HT Italia COMBI521 User manual

Copyright HT ITALIA 2021 Release EN 1.00 - 19/07/2021
COMBI521
User manual

COMBI521
EN - 2
TABLE OF CONTENTS
1.PRECAUTIONS AND SAFETY MEASURES ...............................................................4
1.1.Preliminary instructions ..................................................................................................... 4
1.2.During use......................................................................................................................... 5
1.3.After use............................................................................................................................ 5
1.4.Definition of measurement (overvoltage) category............................................................ 5
2.GENERAL DESCRIPTION ...........................................................................................6
2.1.Instrument functions.......................................................................................................... 6
3.PREPARATION FOR USE ...........................................................................................7
3.1.Initial checks...................................................................................................................... 7
3.2.Instrument power supply ................................................................................................... 7
3.3.Storage.............................................................................................................................. 7
4.NOMENCLATURE........................................................................................................8
4.1.Instrument description....................................................................................................... 8
4.2.Description of measuring leads......................................................................................... 8
4.3.Keyboard description......................................................................................................... 9
4.4.Display description ............................................................................................................ 9
4.5.Initial screen ...................................................................................................................... 9
5.GENERAL MENU.......................................................................................................10
5.1.SET – Instrument settings............................................................................................... 10
5.1.1.Language ............................................................................................................................... 10
5.1.2.Country................................................................................................................................... 11
5.1.3.Electrical system .................................................................................................................... 11
5.1.4.General settings..................................................................................................................... 12
5.1.5.Auto Start feature................................................................................................................... 12
5.1.6.Date and time......................................................................................................................... 12
5.1.7.Information ............................................................................................................................. 12
6.OPERATING INSTRUCTIONS...................................................................................13
6.1.AUTO: Automatic test sequence (Ra , RCD, M)......................................................... 13
6.1.1.Anomalous situations............................................................................................................. 20
6.2.DMM: Digital multimeter function .................................................................................... 21
6.3.RPE: Continuity of protective conductors........................................................................ 23
6.3.1.TMR mode ............................................................................................................................. 25
6.3.2.> < mode ............................................................................................................................. 26
6.3.3.Anomalous situations............................................................................................................. 27
6.4.Lo: Continuity of protective conductors with 10A.......................................................... 28
6.4.1.Anomalous situations............................................................................................................. 30
6.5.M: Measurement of insulation resistance..................................................................... 31
6.5.1.TMR mode ............................................................................................................................. 35
6.5.2.AUTO mode ........................................................................................................................... 36
6.5.3.Anomalous situations............................................................................................................. 37
6.6.RCD: Test on differential switches .................................................................................. 39
6.6.1.AUTO mode ........................................................................................................................... 42
6.6.2.AUTO mode ....................................................................................................................... 43
6.6.3.x½, x1, x5 modes................................................................................................................... 44
6.6.4.mode ................................................................................................................................. 45
6.6.5.Anomalous situations............................................................................................................. 46
6.7.LOOP: Line/Loop impedance and overall earth resistance............................................. 49
6.7.1.Test types............................................................................................................................... 52
6.7.2.Test cable calibration (ZEROLOOP) ..................................................................................... 54
6.7.3.STD Mode – Generic test ...................................................................................................... 56
6.7.4.Br.Cap mode – Verification of the breaking capacity of protection devices .......................... 58
6.7.5.TripT - Verification of protection coordination........................................................................ 60
6.7.6.Ra 2-wire test - Verification of protection against indirect contacts................................... 62
6.7.7.Ra 3-wire test - Verification of protection against indirect contacts................................... 64
6.7.8.Verification of protection against indirect contacts (IT systems) ........................................... 66
6.7.9.Verification of protection against indirect contacts (TT systems) .......................................... 68

