KEWTECH
Distributor
Kewtech Corporation Limited
76 St. Catherine’s Grove
Lincoln LN5 8NA
www.kewtechcorp.com
92-1618
KEWTECH
04-03
KEWTECH
KT61 digital multi function tester
Instruction manual
Contents 1 Safe testing
1
2 Features
3
3 Specification
6
4 Continuity (resistance) tests
9
4.1
Instrument layout
9
4.2
Resistance of test leads
9
4.3
Continuity testing
5 Insulation tests
5.1
The nature of insulation resistance
10
11
11
5.1.2 Capacitive current
11
5.1.3 Conduction current
12
5.1.4 Surface leakage current
12
5.1.5 Total leakage current
13
5.2
Damage to voltage sensitive equipment
13
5.3
Preparation for measurement
14
5.4
Insulation resistance measurement
14
6 Loop Impedance tests
17
6.1
Voltage measurement
17
6.2
What is earth fault loop impedance?
17
6.3
Automatic over temperature cut out
17
6.4
The loop impedance test
17
6.5
Loop impedance at 3 phase equipment
19
7 RCD tests
21
7.1 Purpose of RCD Test
21
7.2 What does the RCD test really do
21
7.3 RCD testing
21
7.4 Testing RCD's used to provide supplementary protection
22
7.5 Testing time delayed RCD's
23
8 General
24
9 Battery replacement
24
10 Fuse replacement
25
11 Servicing
25
12 Case and strap assembly
27
Electricity is dangerous and can cause injury and death. Always 1 Safe Testing
treat it with the greatest of respect and care. If you are not quite
sure how to proceed, stop and take advice from a qualified person.
The symbol
on the instrument means that the user must refer to the
relevant section of this instruction manual for safe operation of the
instrument.
Pay particular attention to all WARNINGS and CAUTIONS in this
instruction manual. WARNING indicates warnings to avoid electric shock
and CAUTION indicates cautions to avoid damage to the instrument.
1 This instrument must only be used by a competent and trained person
and operated in strict accordance with the instructions. Kewtech will
not accept liability for any damage or injury caused by misuse or noncompliance with the instructions or with the safety procedures.
2 It is essential to read and to understand the safety rules contained in
the instructions. They must always be observed when using the
instrument.
3 This instrument is intended only for single phase operation at 230V AC
±10% phase to earth or phase to neutral operation, and then only for
loop and RCD testing. For use in the continuity testing and insulation
testing modes this instrument must be used ONLY on circuits
which are de-energised.
4 When conducting tests do not touch any exposed metalwork
associated with the installation. Such metalwork may become live for
the duration of the test.
5 Never open the instrument case (except for fuse and battery
replacement and in this case disconnect all leads first) because
dangerous voltages are present. Only fully trained and competent
electrical engineers should open the case. If a fault develops, return the
instrument to Kewtech for inspection and repair.
6 If the overheat symbol appears in the display disconnect the
instrument from the mains supply and allow to cool down.
7 For loop impedance tests to prevent unwanted tripping during loop
testing all residual current devices (RCDs) must be taken out of the
circuit and temporarily replaced with a suitably rated MCB unit. The
RCD must be replaced after the loop test is completed.
8 If abnormal conditions of any sort are noted (such as a faulty display,
unexpected readings, broken case, cracked test leads, etc) do not use
the tester and return it to Kewtech for repair.
1
Safe testing 9 For safety reasons only use accessories (test leads, probes, fuses,
cases, etc) designed to be used with this instrument and
recommended by Kewtech. The use of other accessories is prohibited
as they are unlikely to have the correct safety features.
10 When testing, always be sure to keep your fingers behind the safety
barriers on the test leads.
11 During testing it is possible that there may be a momentary
degradation of the reading due to the presence of excessive transients
or discharges on the electrical system under test. Should this be
observed, the test must be repeated to obtain a correct reading. If in
doubt, contact Kewtech.
12 The sliding shutter on the back of the instrument is a safety device. The
instrument should not be used if it is damaged or impaired in any way,
but returned to Kewtech for attention.
