Megger MTB7671 User manual

M
MTB7671/2
Test box
User Guide

GSafety warnings
Safety Warnings and Precautions must be read and
understood before the instrument is used. They must be
observed during use.
Only use the MTB7671/2 when both polarity indicator
LEDs are lit.
The MTB7671/2 is protected by an integral RCD plug which
MUST NOT be removed from the tester.
The interlock protected 13 A socket should only be used with
double insulated RCD and Loop testers.
The instrument should not be used if any part of it is damaged.
Replacement fuses must be of the correct type and rating. Failure
to fit the correctly rated fuse may result in a safety hazard.
Only shrouded test leads should be used when measuring the
230 V a.c. mains supply
Users of this equipment and/or their employers are reminded that Health and
Safety Legislation requires them to carry out valid risk assessments of all electrical
work so as to identify potential sources of electrical danger and risk of electrical
injury such as inadvertent short circuits
CAT II - Measurement category II: Equipment connected between the
electrical outlets and the user’s equipment.
CAT III - Measurement category III: Equipment connected between the
distribution panel and the electrical outlets.
CAT IV - Measurement category IV: Equipment connected between the origin
of the low-voltage mains supply and the distribution panel.
NOTE
THE INSTRUMENT MUST ONLY BE USED BY SUITABLY
TRAINED AND COMPETENT PERSONS.
Symbols used on the instrument:
F Caution: risk of electric shock
GCaution: refer to accompanying notes
tEquipment protected throughout by Double Insulation (Class II)
c Equipment complies with relevant EU Directives
Equipment complies with ‘C tick’ requirements
Do not dispose of in the normal waste stream

Interlock cover AC out supply
Fuse Fuse
RCD and loop test supply socket
Continuity and insulation test select switch
Continuity and insulation connection sockets
Supply check indicators
RCD and loop test select switch
MTB7671/2
LOOP +10Ω

OPERATION
The MTB7671/2 is intended for use with double insulated test
instruments only.
The MTB7671/2 has a combined earth and neutral which stops
it from tripping RCD protected circuits. To prevent the danger of
electric shock the MTB7671/2 is protected by a RCD plug and uses
a safety interlock for all live circuit tests.
1. SWITCHING ON
To switch on the MTB7671/2, plug the unit into the 230 V 50 Hz
mains supply using the integral RCD plug and depress the button
on the top of this plug and release, this will switch the plug on.
The bars on the plug should show red to indicate the unit is pow-
ered and the supply LEDs on the MTB7671/2 will be on.
To test the RCD plug, lightly press the button on the top (‘Test’
button). The red indicator bars should disappear and the supply
LEDs on the MTB7671/2 go out.
2. SUPPLY POLARITY CHECK
2.1 Supply Pass
The supply polarity check section on the MTB7671/2 should be on,
showing 2 green LEDs.
Do not use the test box unless both of these LEDs are lit.
NOTE: The polarity check will not detect if neutral and earth are
reversed.
3. AC Voltage output
The unit provides connection to the input mains supply to provide
a voltmeter check. The status of this supply is indicated by the
[230 V AC] LED. If this is not lit then the protection fuse has blown
and will need to be replaced.
Connect the tester to the voltage output terminals.
✍- Record the reading on the record card.

4. TESTING A CONTINUITY TESTER
Connect the tester to the continuity and insulation connection sock-
ets in the orange and red section of the test box.
Warning: Do not apply more than 250 mA.
4.1 Current Test
Set the continuity and insulation test select switch to [I TEST] and
perform a continuity test. If the test instrument delivers more than
200 mA the [I TEST] pass LED will light.
✍- Record the reading on the record card.
4.2 Voltage Test
Set the continuity and insulation test select switch to [V TEST] and
perform a continuity test.
If the open circuit voltage from the tester is between 4 V and 24 V dc
the [V TEST] pass LED will light.
NOTE: The MFT1700 will require the buzzer to be turned on during
this test.
✍- Record the reading on the record card.
NOTE: If in either of the tests listed above the LEDs fail to light, the
test instrument under test should be returned for a full calibration.
4.3 0.5 ΩTest
Set the continuity and insulation test select switch to [0.5 Ω] and
perform a continuity check. This connects a resistor between the test
sockets of 0.5 Ω+/-3%. The tester should indicate a measured value
of 0.5 Ω(+/- operational errors including the tester’s accuracy).
✍ - Record the reading on the record card.
4.4 5.0 ΩTest
Set the continuity and insulation test select switch to [5 Ω] and
perform a continuity check. This connects a resistor between the test
sockets of 5 Ω+/-3%. The tester should indicate a measured value of
5 Ω(+/- operational errors including the test instrument’s accuracy).
✍- Record the reading on the record card.
4.5 If an instrument fails the above tests, refer to note 5.6 for reverse
polarity instruments.