COMBI521
EN - 3
6.7.10.Verification of protection against indirect contacts (TN systems).......................................... 70
6.7.11.Anomalous situations............................................................................................................. 72
6.8.LoZ: Line/Loop impedance with high resolution.............................................................. 75
6.9.1,2,3: Phase sequence and phase concordance test ..................................................... 76
6.9.1.Anomalous situations............................................................................................................. 79
6.10.LEAK: Leakage current measurement ............................................................................ 80
6.11AUX: Measure environmental parameters with external probes ..................................... 82
6.10.V%: Voltage drop of mainS........................................................................................... 84
6.10.1.Anomalous situations............................................................................................................. 87
6.11PQA: Measuring mains parameters in single-phase systems......................................... 90
6.11EVSE: Safety checks on recharging stations for electric cars......................................... 92
7.STORING RESULTS................................................................................................112
7.1.Saving measures........................................................................................................... 112
7.2.Recall of data to display and memory deletion.............................................................. 113
8.CONNECTING THE INSTRUMENT TO THE PC.....................................................114
9.MAINTENANCE........................................................................................................115
9.1.General information....................................................................................................... 115
9.2.Replacement of the batteries ........................................................................................ 115
9.3.Cleaning the instrument ................................................................................................ 115
9.4.End of life ...................................................................................................................... 115
10.TECHNICAL SPECIFICATIONS...............................................................................116
10.1.Technical characteristics............................................................................................... 116
10.2.Reference guidelines..................................................................................................... 122
10.3.General characteristics.................................................................................................. 122
10.4.Environment .................................................................................................................. 122
10.4.1.Environmental conditions for use......................................................................................... 122
10.5.Accessories................................................................................................................... 122
11.SERVICE..................................................................................................................123
11.1.Warranty conditions....................................................................................................... 123
11.2.Service .......................................................................................................................... 123
12.THEORETICAL APPENDIXES.................................................................................124
12.1.Continuity of protective conductors ............................................................................... 124
12.2.Insulation resistance...................................................................................................... 125
12.2.1.Measurement of polarization index (PI)............................................................................... 126
12.2.2.Dielectric Absorption Ratio (DAR) ....................................................................................... 126
12.3.Checking circuit separation ........................................................................................... 127
12.4.Test on differential switches (RCD)............................................................................... 129
12.5.VerifICATION of the breaking capacity of protection devices ....................................... 130
12.6.Verify of protection against indirect contacts in TN systems......................................... 131
12.7.Ra test in TN systems................................................................................................. 133
12.8.Verify of protection against indirect contacts in TT systems ......................................... 134
12.9.Verify of protection against indirect contacts in IT systems........................................... 135
12.10.Verify of protection coordination L-L, L-N and L-PE...................................................... 136
12.11.Verifiy of voltage drop on MAINS .................................................................................. 138
12.12.Voltage and current Harmonics..................................................................................... 139
12.12.1.Presence of harmonics: causes........................................................................................... 140
12.12.2.Presence of harmonics: consequences............................................................................... 141
12.13.Calculation of powers and power factors ...................................................................... 142

COMBI521
EN - 4
1. PRECAUTIONS AND SAFETY MEASURES
The instrument has been designed in compliance with guidelines IEC/EN61557, BS7671
17th and 18th editions and IEC/EN61010, relevant to electronic measuring instruments.
Before and after carrying out the measurements, carefully observe the following
instructions:
Do not carry out any voltage or current measurement in humid environments.
Do not carry out any measurements in case gas, explosive materials or flammables are
present, or in dusty environments.
Avoid any contact with the circuit to be measured if no measurements are being carried
out.
Avoid contact with exposed metal parts, with unused measuring leads, etc.
Do not carry out any measurement in case you find anomalies in the instrument such
as deformations, breaks, substance leaks, absence of display on the screen, etc.
Pay special attention when measuring voltages higher than 25V in special
environments (such as construction sites, swimming pools, etc.) and higher than 50V in
normal environments, since a risk of electrical shock exists.
Only use original accessories.
The following symbols are used in this manual:
CAUTION: observe the instructions given in this manual; improper use could
damage the instrument, its components or create dangerous situations for the
operator
High voltage danger: electrical shock hazard
Double insulation
AC voltage or current
DC voltage or current
Connection to earth
The symbol indicates that the instrument must not be connected to systems with
phase-to-phase rated delta voltage higher than 415V
1.1. PRELIMINARY INSTRUCTIONS
This instrument has been designed for use in the environmental conditions specified in
§ 10.4.1. Do not use in different environmental conditions.
The instrument may be used for measuring and verifying the safety of electrical
systems. Do not use on systems exceeding the limit values specified in § 10.1
We recommend following the normal safety rules devised to protect the user against
dangerous currents and the instrument against incorrect use.
Only the accessories supplied with the instrument guarantee compliance with safety
standards. They must be in good conditions and be replaced with identical models,
when necessary.
Make sure the batteries are correctly installed.
Before connecting the test leads to the circuit being measured, check that the desired
function has been selected.

