- Designed for BS 7671 installation testing
- Four insulation test voltages up to 1000 V
- Supports Type B and three-phase RCD tests
- Measures phase rotation and clamp current
Megger MFT1721 Multifunction Tester
Built for electricians and electrical contractors testing low-voltage installations to BS 7671, the Megger MFT1721 Multifunction Tester combines the functions required to certify domestic, commercial and industrial fixed wiring. It supports single-phase and three-phase systems, with TRMS voltage and frequency measurement, 100 V, 250 V, 500 V and 1000 V insulation testing, selectable 15 mA or 200 mA continuity, loop impedance and prospective fault-current measurement. Model-specific capabilities include phase rotation, phase-to-phase loop testing, R1 + R2 measurement and leakage-current measurement through the optional MCC1010 clamp.
RCD functions cover Type AC, A, S, B and programmable devices, alongside three-phase testing where no earth connection is available, Auto sequences and ramp testing. Two and three-wire non-trip loop modes support measurements on RCD-protected circuits, while the Confidence Meter analyses circuit noise during 3Lo testing and indicates the confidence of the displayed result. Colour-coded rotary controls, dual TEST and LOCK buttons, a backlit dual-measurement display, automatic test start, IP54 protection and a 300 V CAT IV rating support clear operation across demanding installation environments.
Key Benefits
- Combines insulation, continuity, loop, RCD, voltage, frequency and phase-rotation functions in one tester
- Four insulation test voltages support measurements from 100 V to 1000 V
- Selectable 15 mA and 200 mA continuity currents support different test requirements
- Two and three-wire non-trip loop modes support testing on RCD-protected circuits
- Phase-to-phase loop testing extends operation across three-phase installations
- Zref and R1 + R2 modes automatically deduct the stored reference loop value
- Type B and three-phase RCD functions support tests unavailable on the MFT1711
- Auto RCD testing performs the test sequence at 0° and 180° without further instrument operation
- The optional MCC1010 clamp enables AC leakage-current measurement
- Automatic test starting leaves both hands available for holding the probes
Common Applications
The Megger MFT1721 Multifunction Tester is suitable for a range of low-voltage installation testing tasks, including:
- BS 7671 electrical installation testing and certification
- Domestic fixed wiring installation testing
- Commercial fixed wiring installation testing
- Industrial fixed wiring installation testing
- Single-phase and three-phase system testing
- Insulation resistance and continuity testing
- Loop impedance, PFC and PSCC measurement
- Type AC, A, S, B and programmable RCD testing
- Three-phase RCD testing without an earth connection
- Phase rotation and leakage-current measurement
Why Choose This Model?
The MFT1721 suits electricians who require 100 V insulation testing, 15 mA continuity, phase-to-phase loop measurement, R1 + R2 calculation, phase rotation, Type B and three-phase RCD testing or current measurement through an optional MCC1010 clamp. These model-specific functions are not provided by the MFT1711.
Product Comparison
| Feature | Megger MFT1721 | Megger MFT1711 |
|---|---|---|
| Insulation test voltages | 100 V, 250 V, 500 V and 1000 V | 250 V, 500 V and 1000 V |
| Continuity test currents | 15 mA and 200 mA | 200 mA |
| Phase-to-phase loop testing | ✓ | — |
| R1 + R2 measurement | ✓ | — |
| Phase rotation | L1-L2-L3 and L1-L3-L2 indication | — |
| Type B RCD testing | ✓ | — |
| Three-phase RCD testing | Supported without an earth connection | — |
| Maximum RCD rating | 1000 mA | 500 mA |
| Current measurement | With optional MCC1010 clamp | — |
| SP5 switched probe support | ✓ | — |
General Specifications
| Specification | Details |
|---|---|
| Product type | Multifunction tester for low-voltage electrical installations |
| Model and order code | MFT1721-BS, 1008-123 |
| Supported installations | Domestic, commercial and industrial fixed wiring on single-phase and three-phase systems |
| Display | Large backlit display with Megger digital/analogue arc and dual digital readout |
| Controls | Colour-coded rotary switches with TEST and LOCK buttons at both ends |
| Automatic test start | Automatic continuity testing with selectable loop and RCD auto-start functions |
| Insulation test voltages | 100 V, 250 V, 500 V and 1000 V |
| Insulation alarm thresholds | 0.5 MΩ, 1 MΩ, 2 MΩ, 3 MΩ, 4 MΩ, 5 MΩ, 7 MΩ, 10 MΩ, 50 MΩ, 100 MΩ and 500 MΩ |
| Continuity test currents | 15 mA or 200 mA, user selectable |
| Continuity buzzer thresholds | 0.5 Ω, 1 Ω, 2 Ω, 5 Ω, 10 Ω, 50 Ω and 100 Ω |
