Good day. Let's break down what those readings likely indicate and what could be causing them.

Understanding the Readings



Live-Neutral-Earth (Zs): 4 ohms

This is your Loop Impedance, often referred to as Ze or Zs depending on whether you're testing at the origin (Ze) or at a further point in the circuit (Zs). This reading is generally considered quite high. A higher Zs means a lower fault current will flow during a fault, which can increase the disconnection time of the protective device (MCB, fuse). This can be a safety concern.

Live-Neutral (Zs) - 1 ohm

This is still somewhat high, and suggests that the line impedance is too high and can reduce the voltage available at the outlet/fixture.

Possible Causes and Troubleshooting


Poor Connections

This is the most common culprit.

Loose Connections

Check every connection along the circuit path: At the consumer unit (breaker panel): Incoming Live and Neutral connections The MCB terminals (Live in, Live out) The Neutral bar connection The Earth bar connection At the socket/outlet/fixture you're testing: Live, Neutral, and Earth terminal connections In any junction boxes: Check all connections in junction boxes along the circuit. Ensure all connections are tight and properly made (e.g., no loose wires in terminal blocks, proper crimps on connectors).

Corroded Connections

Look for signs of corrosion (rust, green/white residue) on any connections. If found, clean the connections with a wire brush (power off!) and re-tighten. Consider using a corrosion inhibitor.

Under-Tightened Connections

Even if they look tight, double-check the torque on all screws and terminals. Use the manufacturer's recommended torque settings if available. Over-tightening is also bad.2.

Long Circuit Length

Longer circuits naturally have higher impedance due to the resistance of the conductors. While this contributes, it's unlikely to be the sole cause of a 4-ohm reading unless the circuit is exceptionally long.3.

Undersized Conductors

If the wiring in the circuit is too small for the load it serves, the impedance will be higher. This is a major safety issue.

Inspect Wiring

Check the conductor size (written on the cable sheath). Compare this to the requirements for the expected current and the length of the circuit. Consult an electrician to make the correct assessment.4.

Faulty Wiring



Damaged Cable

Look for any visible damage to the cable insulation. Nicks, cuts, or crushing can compromise the conductor and increase impedance.

Neutral or Earth Conductor Break

A partial break in the Neutral or Earth conductor significantly increases the loop impedance.

High Resistance Joint

A joint in the circuit could be poorly made and is introducing resistance into the circuit.5.

RCD Issues

(Less likely, but possible)

Faulty RCD

A malfunctioning RCD (Residual Current Device/GFCI) can sometimes affect loop impedance readings. Try bypassing the RCD (if safe and you know how, otherwise don't) to see if the reading changes significantly.

WARNING

Bypassing an RCD removes its safety protection. Only do this briefly for testing purposes, and only if you are qualified.6.

Supply Transformer Impedance (Ze)

The supply transformer's impedance contributes to the overall loop impedance. While you can't change this, you should know what it is supposed to be. This is measured at the origin of the installation (Ze). If the Ze is high, it will contribute to a high Zs.7.

Testing Equipment



Calibration

Ensure your loop impedance tester is properly calibrated. Use a proving unit to confirm the meter is functioning correctly before and after testing.

Test Lead Resistance

Compensate for the resistance of your test leads. Many testers have a "null" or "zero" function to do this.

Troubleshooting Steps


Power Down



Turn off the power at the breaker/fuse before doing any visual inspection or tightening of connections. This is absolutely crucial for your safety.2. Visual Inspection

Carefully inspect all accessible connections, cables, and devices in the circuit. Look for loose wires, corrosion, damage, and signs of overheating.3.

Tighten Connections

Systematically tighten all screws and terminals in the circuit. Use the correct screwdriver size and torque appropriately.4.

Re-test

After tightening connections, re-test the loop impedance.5.

Segment the Circuit

If the reading is still high, try isolating sections of the circuit to narrow down the problem area. For example, disconnect the wiring at a junction box to test the loop impedance of just that segment.6.

Consult a Qualified Electrician

If you are uncomfortable with any of these steps, or if you cannot find the cause of the high loop impedance,

call a qualified electrician. Electrical work can be dangerous, and it's essential to have a professional diagnose and repair the problem. A high loop impedance is a safety concern and should be addressed promptly.

Important Considerations



Safety

Always prioritize safety. Work with the power off whenever possible. If you must work with live circuits, use appropriate personal protective equipment (PPE) and take extreme care.

Regulations

Electrical work must comply with local electrical codes and regulations.

Documentation

Keep records of your testing and any work you perform on the electrical system.

In summary, a loop impedance of 4 ohms is concerning and should be investigated. Start by checking all connections for tightness and corrosion. If you are not comfortable doing this, or if the problem persists, consult a qualified electrician. Good luck! Flag for review