Spirax Sarco PA420 User manual

IM-P402-139 AB Issue 1 1
PA420
4 - 20 mA Loop Powered Level Preamplier
Installation and Maintenance Instructions
1. Safety information
2. General
product information
3. Installation
4. Wiring
5. Commissioning
6. Maintenance
7. Fault finding
8. Technical data
IM-P402-139
AB Issue 1
4026150/1
© Copyright 2013
Printed in the UK

IM-P402-139 AB Issue 12

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1. Safety information
Safe operation of the product depends on it being properly installed, commissioned
and maintained by a qualified person (see Section 1.11) in compliance with the
operating instructions.
It is essential to comply with general installation and safety instructions for
pipeline and plant construction, as well as to make proper use of tools and safety
equipment.
The product is designed and constructed to withstand the forces encountered
during normal use. Use of the product for any other purpose, or failure to install the
product in accordance with these Installation and Maintenance Instructions, could
cause damage to the product, will invalidate the marking, and may cause injury
or fatality to personnel.
Additional Safety Notes:
Level control and level limiting / alarm products in steam boilers
Products /systems must be selected, installed, operated, and tested in accordance
with:
-Local or National standards and regulations.
-Guidance Notes, (Health and Safety Executive BG01 and INDG436 in the UK).
-The requirements of Approvals Authorities.
-Boiler inspection bodies.
-Boiler manufacturer’s specifications.
Two independent low water limiting / alarm systems must be installed on steam boilers.
Level probes must be installed in separate protection tubes / chambers, with
sufficient clearance between the tips, and earth.
Each probe must be connected to an independent controller. The alarm relays must
isolate the boiler heat supply at low alarm status.
A high water alarm may be part of the water level control, or a separate system. An
independent high water alarm system must be fitted if it is considered a safety
requirement. In this case, the relays must simultaneously isolate the feedwater supply
and the boiler heat supply at high alarm status. All boiler water limiters / alarms require
regular functional testing.
A suitable water treatment regime must be used to ensure continuous safe and correct
operation of the control and limiter / alarm systems. Consult the above authorities and
a competent water treatment company.

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Warning
This product complies with Electromagnetic Compatibility Directive 2004 / 108 / EC
and all its requirements.
This product is suitable for Heavy Industrial Environments. A fully detailed EMC
assessment has been made and has the reference number UK Supply BH PA420.
The product may be exposed to interference above the limits of Heavy Industrial
Immunity if:
- The product or its wiring is located near a radio transmitter.
- Excessive electrical noise occurs on the mains supply. Power line protectors (ac)
should be installed if mains supply noise is likely. Protectors can combine
filtering, suppression, surge and spike arrestors.
- Cellular telephones and mobile radios may cause interference if used within
approximately 1 metre (39") of the product or its wiring. The actual separation
distance necessary will vary according to the surroundings of the installation and
the power of the transmitter.
If this product is not used in the manner specified by this IMI, then the protection
provided may be impaired.
1.1 Intended use
i) Check that the product is suitable for use with the intended fluid.
ii) Check material suitability, pressure and temperature and their maximum and
minimum values. If the maximum operating limits of the product are lower than
those of the system in which it is being fitted, or if malfunction of the product could
result in a dangerous overpressure or overtemperature occurrence, ensure a safety
device is included in the system to prevent such over-limit situations.
iii) Determine the correct installation situation and direction of fluid flow.
iv) Spirax Sarco products are not intended to withstand external stresses that may
be induced by any system to which they are fitted. It is the responsibility of the
installer to consider these stresses and take adequate precautions to minimise
them.
v) Remove protection covers from all connections before installation.
Safe operation of the product can only be guaranteed if they are properly installed,
commissioned, used and maintained by qualified personnel (see Section 1.11 on this
document) in compliance with the operating instructions. General installation and
safety instructions for pipeline and plant construction, as well as the proper use of
tools and safety equipment must also be complied with.
1.2 Access
Ensure safe access and if necessary a safe working platform (suitably guarded)
before attempting to work on the product. Arrange suitable lifting gear if required.
1.3 Lighting
Ensure adequate lighting, particularly where detailed or intricate work is required.