13 Do not operate the function selector whilst the instrument is
connected to a circuit. If, for example, the instrument has just
completed a continuity test and an insulation test is to follow,
disconnect the test leads from the circuit before moving the selector
switch.
14 Do not rotate function dial when test button is depressed. If the
function switch is inadvertently moved to a new function when the test
button is depressed or in lock-down position the test in progress will
be halted. To reset, release test button and press again to restart
testing on new function.
15 Use a damp cloth and detergent for cleaning the instrument. Do not
use abrasives or solvents.
16 Before using the instrument, please install the batteries in
accordance with ‘Battery replacement’ of page 24.
With no batteries installed, the functions of the instrument will not
work.
2
2 Features
Connector
Live circuit LED
Wiring check LED
LCD display
RCD rated tripping
current switch
Test button
Function switch
Test Lead with IEC Connector
LCD display
Test Lead for Continuity
and Insulation Testing
Fig. 1
3
Features The KT61 Multi-Function tester performs five functions in one instrument.
1
Continuity tester
2
Insulation resistance tester
3
Loop impedance tester
4
RCD tester
5
Mains voltage warning when operating the loop impedance and
RCD mode.
The tester is designed to Safety Standard IEC 1010-1/BS EN 61010-1
CAT III(300V).
Dust proof construction in conformance with IP50, IEC529
The instrument is supplied with:
2 A lead for LOOP/RCD testing at socket outlets.
3 A lead for insulation and continuity testing.
In the insulation resistance testing mode the instrument provides a rated
current of1mA as required in IEC 61557-2/EN 61557-2 1997.
In the continuity testing mode the instrument provides a short circuit
current of 200mA as required in IEC 61557-2/EN 61557-2 1997.
Continuity and insulation resistance functions have the following features:
Live circuit warning
A colour coded LED warns if the circuit
under test is live.
Auto discharge
Electric charges stored in capacitive circuits
are discharged automatically after testing by
releasing the test button.
Test current
Warning Beeper
Warns when the test current exceeds
200mA (IEC 61557-4) during continuity
measurement.
Loop impedance and RCD testing functions have the following features:
4
Voltage level
In the loop impedance mode, supply voltage is
displayed when the instrument is connected
to the supply until the test button is pressed.
Wiring check
Three LEDs indicate if the wiring of the circuit
under test is correct.
Over temperature
protection
Detects overheating of the internal resistor
(used for loop and RCD tests) and of the
current control MOS FET (used for RCD
tests) displaying a warning symbol and
automatically halting further measurements.
Features
Phase angle selector
The test can be selected from either the
positive (0˚) or from the negative (180˚) halfcycle of voltage. This will prevent tripping of
some polarised RCDs when loop testing and
may give a more accurate reading when
testing RCDs.
Auto data hold
Holds the displayed reading for a time after
the test is complete.
Auto power off
Automatically switches the instrument off
after a period of approximately one minute.
V-NE Monitoring
Circuit
Automatically aborts measurement when the
N-E voltage rises to 50V or greater on RCD
ranges.
Optional Accessory
ACC 016E distribution board or lighting
circuit test lead for LOOP/RCD testing.
5
Specification
Measurement Specification
Continuity (to IEC61557-4)
Open Circuit
Voltage (DC)
Short Circuit
Current
Greater than
200mA
Greater than 4V
Range
Accuracy
20/200Ω
Auto-Ranging
Up to 2Ω
±(3%rdg +4dgt)
Over 2Ω
±(3%rdg +3dgt)
Operating range (as in IEC61557) 20Ω range: 0.2Ω~19.99Ω/200Ω range:
20Ω~199.9Ω
Insulation resistance (to IEC61557-2)
Open Circuit
Voltage (DC)
Rated
Current
Range
Accuracy
500V+20% -0%
1mA or greater
@ 500kΩ
20/200MΩ
Auto-Ranging
±(3%rdg +3dgt)
Operating range (as in IEC61557) 20MΩ range: 0.5MΩ~19.99MΩ/
200MΩ range: 20MΩ~100MΩ
Loop Impedance (to IEC61557-3)
Rated
Voltage (AC)
Nominal Test
Current at 0Ω
External Loop
Range
Accuracy
230V+10%
-15% 50Hz
25A/10ms
20Ω
±(3%rdg +8dgt)
15mA/350ms max.