| Loop test modes | 3Lo three-wire non-trip, 2Lo two-wire non-trip and 2Hi two-wire high current |
| Loop functions | Z, Zmax, Zref, R1 + R2, PFC and PSCC |
| Loop result display | Loop impedance and prospective fault current displayed simultaneously |
| RCD types | Type AC, A, S, B, programmable and three-phase RCDs |
| RCD test functions | 1/2 x I, 1 x I, 5 x I, ramp and Auto testing at 0° and 180° |
| RCD ratings | 10 mA, 30 mA, 100 mA, 300 mA, 500 mA and 1000 mA |
| Phase rotation indication | L1-L2-L3 and L1-L3-L2 |
| Clamp current measurement | Supported with the optional MCC1010 current clamp |
| Input protection | Protection against live circuits up to 600 V during insulation testing, including when the test is locked on |
| Fuse type | 2 x F2 1000 V 30 kA fuses |
| Ingress protection | IP54 |
| Installation category | 600 V CAT III / 300 V CAT IV, maximum phase-to-phase voltage 550 V |
| Safety standards | BS EN 61010-1:2010 and BS EN 61010-30:2010 |
| Measurement standard | IEC 61557:2007 parts 1 to 10 |
| EMC | IEC 61326 edition 2, Class B locations |
| Power supply | 6 x 1.5 V IEC LR6 AA alkaline cells or 6 x 1.2 V NiMH HR6 rechargeable cells |
Measurement and Accuracy Specifications
| Measurement Function | Range and Resolution | Accuracy |
|---|---|---|
| 1000 V insulation resistance | 10 kΩ to 999 MΩ | ±3% ±2 digits |
| 500 V insulation resistance | 10 kΩ to 500 MΩ Greater than 500 MΩ |
10 kΩ to 500 MΩ: ±3% ±2 digits Greater than 500 MΩ: ±10% ±4 digits |
| 250 V insulation resistance | 10 kΩ to 250 MΩ Greater than 250 MΩ |
10 kΩ to 250 MΩ: ±3% ±2 digits Greater than 250 MΩ: ±10% ±4 digits |
| 100 V insulation resistance | 10 kΩ to 100 MΩ Greater than 100 MΩ |
10 kΩ to 100 MΩ: ±3% ±2 digits Greater than 100 MΩ: ±10% ±4 digits |
| Insulation test output | Short-circuit current: 1.5 mA nominal Test current on load: ≥1 mA at minimum insulation pass values |
Output voltage: -0% +20% at rated load or less Voltage display: ±3% ±3 digits ±0.5% of rated voltage |
| Continuity and resistance | 0.01 Ω to 99.9 Ω 100 Ω to 99.9 kΩ Open-circuit voltage: 5 V ±1 V Test current: >200 mA or >15 mA at ≤2 Ω |
0.01 Ω to 99.9 Ω: ±2% ±2 digits 100 Ω to 99.9 kΩ: ±5% ±2 digits Maximum service error: ±12% ±2 digits |
| 2Hi loop test | L-PE, L-N and L-L Display range: 0.01 Ω to 1000 Ω Supply: 48 V to 480 V, 45 Hz to 65 Hz Test current: 4.0 A at 230 V PSCC range: 20 kA |
Intrinsic accuracy: ±5% ±3 digits Maximum service error: ±10% ±2 digits |
| 3Lo and 2Lo loop test | L-E display range: 0.01 Ω to 1000 Ω Supply: 48 V to 280 V, 45 Hz to 65 Hz Test current: pulsed PFC range: 20 kA |
0.01 Ω to 39.9 Ω: ±5% ±5 digits 40.0 Ω to 999 Ω: ±10% ±5 digits Maximum service error: ±10% ±2 digits |
| RCD testing | 1/2 x I, 1 x I, 5 x I, ramp and Auto tests Type AC, A, S, B, programmable and three-phase RCDs |
No-trip current: -10% to 0% Trip current: +0% to +10% Ramp current: ±5% ±1 digit Trip time: ±1% ±1 ms |
| Programmable RCD | 10 mA to 50 mA: 1 mA steps 50 mA to 500 mA: 5 mA steps 500 mA to 1000 mA: 10 mA steps |
Maximum service error: ±10% ±2 digits |
| TRMS voltage | 10 V to 600 V | Intrinsic accuracy: ±2% ±1 V Maximum service error: ±5% ±2 digits |
| Frequency | 15 Hz to 400 Hz Resolution: 0.1 Hz |
Intrinsic accuracy: ±0.5% ±2 digits Maximum service error: ±5% ±3 digits |
| Current via optional clamp | 0.5 mA to 199 A AC Resolution: 0.1 mA |
Intrinsic accuracy: ±5.0% ±3 digits Maximum service error: ±10% ±2 digits |
Mechanical and General Information
| Specification | Details |
|---|---|
| Operating temperature | -10 °C to +55 °C |
| Storage temperature | -25 °C to +70 °C |
| Humidity | 90% R.H. at +40 °C maximum |
| Maximum altitude | 2000 m to full safety specification |
| Dimensions | 150 mm high x 85 mm wide x 235 mm deep |
| Weight | 1000 g ±10%, including batteries but excluding test leads, accessories and carry case |
| Case protection | Rubber overmould for protection and grip |
| Operating positions | Handheld, floor standing, placed on a ladder shelf or platform, or suspended around the neck |
| Automatic power off | Selectable 2-minute or 20-minute inactivity period |
| Backlight duration | 20 seconds in manual mode, with selectable Auto mode |
Specification Notes
- Insulation testing is inhibited when circuit voltage exceeds 50 V, with a warning displayed above 25 V
- Type B RCD testing uses the 1 x I range, with 10 mA, 30 mA, 100 mA and 300 mA options for DC testing
- R1 + R2 measurement requires a Zref measurement, which is automatically deducted from the measured loop impedance
Meta Description
Megger MFT1721 Multifunction Tester supports BS 7671 testing with 100 V insulation, Type B RCD testing and phase rotation.
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