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1.4 Hazardous liquids or gases in the pipeline
Consider what is in the pipeline or what may have been in the pipeline at some
previous time. Consider: flammable materials, substances hazardous to health,
extremes of temperature.
1.5 Hazardous environment around the product
Consider: explosion risk areas, lack of oxygen (e.g. tanks, pits), dangerous gases,
extremes of temperature, hot surfaces, fire hazard (e.g. during welding), excessive
noise, moving machinery.
1.6 The system
Consider the effect on the complete system of the work proposed. Will any proposed
action (e.g. closing isolation valves, electrical isolation) put any other part of the
system or any personnel at risk?
Dangers might include isolation of vents or protective devices or the rendering
ineffective of controls or alarms. Ensure isolation valves are turned on and off in a
gradual way to avoid system shocks.
1.7 Pressure systems
Ensure that any pressure is isolated and safely vented to atmospheric pressure.
Consider double isolation (double block and bleed) and the locking or labelling of
closed valves. Do not assume that the system has depressurised even when the
pressure gauge indicates zero.
1.8 Temperature
Allow time for temperature to normalise after isolation to avoid danger of burns.
1.9 Tools and consumables
Before starting work ensure that you have suitable tools and/or consumables
available. Use only genuine Spirax Sarco replacement parts.
1.10 Protective clothing
Consider whether you and / or others in the vicinity require any protective clothing
to protect against the hazards of, for example, chemicals, high / low temperature,
radiation, noise, falling objects, and dangers to eyes and face.
1.11 Permits to work
All work must be carried out or be supervised by a suitably competent person.
Installation and operating personnel should be trained in the correct use of the
product according to the Installation and Maintenance Instructions.
Where a formal 'permit to work' system is in force it must be complied with. Where
there is no such system, it is recommended that a responsible person should know
what work is going on and, where necessary, arrange to have an assistant whose
primary responsibility is safety.
Post 'warning notices' if necessary.

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1.12 Handling
Manual handling of large and/ or heavy products may present a risk of injury. Lifting,
pushing, pulling, carrying or supporting a load by bodily force can cause injury
particularly to the back. You are advised to assess the risks taking into account the
task, the individual, the load and the working environment and use the appropriate
handling method depending on the circumstances of the work being done.
1.13 Residual hazards
In normal use the external surface of the product may be very hot.
Many products are not self-draining. Take due care when dismantling or removing the
product from an installation.
1.14 Freezing
Provision must be made to protect products which are not self-draining against
frost damage in environments where they may be exposed to temperatures below
freezing point.
1.15 Disposal
Unless otherwise stated in the Installation and Maintenance Instructions, this
product is recyclable and no ecological hazard is anticipated with its disposal
providing due care is taken.
1.16 Returning products
Customers and stockists are reminded that under EC Health, Safety and
Environment Law, when returning products to Spirax Sarco they must provide
information on any hazards and the precautions to be taken due to contamination
residues or mechanical damage which may present a health, safety or environmental
risk. This information must be provided in writing including Health and Safety
data sheets relating to any substances identified as hazardous or potentially
hazardous.

