ALENCON GARD-1000-V2.2 User manual

GROUND AND ARC RAPID DISCONNECT (GARD)
A unique device for detecting ground and arc faults in PV arrays and
rapidly disconnecting the impacted PV strings.
INSTALLATION, OPERATION AND MAINTENANCE MANUAL
FOR USE WITH THE GARD V2.2
PM006 Revision 7
Alencon Systems LLC
330 Warminster Rd., Suite 380 | Hatboro, PA 19040 | USA
© 2009-2019 by Alencon Systems LLC

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This document is the confidential and proprietary information of Alencon Systems LLC. No part of
this document may be photocopied, reproduced, stored in a retrieval system, or transmitted in any
form or by any means whether electronic, mechanical, or otherwise without prior written
permission. Alencon Systems LLC reserves the right to change details in this publication without
notice.
Copyright Information: Any product names listed in this manual that are not registered
trademarks of Alencon Systems LLC and/or organization names mentioned may be trademarks
and/or registered trademarks of their respective companies.
Publication Number: PM006
Date and Revision
Revision ECO Date Author Approval Comment
0 8569 06/26/2019 Oleg Fishman PS Original Manual
1 8570 07/23/2019 Prahalad
Shivshankaran
MM Formatting, content and
installation information
2 8571 01/15/2020 Prahalad
Shivshankaran
ZD Adding more relevant
information to the manual
3 8572 3/13/2020 Zach Dereli PS Changes required for the
Certification
4 8573 Zach Dereli PS Changes required for the
Certification
5 8574 06/19/2020 Zach Dereli PS Changes required for the
Certification
6 8575 02/01/2022 Prahalad
Shivshankaran
PS Added Arc Detection
material into the manual.
7 8576 08/12/2022 Jacob Faber HF Updated for GARD V2.2

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Table of Contents
1 General Information ................................................................................................................ 4
1.1 Purpose .......................................................................................................................... 4
1.2 Glossary .......................................................................................................................... 4
1.3 Product Warranty ............................................................................................................ 5
1.4 Technical Support and Assistance .................................................................................. 6
1.5 Warnings, Cautions and Notes ....................................................................................... 6
1.6 Packing List .................................................................................................................... 7
1.7 Ordering Information ....................................................................................................... 7
2 IMPORTANT SAFETY INSTRUCTIONS ................................................................................ 8
3 Introduction ........................................................................................................................... 10
3.1 PV Safety ...................................................................................................................... 10
3.2 Grounding ..................................................................................................................... 10
3.3 Arc Faults ...................................................................................................................... 11
3.4 Serial arcing .................................................................................................................. 11
3.5 Parallel arcing ............................................................................................................... 11
4 Detect and Isolate Ground and Arc Faults in Your PV Array ................................................ 12
4.1 The Ground & Arc Rapid Disconnect Unit (GARD) ....................................................... 12
4.2 Unique Features & Benefits of the Alencon GARD ....................................................... 12
4.3 GARD Specifications .................................................................................................... 13
4.4 GARD Functionality and Operation ............................................................................... 14
Functionality .............................................................................................................. 14
Instructions when Ground Fault is Detected .............................................................. 14
Instructions when ARC Fault is Detected .................................................................. 15
Principle of Operation ................................................................................................ 15
4.5 GARD Hardware ........................................................................................................... 18
5 Firmware............................................................................................................................... 19
5.1 GARD State Machine.................................................................................................... 19
6 Communication ..................................................................................................................... 21
7 GARD Installation ................................................................................................................. 21
7.1 Understanding GARD Hardware ................................................................................... 21
7.2 Communication Ports.................................................................................................... 22
7.3 GARD Mounting ............................................................................................................ 23
7.4 Cable Terminations ....................................................................................................... 24
GARD + SPOT .......................................................................................................... 25
External Fusing and Disconnects .............................................................................. 26
8 Interfacing with the GARD .................................................................................................... 27
8.1 Unit Power .................................................................................................................... 27
8.2 Control System ............................................................................................................. 27
9 Further information ............................................................................................................... 27

