socket and replace the 3 screws.

IMPORTANT: The catalytic sensor is very susceptible to shock – when working with the sensor do not hit it. Manually loosen then senso. When replacing the fitting does not have to be pressurized, so minimal tightness is all that is required.

NOTE: Temperature affects calibration. If the sensor is being used in an extreme temperature range, the sensor should be re-calibrated in that temperature range. If the replacement sensor is not installed within two weeks of delivery, the sensor may require a longer warm up time to stabilize (approximately 48 hours) and provide accurate readings.

MAINTENANCE

There are no serviceable elements other than the calibration instructions outlined in this manual. There are no replaceable components except the sensor. The cGas Ammonia Vent Line Detector requires no assembly and very little maintenance. The transmitter should be regularly inspected and monitored for possible damaging conditions.

• If in a damp location, source of water should be shielded from continually contacting the top of the transmitter. It is important to ensure that excess water and/or dust is not somehow entering the enclosure and physically damaging the circuit board or internal components.
• If painting is to be conducted in the transmitter’s location the transmitter needs to be protected from over spray.
• If mounted outside in very cold temperatures (> -20°C / -4°F ), encasing the transmitter in a suitable insulated box may be necessary.

TROUBLESHOOTING

cGas Detector won’t power up. (blank display)
Is the power properly connected? Check the wiring connections. Refer to Wiring Connections in the Installation Manual.

Display shows “SPAN FAULT” message.
Check all connections and possible interferences and try a complete calibration procedure from the beginning again to see if this corrects the fault. If a second calibration does not resolve the fault then the sensor needs to be replaced. Check to make sure the gas cylinder isn’t empty.

Frequent, unexpected alarm signal sent to BAS/DDC.
Check to see if EMI and RF interference is causing the equipment to react this way. Refer to EMI and RF Interference Considerations in the Installation Manual for more information.

Display shows “COMM” message.
Modbus® or BACnet output signal has not been connected properly; will also occur if no requests are being made from the controller to the transmitter, ie addressing is not proper. Check the wiring connections and the network settings.

List of Possible cGas Error Codes
(appears on the display in place of the units for a channel)

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