1 Safety information
Safe operation of this product depends on its correct installation, commissioning and maintenance by qualified personnel in accordance with the operating instructions (see Section 1.11).
Compliance with basic installation and safety instructions for pipeline and plant construction, together with the correct use of tools and the provision of suitable safety equipment, is also required.
This product is designed and manufactured to withstand the forces encountered during normal use.
Use for any purpose other than its intended application, or failure to install the product in accordance with the Installation and Maintenance Guide, may damage the product, invalidate the CE marking and cause injury or death.
Additional safety considerations for steam boiler level control and level limit/alarm products
The selection, installation, operation and testing of the product/system must comply with:
- Local and national standards and regulations
- Guidance documents, including BG01 and INDG436 from the UK Health and Safety Executive
- Requirements of the approval authorities
- Boiler inspection bodies
- Boiler manufacturer’s specifications
Two independent low-level limit/alarm systems must be installed on steam boilers. The level alarm probes must be installed in separate protection tubes/chambers, with sufficient clearance between the top and bottom.
Each probe must be connected to an independent controller. The alarm relay must disconnect the boiler heat input when a low-level alarm condition occurs.
A high-level alarm may be part of the level control system or a separate system. If it is considered a safety requirement, an independent high-level alarm system must be installed. In this case, the relay must simultaneously disconnect the feedwater supply and boiler heat input when a high-level alarm condition occurs. All boiler level limiters/alarms require regular functional testing.
A suitable water treatment regime must be used to ensure the continued safe and correct operation of the control and limiter/alarm systems. Consult the organizations listed above and a qualified water treatment company.
Warning
This product complies with the Electromagnetic Compatibility Directive 2014/30/EU and all of its requirements.
The product may be exposed to interference above the industrial immunity limits in the following circumstances:
- The product or its wiring is located close to a radio transmitter
- Excessive electrical noise on the mains supply circuit. Where mains noise is likely, the AC supply should be fitted with protective devices. Such devices include filtering, tuning, voltage regulation and peak suppression equipment
- Mobile telephones and portable radios may cause signal interference when located approximately 1 m (39”) from the product or its wiring. However, the actual required separation distance will vary according to the installation and the surrounding environment of the transmitter power source
Failure to use this product in the manner specified in this Installation and Maintenance Guide may impair the protection provided.
1.1 Intended use
The PA420 level preamplifier is intended for use with Spirax Sarco level controllers. When used with other controllers, a safety power supply providing safe extra-low voltage (SELV) must be used to power the controller/level preamplifier.
- Check that the product is suitable for use with the intended fluid.
- Check material suitability and the pressure and temperature ranges, including their maximum and minimum values. If the upper limit of the product’s operating range is lower than the requirements of the system in which it is installed, or if product failure could result in a dangerous overpressure or overtemperature condition, ensure that the system is fitted with suitable safety devices to prevent such conditions.
- Ensure that installation and fluid flow direction are correct.
- Spirax Sarco products are not designed to withstand external stresses imposed by the system in which they are installed. The installer must consider all possible stresses and take adequate precautions to minimize them.
- Remove all protective covers from connections before installation.
Correct installation, commissioning, operation and maintenance by qualified personnel (see Section 1.11) in accordance with the operating instructions is the only guarantee of safe operation of this product. Compliance with basic installation and safety instructions for pipeline and plant construction, together with the correct use of tools and the provision of suitable safety equipment, is also required.
1.2 Access
Before attempting to operate this product, ensure that safe access and egress are available and, if necessary, provide a safe working platform with suitable protection. Where necessary, provide suitable lifting equipment.
1.3 Lighting
Ensure that adequate lighting is provided, particularly where detailed or complex work is required.
1.4 Hazardous fluids and gases in the pipeline
Consider what fluids are, or may have been, present in the pipeline. Pay particular attention to flammable substances, substances hazardous to health and extreme temperatures.
1.5 Hazardous environments around the product
Consider the risks of explosion, lack of oxygen, such as in tanks or pits, extreme temperatures, hot surfaces, ignition hazards, such as during welding, excessive noise and moving machinery.
1.6 The system
Consider the effect of the planned work on the complete system. Could the proposed action, such as closing isolation valves or switching off the power supply, put any other part of the system or personnel at risk?
Hazards may include the isolation of vents or protective devices, or the failure of controls or alarms. Ensure that isolation valves are opened and closed gradually to avoid system shocks.
