Megger MIT221 User manual

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M
MFT1700 series
Multifunction testers
User manual

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Contents
SAFETY WARNINGS .................................................................................................................................................................3
1. Introduction.............................................................................................................................................................................4
2. Overview .................................................................................................................................................................................4
2.1 Front panel and controls .................................................................................................................................................6
2.2 Waste electrical and electronic equipment.......................................................................................................................6
2.3 Battery and fuse location, fitting and replacement ..........................................................................................................6
3. Operation .......................................................................................................................................................................7
3.1 General operation – all models........................................................................................................................................7
3.2 Mode button functions...................................................................................................................................................7
3.3 Test inhibit ......................................................................................................................................................................7
4. Voltage, frequency, current and temperature measurement..........................................................................................................8
4.1 Making a voltage measurement......................................................................................................................................8
5. Continuity / resistance measurement............................................................................................................................................10
5.1 Nulling test lead resistance (up to 9.99 ohms) ...............................................................................................................10
5.2 Making a CONTINUITY measurement..............................................................................................................................11
5.3 Storing / downloading results (MFT1731 only).................................................................................................................11
5.4 Continuity Buzzer ON/OFF...............................................................................................................................................11
5.5 Switch probe (SP5)..........................................................................................................................................................11
5.6 Buzzer threshold .............................................................................................................................................................12
5.7 Measurement methods and sources of error ...................................................................................................................12
6. Insulation resistance ...............................................................................................................................................................12
6.1 Making an INSULATION measurement.............................................................................................................................12
6.2 Insulation test lock..........................................................................................................................................................13
6.3 Measurement methods and sources of error ...................................................................................................................13
7. Loop Impedance testing...........................................................................................................................................................13
7.1 Range selection and test leads ........................................................................................................................................14
7.2 Making a loop impedance measurement.........................................................................................................................15
7.3 Phase to Neutral (or Phase to Phase) testing....................................................................................................................19
7.4 Prospective Fault Current and Short Circuit calculation (PFC & PSCC) ..............................................................................20
7.5 Zmax test mode..............................................................................................................................................................20
7.6 Making a Zmax loop impedance measurement ...............................................................................................................20
7.7 Making an R1+R2 loop impedance measurement (MFT1721 only)...................................................................................21
7.8 Measurement methods and sources of error ...................................................................................................................22
8. Residual Current Device testing................................................................................................................................................22
8.1 Making an RCD measurement ........................................................................................................................................23
8.2 Selecting RCD type .........................................................................................................................................................23
8.3 ½ x I RCD current rating (No-trip test) ...........................................................................................................................23
8.4 1 x I RCD current rating (Tripping test on 30mA RCD) ...................................................................................................24
8.5 5 x I RCD current rating (Tripping test on 30mA RCD) ...................................................................................................25
8.6 Ramp Test.......................................................................................................................................................................25
8.7 Type A (DC sensitive) RCD test ......................................................................................................................................26
8.8 Type B (Pure DC) RCD test...............................................................................................................................................26
8.9 Variable RCDs (not MFT1711) .........................................................................................................................................27
8.10 AUTO RCD testing ..........................................................................................................................................................27
8.11 3 Phase RCD testing........................................................................................................................................................27
8.12 Touch voltage display......................................................................................................................................................29
8.13 Measurement methods and sources of error ...................................................................................................................29
8.14 Useful information..........................................................................................................................................................29
9. Earth resistance measurement..................................................................................................................................................29
9.1 Connection terminals......................................................................................................................................................29
9.2 Touch voltage limit..........................................................................................................................................................29
9.4 Making a measurement – Three terminal resistance measurement ..................................................................................30
9.5
9.6
10. Setup options ..........................................................................................................................................................................31
11. Warning messages...................................................................................................................................................................32
11.1 Startup warnings ............................................................................................................................................................32
11.2 Battery............................................................................................................................................................................32
11.3 Battery charger ...............................................................................................................................................................32
11.4 Fuse warning ..................................................................................................................................................................32
11.5 Invalid rotary switch setting.............................................................................................................................................32
11.6 Continuity test................................................................................................................................................................32
11.7 Insulation test .................................................................................................................................................................32
11.8 RCD Test.........................................................................................................................................................................32
11.9 RCD range selection errors..............................................................................................................................................32
11.10 Loop Test.......................................................................................................................................................................32
11.11 Earth test.......................................................................................................................................................................32
11.12 Test will not start ...........................................................................................................................................................32