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Table of Figures
FIGURE 1: THE GARD UNIT ............................................................................................................. 7
FIGURE 2: THE GRAPHIC ABOVE INDICATES THAT THE GARD IS A GROUNDING CONDUCTOR. .................. 8
FIGURE 3: THE GRAPHIC ABOVE INDICATES THAT THE GARD ACTS AS A DIRECT CURRENT SUPPLY. ........ 8
FIGURE 4: GROUNDING SCHEMES ................................................................................................... 10
FIGURE 5: ARCING ......................................................................................................................... 11
FIGURE 6: AFD PCB ..................................................................................................................... 16
FIGURE 7: SYSTEM NOISE SIGNATURE DURING AN ARC EVENT ............................................................ 17
FIGURE 8 : PV SPOT INVERTER SYSTEM NOISE SIGNATURE ....................................................... 17
FIGURE 9: GLID/AFD STATE MACHINE ............................................................................................ 20
FIGURE 10: EMERGENCY SWITCH ................................................................................................... 21
FIGURE 11: RESET SWITCH ............................................................................................................ 21
FIGURE 12: GARD BOTTOM VIEW ................................................................................................... 22
FIGURE 13: REMOTE E-STOP ........................................................................................................ 23
FIGURE 14: GARD PRIOR TO MOUNTING ON THE UNISTRUT .............................................................. 24
FIGURE 15: AMPHENOL TERMINATIONS ON GARD ........................................................................... 25
FIGURE 16: GARD TO SPOT CONNECTOR ...................................................................................... 26

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1 General Information
All efforts have been made to ensure the accuracy of material provided in this document at the
time of release. Items are subject to continuous development and improvements. All
specifications and descriptions are subject to change without notice.
1.1 Purpose
This manual provides information about installing, operating, maintaining, and troubleshooting the
Alencon’s Ground Rapid Disconnect Unit.
Who Should Read this Manual?
This manual should be read by anyone who needs to:
- Understand the product
- Plan the installation
- Install the product
- Commission the product
- Operate the product
- Maintain the product,
1.2 Glossary
Word(s)/Acronyms
Definition
GARD
Ground Rapid Disconnect
BOSS
Bi
-
directional Optimizer for Storage Systems
SPOT
String Power Optimizer and Transmitter
ACE Alencon Communication Environment – a communication system
containing hardware and software elements provided by Alencon to
control power conversion equipment
PODD Site / HUB Alencon Communication, Monitoring and Control Software
AFD Arc Fault Detector

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1.3 Product Warranty
Alencon Systems warrants to you, the original purchaser, that each of its products will be free from
defects in materials and workmanship for three years from the date of purchase. Extended
warranty of up to 10 years are also available for purchase.
This warranty does not apply to any products which have been repaired or altered by persons
other than repair personnel authorized by Alencon System, or which have been subject to misuse,
abuse, accident or improper installation. This warranty does not cover the repair or replacement
of any goods which fail as a result of damage in transit, misuse, neglect, accident, Act of God,
abuse, improper handling, misapplication, modification, improper storage, excessive stress, faulty
or improper installation, testing or repair, negligent maintenance or failure to comply with the
written instructions for installation, testing, use or maintenance (if any) provided by Alencon
Systems. Alencon Systems assumes no liability under the terms of this warranty as a consequence
of such events.
Because of Alencon Systems’ high quality-control standards and rigorous testing, most of our
customers never need to use our warranty service. If an Alencon Systems product is defective, it
will be repaired or replaced at no charge during the warranty period. For out-of-warranty repairs,
you will be billed according to the cost of replacement materials, service time and freight. Please
consult Alencon Systems for more details. If you think you have a defective product, follow these
steps:
1. Collect all the information about the problem encountered. (For example, issues you are
encountering in your PV array or battery system) Note anything abnormal when the problem
occurs.
2. Call Alencon Systems or your licensed Alencon Systems dealer and describe the problem.
Please have your manual, product, and any helpful information readily available.
3. If your product is diagnosed as defective, obtain an RMA (return merchandise authorization)
number from your Alencon Systems. This allows us to process your return more quickly.
4. Carefully pack the defective product (preferably in the original packaging material it was
shipped in), a fully-completed Repair and Replacement Order Card and a photocopy proof
of purchase date (such as your sales receipt) in a shippable container. A product returned
without proof of the purchase date is not eligible for warranty service.
5. Write the RMA number

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1.4 Technical Support and Assistance
1. Visit the Alencon Systems web site at www.alenconsystems.com where you can find the
latest information about the product.
2. Contact your distributor, sales representative, or Alencon Systems' customer service center
for technical support if you need additional assistance. Please have the following
information ready before you call:
– Product name, LIN and serial number (see section 6.5 for more information the location
of the LIN and serial number)
– Description of your peripheral attachments including fusing and cables
1.5 Warnings, Cautions and Notes
Warning! Warnings indicate conditions, which if not observed, can cause
personal injury!
Caution! Cautions are included to help you avoid damaging hardware or
losing data.
Note! Notes provide optional additional information.