2000Ω
±(3%rdg +8dgt)
Operating range (as in IEC61557) 20Ω range: 2Ω~19.99Ω/ 2000Ω range:
100Ω~1999Ω
RCD testing (to IEC61557-6)
Function
Trip Current Trip Current
Rated
Duration
Settings
Voltage (AC)
RCD
x 1/2
230V+10% 10/30/100/300/
-15% 50Hz
500mA
2000ms
RCD
x1
230V+10% 10/30/100/300/
-15% 50Hz
500mA
2000ms
FAST
230V+10%
-15% 50Hz
150mA
50ms
Accuracy
Trip Current:
-8% ~-2%
Trip
Time±
Trip Current: (1% rdg
+2% ~+8% +3dgt)
Trip Current:
+2% ~+8%
Voltage Measurement
6
Rated voltage
Measuring Range
100~250V 50Hz
100~250V 50Hz
Accuracy
3% rdg
To prevent wrong connection of test leads and to maintain safety, the Specification
dedicated terminals used for continuity and insulation tests are
automatically covered when using the terminals for loop impedance and
RCD tests.
Instrument dimensions 175 X 115 X 86mm
Instrument weight
780g including batteries.
Reference conditions
Specifications are based on the following
conditions except where otherwise stated:1 Ambient temperature: 23±5˚C
2 Relative humidity 45% to 75%
3 Position: horizontal
4 AC power source 230V, 50Hz
5 DC power source: 12.0 V, ripple content
1% or less
6 Altitude up to 2000m
Battery type
Eight R6 or LR6 batteries.
Low battery warning
symbol appears in the display if the battery
voltage drops below 8V.
Maximum numbers
of measurements
Approx. 700 times for use by continuity
range or approx. 1000 times for use by
insulation resistance range.
+
_
LO
Operating temperature 0 to +40˚C, relative humidity 80% or less, no
and humidity.
condensation.
Storage temperature -10 to +50˚C, relative humidity 75% or less,
and humidity
no condensation.
LED indication of live Illuminates if there is an alternating voltage of
circuit warning
20V AC or more in the circuit under test
before continuity or insulation resistance tests.
When DC voltage is detected across the
measuring terminal the LED lights up.
LED indication of
correct polarity
The P-E and P-N LEDs illuminate when the
wiring of the circuit under test is correct.
7
Specification
The reverse lamp is lit when P and N are
reversed.
Auto data hold
In the loop impedance and RCD test functions,
the LCD reading is automatically frozen for 5
seconds after measurement.
Display
The liquid crystal display has 3 1/2 digits with a
decimal point and units of measurement (Ω,
MΩ, V and ms) relative to selected function.
The display is updated approximately five times
per second.
Overload protection
The continuity test circuit is protected by a
0.5A 600V fast acting (HRC) ceramic fuse
mounted in the battery compartment, where a
spare fuse is also stored.
The insulation resistance test circuit is
protected by a resistor against 600V AC for
10 seconds.
Mains Voltage
Indication
Symbols used on
the instrument
On connecting test leads to the circuit under
test on LOOP and RCD ranges, the LCD
reads V-PE. Sign ‘V-PE Lo’ or ‘V-PE Hi’ is also
shown when the voltage is 100V or less, or
260V or greater respectively.
Equipment protected throughout by double
insulation or reinforced insulation
Caution, risk of electric shock
Caution (refer to accompanying instruction
manual)
8
Warning: Ensure that circuits to be tested are not live.
Disconnect the instrument from the circuit under test before
operating the function switch.
To select the low resistance range select ‘CONTINUITY’.
4.1 Instrument layout - see Fig 1 on page 3.
4.2 Resistance of test leads
The object of testing is to measure the resistance of parts of the wiring
system alone and this should not include the resistance of any test leads
used. The procedure is to measure the resistance of the test leads and to
subtract this from the instrument reading which includes the lead
resistance. Proceed as follows:-
Fig. 2
1 Press the test button once to switch the instrument on.
2 Connect the ends of the test leads in use firmly together (see Fig ) and
operate the test button.
