Datasheet

LTW300
2 Wire loop impedance testers
b) Auto test extension
Automatically extends a test up to a further 10 seconds if
noise is detected, to improve the accuracy of the test.
AUTO START
An auto-start function will start the loop test running as
soon as the test leads are connected. No need to press the
test button means much safer testing.
Operating voltage
The instruments will operate on a wide range of electrical
voltages (see table below) from 50 V a.c to 300 V a.c single
phase supplies and up to 440 V a.c on 3 phase installations.
These include centre tapped 110 V a.c circuits, with 55 V
phase to earth.
LTW315 is limited between 100 V – 280 V.
High resolution test
The LTW425 offers a high current high resolution loop test
to three decimal places. This is ideal for establishing the
correct Ze on an incoming supply, especially on PME
installations. Results of this test can also be used to
calculate higher PFC results.
PFC Display
All instruments can calculate up to 20 KA.
The LTW425 can calculate up to 40 KA using the 0.001 Ω
high current, resolution test range.The calculation uses the
measured loop impedance and the measured line voltage to
calculate the appropriate PFC.
Standards
All the Megger LTW300 series Loop testers meet or exceed
the UK and International Wiring Regulations, including
requirements of BS7671 and VDE 0413 parts 1 and 4, HD
384, IEC 364, NFC15-100, and NEN3140 and EN 61557.
In addition the range meets the requirements of BSEN
61010-1 for safe connection to Category IV supplies (300 V
Phase to Earth).
All LTW300 series instruments are warranted for a period of
3 years.
Calibration Certificate
All LTW300 series instruments are supplied with a Megger
calibration certificate, produced at the time of manufacture.
APPLICATIONS RADIAL CIRCUITS
Measurement of impedance of a ‘live’ electrical circuit
cannot be made using a continuity tester. Thus an earth
loop tester must be used.
Earth loop testers measure circuit loop IMPEDANCE.
Single and 3 Phase supplies with RCD protection
Radial circuits can now be tested as easily as a wall socket
or distribution panel using the 2 wire tester, where it can be
impractical, very difficult or even impossible to connect a 3
wire tester.
NON-RCD PROTECTED ELECTRICAL CIRCUITS
Any single or three phase supply not exceeding 300 V phase
to earth or 440 V phase to phase can safely be tested.
RADIAL CIRCUITS
Radial circuits where the circuit does not return to the ori-
gin are as easy to test as ring circuits, using the 2 wire tester,
even where only a phase and neutral contacts are available.
110 V INSTALLATIONS
110 V a.c systems including 110 V Centre tap to earth (55
V phase to earth) can be tested on the secondary winding,
either at 110 V or 55 V on the centre tap to earth.
AUTOMOTIVE ELECTRICAL DISTRIBUTION
SYSTEMS
Typically consisting of 230 V, 415 V and 110 V (centre taped)
distributed supplies, driving an auxiliary generator off the
engine. Automotive supplies can present particulary difficult
with variable voltages depending on engine RPM and
voltage specifications that may exceed standard utility
voltages.
LTW SUMMARY CHART
LTW315 LTW325 LTW335 LTW425
Loop testing
2 wire non-tripping
Loop testing n n n n
2 wire fast test
(high current) n n n n
110 V to 280 V applications n n n n
50 V to 440 V applications n n n
Phase to Phase testing n n n
20 KA PFC range n n n n
40 KA PFC range n
0.01 Ω resolution n n n n
0.001 Ω resolution n
AUTO noise detection n n n n
AUTO Start loop test n n n n
Voltage measurement n n n n
Frequency measurement n n n n
Max Zs display n n n
R1+R2 display n n n