COMBI521
EN - 5
1.2. DURING USE
Please carefully read the following recommendations and instructions:
CAUTION
Failure to comply with the caution notes and/or instructions may damage
the instrument and/or its components or be a source of danger for the
operator.
Before changing function, disconnect the test leads from the circuit under test.
When the instrument is connected to the circuit under test, never touch any terminal,
even if unused.
Avoid measuring resistance if external voltages are present. Even if the instrument is
protected, excessive voltage could cause damage.
1.3. AFTER USE
When measurements are completed, turn off the instrument by pressing and holding the
ON/OFF key for some seconds. If the instrument is not to be used for a long time, remove
the batteries and follow the instructions given in § 3.3.
1.4. DEFINITION OF MEASUREMENT (OVERVOLTAGE) CATEGORY
Standard “IEC/EN61010-1: Safety requirements for electrical equipment for measurement,
control and laboratory use, Part 1: General requirements” defines what measurement
category, commonly called overvoltage category, is. § 6.7.4: Measured circuits, reads:
circuits are divided into the following measurement categories:
Measurement category IV is for measurements performed at the source of a low-
voltage installation.
Examples are electricity meters and measurements on primary overcurrent protection
devices and ripple control units.
Measurement category III is for measurements performed on installations inside
buildings.
Examples are measurements on distribution boards, circuit breakers, wiring, including
cables, bus-bars, junction boxes, switches, socket-outlets in fixed installation, and
equipment for industrial use and some other equipment, for example, stationary motors
with permanent connection to fixed installation.
Measurement category II is for measurements performed on circuits directly
connected to the low-voltage installation.
Examples are measurements on household appliances, portable tools and similar
equipment.
Measurement category I is for measurements performed on circuits not directly
connected to MAINS.
Examples are measurements on circuits not derived from MAINS, and specially
protected (internal) MAINS-derived circuits. In the latter case, transient stresses
are variable; for that reason, the standard requires that the transient withstand
capability of the equipment is made known to the user.

COMBI521
EN - 6
2. GENERAL DESCRIPTION
2.1. INSTRUMENT FUNCTIONS
The instrument can perform the following tests:
RPE Continuity test of earth, protective and equipotential conductors with
test current higher than 200mA and open-circuit voltage between 4V
and 24V.
MMeasurement of insulation resistance with continuous test voltage of
50V, 100V, 250V, 500V or 1000V DC.
LOOP Measurement of line/fault loop impedance P-N, P-P, P-E with
calculation of the prospective short-circuit current, overall earth
resistance without causing the RCD’s tripping (RA ), check of the
breaking capacity of magnetothermal protections (MCB) and fuses,
protection check in case of indirect contacts with 2-wire and 3-wire
connection
LoZ Measurement of line impedance/Loop P-N, P-P, P-E with calculation of
the prospective short-circuit current with high resolution (0.1m) (by
means of optional accessory IMP57)
ΔV% Measurement of percentage voltage drop on mains.
LoContinuity test of earth, protective and equipotential conductors with
test current higher than 10A (by means of optional accessory
EQUITEST)
RCD Test on molded-case standard, General and Selective RCDs of type A
() and AC ( ) and B ( ) of the following parameters: tripping time,
tripping current, contact voltage.
AUTO Automatic sequence measurements of RA , RCD, Mfunctions with 3-
wire connection.
1,2,3 Indication of phase sequence with 1-terminal method.
DMM Multimeter function for Phase-Neutral, Phase-Phase, Phase-PE voltage
and frequency measurements.
AUX Measurement of environmental parameters (illuminance with white light
source and LED source, air temperature, humidity) by means of
optional external probes and DC voltage signals
PQA Real time measurement of main parameters (powers, harmonics, power
factor/cos) in Single phase systems
LEAK Measurement of leakage current (by means of the optional accessory
HT96U)
EVSE Automatic sequence of safety tests on mode 2 and 3 electric car
charging stations (by means of optional accessory EV-TEST100)

COMBI521
EN - 7
3. PREPARATION FOR USE
3.1. INITIAL CHECKS
Before shipping, the instrument has been checked from an electric as well as a
mechanical point of view. All possible precautions have been taken so that the instrument
is delivered undamaged. However, we recommend checking it to detect any damage
possibly suffered during transport. In case anomalies are found, immediately contact the
Dealer. We also recommend checking that the packaging contains all the components. In
case of discrepancy, please contact the Dealer. In case the instrument should be returned,
please follow the instructions given in § 11.
3.2. INSTRUMENT POWER SUPPLY
The instrument is powered by 6x1.5V alkaline batteries of type AA LR06 supplied with the
instrument. The “ ” symbol indicates the charge level of the batteries. To replace the
batteries, refer to § 9.2.
The instrument is capable of keeping data stored even without batteries.
The instrument has an AutoPower OFF function (which can be deactivated) after 5
minutes’ idling.
3.3. STORAGE
In order to guarantee precise measurement, after a long storage time under extreme
environmental conditions, wait for the instrument to come back to normal condition (see §
10.4.1).

COMBI521
EN - 8
4. NOMENCLATURE
4.1. INSTRUMENT DESCRIPTION
CAPTION:
1. Inputs
2. LCD display
3. ,, , , SAVE/ENTER
keys
4. Compartment of the
connector for optical
cable/USB port C2006
5. GO/STOP key
6. HELP/ key
7. ESC/MENU key
8. ON/OFF key
Fig. 1: Description of the front part of the instrument
CAPTION:
1. Connector for remote switch
probe
2. B1, B3, B4 inputs
3. In1 input
Fig. 2: Description of the upper part of the instrument
CAUTION
The instrument checks voltage on PE by comparing the voltage at B4 input to
the ground potential induced on the instrument’s side through the user’s
hand. Therefore, in order to check voltage on PE, it is mandatory to hold
the instrument case on the left or on the right side.
4.2. DESCRIPTION OF MEASURING LEADS
CAPTION:
1. Hand protection
2. Safe area
Fig. 3: Description of measuring leads