3 The display will read the resistance of the test leads,and a careful note
should be made of the reading.
9
4 Continuity
(resistance) tests
Continuity 4.3 Continuity testing
(resistance) tests
Temporary link
Test at socket
between L and E
Fig 3
1 Press the test button once. Then, the instrument switches on.
2 Select the continuity test by rotating the function dial.
3 Connect the test leads to the circuit whose resistance is required (see
Fig 3) having first made sure that the circuit is not live. Note that
the live circuit warning lamp will illuminate if the circuit is live - but
check first anyway!
4 Press the test button and read the circuit resistance from the display.
5 Note that if the circuit resistance is greater than 20Ω the instrument
will autorange to the 200Ω range.
6 Subtract the test lead resistance (measured in 4.2 above) from the
display reading.
7 The result will be the resistance of the circuit under test.
Note:
If the reading is greater than 200Ω the over range symbol ‘OL’
will remain displayed.
The results of measurements can be adversely affected by
impedances of additional operating circuits connected in parallel
or by transient currents.
10
Warning: Ensure that circuits to be tested are not live.
5 Insulation tests
Disconnect the instrument from the circuit under test before
operating the function switch.
To select the insulation resistance range select ‘INSULATION’.
5.1 The nature of insulation resistance
Live conductors are separated from each other and from earth metal by
insulation, which has a resistance which is high enough to ensure that the
current between conductors and to earth is kept at an acceptably low
level. Ideally insulation resistance is infinite and no current should be able
to flow through it. In practice, there will normally be a current between
live conductors and to earth, and this is known as leakage current. This
current is made up of three components, which are:1.
2.
3.
capacitive current
conduction current, and
surface leakage current.
5.1.2 Capacitive Current
The insulation between conductors which have a potential difference
between them behaves as the dielectric of a capacitor, the conductors
acting as the capacitor plates. When a direct voltage is applied to the
conductors, a charging current will flow to the system which will die away
to zero (usually in less than a second) when the effective capacitor
becomes charged. This charge must be removed from the system at the
end of the test, a function which is automatically performed by the KT61.
If an alternating voltage is applied between the conductors, the system
continuously charges and discharges as the applied voltage alternates, so
that there is a continuous alternating leakage current flowing to the
system.
11
Insulation tests
Insulation (acting as dielectric)
Conductor (acting
as capacitor plates)
Fig 4
Capacitive effect
5.1.3 Conduction Current
Since the insulation resistance is not infinite, a small leakage current flows
through the insulation between conductors. Since Ohm's Law applies, the
leakage current can be calculated from
applied voltage (V)
Leakage current (µA) =
insulation resistance (MΩ)
Insulation (acting as resistance)
Conductors
Resistance effect
Fig 5
5.1.4 Surface Leakage Current
Where insulation is removed, for the connection of conductors and so on,
current will flow across the surfaces of the insulation between the bare
conductors. The amount of leakage current depends on the condition of
the surfaces of the insulation between the conductors. If the surfaces are
clean and dry, the value of the leakage current will be very small. Where
the surfaces are wet and/or dirty, the surface leakage current may be
significant. If it becomes large enough, it may constitute a flashover
between the conductors.
Whether this happens depends on the condition of the insulation surfaces
and on the applied voltage; this is why insulation tests are carried out at
higher voltages than those normally applying to the circuit concerned.
Insulation
Conductors
Surface leakage current
12
Fig 6
5.1.5 Total Leakage Current
Insulation tests
The total leakage current is the sum of the capacitive, conduction and
surface leakage current described above. Each of the currents, and hence
the total leakage current, is affected by factors such as ambient
temperature, conductor temperature, humidity and the applied voltage.
If the circuit has alternating voltage applied, the capacitive current (5.1.2)
will always be present and can never be eliminated. This is why a direct
voltage is used for insulation resistance measurement, the leakage current
in this case quickly falling to zero so that it has no effect on the
measurement. A high voltage is used because this will often break down
poor insulation and cause flashover due to surface leakage (see 5.1.4), thus
showing up potential faults which would not be present at lower levels.