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Button to set the 20 mA
water level
CAUTION: Suitable anti-static precautions
must be observed during installation and maintenance.
2.1 Description
The PA420 preamplier is a loop powered level transmitter for use with a Spirax Sarco
capacitance probe. It outputs 4 - 20 mA current signal, proportional to the water level in a
tank or boiler. This signal is compatible with Spirax Sarco and standard industrial controls
which are used to control or monitor level.
It has two buttons and a dual coloured light (red and green) for use at commissioning.
It consists of a tubular austenitic stainless steel body which screws onto the top of the probe,
and has a DIN 43650 connector with a Pg 11 cable gland (see Figure 1) - Do not replace
the gland with anything other than a Pg 11.
2. General product information
Button to set the 4 mA
water level
Dual coloured light:
Green – Confirm calibration
Red – Error or alarm
Body
Pg 11 cable gland
Cable socket
Central screw
Fig. 1 Standard version

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CAUTIONS:
-Do not install the PA420 outdoors without additional weather protection.
-Suitable anti-static precautions must be observed during installation.
-Use of a wrench will cause damage to the 'O' ring and may damage the preamplifier.
The preamplifier may be fitted to the capacitance probe before or after installation in the boiler
or tank. Always allow the PA420 to stabilise at its normal operating temperature for at least
15 minutes before commissioning the controller / transmitter.
- Fit the 'O' ring supplied with the unit to the base of the male thread on the capacitance probe.
Note: Both the probe and the PA420 are provided with an 'O' ring - fit only one of these.
-Fit the preamplifier to the probe and hand tighten only.
3. Installation
Fig. 2
4. Wiring
4.1 General information
Cabling should be installed in accordance with BS 6739 - Instumentation in Process Control
Systems: Installation design and practice or local equivalent. For the US and Canadian
installation, the preamplifier must be wired in accordance with local and National Electrical
Codes (NEC) or Canadian Electrical Code (CEC).
Ensure that sufficient cable length is provided to allow removal of the preamplifier, and to
ensure that no strain is placed on the unit or cable socket.
See technical specification for the cable specification.
CAUTION:
Do not install signal cables near high voltage cables or switchgear.
Probe cabling must not use the same conduit / wiring trays as power cables.
Suitable anti-static precautions must be observed during installation and maintenance.
'O' ring
Capacitance probe
PA420

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4.2 Wiring diagram and screen connection
An earth current loop is created if a wire or screen is connected between two earth points,
which are at different potential (voltage). If the instructions are followed correctly, then the
preamplifier and controller screen will only be connected to earth at one end (See Figure 3).
The PA420 earth terminal is for the connection of the screen only. It provides a sink / drain
for any electrical interference rather than a protective earth. A protective earth provides
protection from electric shock under a single fault condition. This product does not require a
protective earth.
CAUTION:
Do not connect the common terminal to an earth local to the controller. To do so
may induce an earth current loop, which may reduce the performance or damage
the product. Ensure resistance from probe body to pipework / boiler shell is less
than 1 .
PA420
Preamplifier
Screen
Loop +
Internally
connected to
PA420 body
(earthed)
DO NOT connect to any
other earth.
Follow the installation
instructions of the
instrument the PA420 is
connected to.
4.3 Cable socket
To unplug the cable socket, remove the central screw (see Figure 1).
Note: To provide environmental protection the PA420 is supplied with a square
flat gasket between the cable socket and the preamplifier connector. To maintain
environmental integrity, ensure that the gasket is always present when reconnecting
the cable socket and that all contact surfaces are undamaged and clean.
To gain access to the connector block within the cable socket, remove the central screw and
withdraw the hinged cover.
The connector block on the standard PA420 may be rotated in 90osteps to facilitate wiring:
-Remove the retaining screw and hinged cover and withdraw the socket.
WARNING
Before applying power to the PA420, disconnect the cable socket and ensure that
the supply voltage between Pin 1 and Pin 2 is within the specified rating.
See Section 8 'Technical data': Exceeding the maximum voltage rating will damage
the PA420.
Loop -
TEST
Fig. 3