1.7 Pressure systems
Ensure that all pressure is isolated and safely vented to atmospheric pressure. Consider double isolation, including double block and bleed, and the locking and labeling of closed valves. Do not assume that the system is depressurized even when the pressure gauge indicates zero.
1.8 Temperature
Allow time for the equipment to cool to normal temperature after isolating the valves to avoid burns.
1.9 Tools and consumables
Before starting work, ensure that suitable tools and/or consumables are available. Use only replacement parts supplied by Spirax Sarco.
1.10 Protective clothing
Consider whether you and others in the vicinity require protective clothing to protect against hazards from chemicals, high or low temperatures, radiation, noise, falling objects and injury to the eyes and face.
1.11 Work permits
All work must be carried out or supervised by suitably qualified personnel.
Installation and operating personnel must be trained to use this product correctly in accordance with the Installation and Maintenance Guide.
Where a formal work permit system is in force, it must be complied with. Where no such system exists, the person responsible must be aware of the nature of the work and, where necessary, arrange for an assistant whose primary responsibility is safety.
If necessary, display warning notices.
1.12 Handling
Manual handling of large and/or heavy items may cause injury. Lifting, pushing, pulling, carrying or supporting heavy loads by bodily force may cause back injury in particular. It is recommended that risks be assessed, taking into account the task, the individual, the load and the working environment, and that suitable handling methods be used according to site conditions.
1.13 Residual hazards
Under normal operating conditions, the external surface temperature of this product may be high.
Many products are not self-draining. Exercise extreme caution when dismantling the product.
1.14 Freezing
For products that are not self-draining, protection must be provided against freezing where ambient temperatures may fall below freezing point.
1.15 Disposal
Unless otherwise stated in this Installation and Maintenance Guide, this product is recyclable and can be disposed of properly without causing environmental harm.
1.16 Returning products
Customers and distributors are reminded that, under European health, safety and environmental regulations, when returning products to Spirax Sarco, information about residues of contaminants and the health, safety and environmental risks that may result from mechanical damage must be provided, together with the precautions required. This information must be supplied in writing and include health and safety data sheets for substances identified as hazardous or potentially hazardous.
2 General product information
Warning: Appropriate anti-static precautions must be taken during installation and maintenance.
2.1 Introduction
The PA420 preamplifier is a loop-powered transmitter used with Spirax Sarco LP20 and LP21 capacitance level sensors. It provides a 4-20 mA current signal proportional to the liquid level in a tank or boiler. The signal is compatible with Spirax Sarco controllers and standard industrial controllers used to control or monitor level.
It has two buttons for commissioning and a dual-color indicator light, red and green.
It consists of a tubular austenitic stainless steel body that is threaded onto the top of the level probe. It also has a DIN 43650 connector with a Pg 11 cable gland (see Figure 1). Never replace the gland with anything other than a Pg 11 gland.
Approvals
- TÜV, VdTÜV-Merkblatt, Wasserstand 100
- Electromagnetic Compatibility Directive 2014/30/EU
Figure 1
3 Installation
Warning:
- Do not install the PA420 outdoors without additional environmental protection.
- Appropriate anti-static precautions must be taken during installation.
- Using a spanner will damage the O-ring and may damage the preamplifier.
The preamplifier can be installed on the capacitance probe before or after the probe is installed in the boiler or tank. Always allow the PA420 to stabilize at its normal operating temperature for at least 15 minutes before commissioning the controller.
Fit the supplied O-ring to the bottom of the external thread on the capacitance probe.
Note: Both the probe and the PA420 are supplied with an O-ring. Only one of them needs to be installed.
Fit the preamplifier onto the probe and tighten by hand only.
Figure 2
4 Wiring
4.1 Introduction
Cable installation must comply with BS 6739 - Process control instrumentation systems: Installation design and practice - or the local equivalent standard. For installations in the United States and Canada, wiring of the preamplifier must comply with the National Electrical Code (NEC) or the Canadian Electrical Code (CEC), as applicable.
Ensure that the cable is long enough to allow removal of the preamplifier and that no stress is applied to the equipment or cable socket.
See the technical specifications for cable requirements.
Note:
- Never install signal cables near high-voltage cables or switchgear.
- Probe wiring must not use the same conduit or junction box as power wiring.
- Appropriate anti-static precautions must be taken during installation and maintenance.
4.2 Wiring diagram
Note: Ensure that the resistance from the probe body to the pipe or boiler shell is less than 1 Ω.