The insulation tester measures the applied voltage level and the leakage
current through the insulation. These values are internally calculated to
give the insulation resistance using the expression:-
Insulation resistance (MΩ) =
Test voltage (V)
Leakage current (µA
As the capacitance of the system charges up, so the charging current falls
to zero and a steady insulation resistance reading indicates that the
capacitance of the system is fully charged. The system is charged to the full
test voltage, and will be dangerous if left with this charge. The KT61
provides an automatic path for discharging current as soon as the test
button is released to ensure that the circuit under test is safely discharged.
If the wiring system is wet and/or dirty, the surface leakage component of
the leakage current will be high, resulting in low insulation resistance
reading. In the case of a very large electrical installation, all the individual
circuit insulation resistances are effectively in parallel and the overall
resistance reading will be low. The greater the number of circuits
connected in parallel the lower will be the overall insulation resistance.
5.2 Damage to Voltage-Sensitive Equipment
An increasing number of electronic-based items of equipment are being
connected to electrical installations. The solid state circuits in such
equipment are likely to be damaged by the application of the levels of
voltage used to test insulation resistance. To prevent such damage, it is
important that voltage-sensitive equipment is disconnected from the
installation before the test is carried out and reconnected again
immediately afterwards. The devices which may need to be disconnected
13
Insulation tests before the test include:▲
▲
▲
▲
▲
▲
▲
▲
▲
▲
▲
Electronic fluorescent starter switches
Passive infra-red detectors (PIRs)
Dimmer switches
Touch switches
Delay timers
Power controllers
Emergency lighting units
Electronic RCDs
Computers and printers
Electronic point-of-sale terminals (cash registers)
Any other device which includes electronic components.
5.3 Preparation for measurement
Before testing, always check the following:_
1
The ‘low battery’ Indication
2
There is no visually obvious damage to the tester or to the test
leads
3
Test the continuity of the test leads by switching to continuity test
and shorting out the lead ends. A high reading will indicate that
there is a faulty lead or that the fuse is blown.
4
Make sure the circuit to be tested is not live. A warning
lamp is lit if the instrument is connected to a live circuit but test
the circuit as well!
+
LO
is not displayed
5.4 Insulation resistance measurement
The KT61 has a single test voltage of 500V DC.
14
1
Press the test button once, the instrument then switches on.
2
Select the insulation resistance setting by rotating the function
dial to ‘INSULATION’ test section of the functional switch, after
making sure that the instrument is not connected to a live circuit.
3
Attach the test leads to the instrument and to the circuit or the
appliance under test (see Figs 7 & 8)
All fuses in or circuit
breakers closed
Mains switch off
Equipment disconnected
Switches closed
Insulation tests
Lamps out
Reading not less
than 0.5 MΩ
Main
switch
open
Fig 7
Fig 7
4 If the mains warning lamp lights and/or the buzzer sounds do not
press the test button but disconnect the instrument from the circuit.
Make the circuit dead before proceeding.
Fig 8
5 Press the test button when the display will show the insulation
resistance of the circuit or the appliance to which the instrument is
connected.
6 Note that if the circuit resistance is greater than 20MΩ the instrument
will automatically range to the 200MΩ reading.
7 When testing is complete release the test button before disconnecting
the test leads from the circuit or from the appliance. This will ensure
that the charge built up by the circuit or the appliance during insulation
test is dissipated in the discharge circuit. In the discharging process, an
15
Insulation tests
LED illuminates and the live circuit warning buzzer will sound.
CAUTION
Never turn the function dial whilst the test button is depressed as
this may damage the instrument. Never touch the circuit, test lead
tips or the appliance under test during insulation testing.
Note:
16
If the reading measured greater than 200MΩ the over range
reading ‘OL’ will be displayed.
Disconnect the instrument from the circuit under test before 6 Loop impedance
operating the function switch.
tests
To select the loop testing range select ‘LOOP’.
6.1 Voltage Measurement
Press the test button once to switch the instrument on. When the tester
is set to the loop test function, mains voltage is displayed as soon as the
instrument is connected for test. This voltage display is automatically
updated five times every seconds. The voltage function operates
whenever the test button is in the up position.