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5. Commissioning
5.1 Water level calibration
The PA420 can be congured to output between 4 mA and 20 mA for a range of water
levels. The product can output 20 mA at a high water level and 4 mA for a low water level.
Alternatively the product can output 4 mA at a high water level and 20 mA for a low water
level. Commissioning is performed using two buttons and a dual coloured light.
Refer to Section 8 for the minimum / maximum calibration span.
To configure the water levels:
Step 1: Set the water level to the desired 4 mA or 20 mA level.
Step 2: Press the 4 mA or 20 mA button
for three seconds
Step 6: Repeat the above to congure the second water level.
Note: Holding or releasing the button for longer or shorter periods of times, will result in
the LED ashing red. The new calibration will not be saved.
Figure 4 gives an example how to commission the PA420 in relation to the gauge glass.
Step 3: The light will ash green once.
Step 4: Release the button. (You will be
allowed two seconds to do this)
Step 5: The light will ash green again to
conrm the level has been saved in non-
volatile memory.
Control band 20%
(symmetrical about the
set point)

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6. Maintenance
CAUTION: Suitable anti-static precautions
must be observed during any maintenance procedure.
Probe body cleaning instructions - Use a cloth dampened with tap / de-ionised water or
isopropyl alcohol. Use of other cleaning materials could damage the product and invalidate
the warranty.
Boiler water level controls - Require regular testing and inspection. For specic testing
instructions for Spirax Sarco systems please see separate literature.
100% = 20 mA
Absolute maximum safe
water level
Set point 50%
0% = 4 mA
Absolute minimum water
level (water must always
be visible in glass)
High alarm 85%
Control band 20%
(symmetrical about the
set point)
Low alarm 20%
60%
40%
Warning: If the product detects a fault, the light will ash red once a second and the output
will transmit a low level signal. See Section 8, Technical Data, Alarm state and Section 7
Fault nding. Ensure the controlling product is congured to shut the system down safely.
Fig. 5

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7. Fault finding
Symptom Explanation Action
1
No output
current
No signal
There is not enough
voltage to power the
product or the product
has been damaged.
Product may recover if
the fault is removed.
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
Check that the ambient temperature is
within specication - See Section 8.2.
Unplug the connector.
Check that all wiring is correct - See
Section 4.
Check that the wiring is secure.
Check the voltage across terminals 1 and 2
and ensure it is within specication - See
Section 8.3.
Check the polarity of the supply.
Plug the connector back in.
Check the loop current is within
specication - See Figure 6.
Check the probe wire screen is correctly
connected - See Figure 3.
Check the probe wire is not routed beside
other cable that may interfere with the
product (e.g. mains cables).
Check the product is not located beside a
radio transmitting device.
WARNING:
Before commencing fault finding, read the Safety information in Section 1
Introduction
The most likely time for faults to occur is during installation and commissioning.
7.1 Generic faults

IM-P402-139 AB Issue 1 13
Symptom Explanation Action
1
Light ashing
red repeatedly
and
alarm output
Program integrity
The product program has
been corrupted.
1.
2.
Return product to your local
Spirax Sarco representative.
Before installing a
replacement product, follow
the actions in Section 7.1
'Generic faults'.
2
Light ashes
red 2 times
repeatedly
and
alarm output
Level input was too low
The measured level signal
from the LP20 was too low.
1.
2.
3.
4.
Check probe installation.
Check the connection
between the LP20 and
vessel.
Check the connection
between the probe and the
preamplier.
Before installing a
replacement product, follow
the actions in Section 7.1
'Generic faults'.
3
Light ashes
red 3 times
repeatedly
and
alarm output
Level input was too high
The measured level signal
from the LP20 was too
high.
1.
2.
3.
4.
5.
Check probe installation.
Check the distance between
the probe and any metal
work.
Check the connection
between the probe and the
preamplier.
Verify the insulation on the
LP20 has not been damaged.
Before installing a replacement
product, follow the actions in
Section 7.1 'Generic faults'.
7.2 System alarms
When an alarm occurs, the light will ash red and set the current output to the alarm state.
See technic al data section. To assist in diagnosis, the light ashes in a c ontinuous sequence,
separated with a pause. The alarm can be cleared by power cycling the product, once the
fault is corrected