COMBI521
EN - 9
4.3. KEYBOARD DESCRIPTION
The keyboard includes the following keys:
ON/OFF key to switch on/off the instrument
ESC key to exit the selected menu without confirming
MENU key to go back to the general menu at any time
keys to move the cursor through the different screens in order to
select the desired programming parameters
SAVE/ENTER key to save the selected setup parameters (SAVE) and to select the
desired function (ENTER) from the menu
GO key to start measurement
STOP key to stop measurement
HELP key to access the online help and display the possible connections between
the instrument and the system for each selected function
key (continuos pressure) to adjust the display backlight
4.4. DISPLAY DESCRIPTION
The display is a COG LCD module, 128x128 points. The first
line of the display indicates the type of active measurement,
the date/time and the battery charge indication.
RPE 15/10 – 18:04
R = - - - 
Itest = - - - mA
Measuring…
STD 2.000.12
MODE Lim
> <
4.5. INITIAL SCREEN
When switching on the instrument, the initial screen appears
for a few seconds. It shows:
The instrument model
The manufacturer
The serial number (SN:) of the instrument
The Firmware version of the two instrument's internal
microprocessors (FW and HW)
The date of instrument calibration (Calibration date:)
COMBI521
HT ITALIA
SN: 21100100
HW: 2.00
FW: 2.00
Calibration date:
15/06/2021
After a few seconds, the instrument switches to general menu screen.

COMBI521
EN - 10
5. GENERAL MENU
Pressing the MENU/ESC key in any condition of the instrument allows going back to the
general menu in which internal parameters may be set and the desired measuring function
may be selected.
MENU 15/10 – 18:04
AUTO :
Ra
, RCD, M 
DMM : Voltage/Freq.
RPE : Continuity
Lo  : 10A RPE.Test
M  : Insulation
RCD : Auto, Ramp, Man
LOOP : ZE/ZS Impedance

MENU 15/10 – 18:04
LoZ : High Res. Loop
1,2,3 : Phase Sequence
LEAK : Leakage
AUX : Environmental
 V% : Voltage drop
PQA : Power Analyser
EVSE : EVSE Safety Test.

MENU 15/10 – 18:04
SET : Settings
MEM : Data saved
PC : Data transfer

Upon selecting one of the listed measurements with the cursor and confirming with
ENTER, the instrument shows the desired measurement on the display.
5.1. SET – INSTRUMENT SETTINGS
Move the cursor to SET by means of the arrow keys (,)
and confirm with ENTER. Subsequently, the displays shows
the screen which allows accessing the various instrument
settings.
The settings will remain valid also after switching off the
instrument.
SET 15/10 – 18:04
Language
Country
Electrical system
General settings
Date and time
Information
5.1.1. Language
Move the cursor to Language by means of the arrow keys
(,) and confirm with ENTER. Subsequently, the display
shows the screen which allows setting the instrument
language.
Select the desired option by means of the arrow keys (,).
To store settings, press the ENTER key, to quit without
confirming the changes made, press the ESC key.
SET 15/10 – 18:04
English
Italiano
Español
Deutsch
Français
Portugues

COMBI521
EN - 11
5.1.2. Country
Move the cursor to Country by means of the arrow keys
(,) and confirm with ENTER. Subsequently, the display
shows the screen which allows selecting the country of
reference, which will influence the LOOP and Ra
measurements.
Select the desired option by means of the arrow keys (,).
To store settings, press the ENTER key, to quit without
confirming the changes made, press the ESC key.
SET 15/10 – 18:04
Europe
Extra Europe
Germany
UK
Norway
USA
Australia/New Zealand
5.1.3. Electrical system
Move the cursor to Electrical system by means of the arrow
keys (,) and confirm with ENTER. Subsequently, the
display shows the screen which allows setting the following
parameters:
Vnom Phase-Neutral or Phase-PE nominal voltage
(110V,115V,120V,127V,133V,220V,230V,240V) to be
used in the calculation of prospective short-circuit current
Frequency system frequency (50Hz, 60Hz)
System type of electric power supply system (TT, TN
or IT)
Contact Volt limit of contact voltage (25V, 50V)
I RCD type of trip-out RCD current visualization (Real,
Nom). With the “Nom” option, the instrument shows the
normalized value of trip-out current (referred to the
nominal current). Example: for RCD type A with
Idn=30mA, the actual value of normalized trip-out current
can be up to 30mA. With the “Real” option, the instrument
shows the actual value of trip-out current by considering
the coefficients indicated by guidelines IEC/EN61008 and
IEC/EN61009 (1.414 for RCD type A, 1 for RCD type AC,
2 for RCD type B). Example: for RCD type A with
Idn=30mA, the actual value of trip-out current can be up to
30mA * 1.414 = 42mA.
RCD/RCCB When selecting the “RCD” option, the
instrument performs the tripping time test with all
multipliers in normal conditions. When selecting the
“RCCB” option, only for 30mA devices, the instrument
performs the tripping time test with x5 multipliers with a
test current of 250mA (type AC) and 350mA (type A).
Isc Factor (only for Norway) possibility to select the
value of the ISC factor (0.01 ÷ 1.00) to be used in the
calculation of prospective short-circuit current.
Select the desired option by means of the arrow keys (,).
To store settings, press the ENTER key, to quit without
confirming the changes made, press the ESC key
SET 15/10 – 18:04
Vnom. :230V 
Frequency :50Hz 
System :