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1.6 Packing List
Before installation, please ensure the following items have been shipped:
 Correct # of GARD Units specified for your plant with appropriate mounting hardware
Figure 1: The GARD Unit
1.7 Ordering Information
Model Number Description
Model Number Description
GARD–1000–V2.2 Ground Rapid Disconnect Unit. 4 INPUT/OUTPUT

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2 IMPORTANT SAFETY INSTRUCTIONS
WARNING! SAVE THESE INSTRUCTIONS– This manual contains important
instructions for use with the GARD that shall be followed during
installation and maintenance of these devices.
Figure 2: The graphic above indicates that the GARD is a grounding conductor.
Figure 3: The graphic above indicates that the GARD acts as a direct current supply.
Installation of this equipment must be performed by an authorized electrician in accordance
with the local and NEC ANSI/NFPA 70 and OSHA requirements. Installation shall be in
accordance with the Canadian Electrical Code, Part I when installed in Canada.
1. Before installing and using the GARD, read all instructions presented in this manual and the
cautionary markings shown on the GARD's enclosure.
2. The GARD contains no user-serviceable parts. For service and maintenance, the GARD
should be returned to Alencon Systems LLC or a certified Alencon Systems service center.
3. During operation, hazardous voltages and currents may be present. Only authorized and
qualified personnel should perform servicing/installation.
4. The metallic enclosure surface may become hot during certain operation circumstances.
5. Exposed PV strings to sunlight represent a shock hazard at the PV wires and exposed
terminals. Cover the PV modules with dark material when performing the installation in order
to reduce the risk of shock during the process. Test any wire or terminal for the voltage before
touching them.
6. Use only accessories recommended or approved by the manufacturer.

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7. Ensure that wiring is in good conditions and that all wiring is sized accordingly. Ignoring to do
so may result in a risk of fire.
8. PV modules produce electrical energy when exposed to light and thus can create an electrical
shock hazard. Wiring of the PV modules should only be performed by qualified personnel.
9. Always have GARD manual in hand.
WARNING! GARD is NOT a field serviceable product. Please contact
Alencon Systems for any issues with the product.

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3 Introduction
3.1 PV Safety
As with any electrical appliance, solar panels can be at risk to certain electrical damages and
dangers, such as solar panel fires and power surges. Luckily, there are plenty of measures in
place to ensure safe PV operation. This document provides a brief on the safety issues often seen
on PV systems and Alencon’s preventive approach to safe operation through the Ground & Arc
Rapid Disconnect unit – the GARD.
3.2 Grounding
All bodies including equipment frames and people in contact with Earth are charged to Earth
(ground) potential. Therefore, touching grounded equipment frames is safe.
Electrical sources like solar panels or electrical batteries generate voltage or difference of electrical
potentials between two terminals. When the terminals are connected to a conductive load, the
current begins to flow from the source to the load thereby generating power.
Figure 4: Grounding schemes
A ground fault is an inadvertent contact between an energized conductor and ground or equipment
frame, thereby providing an alternative pathway for the current to “leak” to ground. The return
path of the fault current is through the grounding system and any personnel or equipment that
becomes part of that system. Ground faults are frequently the result of insulation breakdown -
damp, wet, and dusty environments expose the grounding system to degradation of insulation and
increase the potential for hazards to develop.
The common grounding schemes found in a PV system are –
 Negatively Grounded PV
 Positively Grounded PV
 Ungrounded/Floating System
Either the positive or negative terminal of the source/load system can be connected to ground
potential. In this case the voltage on the second source terminal is referenced to ground or to the
equipment frame and defines the break down insulation strength.