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Appendix A – Sending, storing, deleting and recalling test results........................................................................................................33
Appendix B – Downloading data using Bluetooth®.............................................................................................................................35
Appendix C – Installation category definitions.....................................................................................................................................36
Appendix D – Safe working practice....................................................................................................................................................36
Appendix E – Cleaning and maintenance ............................................................................................................................................37
Appendix F – Earth resistance testing – Basic principles .......................................................................................................................37
General specification...........................................................................................................................................................................38
Repair and warranty............................................................................................................................................................................41
GSAFETY WARNINGS
Safety warnings and precautions must be read and understood before the instrument is used. They must be observed during use.
■The circuit under test must be switched off, de-energised and isolated before test connections are made when carrying out insulation
and continuity tests.
■Continuity of protective conductors and earthed equipotential bonding of new or modified installations must be verified before
carrying out an earth fault loop impedance test, RCD or earth testing
■Do not touch circuit connections and exposed metalwork of an installation or equipment under test. Under fault conditions the
system earth could become hazardous live.
■Do not touch the earth stakes, test leads and their terminations (including connections to the earthing system under test) if an
installation earth fault can arise, unless adequate precautions are taken.
■The ‘live circuit warning’ and ‘automatic discharge’ functions are additional safety features and should not be regarded as a substitute
for normal safe working practices.
■Do not move the rotary switch positions while a test is in progress.
■Do not operate the instrument or connect it to any external system if it shows any visible signs of damage or if it has been stored
for prolonged periods in unfavourable conditions.
■Do not operate the instrument or connect it to any external system if the battery compartment or casing is open or any parts of the
case (including keypad, selector switch, display window, etc.) are missing.
■Always disconnect the instrument from all systems while batteries are being changed or the fuse replaced
■Do not replace rechargeable cells in the instrument with non-rechargeable “dry” cells and attempt to charge the cells. This can
cause explosion or fire.
■Do not operate charging equipment supplied with the instrument in damp or wet environments or outdoors. All test leads must be
removed from the instrument while charging.
■After insulation tests, capacitive circuits must be allowed to discharge before disconnecting test leads. Locking the insulation test
ON should only be used where there is no risk of a circuit holding a charge.
■The instrument should not be used if any part of it is damaged.
■Test leads, probes and crocodile clips must be in good order, clean and with no broken or cracked insulation.
■All test leads supplied with the instrument form part of the measuring circuit of the instrument. They must not be modified or
changed in any way, or be used with any other electrical instrument or appliance.
■A plug severed from the power cord MUST be destroyed, as a plug with bare conductors is hazardous in a live socket outlet.
■Ensure that hands remain behind guards of probes/clips when testing.
■U.K. Safety Authorities recommend the use of fused test leads when measuring voltage on high energy systems.
■Replacement fuses must be of the correct type and rating.
■Failure to fit the correctly rated fuse will result in damage to the instrument in the event of an overload.
■Special precautions are necessary when operating in situations where “live” earths may be encountered: isolation switches and fuses
(not supplied with this instrument) must be used.
■Special precautions are necessary when working near high tension systems (MV and HV): rubber gloves and shoes (not supplied with
this instrument) should be worn.
■Special precautions are necessary when working in wet conditions or in agricultural areas: observe the local safety standards and
take all necessary special precautions applicable to the particular location and do not touch the test leads with bare hands.

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LIVE EARTH SAFETY PRECAUTIONS
A ‘Live’ earth is one that carries current from the mains supply, or could do so under fault conditions. The following warnings apply in
addition to those listed previously.
■All persons involved must be trained and competent in isolation and safety procedures for the system to be worked on. They
must be clearly instructed not to touch the earth electrode, test stakes, test leads, or their terminations if any ‘Live’ earths may be
encountered. It is recommended that they wear appropriate rubber gloves, rubber soled shoes, and stand on a rubber mat.
■The earth electrode under test should be isolated from the circuit it is protecting before testing commences. If this is not possible,
ART (attached Rod Technique) may be used to measure electrode resistance.
■The instrument terminals should be connected to the system under test through isolation switches that are rated to handle the likely
maximum fault voltages and currents that could be encountered at the installation. The isolation switch must be open whilst any
personal contact is made with the remote test stakes, or the connecting leads, e.g. when changing their position.
■The instrument terminals should be connected to the system under test through fuses that are rated to handle the likely maximum
fault voltages and currents that could be encountered at the installation.
NOTE
THE INSTRUMENT MUST ONLY BE USED BY SUITABLY TRAINED AND COMPETENT PERSONS
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. Where the assessments show that the risk is significant then the use of fused test leads constructed in accordance with
the HSE guidance not GS38 ‘Electrical Test Equipment for use by Electricians’ should be used .
This instrument is internally protected against electrical damage when used for the purposes of testing low voltage electrical installations
as defined herein. If used in a manor other than those defined in this user guide, the protection capabilities could be impaired with
potential risk to the operator and the instrument.
Symbols used on the instrument are:
GCaution: Refer to accompanying notes
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Maximum 300 V a.c. CAT IV to earth
> 600 V Maximum nominal system voltage of 600 V
fInstrument protected by 2 x F2 1000 V 30 kA fuses
cEquipment complies with current EU Directives
This equipment should be recycled as electronic waste
Equipment complies with ‘C tick’ requirements
12 V DC charger socket