TN

Contact Volt :

5
0
V

I RCD :Nom. 
RCD/RCCB :RCD 
Isc Factor :0.75 

COMBI521
EN - 12
5.1.4. General settings
Move the cursor to General settings by means of the arrow
keys (,) and confirm with ENTER. Subsequently, the
display shows the screen which allows enabling/disabling the
auto power off function, the sound of the function keys and
the Auto Start (automatic start) function in the RCD and
LOOP functions (see § 5.1.5).
Select the desired option by means of the arrow keys (,)
and (, ). To store settings, press the ENTER key, to quit
without confirming the changes made, press the ESC key
SET 15/10 – 18:04
Auto Power Off :OFF 
Keys Beep :OFF 
AutoStart :

O
FF

(RCD/LOOP)
5.1.5. Auto Start feature
The AutoStart feature allows automatically performing the RCD and LOOP measurements.
In order to correctly use the AutoStart mode, it is NECESSARY to run the FIRST test
by pressing the GO/STOP key on the instrument or the START key on the remote
switch probe.
After completing the first test, as soon as the instrument detects a steady input voltage
within the allowed range, it runs the test automatically with no need to press the GO/STOP
key on the instrument or the START key on the remote switch probe.
5.1.6. Date and time
Move the cursor to Date and time by means of the arrow
keys (,) and confirm with ENTER. Subsequently, the
display shows the screen which allows setting the system
date/time. Select “Format” to set the European system
(“DD/MM/YY, hh:mm” EU format) or the American system
(“MM/DD/YY hh:mm” USA format).
Select the desired option by means of the arrow keys (,)
and (, ). To store settings, press the ENTER key, to quit
without confirming the changes made, press the ESC key.
SET 15/10 – 18:04
Format. :EU 
Year :19 
Month :

10

Day :

1
4

Hour :17. 
Minute :38 
5.1.7. Information
Move the cursor to Info by means of the arrow keys (,)
and confirm with ENTER. Subsequently, the display shows
the initial screen as indicated in the screen to the side.
Press the ESC key to return to the main menu.
SET 15/10 – 18:04
COMBI521
HT ITALIA
SN: 21100100
HW: 2.00
FW: 2.00
Calibration date:
15/06/2021

COMBI521
EN - 13
6. OPERATING INSTRUCTIONS
6.1. AUTO: AUTOMATIC TEST SEQUENCE (RA , RCD, M)
This function allows performing the following measurements in an automatic sequence:
Overall earth resistance without causing the RCD’s tripping (Ra )
Tripping current and tripping time of General RCDs type A ( ), AC ( ) or B ( )
Insulation resistance with test voltages 50, 100, 250, 500, 1000 VDC
CAUTION
Some combinations of test parameters could be unavailable in compliance with
the technical specifications of the instrument and the RCD tables (see § 10.1 –
empty cells of RCD tables mean unavailable situations)
CAUTION
Testing the RCD’s tripping time causes the RCD’s tripping. Therefore, check
that there are NO users or loads connected downstream of the RCD
being tested which could be damaged by a system downtime. Disconnect
all loads connected downstream of the RCD as they could produce leakage
currents further to those produced by the instrument, thus invalidating the
results of the test.
Fig. 4: Instrument connection through mains plug
Fig. 5: Instrument connection by means of single cables and remote switch probe

COMBI521
EN - 14
TN systems
1. Press the MENU key, move the cursor to AUTO in the
main menu by means of the arrow keys (,) and
confirm with ENTER. Subsequently the instrument
displays a screen similar to the one reported here to the
side.
Select “UK” as a country (see § 5.1.2), the options “TN”,
“25 or 50V”, “50Hz or 60Hz” and the reference voltage in
the general settings of the instrument (see § 5.1.3).
AUTO 15/10 – 18:04
TN >