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Alternatively, any point on the load can be grounded, establishing the positive and negative
potentials to ground. Finally, no point in an electrical system is grounded. In this case the positive
and negative potentials are undefined and considered “floating”. This network is used in very
sensitive applications like, for example, high voltage Lithium Ion batteries where ground leak
current can result in an explosion.
Alencon’s GARD is designed to detect leakage currents for grounded systems as shown in
Figure 4 by measuring the current difference in positive and negative terminals. Thus, the GARD
is UL listed to detect grounds faults in either positively or negatively grounded systems. The
GARD, by default, will negatively ground the system in front of the SPOT. Should you wish to
positively ground the system, this should be indicated prior to order. As the GARD is designed
for use with the SPOT, the grounding of the PV array will appear as floating on the output of the
SPOT since the SPOT is galvanically isolated.
3.3 Arc Faults
PV systems are subject to arcing of electrical wires. There are two types of arc faults that can
occur in a PV system:
Figure 5: Arcing
3.4 Serial arcing
This type of arcing happens inside the wire, when a conductor is broken but the insulation is still
intact. In such cases, the wire is still intermittently conducting trough the arc. Serial arcs produce
extreme local heat and can cause wire insulation to catch fire. The GARD has been designed to
detect serial arcing only.
3.5 Parallel arcing
This type of acing happens between a wire and exposed ground potential when the wire insulation
is compromised. Alternatively, the arc can strike between positive and negative wires if insulation
on both is damaged. The GARD has not been designed to detect parallel arcing.

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4 Detect and Isolate Ground and Arc Faults in Your PV Array
4.1 The Ground & Arc Rapid Disconnect Unit (GARD)
Alencon’s Ground and Rapid Disconnect unit, the GARD, is a unique solution for detecting harmful
ground and arc faults in your PV array at the string level. When detecting these faults, the GARD
automatically disconnects the faulty string. The GARD communicates with the customer’s SCADA
system via a MODBUS RTU communication link.
The GARD also offers the ability to rapidly and safely disconnect PV strings with either a local or
global E-STOP switch or via remote MODBUS commands. The GARD can be deployed as a
standalone device or in conjunction with Alencon’s String Power Optimizer and Transmitter – the
SPOT. Additionally, it can be used with or without remote communications.
The GARD can be installed in new PV systems or as a retrofit to existing solar plants.
4.2 Unique Features & Benefits of the Alencon GARD
 Detect and isolate potentially dangerous ground leakages and arc flashes at the string level
 Quickly turn off faulted strings
 Reduce O&M costs by determining precisely where faults are occurring in a PV array
 Maintain power production during maintenance by not having to shut down entire combiners
or arrays when repairing electrical faults
 Remote Control via an external E-STOP and Modbus Commands

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4.3 GARD Specifications
Overall Device Capabilities
Fault Detection and Interruption Combined Ground and ARC fault detector and
interrupter/disconnect for PV strings
Max Voltage Rating Per
Input (Voc)
1000 VDC
Operating Voltage Range 200 – 1000 VDC
Max Current Rating Per Input
25A
Short Circuit Current Per Input (Isc)
30A
Number of Individual Inputs 4
Communication Modbus TCP via Alencon Communications
Environment (ACE)
Fault Detection
and Disconnect Level
Faults are detected per input, i.e. PV string level
Fault Latch Yes
Disconnect
Yes
Reset Yes
Fault/Status indicators
Yes
Ground Fault Detector Capabilities
Common grounding Negative / Positive
Ground fault current trip
levels
Configurable from 500 mA to 1 A
Overvoltage Class OV II
ARC Fault Detector Capabilities
Insulation > 3000V
Self Input Test
Yes
ARC Detect Output
Yes
Photovoltaic DC Arc – Fault Circuit –
Protection
Type 1
Power Supply
Internal On Board
+24 V
Indicators
Power ON
Red
LED
Channel status (4)
Green
– Relays Closed
Red
– Relays disconnected
Controls
Stop
Local E
-
STOP, Global E
-
STOP, Modbus
command
Reset Local Reset, Modbus command
Standards & Compliance
Certifications UL1741, CSA C22.2#107.1 (Ground Fault),
UL1699B (Arc Fault)
Environmental
Storage Temperature
-
40°C to 60°C
Environmental Rating NEMA 3R & IP 36
Cooling
Convection
Humidity
0
–
95 %
Operating Ambient Temp. -30°C to 50°C
Pollution Degree
PD III
Physical Characteristics
Size (H x W x D)
.46 M × .37 M × .17 M
Weight
10.5 kg