Figure 3
4.3 Cable socket
To disconnect the cable socket, remove the center screw (see Figure 1).
Note: A square flat washer is fitted between the cable socket and the preamplifier terminals to provide environmental protection for the PA420. To maintain environmental integrity, ensure that the washer is always present when reconnecting the cable socket and that all contact surfaces are undamaged and clean.
To access the terminal block inside the cable socket, remove the center screw and withdraw the hinged cover.
The terminal block on the standard PA420 can be rotated through 90° to facilitate wiring. Remove the retaining screw and hinged cover, then remove the cable socket.
Warning
Before supplying power to the PA420, disconnect the cable socket and ensure that the supply voltage between pins 1 and 2 is within the specified rated range.
See Section 8, “Technical data”: exceeding the maximum rated voltage will damage the PA420.
5 Commissioning
5.1 Level Calibration
The PA420 can be configured to provide a 4 mA to 20 mA output over the required level range. It can output 20 mA at high level and 4 mA at low level, or 4 mA at high level and 20 mA at low level. Commissioning is performed using two buttons and a bi-colour LED.
For minimum and maximum calibration ranges, see Section 8.
To configure the level:
Step 1: Adjust the level to the required 4 mA or 20 mA level.
Step 2: Press and hold the 4 mA or 20 mA button for three seconds.
Step 3: The bi-colour LED will flash green once.
Step 4: Release the button. You have two seconds to do this.
Step 5: The bi-colour LED will flash green again to confirm that the level has been saved to memory.
Step 6: Repeat the above procedure to configure the second level.
Note: Holding or releasing the button for too short a time will cause the LED to flash red, and the setting will not be saved.
Figure 4 shows an example of how to commission the PA420 level transmitter.
Figure 4
Warning: If a fault is detected, the indicator will flash red once and an alarm signal will be output. See Section 8, “Technical Data”, and Section 7, “Fault Finding”. Ensure that the product is configured so the system can shut down safely.
6 Maintenance
Warning: Appropriate anti-static precautions must be taken during maintenance.
Probe body cleaning instructions: Use a cloth moistened with tap water, deionised water, or isopropyl alcohol. The use of other cleaning materials may damage the product and invalidate the warranty.
Boiler level controllers require regular testing and inspection. For specific testing instructions for Spirax Sarco systems, refer to the separate documentation.
Figure 5: Measuring loop current. Note that it is not necessary to disconnect the installation wiring.
7 Fault Finding
Warning: Read Section 1, “Safety Information”, before starting fault finding.
Faults are most likely to occur during installation and commissioning.
7.1 General Faults
Symptom 1: No output current
Description: No signal. There is insufficient voltage to power the product, or the product is damaged. The product may recover if the fault is cleared.
Action:
- Check that the ambient temperature is within the specified range. See Section 8.2.
- Disconnect the wiring connector.
- Check that all wiring is correct. See Section 4.
- Check that the wiring connections are secure.
- Check the voltage between terminals 1 and 2 and ensure it is within the specified range. See Section 8.3.
- Check the power supply polarity.
- Reconnect the wiring connector.
- Check that the loop current is within the specified range. See Figure 5.
- Check that the probe cable screen is correctly connected. See Figure 3.
- Check whether the probe cable is adjacent to other cables that may interfere with the product, such as power cables.
- Check whether the product is located next to radio transmitting equipment.
7.2 System Alarms
When an alarm occurs, the indicator flashes red and the current output is set to the alarm state. See the “Technical Data” section. To assist diagnosis, the indicator flashes continuously with pauses between flash sequences. Once the fault has been corrected, the alarm can be cleared by restarting the product.
Symptom 1: The indicator repeatedly flashes red once and provides an alarm output. See Section 8, “Technical Data - Alarm State”.
Description: Program integrity. The product program has been corrupted.
Action:
- Return the product to your local Spirax Sarco representative.
- Before installing a replacement product, follow the actions in Section 7.1, “General Faults”.
Symptom 2: The indicator repeatedly flashes red twice and provides an alarm output
Description: Level input too low. The measured level signal from the probe is too low.
Action:
- Check the probe installation.
- Check the connection between the probe and the vessel.
- Check the connection between the probe and the preamplifier.
- Before installing a replacement product, follow the actions in Section 7.1, “General Faults”.
Symptom 3: The indicator repeatedly flashes red three times and provides an alarm output
Description: Level input too high. The measured level signal from the probe is too high.