<
Isc=--- A ZL-N=--- Ω
Ifc=--- A ZL-PE=---Ω
Trcd=---ms Ircd=---mA
FREQ=0.00Hz Ut=---V
VL-PE=0V VL-N=0V
30mA 500V 1.00M
In Type Vtest Lim
2. Use the , keys to select the parameter to be modified, and the , keys to
modify the parameter value:
InThe virtual key allows setting the nominal value of the RCD’s tripping
current, which may be: 6mA, 10mA, 30mA.
Type The virtual key enables the selection of the RCD type, which may be: AC
(), A () or B ( )
Vtest This key allows selecting the DC test voltage generated during
measurement. The following values are available: 50V, 100V, 250V, 500V, 1000V.
Lim This key allows the selection of the minimum limit threshold in order to
consider the insulation measurement correct. The following values are available:
0.05M, 0.10M, 0.23M, 0.25M, 0.50M, 1.00M, 100M.
CAUTION
Make sure to select the correct value when setting the RCD’s test current.
If setting a current higher than the nominal current of the device being
tested, the RCD would be tested at a current higher than the correct one,
thus facilitating a faster tripping of the switch.
The “ ” symbol indicates that the test cables or the plug cable have
already been calibrated in the LOOP section (see § 6.7.2). The AUTO
function takes this value as a reference.
3. Insert the green, blue and black connectors of the three-pin plug cable into the
corresponding inputs B1, B3 and B4 of the instrument. As an alternative, use the
single cables and apply the relevant alligator clips to the free ends of the cables. It is
also possible to use the remote switch probe by inserting its multipolar connector into
the input B1. Connect the plug, the alligator clips or the remote switch probe to the
electrical mains according to Fig. 4 or Fig. 5
4. Note the correct voltage values between L-N and L-PE as
shown in the screen to the side.
AUTO 15/10 – 18:04
TN >

<
Isc=--- A ZL-N=--- Ω
Ifc=--- A ZL-PE=---Ω
Trcd=---ms Ircd=---mA
FREQ=50.00Hz Ut=---V
VL-PE=231V VL-N=232V
30mA 500V 1.00M
In Type Vtest Lim

COMBI521
EN - 15
5. Press the GO/STOP key on the instrument or the START key on the remote switch
probe. The instrument will start the automatic test sequence.
CAUTION
If message “Measuring…” appears on the display, the instrument is
performing measurement. During this whole stage, do not disconnect the
test leads of the instrument from the mains.
6. The Ra test starts and the screen to the side appears on
the display. After approx. 20s, the Ra ends and the
values of ZL-N, Z
L-PE, ISCMin, IFCMin immediately appear on
the display.
In case of a positive result of all the tests sequentially
performed as Ra (ZL-N and Z
L-PE<199), the instrument
goes on with the test on the trip-out current and trip-out
time of the RCD.
AUTO 15/10 – 18:04
TN >

<
Isc=1437A ZL-N= 0.16Ω
Ifc=1277A ZL-PE=0.18Ω
Trcd=---ms Ircd=---mA
FREQ=50.00Hz Ut=---V
VL-PE=231V VL-N=232V
Measuring...
30mA 500V 1.00M
In Type Vtest Lim
7. The RCD test starts and the screen to the side appears
on the display. The trip-out current and the trip-out time
values appear on the display.
In case of a positive result of all the tests sequentially
performed during the RCD test (Trcd and Ircd
parameters) (see § 12.4), the instrument goes on with the
test on insulation resistance between L-N, L-PE and N-
PE conductors.
AUTO 15/10 – 18:04
TN >

<
Isc=1437A ZL-N= 0.16Ω
Ifc=1277A ZL-PE=0.18Ω
Trcd=25ms Ircd=27.0mA
FREQ=50.00Hz Ut=1.5V
VL-PE=231V VL-N=232V
Measuring...
30mA 500V 1.00M
In Type Vtest Lim
8. The insulation test starts and the screen to the side
appears on the display. The RL-N, RL-PE and RN-PE
values appear on the display.
In case of a positive result of all the tests sequentially
performed during the insulation test (insulation resistance
> minimum limit threshold), the instrument has completed
its tasks, shows the “OK” message and displays the
screen to the side.
Press (, ) in order to display the values of the second
available page.
AUTO 15/10 – 18:04
TN >

<
RL-N >999MVt= 523V
RL-PE >999MVt= 524V
RN-PE >999MVt=522V
FREQ=50.00Hz Ut=1.5V
VL-PE=0V VL-N=0V
OK 
30mA 500V 1.00M
In Type Vtest Lim

COMBI521
EN - 16
9. In case of a negative result of the Ra test (ZL-N and/or
ZL-PE >199), the auto test is automatically blocked, the
message “NOT OK” is shown and the screen to the side
is displayed.
AUTO 15/10 – 18:04
TN >

<
Isc=1437A ZL-N= 0.16Ω
Ifc=---A ZL-PE >199Ω
Trcd=---ms Ircd=---mA
FREQ=50.00Hz Ut=---V
VL-PE=231V VL-N=232V
NOT OK ...
30mA 500V 1.00M
In Type Vtest Lim
10. In case of a negative result of the RCD test (Trcd
>300ms or Ircd > 33.0mA), the auto test is automatically
blocked, the message “NOT OK” is shown and the screen
to the side is displayed.
AUTO 15/10 – 18:04
TN >