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4.4 GARD Functionality and Operation
Functionality
The SPOT or any upstream equipment is connected to the PV System via the GARD. The
communication with GFDI/AFD is carried out via MODBUS.
The GFDI provide ground and arc fault protection features to the existing SPOTs. The GARD
generates its own control voltages. A microcontroller monitors the currents and voltages in all four
PV channels and controls and monitors the AFD module. Self-tests on the GFDI and AFD are
performed automatically every day.
In the event of a fault, the faulty channel is disconnected preventing ground leakages and arc
flashes on the commensurate input PV wires. Local indicators report the status of the GARD. A
remote monitoring facility is available via MODBUS. The operator can enforce the disconnection
manually by using an external switch (E-STOP) or remotely by sending MODBUS commands.
After the system is safely shutdown and the fault cleared, the GARD can be manually reset using
the reset push button available locally on the GARD or via a Modbus Reset command.
Instructions when Ground Fault is Detected
In the event of a ground fault, the faulty channel is disconnected preventing ground currents from
flowing. Local indicators report the status of the GARD. A remote monitoring facility is available
via MODBUS. Follow the suggested actions below;
1. When a ground fault is indicated the corresponding channel will trip and indicate a ground
fault. The ground current will be interrupted by the GARD. When the unit is tripped the LED
for the tripped channel on the GARD will turn RED. The status of the GARD can be
monitored on the HUB user interface. Refer to the HUB manual for more information.
2. When a ground fault is indicated normally grounded conductors may be ungrounded and
energized or normally ungrounded conductors may be grounded.
3. The ground fault will be on the channel that tripped due to ground fault.
4. Press E-Stop button to disconnect all other channels.
5. Check the input and output wires of the tripped channel to make sure there is no current
flowing.
6. After ensuring that there is no current flowing through the tripped GARD channel,
disconnect the input and the output wires.
7. Once the tripped channel is safely disconnected, reset the GARD by disengaging the E-
STOP button and pushing the Reset switch. The GARD can also be reset using the HUB
user interface.
8. Disconnected PV strings must be inspected by the authorized maintenance personnel.
9. Once the faulty string(s) are restored they can be reconnected back to the GARD channel.

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Instructions when ARC Fault is Detected
In the event of an arc fault, the faulty channel is disconnected and isolated preventing arc flashes.
Local indicators report the status of the GARD. A remote monitoring facility is available via
MODBUS. Follow the suggested actions below;
1. When an arc fault is detected all channels will be disconnected with the GARD status
indicators OFF and the status telemetry reading”ARC Fault Detected”.
2. After an arcing even, the GARD transitions to the “self-test” state and sequenctially cycles
power through individual channels A,B,C & D for 150 seconds each.
a. During the 150 seconds, if an arc is detected, the channel is disconnected and a flag
is raised on the Alencon HMI.
3. Faulted channels will be disconnected with the status indicators glowing RED while
unfaulted channels will be re-energized with indicators glowing green.
4. Alencon HMI will update the status and indicate faulted channels to the user.
5. If servicing is to be completed, press the E-Stop button to disconnect all other channels.
6. Check the input and output wires of the tripped channel to make sure there is no current
flowing.
7. After ensuring that there is no current flowing through the tripped GARD channel,
disconnect the input and the output wires.
8. Once the tripped channel is safely disconnected, reset the GARD by disengaging the E-
STOP button and pushing the Reset switch. The GARD can also be reset using the HUB
user interface.
9. Disconnected PV strings must be inspected by the authorized maintenance personnel.
10. Once the faulty string(s) are restored they can be reconnected back to the GARD channel.
Principle of Operation
4.4.4.1 Manual Operation
The GARD operates autonomoously. The connected input PV strings power up the GARD. The
GARD automatically performs a self-test of the GFDI and AFD before transitioning to normal
operation i.e. RUN. If no faults are detected, the channel LED’s (A, B, C, D) turn GREEN. If a fault
is detected on one of the channels, the indicator light on this channel turns RED.
The reason for a fault should be investigated and the fault should be repaired. Once a fault is
cleared, the red indicator may be cleared by depressing the RESET pushbutton.
4.4.4.2 Remote Monitoring and Control
The GARD is a very intelligent device. The software controls operating as a State Machine is
described in sections below. The states and statuses are communicated via Modbus RTU as
described in section 6.