5. TESTING AN INSULATION TESTER
Connect the test instrument to the continuity and insulation connec-
tion sockets in the orange and red section of the test box.
Warning: Do not apply more than 1250 V d.c.
5.1 Voltage load test @ 250 V
Set the continuity and insulation test select switch to [250 V] and per-
form an insulation test with the test instrument set to 250 V output.
If the test voltage is 250 V d.c. the [V] LED will be on. If the current
delivered from the unit is greater than 1 mA the [I] LED will also be
on, showing that the test criteria have been met. A fixed resistor of
0.25 MΩ+/-3% is used to provide the test reference. The test instru-
ment should indicate a measured value of 0.25 MΩ(+/- operational
errors including the test instrument’s accuracy).
If either of the LEDs fail to light the test instrument should be re-
turned for a full calibration.
✍Record the reading on the record card.
5.2 Voltage load test @ 500 V
Set the continuity and insulation test select switch to [500 V] and per-
form an insulation test with the test instrument set to 500 V output.
If the test voltage is 500 V d.c. the [V] LED will be on. If the current
delivered from the unit is greater than 1 mA the [I] LED will also be
on, showing that the test criteria have been met. A fixed resistor
of 0.5 MΩ+/-3% is used to provide the test reference. The tester
should indicate a measured value of 0.5 MΩ(+/- operational errors
including the test instrument’s accuracy).
If either of the LEDs fail to light the tester should be returned for a
full calibration.
✍Record the reading on the record card.
5.3 Voltage load test @ 1 kV
Set the continuity and insulation test select switch to [1 kV] and per-
form an insulation test with the test instrument set to 1 kV output.
If the test voltage is 1 kV dc the [V] LED will be on. If the current de-
livered from the unit is greater than 1 mA the [I] LED will also be on,
showing that the test criteria have been met. A fixed resistor of

1 MΩ+/-3% is used to provide the test reference. The tester should
indicate a measured value of 1 MΩ(+/- operational errors including
the tester’s accuracy).
If either of the LEDs fail to light the tester should be returned for a
full calibration.
✍ Record the reading on the record card.
5.4 9 MΩTest
Set the continuity and insulation test select switch to [9 MΩ] and
perform an insulation check using the tester. This connects a
9.0 MΩ+/-3% resistor between the test sockets. This test can be
performed at any voltage up to 1 kV. The tester should indicate
a measured value of 9.0 MΩ(+/- operational errors including the
tester’s accuracy).
✍Record the reading on the record card.
5.5 90 MΩTest
Set the continuity and insulation test select switch to [90 MΩ] and
perform an insulation check using the tester. This connects a 90 MΩ
+/-3% resistor between the test sockets. This test can be performed
at any voltage up to 1 kV. The tester should indicate a measured val-
ue of 90 MΩ(+/- operational errors including the tester’s accuracy).
✍Record the reading on the record card.
5.6 In some instances contintuity and insulation testers have reversed
outputs. If the voltage and current LEDs are not lit when checking
the testers outputs it is recommended that you reverse the polrity
connections i.e. connect the RED test lead to the black continuity/
insulation socket and the BLACK test lead to the RED continuity/insu-
lation socket and repeat the tests.

6. TESTING A LOOP TESTER
Connect the tester to the RCD and loop test supply socket. When
the interlock cover is closed, the earth pin of this socket is connected
to the supply neutral.
Note: The MTB7671/2 can be used to perform either ‘No Trip’ or
‘High Current’ loop tests.
6.1 Conducting a Loop Test
Set the RCD and loop test select switch to [Loop] and perform a loop
test using the tester. This returns a value for the initial test condi-
tions.
✍Record the reading on the record card
6.2 Conducting a +10 ΩLoop Test
Set the RCD and loop select switch to [Loop + 10 Ω] and perform a
loop test using the tester. Check that the loop impedance reading
has increased from the reading in 6.1 by a nominal 10 Ω.
NOTE: allow at least 10 seconds between tests if conducting a high
current loop test.
✍- Record the reading on the record card.
6.3 Conducting a +180 Ωloop test
Set the RCD and loop select switch to [Loop + 180 Ω] and perform
a loop test using the tester. Check that the loop impedance reading
has increased from the reading in 6.1 by a nominal 180 Ω.
✍- Record the reading on the record card.
NOTE: Some 3 wire loop testers give a >50 V touch voltage on this
range. A 2 wire test can be used for calibration checks.
6.4 Performing a PFC test
Set the RCD and loop select switch to [PFC] and perform a loop test
using the tester. The tester will perform a PFC test using
[Loop + 10 Ω] circuit.
NOTE: allow at least 10 seconds between tests if conducting a high
current PFC test.
✍Record the result on the record card
NOTE: The MTB7671/2 performs a real loop test, the test results for
which can vary from test to test, particularly with ‘No Trip’ tests. It
is recommended that several (No Trip) tests are performed and the
average result recorded.