<
Isc=1437A ZL-N= 0.16Ω
Ifc=1277A ZL-PE=0.18Ω
Trcd=>300ms Ircd >33.0mA
FREQ=50.00Hz Ut=1.5V
VL-N=232V VL-PE=231V
NOT OK 
30mA 500V 1.00M
In Type Vtest Lim
11. In case of a negative result of the Insulation test
(insulation resistance < minimum limit threshold), the auto
test is automatically blocked, the message “NOT OK” is
shown and the screen to the side is displayed.
AUTO 15/10 – 18:04
TN >

<
RL-N >999MVt= 523V
RL-PE=0.03MVt= 57V
RN-PE >999MVt=522V
FREQ=50.00Hz Ut=1.5V
VL-PE=0V VL-N=0V
NOT OK 
30mA 500V 1.00M
In Type Vtest Lim
12.Press the SAVE key to store the test result in the instrument’s memory (see § 7.1) or
the ESC/MENU key to exit the screen without saving and go back to the main
measuring screen.

COMBI521
EN - 17
TT/IT systems
1. Press the MENU key, move the cursor to AUTO in the
main menu by means of the arrow keys (,) and
confirm with ENTER. Subsequently, the instrument
displays a screen similar to the one reported here to the
side.
Select “UK” as a country (see § 5.1.2), the options “TN”,
“25 or 50V”, “50Hz or 60Hz” and the reference voltage in
the general settings of the instrument (see § 5.1.3)
AUTO 15/10 – 18:04
TT >

<
RA=--- Ut=--- V
Trcd=---ms Ircd=---mA
FREQ=0.00Hz
VL-PE=0V VL-N=0V
30mA 500V 1.00M
In Type Vtest Lim
2. Use the , keys to select the parameter to be modified, and the , keys to
modify the parameter value.
InThe virtual key allows setting the nominal value of the RCD’s tripping
current, which may be: 6mA, 10mA, 30mA.
Type The virtual key enables the selection of the RCD type, which may be: AC
(), A () or B ( )
Vtest This key allows selecting the DC test voltage generated during
measurement. The following values are available: 50V, 100V, 250V, 500V, 1000V.
Lim This key allows the selection of the minimum limit threshold in order to
consider the insulation measurement correct. The following values are available:
0.05M, 0.10M, 0.23M, 0.25M, 0.50M, 1.00M, 100M.
CAUTION
Make sure to select the correct value when setting the RCD’s test current.
If setting a current higher than the nominal current of the device being
tested, the RCD would be tested at a current higher than the correct one,
thus facilitating a faster tripping of the switch.
The “ ” symbol indicates that the test cables or the plug cablehas
already been calibrated in the LOOP section (see § 6.7). The AUTO
function takes this value as a reference.
3. Insert the green, blue and black connectors of the three-pin plug cable into the
corresponding inputs B1, B3 and B4 of the instrument. As an alternative, use the
single cables and apply the relevant alligator clips to the free ends of the cables. It is
also possible to use the remote switch probe by inserting its multipolar connector into
the input B1. Connect the plug, the alligator clips or the remote switch probe to the
electrical mains according to Fig. 4 or Fig. 5.
4. Note the correct voltage values between L-N and L-PE as
shown in the screen to the side.
AUTO 15/10 – 18:04
TT >

<
RA=--- Ut=--- V
Trcd=---ms Ircd=---mA
FREQ=50.00Hz Ut=---V
VL-PE=231V VL-N=232V
30mA 500V 1.00M
In Type Vtest Lim
5. Press the GO/STOP key on the instrument or the START key on the remote switch
probe. The instrument will start the automatic test sequence.

COMBI521
EN - 18
CAUTION
If message “Measuring…” appears on the display, the instrument is
performing measurement. During this whole stage, do not disconnect the
test leads of the instrument from the mains.
6. The Ra test starts and the screen to the side appears on
the display. After approx. 20s, the Ra ends and ithe
values of RA (overall earth resistance) and Ut (contact
voltage) immediately appear on the display.
In case of a positive result of the Ra test (see § 12.8),
the instrument goes on with the test on the trip-out current
and trip-out time of the RCD.
AUTO 15/10 – 18:04
TT >

<
RA=48.8 Ut=1.5 V
Trcd=---ms Ircd=---mA
FREQ=50.00Hz
VL-PE=231V VL-N=232V
Measuring...
30mA 500V 1.00M
In Type Vtest Lim
7. The RCD test starts and the screen to the side appears
on the display. The trip-out current and the trip-out time
values appear on the display.
In case of a positive result of all the tests sequentially
performed during RCD test (Trcd and Ircd parameters)
(see § 12.4), the instrument goes on with the test on
insulation resistance between L-N, L-PE and N-PE
conductors.
AUTO 15/10 – 18:04
TT >