6.2 What is earth fault loop impedance?
The path followed by fault current as a result of a low impedance fault
occurring between the phase conductor and earth is called earth fault
loop. Fault current is driven round the loop by the supply voltage, the
amount of current depending on the voltage of the supply and on the
impedance of the loop. The higher the impedance, the lower will be the
fault current and the longer it will take for the circuit protection (fuse or
circuit breaker) to operate and interrupt the fault.
To make sure that fuses will blow or that circuit breakers will operate
quickly enough in the event of a fault, the loop impedance must be low, the
actual maximum value depending on the characteristics of the fuse or the
circuit breaker concerned. Every circuit must be tested to make sure that
the actual loop impedance does not exceed that specified for the
protective device concerned.
6.3 Automatic over-temperature cut-out
During the short test period the instrument dissipates power of about
6kW. If frequent tests are conducted over a prolonged period of time, the
internal test resistor will overheat. When this happens, further tests are
automatically inhibited and the over-temperature symbol appears in the
display. The instrument must then be left to cool down, after which testing
may be resumed.
6.4 The loop impedance test
Since the earth fault loop is made up of conducting path which includes the
supply system back to the supply transformer, it follows that loop testing
can only be carried out after the mains supply has been connected. In
many cases, any RCD in the circuit will be tripped by this test, which draws
current from the phase and returns it through the earth system. The RCD
will see this as the type of fault it is designed to protect against, and will
17
Loop impedance trip. To prevent this unwanted RCD tripping during loop testing, any RCD
tests must be taken out of circuit and temporarily replaced with a suitably rated
MCB unit. The RCD will need to be replaced after the loop test is
completed.
WARNING
Do not proceed with testing unless the P-E and P-N lamps are lit
to confirm that the wiring is correctly connected. Should these two
lamps not be lit, investigate the wiring connections of the
installation and rectify any faults before proceeding with the test.
If the red LED is lit do not proceed.
1 Press the test button once to switch the instrument on
2 Set the instrument to loop test 20Ω range.
3 If testing sockets, connect the plug lead to the KT61 and push the
moulded plug into the socket to be tested (see Fig 9).
4 Check that the wiring lamps are lit (see above).
5 Note the mains voltage displayed by the instrument.
6 Press the ‘Press to test’ button. The value of the measured loop
impedance will be displayed with the appropriate units.
7 If testing lighting or other circuits, connect the three-wire lead to the
KT61, connect the red (phase) lead to the phase connection of the
circuit under test, connect the black (neutral) lead to the neutral
connection of the circuit under test, and connect the earth lead to the
earth associated with the circuit. (see Fig 10).
8 If any RCD associated with the circuit trips out, reset the RCD and try
testing again, this time operating the phase selector switch once prior
to pressing the test button. This will change the period of the
waveform over which the instrument performs the loop test. This may
result in the RCD not tripping out. If the RCD still trips, temporarily
replace it with a suitably rated MCB for the duration of the test.
9 If the instrument measures greater than 20Ω the over-range symbol
‘OL’ will be displayed. If this is the case, switch the instrument up a
range to the 2000Ω range and repeat the test to obtain a satisfactory
reading. If the instrument is set to the ‘loop2000Ω’ position, the test
will be carried out at the reduced current of 15mA flowing. This
setting will be very unlikely to trip out the circuit RCD.
Note: Do not connect phase to phase as this instrument is rated at 230V.
18
6.5 Loop impedance at 3 phase equipment
Use the same procedure as in 6.4 above ensuring that only one phase is
connected at a time i.e.:
First Test: red prod to phase 1, black prod to neutral,
green crocodile clip to earth.
Second Test: red prod to phase 2, black prod to
neutral, green crocodile clip to earth etc.
WARNING
Never connect the instrument to two phases at the same time.
Testing as described in 6.4 and 6.5 above will measure the Phase-Earth
loop impedance. If you wish to measure the Phase-Neutral loop
impedance then the same procedure should be followed except the earth
clip should be connected to the neutral of the system i.e.: the same point
as the black neutral probe.