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1. Introduction
Congratulations on your purchase of a genuine Megger Multifunction tester. The MFT1700 series Multi-function tester is a compact
instrument designed to perform all of the functions required by the electrical contractor to fully test domestic, commercial and industrial
wiring. Specially designed to comply with U.K., European and other International wiring regulations and standards, the MFT1700 may
be used on all single and three phase systems with rated voltages up to 300 V AC. rms to earth (ground).
2. Overview
2.1 Front panel and controls
2.1.1 Display
NOTE: Some features detailed within this user guide are model dependent. Not all features appear
on all models
Test button
Lead Null
Test lock
Setup selector
Results store
Test lock
Setup selector
Touch voltage
contact point
Mode
Display
backlight
Display
Primary
functions
Secondary
functions
Test button
Lead Null

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Display symbols
Symbol Meaning Symbol Meaning
lTest function locked on (also used to indicate a
change is saved in setup) GWarning triangle – instruction to refer to this user
guide
zTest lead null active fFuse blown
UL= 50V Touch voltage limit (and Earth test voltage) set to
50 V (change setup) Battery indicator
Buzzer enabled NiMH Battery type set to rechargeable NiMH - Change
in setup section 10
AUTO RCD test in AUTO mode >100 V
Indicates that the ground noise voltage exceeds
the instrument measurement capability (test is
inhibited)
Type AC RCD selected Rp (Rs)
Potential stake (P stake)
resistance exceeds range for accurate
measurement
Type A RCD selected Rc (RH)
Current stake (C Stake)
resistance exceeds range for accurate
measurement
SType S RCD (Type AC) V Ground noise voltage exceeds range for accurate
measurement of resistance
SType S RCD (Type A) V VCLAMP error
Type B RCD selected I ICLAMP error
Fast or Full RAMP test selected Bluetooth®enabled
TEST Instrument is running a test TInstrument is too hot, allow to cool
Earth loop noise detected.
N<->L Live and neutral connections reversed
Zref Reference loop measurement
R1+R2 Loop measurement with Zref value automatically
deducted
ZMAX Loop maximum measurement
2.2 Waste electrical and electronic equipment
WEEE
The crossed out wheeled bin placed on Megger products is a reminder not to dispose of the product at the end of its life with
general waste.
Megger is registered in the UK as a producer of electrical and electronic equipment. The Registration No is WEE/HE0146QT
2.3 Battery and fuse location, fitting and replacement
Battery type: 6 x 1.5 V Alkaline LR6 (AA) or NiMH HR6 rechargeable
Fuse type: 2 x F2 1000 V 30 kA fuses

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Battery condition is shown by the following display symbols:
Where NiMH rechargeable batteries are fitted, the battery condition display can be adjusted accordingly. Refer to section 10 Setup
options to change between alkaline and rechargeable batteries.
When set to NiMH batteries, the battery indicator in the display wil show NiMH under the battery status symbol as below: (Feature
available on all models).
To replace batteries or fuse:
Switch off the instrument.
Disconnect the instrument from any electrical circuits.
Remove the battery cover from the base.
For battery replacement:
a) Remove old cells and refit new batteries following correct polarity as marked on the battery holder.
c) Replace the battery cover.
Incorrect battery cell polarity can cause electrolyte leakage, resulting in damage to the instrument.
For fuse replacement
a) Withdraw each fuse in turn and check for failure. The blown fuse must be replaced with a F2 1000 V 30 kA fuse.
Rechargeable batteries and battery charging
Some models are supplied with rechargeable NiMH cells. These batteries can be charged in the instrument, using the supplied Megger
charger.
To charge the batteries:
Ensure fitted batteries are of the rechargeable NiMH type.
Connect the 12 V DC plug of the charger to the socket on the front of the MFT marked
Warning: Whenever battery cells are being recharged, there should be no connections to the instrument terminals and the instrument
should be switched off.
Warning: Do not attempt to recharge non-rechargeable (Primary) cells. Doing so may result in instrument damage and may
cause personal injury.
Ensure ambient temperatures are between 4 ºC and 40 ºC while charging the MFT.
Note: The crossed out wheeled bin placed on the batteries is a reminder not to dispose of them with general waste at the end of their
life.
Spent Alkaline and NiMH batteries are classified as portable batteries and should be disposed of in the UK in accordance with Local
Authority requirements. For disposal of batteries in other parts of the EU contact your local distributor.
Megger is registered in the UK as a producer of batteries.
The Registration number is BPRN00142