<
RA=48.8 Ut=1.5 V
Trcd=25ms Ircd=27.0mA
FREQ=50.00Hz
VL-PE=231V VL-N=232V
Measuring...
30mA 500V 1.00M
In Type Vtest Lim
8. The insulation test starts and the screen to the side
appears on the display. The RL-N, RL-PE and RN-PE
values appear on the display.
In case of a positive result of all the test sequentially
performed during insulation test (insulation resistance >
minimum limit threshold), the instrument has completed
its tasks, shows the “OK” message and displays the
screen to the side.
Press (, ) in order to display the values of the second
available page.
AUTO 15/10 – 18:04
TT >

<
RL-N >999MVt= 523V
RL-PE >999MVt= 524V
RN-PE >999MVt=522V
FREQ=50.00Hz
VL-PE=0V VL-N=0V
OK 
30mA 500V 1.00M
In Type Vtest Lim

COMBI521
EN - 19
9. In case of a negative result of the Ra test (see § 12.8),
the auto test is automatically blocked, the message “NOT
OK” is shown and the screen to the side is displayed.
AUTO 15/10 – 18:04
TT >

<
RA=1824 Ut=54.7 V
Trcd=---ms Ircd=---mA
FREQ=50.00Hz
VL-PE=231V VL-N=232V
NOT OK ...
30mA 500V 1.00M
In Type Vtest Lim
10. In case of a negative result of the RCD test (Trcd
>300ms or Ircd > 33.0mA), the auto test is automatically
blocked, the message “NOT OK” is shown and the screen
to the side is displayed.
AUTO 15/10 – 18:04
TT >

<
RA=48.8 Ut=1.5 V
Trcd=>300ms Ircd >33.0mA
FREQ=50.00Hz
VL-PE=231V VL-N=232V
NOT OK 
30mA 500V 1.00M
In Type Vtest Lim
11. In case of a negative result of the Insulation test
(insulation resistance < minimum limit threshold), the auto
test is automatically blocked, the message “NOT OK” is
shown and the screen to the side is displayed.
AUTO 15/10 – 18:04
TT >

<
RL-N >999MVt= 523V
RL-PE=0.03MVt= 57V
RN-PE >999MVt=522V
FREQ=50.00Hz Ut=1.5V
VL-PE=0V VL-N=0V
NOT OK 
30mA 500V 1.00M
In Type Vtest Lim
12.Press the SAVE key to store the test result in the instrument’s memory (see § 7.1) or
the ESC/MENU key to exit the screen without saving and go back to the main
measuring screen.

COMBI521
EN - 20
6.1.1. Anomalous situations
1. If the instrument detects a L-N or L-PE voltage higher
than the maximum limit (265V), it does not carry out the
test and displays a screen like the one to the side. Check
the connection of measuring cables.
AUTO 15/10 – 18:04
TN
Isc=--- A ZL-N=--- Ω
Ifc=--- A ZL-PE=---Ω
Trcd=---ms Ircd=---mA
FREQ=50.00Hz Ut=---V
VL-PE=270V VL-N=272V
Voltage > 265V
30mA 500V 1.00M
In Type Vtest Lim
2. If the instrument detects a L-N or L-PE voltage lower than
the minimum limit (100V), it does not carry out the test
and displays a screen like the one to the side. Check that
the system being tested is supplied.
AUTO 15/10 – 18:04
TN
Isc=--- A ZL-N=--- Ω
Ifc=--- A ZL-PE=---Ω
Trcd=---ms Ircd=---mA
FREQ=50.00Hz Ut=---V
VL-PE=15V VL-N=15V
Voltage < 100V
30mA 500V 1.00M
In Type Vtest Lim
3. If the instrument detects that the phase and neutral leads
are inverted, it does not carry out the test and a screen
similar to the one reported to the side is displayed. Rotate
the mains plug or check the connection of the measuring
cables.
AUTO 15/10 – 18:04
TN
Isc=--- A ZL-N=--- Ω
Ifc=--- A ZL-PE=---Ω
Trcd=---ms Ircd=---mA
FREQ=--- Hz Ut=---V
VL-PE=--- V VL-N=--- V
Exchange L-N
30mA 500V 1.00M
In Type Vtest Lim
4. If the instrument detects a dangerous voltage on PE
conductor, it does not carry out the test and displays a
screen like the one to the side.
AUTO 15/10 – 18:04
TN
Isc=--- A ZL-N=--- Ω
Ifc=--- A ZL-PE=---Ω
Trcd=---ms Ircd=---mA
FREQ=--- Hz Ut=---V
VL-PE=--- V VL-N=--- V
Voltage on PE
30mA 500V 1.00M
In Type Vtest Lim