Action:
- Check the probe installation.
- Check the clearance between the probe and any metal parts.
- Check the connection between the probe and the preamplifier.
- Check whether the insulation on the probe is damaged.
- Before installing a replacement product, follow the actions in Section 7.1, “General Faults”.
7.3 System Errors
When an error occurs, the indicator flashes red. To assist diagnosis, the indicator flashes continuously with pauses between flash sequences. The error can be cleared by pressing either button. The product will continue to output a current proportional to the level, and the current parameters will remain stored in memory.
Symptom 1: The red LED flashes once
Description: Button pressed for too short a time. During commissioning, the button was not pressed long enough and the level input was not saved to memory.
Action:
- Repeat the commissioning procedure in Section 5.
- Follow the actions in Section 7.1, “General Faults”.
Symptom 2: The red LED repeatedly flashes twice
Description: Button pressed for too long. During commissioning, the button was pressed for too long and the level input was not saved to memory.
Action:
- Repeat the commissioning procedure in Section 5.
- Follow the actions in Section 7.1, “General Faults”.
Symptom 3: The red LED repeatedly flashes three times
Description: Both buttons pressed. If both buttons are pressed at the same time, the product ignores the buttons and the level input is not saved to memory.
Action:
- Check whether the buttons are damaged.
- Check around the product and ensure that nothing is pressing the buttons.
- Follow the actions in Section 7.1, “General Faults”.
Symptom 4: The red LED repeatedly flashes four times
Description: Commissioning level input out of range. During commissioning, the calibration points are too close together and the level input is not saved to memory.
Action:
- Repeat the commissioning procedure in Section 5, ensuring that the minimum distance between the two calibration points is maintained. See Section 8, “Technical Data”.
Symptom 5: The red LED repeatedly flashes five times
Description: Memory content conflict. During commissioning, the product attempted to save the level signal to memory. However, an unexpected value was read back.
Action:
- Follow the actions in Section 7.1, “General Faults”.
- Repeat the commissioning procedure in Section 5.
Symptom 6: The red LED repeatedly flashes six times
Description: Watchdog timeout. The internal microcontroller temporarily stopped and recovered automatically.
Action:
- Follow the actions in Section 7.1, “General Faults”.
- Monitor, acquire, and record the power supply voltage over a period of time.
If the problem persists, contact your local Spirax Sarco representative.
8 Technical Data
8.1 Operating Limits
| Item | Value |
|---|---|
| Ambient temperature range | 0 - 70 °C (32 - 158 °F) |
| Pollution degree | 3 |
| Water conductivity | 5 μS/cm or 5 ppm |
| Maximum cable length | 100 m (328 ft), shielded (see the controller installation and maintenance manual) |
| Conductor cross-section | 0.5 - 1.5 mm² (20 - 16 AWG) |
| Recommended cable | 2-core shielded cable, minimum 0.5 mm² (AWG20). See the controller installation and maintenance manual. |
| Protection rating | IP54 |
8.2 Technical Data
| Item | Value |
|---|---|
| Voltage drop (across the device) | 9 - 26.4 Vdc |
| Loop current | 4 - 20 mA |
| Alarm condition (high level = 20 mA, low level = 4 mA) | 3.8 mA |
| Alarm condition (high level = 4 mA, low level = 20 mA) | 22 mA |
| Maximum load | 500 Ω |
| Linearity | 2% FSD |
| Insulation | 100 Vdc (capacitive) |
| Calibration level (minimum) | 0 mm |
| Calibration level (maximum) | 1500 mm |
| Calibration range (minimum) | 50 mm |
| Calibration range (maximum) | 1500 mm |
| Resolution | 1 mm |
8.3 Approvals
- TÜV, VdTÜV-Merkblatt, Wasserstand 100 - 2017
- Electromagnetic Compatibility Directive 2014/30/EU
9 Technical Support
Contact your local Spirax Sarco representative.
Return of Faulty Equipment
Return the complete device to your local Spirax Sarco representative. Ensure that the complete device is suitably packaged for transport, preferably in the original packaging.
The following information is required when returning equipment:
- Your name/company name/address and telephone number/order number and invoice, and return shipping address.
- Description and serial number of the returned equipment.
- Full description of the fault or repair required.
- For equipment returned under warranty, please state: a. Date of purchase. b. Original order number.
Spirax Sarco Ltd Runnings Road Cheltenham GL51 9NQ United Kingdom