If the system has no neutral then you must connect the black neutral probe
to the earth i.e.: the same point as the green earth clip. This will only work
if there is no RCD in this type of system.
Note: Before commencing the test, please clearly eliminate the load which
remains in the circuit to be tested, otherwise it may affect the accuracy of
the measurement.
When the mains voltage is lower than 100V, the ‘low voltage’ indication
‘Lo’ is displayed in the LCD display. Also, when the mains voltage is higher
than 260V, the ‘high voltage’ indication ‘Hi’ is displayed in the LCD display.
In either case, testing cannot be carried out as the test button does not
function even if you press it.
19
Loop impedance
tests
Loop impedance
tests
Fig 9
Black Red
neutral phase
Green
earth
Fig 10
20
Disconnect the instrument from the circuit under test before 7 RCD tests
operating the function switch.
To select the RCD test range select ‘RCD’.
7.1 Purpose of the RCD test
The RCD must be tested to ensure that operation takes place quickly
enough to ensure that there is unlikely to be serious danger to a person
experiencing an electric shock from the system. This test must NOT be
confused with that taking place when the ‘test’ button on the RCD is
pressed; operation of the test button simply trips the breaker to ensure
that it is working, but does not measure the time taken to break the
circuit.
7.2 What does the RCD test really do?
The RCD is designed to trip out when the difference between the phase
current and the neutral current (this is called the residual current) reaches
the tripping value (or rating) of the device. The tester provides a carefully
preset value of residual current depending on its setting and then
measures the time lapse between the application of the current and the
operation of the RCD.
7.3 RCD testing
1
Press the test button once to switch the instrument on.
2
Set the RCD rated tripping switch to the trip rating of the RCD
under test.
3
Set the function switch to x1/2 for the ‘no trip’ test, which
ensures that the RCD is operating within its specification and is
not too sensitive.
4
Set the ‘LOOP/RCD’ switch to 0˚.
5
Connect the instrument to the RCD to be tested either via a
suitable socket outlet (see fig 9) or using the test lead set
(see fig 10).
6
Make sure that the P-E and P-N wiring check lamps are lit and the
wiring incorrect
LED is not lit. If they are not, disconnect the
tester and check the wiring for a possible fault.
7
If the lamps are correctly lit, press the test button to apply half
the rated tripping current for 2000ms, when the RCD should
not trip. The PN and PE LEDs should remain on indicating the
21
RCD tests
RCD has not tripped.
8
Repeat the test with the ‘LOOP/RCD’ switch at 180˚
9
In the event of the RCD tripping, the trip time will be displayed,
but the RCD maybe faulty.
10
Set the function switch to x1 for the ‘trip’ test, which measures
the time taken for the RCD to trip with the set residual current.
11
Set the ‘LOOP/RCD’ switch to 0˚ on the display.
12
Make sure that the P-E and P-N wiring check lamps are lit. If they
are not, disconnect the tester and check the wiring for a possible
fault.
13
If the lamps are lit, press the test button to apply full rated
tripping current and the RCD should trip, the tripping time being
shown on the display. If the RCD has tripped the PN and PE
LEDs should be off. Check this is so.
13
Repeat the test with the ‘LOOP/RCD’ switch at 180˚
15
Make sure to keep clear of earthed metal during the
operation of these tests.
7.4 Testing RCDs used to provide supplementary protection. (Fast trip
test)
RCDs rated at 30mA or less are sometimes used to provide extra
protection against electric shock. Such RCDs require a special test
procedure as follows:-
22
1
Set the ‘RCD’ switch to ‘150 Fast’
2
Set the ‘LOOP/RCD’ switch to 0˚.
3
Connect the test instrument to the RCD to be tested.
4
Make sure that the P-E and P-N wiring check lamps are lit. If they
are not, disconnect the tester and check the wiring for a possible
fault.
5
If the lamps are lit, press the test button to apply a test current
of 150mA where the RCD should trip within 40ms, the tripping
time being shown on the display.
6
Repeat the test with the ‘LOOP/RCD’ switch at 180˚.
7
Make sure to keep clear of earthed metal during the
operation of this tests.