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4.4.4.3 GFDI Principle
GFDI monitors the ground leak current in each of the GARD’s four channels. The GFDI measures
the input current on the PV positive and negative terminals and compares the values. If the current
difference exceeds a preset magnitude, the GFDI will disconnect the faulty channel both on the
positive and negative terminals. The FAULT flag is recorded into the GARD’s non-volatile memory
and the channel indicator turns from GREEN to RED. Faults can be cleared only by the operator
either by activating the RESET button on the GFDI face plate or by sending a RESET command
via MODBUS RTU. GFDI can be configured to detect a ground leak either for negatively grounded,
positively grounded or floating PV systems.
4.4.4.4 Arc Detection
The arc fault detector has been designed to work in conjunction with Alencon’s ground fault
detector and interrupter. The board has been designed and developed to detect an arc and provide
an interrupting signal to theground fault PCB. If an ARC signal is generated by the detector, the
GARD relays turn-off interrupting the current, thereby disconnecting the string.
Figure 6: AFD PCB
Arc fault detection is based on the arc noise signature analysis. The noise floor spectrum is not a
fixed waveform but a function of the power electronic equipment in-line, the operating conditions
and current transients. Detection schemes must be capable of handling the various peaks without
false tripping.

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Figure 7: System noise signature during an arc event
Figure 8 : PV SPOT Inverter system noise signature
During the operation of a PV system, the noise floor fluctuates depending on operating conditions,
transient’s etc. Alencon’s AFD is conctantly monitoring the noise floor for deviations in spectrum
magnitude. During a sustained arc event, the system noise signature rises in magnitude. The
differential change in magnitude is observed, recorded and displayed and a signal is sent to the
microprocessor to throw an arc fault flag.

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4.5 GARD Hardware
Internally, the GARD is implemented as a single PCB motherboard and one daughter PCB.
The motherboard provides the following functions:
 Controls
 Ground Leak/Fault Detection
 Arc Detection Board
 PV Disconnect upon fault
 Channel Status
The Motherboard houses:
 Auxiliary Power Supply
 8 DC Current Sensors: 2 per channel
 8 High Voltage Relays: 2 per channel
 Microprocessor Controls
 Self-Test, Pre-\Circuits
 AFD Sensor

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5 Firmware
All of the GARD’s control tasks are executed by the firmware stored in the microcomputer memory
mounted on the GARD’s main PCB. The program is constructed as a “State Machine”.
5.1 GARD State Machine
The GARD’s “State Machine” contains seven main states. The control transition from state to
state is shown in Figure 9.
 INITIALIZE: Upon power up, or receiving a SHUTDOWN, RESET, CLEAR_FLAGS or
TESTMODE command, the GLID/AFD enters the INITIALIZE state. In the INITIALIZE state,
the MCU resets and checks for the fault flags. If the flags SHUTDOWN or TESTMODE are
not set, the microprocessor proceeds into the STANDBY state.
 STANDBY: In the STANDBY state, the microprocessor checks that the control voltages
and all the sensors are in operating range and then proceeds into a SELF-TEST state.
 SELF-TEST: In the SELF-TEST state, the microprocessor performs a set of self-tests that
essentially check the quality of the GARD sensors i.e. current sensor.
CT Check – GARD injects a current into the circuit that flows through the negative current
sensor. This difference should simulate a current fault. If any of the channels fail to detect
the “simulated fault” they will be disconnected and a fault flag will be recorded in the
GARD’s non-volatile memory (NVM). If at least one channel is found to be good the
microprocessor proceeds into PRECHARGE state for that commensurate channel.
AFD_self_test – A sample arc signature is generated during self-test and the AFD board
reacts to the sample signature and a flag is generated. This is a self-evalution that must
pass prior to the relays closing.
 PRECHARGE: In the PRECHARGE state, the GARD pre-charges the capacitors available
on the output for a dedicated time period defined by the configuration file. In this state, the
relays on the negative terminal are closed, while the open contacts are bypassed by a “soft-
start” resistor. This feature preserves the life of relay contacts. Once the load capacitors
are charged, the relay on the positive terminal is closed. When the PRECHARGE process
is complete on all four channels the microprocessor proceeds into RUN state.
 RUN: The RUN state is the main state of the GLID/AFD. In RUN state the microcontroller
is looking for a ground leak fault.
 Ground leak: The leak-locator hardware on the board helps indetifying groundfault before
the relay contacts close.