7. TESTING AN RCD TESTER
Connect the tester to the RCD and loop test supply socket. When the
interlock cover is closed, the earth pin of this socket is connected to
the supply neutral.
7.1 Pre-Test Setup
Set the RCD test current on the tester and move the RCD and loop
test select switch to the appropriate position (e.g.10 mA, 30 mA or
100 mA). Check that the “mains socket power on” LED is lit. If not
then press the [reset] button.
7.2 Conducting 1/2 I Test
To perform a 1/2 I test set the tester to 1/2 I mode and perform the
test. The tester should not indicate a tripped RCD (if it does then it
should be returned for a full calibration). This can be repeated for
180° 1/2 I if provided on tester.
- Record the results on the record card
7.3 Conducting an I @ 0° Test
To perform a 0° I test set the tester to 0° I mode and perform the
test. The test box will trip and disconnect power. The [Tripped] LED
will light. The trip time should be a nominal 40 ms.
If the tester fails to indicate a tripped RCD then the tester should be
returned for a full calibration.
✍- Record the reading on the record card.
To reset the test box press the [reset] button in the yellow panel.
7.4 Conducting an I @ 180° Test
To perform a 180° I test set the tester to 180° I mode and perform
the test. The test box will trip and disconnect power. The [Tripped]
LED will light. The trip time should be a nominal 50 ms.
If the tester fails to indicate a tripped RCD then the tester should be
returned for a full calibration.
✍- Record the reading on the record card.
To reset the test box press the [reset] button in the yellow panel.
7.5 Conducting a 5I @ 0° Test
To perform a 0° 5I test set the tester to 0° 5I mode and perform the
test. The test box will trip and disconnect power. The [Tripped] and [5
I TEST] LEDs will light. The trip time should be a nominal 10 ms.

If the tester fails to indicate a tripped RCD then the tester should be
returned for a full calibration.
✍- Record the reading on the record card.
To reset the test box press the [reset] button in the yellow panel.
7.6 Conducting a 5I @ 180° Test
To do a 180° 5I test set the tester to 180° 5I mode and perform the
test. The unit will trip and disconnect power. The [Tripped] and
[5 I TEST] LEDs will light. The trip time should be a nominal 20 ms.
If the tester fails to indicate a tripped RCD then the tester should be
returned for a full calibration.
✍- Record the reading on the record card.
To reset the test box press the [reset] button in the yellow panel.
7.7 Conducting 10 mA, 30 mA and 100 mA tests
The test sequence can be repeated for the 10 mA, 30 mA and
100 mA tests by selecting the appropriate current setting on the RCD
and loop test select switch and repeating the tests as described in
sections 7.2 to 7.6.
NOTE: RCD Protection
In order to protect the current sense circuit the RCD simulator is
protected by a 500 mA fuse. If the fuse blows then the earth pin of
the RCD and loop supply socket will float. If an RCD test is attempted
the fuse blown LED will light. Note that this will only illuminate if the
test instrument does not inhibit testing if the correct voltages are not
present, or the test instrument provides sufficient leakage to light the
LED when connected.
8. Fuse replacement
The MTB77671/2 is protected by two x 500 mA (F) fuses and a 7 A
fuse in the RCD plug. Fuse failure is indicated by either the 230 V
AC LED failing to light or the [Fuse Blown] LED lighting. In the event
of a fuse failing, fuses must be replaced with the same fuse type.
Disconnect the test box from the mains supply. Disconnect any test
instruments from the test box. Remove the failed fuse from the fuse
holder and replace with an identical fuse:
Fuse Type: 500 mA (F) 20 mm
7 A BS1362