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3. Operation
3.1 General operation – all models
3.1.1 Switching on
Turn the rotary knob away from the off position.
The instrument will perform internal self tests then display the appropriate test screen, depending on the position of the function knobs.
3.1.2 Switching off
Turn the primary function knob to the OFF position.
The instrument will automatically turn itself off after 20 minutes* of inactivity. Press any button or turn either of the rotary knobs to turn
back on.
* 2 minute option in Setup, refer to section 10.
3.1.3 Backlight
Press the backlight button. The backlight will operate for 20 seconds.
3.1.4 Test buttons
Test buttons are duplicated on the left and right. Both buttons perform the same function except, when the is displayed, in this case
the right hand buttons perform a scrolling function. The left RED button also performs storage and lock functions on the MFT1731.
3.1.4 Test button lock
To lock the test button, hold down either of the RED test lock buttons with the Lsymbol, whilst holding down the test button. If is
displayed, the right hand buttons perform a scrolling function.
3.2 Mode button functions
The function of the mode button is dependent on the test function selected:
Test selected Function Options Comments
V/ºC Volts (mv model specific) Temperature requires suitable transducer
Continuity
RLO
Buzzer
ENABLE/DISABLE
Buzzer ON
Buzzer OFF
Buzzes on <2 Ω
May be changed in SETUP.
Refer to Section 10.
Insulation
RSIO Buzzer
ENABLE/DISABLE
Buzzer ON
Buzzer OFF
Buzzes on <1 MΩ
May be changed in SETUP.
Refer to Section 10.
Loop impedance (Z)
L-PE
3Lo - 3 wire no trip
2Hi – 2 wire high current
2Lo – 2 wire no trip
3Lo
2Hi
2Lo
3Lo default measurement
2Lo not available if 3 wire connection is
detected
RCD/GFCI
0º /180º selection 0º
180º (Press and release)
RCD Type
AC
A
AC(s)
A(s)
B
(Press and HOLD)
Type B available on MFT1721 and
MFT1731 only
EARTH (RE) Touch voltage limit 50 V/ 25 V (Press and release)
MFT1731 only
SETUP Refer to instrument setup
section 10.

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3.3 Test inhibit
Each test mode has conditions under which testing will be inhibited, as below:
3.3.1 Insulation
Detection of a circuit voltage above 50 V (a warning is displayed at 25 V)
3.3.2 Continuity
Detection of a circuit voltage above that used by the instrument will inhibit testing
3.3.3 Earth loop impedance
Touch voltage exceeds 50 V (or 25 V depending on instrument configuration)
Supply voltage over range or under range
Supply frequency out of specification
3.3.4 RCD/GFCI testing
Touch voltage detected or predicted to exceed 50 V (or 25 V depending on instrument configuration)
Supply voltage over range or under range
Supply Frequency out of specification
3.3.5 Earth testing
External voltage greater than 25 V present
Leads not connected as per the test requirements
Potential stake not within range (Rp)
Current stake not within range (Rc)
Other conditions that will inhibit testing include:
3.3.6 Battery exhausted
All testing will be inhibited in the event of a flat battery, refer to section 2.3.

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4. Voltage, frequency, current and temperature measurement
4.1 Making a voltage measurement
1. Set the Main rotary range knob to volts

(The position of the right hand rotary range knob does not matter)
2. Using two test leads, connect test leads to the L1 (+ve) and L2 (-ve) terminals
L1
L2
L3
N
E
L1
L2
L3
N
E
OR if Using the Mains plug Lead SAI10:
a. For Live to Neutral measurements, connect the Red connector to the L1 terminal and the Blue connector to the
L2 terminal
b. For Live to Earth measurements connect the Red test to the L1 terminal and the Green connector to the
L2 terminal
L1
N
E
L1
N
E
Connection (a) Connection (b)
Note: When connecting all three test leads (eg Phase, Neutral and Earth) or the mains plug test lead, the voltage displayed
is the highest of the three possible voltages.
Pressing either TEST button scrolls through L-E, N-E and L-N individual voltages. When the frequency of supply is shown, the voltage
displayed reverts to the maximum voltage across all 3 terminals.
On models with a dedicated mV range this is selected using the Mode button to select mV mode.
4.2 Frequency measurement
1. Automatically displayed when connecting to a live circuit as per 4.1 above
4.3 Phase rotation (Not MFT1711)
Display of Phase rotation is Automatic when all three test leads are connected to the 3 phase supply as below:
1. Set the main rotary range knob to volts V
(The position of the right hand rotary range knob does not matter)