RCD tests
7.5 Testing time delayed RCDs
RCDs with a built-in time delay are used to ensure discrimination, that is,
that the correct RCD operates first. Testing is carried out in accordance
with item 7.3 above, except that the displayed tripping times are likely to
be longer than those for a normal RCD. Since the maximum test time is
longer, there may be danger if earthed metal is touched during the test.
Make sure to keep clear of earthed metal during the operation of
this test.
Note:
If the RCD does not trip the tester will supply the test current for
a maximum of 2000ms on the X1/2 and X1 ranges. The fact that
the RCD has not tripped will be evident because the PN and PE
LEDs will still be on.
On RCD ranges, when the N-E voltage rises to 50V or greater,
the measurement is automatically suspended and ‘VNE Hi’ is
displayed in the LCD display.
Leakage currents in the circuit following the RCD may influence
the measurements.The earth electrode resistance of a measuring
circuit with a probe shall not exceed 50Ω at 500mA range.
The potential fields of other earthing installations may influence
the measurement. When the mains voltage is lower than 100V,
the ‘low voltage’ indication ‘Lo’ is displayed in the LCD display.
Also, when the mains voltage is higher than 260V, the ‘high
voltage’ indication ‘Hi’ is displayed in the LCD display.In either
case, testing cannot be carried out as the test button does not
function even if you press it .
When making a test with the range larger than the RCD rated
tripping current, it can happen that RCD trips and ‘no’ is shown
on the display.
23
8 General The test button can be locked down for ease of use by pressing it and
turning clockwise. Do not forget to release test button by turning it anticlockwise before disconnecting the instrument from the test points.
Failure to do so may leave the tested circuit in a charged condition when
carrying out insulation tests.
The instrument is provided with a sliding cover to ensure that leads for
testing continuity and insulation resistance cannot be connected at the
same time as test leads for loop testing and RCD testing. If this sliding
cover is damaged so that it fails to perform its function, do not use the
instrument and return it to Kewtech for attention.
+
_
9 Battery When the display shows the low battery indication, LO , disconnect the
replacement test leads from the instrument. Remove the battery cover and the
batteries. Replace with eight (8) new 1.5V AA batteries, taking care to
observe correct polarity. Replace the battery cover.
Note:
The instrument is sometimes powered on when connecting a
battery. But when the instrument isn't connected with the main
power and the test button is also not pressed, the instrument is
automatically powered off in about one minute.
10 Fuse The continuity test circuit is protected by a 600V 0.5A HRC ceramic type
replacement fuse situated in the battery compartment, together with a spare. If the
instrument fails to operate in the continuity test mode, first disconnect the
test leads from the instrument. Next remove the battery cover, take out
the fuse and test its continuity with another continuity tester. If it has failed,
replace it with a spare, before refitting the battery cover. Do not forget to
obtain a new fuse and place it in the spare position.
If the instrument will not
operate
in
the
loop
impedance and RCD modes,
it may be that the protective
fuses fitted on the printed
circuit board have blown. If
you suspect that the fuses
have failed, return the
instrument to Kewtech for
service - do not attempt to
replace the fuses yourself.
24
Fig 11
If this tester should fail to operate correctly, return it to Kewtech stating 11 Servicing
the exact nature of the fault. Before returning the instrument ensure that:
1
The leads have been checked for continuity and signs of damage.
2
The continuity mode fuse (situated in the battery compartment)
has been checked.
3
The batteries are in good condition.
Please remember to give all the information possible concerning
the nature of the fault, as this will mean that the instrument will
be serviced and returned to you more quickly.
Return the instrument to:
Service Department
Kewtech Corporation Limited
76 St. Catherine’s Grove
Lincoln LN5 8NA
Regular re-calibration is recommended for this instrument. Kewtech
recommends that with normal use, the instrument be calibrated at least
once in every 12 month interval. When the instrument is due for recalibration return it to the address above marked for the attention of the
Calibration Department and be sure to include all accessory leads, as these
are part of the calibration procedure.
Correct assembly is shown below. By hanging the instrument round the 12 Case and
neck, both hands will be left free for testing.
strap assembly
25
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