IM-P402-139 AB Issue 114
Symptom Explanation Action
1
Light ashes
red once
Button not held long
enough
During commissioning the
button was not held down
long enough.
The level input was not
saved in memory.
1.
2.
Repeat the commissioning
routine in Section 5.
Follow the actions in Section
7.1 'Generic faults'.
2
Light ashes
red 2 times
repeatedly
Button held too long
During commissioning the
button was held down for
too long.
The level input was not
saved in memory.
1.
2.
Repeat the commissioning
routine in Section 5.
Follow the actions in Section
7.1 'Generic faults'.
3
Light ashes
red 3 times
repeatedly
Both buttons pressed
The product is designed
to ignore the buttons
if both are pressed
together.
The level input was not
saved in memory.
1.
2.
3.
Check the button has not
been damaged.
Check around the product,
to ensure that nothing is
pressing on the buttons.
Follow the actions in Section
7.1 'Generic faults'.
4
Light ashes
red 4 times
repeatedly
Commissioning level
input out-of-range
During commissioning the
level calibration points
were too close.
The level input was not
saved in memory.
1. Repeat the commissioning
routine in Section 5 ensuring
that the minimum distance
between the two calibration
points is maintained. See
Section 8 'Technical data'.
7.3 System errors
When an error occurs, the light will ash red. To assist in diagnosis, the light will ash in a
continuous sequence, separated with a pause. The error can be cleared by pressing one of
the buttons. The product will continue to output a current proportional to water level, with the
parameters currently saved in memory.

IM-P402-139 AB Issue 1 15
Symptom Explanation Action
5
Light ashes
red 5 times
repeatedly
Memory contents
conict
During commissioning, the
product attempted to save
the level signal into non-
volatile memory. However
an unexpected value was
read back.
1.
2.
Follow the actions in Section
7.1 'Generic faults'.
Repeat the commissioning
routine in Section 5.
6
Light ashes
red 6 times
repeatedly
Watchdog timeout
The internal
microcontroller has briey
stopped and recovered
automatically.
1.
2.
Follow the actions in Section
7.1 'Generic faults'.
Monitor, data log and record
the supply voltage over a
period of time.
If the problem persists, return the product to your local Spirax Sarco representative.

A COM
V 
OFF
V
V
A
A
PA420
Preamplifier
Screen
Loop +
Internally
connected to
PA420 body
(earthed)
Loop -
TEST
Fig. 6 Measuring the loop current
(Please note that you don't need to disconnect the installation wiring)

IM-P402-139 AB Issue 116
8. Technical data
8.1 For technical assistance
Contact your local Spirax Sarco representative. Details can be found on accompanying
order /delivery documentation or on our web site:
www.spiraxsarco.com
Returning faulty equipment
Return all items to your local Spirax Sarco representative. Ensure all items are suitably packed
for transit (preferably in the original cartons).
Please provide the following information with any equipment being returned:
1. Your name, company name, address and telephone number, order number and invoice
and return delivery address.
2. Description and serial number of equipment being returned.
3. Full description of the fault or repair required.
4. If the equipment is being returned under warranty, please indicate:
a. Date of purchase.
b. Original order number.
8.2 Limiting conditions
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) screened
2-core, 1 mm² (18-16 AWG),
Recommended cable High temperature screened cable e.g.:
Pirelli FP 200 or Delta Crompton Firetuf OHLS
8.3 Technical data
Voltage drop (across the device) 9 - 26.4 Vdc
Loop current 4 - 20 mA
High level = 20 mA
Alarm state Low level = 4 mA 3.8 mA
High level = 4 mA
Low level = 20 mA 22 mA
Maximum load 500 
Linearity 2% FSD
Isolation 100 Vdc (capacitive)
Calibration level Minimum 0 mm
Maximum 1 500 mm
Calibration span Minimum 50 mm
Maximum 1500 mm
Resolution 1 mm