An earth loop impedance test is conducted to make sure that, if a fault occurs in an electrical circuit, the fault current will strong be enough to set off the circuit protection. If a fault current is left undetected, circuits can overheat and catch on fire.

Electricity takes the path of least resistance to the ground. Electrical wiring systems in buildings are often connected to the ground. This is referred to as an earth return circuit. The grounding wire is there for electrical current to pass through when a short circuit happens.

Resistance is a measure of how an electrical current is affected by its path. The resistance in the grounding wire needs to be low so that the fault current can travel down into the ground without causing damage to the system.

If the resistance in the earth return circuit is too high, the fault current may be too low to be detected, and the fault current will continue to travel around the main circuit – causing a short circuit. The circuit protection detects activity along the earth wiring and kicks in when the current is detected. If the resistance is too high, the circuit protection may not operate.

Why is impedance testing important? Well, if you care about the ongoing quality of the circuitry in your building, it’s very important. In order to prevent overheating and fires, the loop impedance needs to operate at a certain level. The only way to maintain this optimum level is with regular testing.

Ensure Safety in Your Building

An impedance check is essential for ensuring safety in your building. Overheated circuitry and damaged wiring are a recipe for disaster. If left unchecked, you might be evacuating your workers during a fire in the near future, wondering where you went wrong.

The best way to run a safe business is to be thorough and invest in preventative measures. Consider all parts of electrical safety and don’t forget your earth return circuits – they’re in place to keep you safe.

Why is impedance testing important for business owners?

If you run a business, you are required to provide a safe working environment for your employees. Fires caused by short circuits will endanger your staff members and have many potential costly ramifications. Every year, the New Zealand Fire Service attend over 20,000 fires. Don’t become part of the statistics – protect your property today.

Why is impedance testing important at home?

Short circuits can occur in any type of dwelling. If you’re a homeowner, landlord, or property manager, we encourage thorough electrical testing throughout your domestic environment. Safety is nothing to mess around with – whether you’re at home or at work.

What happens during a test?

During a resistance test, the technician will use an impedance tester to inspect the earth return circuit. The technician does this by plugging the test machine into a power socket or supply source. Two earth fault loop impedances will be measured. This will be the external impedance (the Ze) and the total system impedance (the Zs). The Zs is a sum of the external resistance, the phase conductor resistance, and the earth conductor resistance.

At Jim’s Test & Tag, we use electrical testing devices that operate a with a low electrical current. We take our readings at this level so that we don’t trip the RCD attached to your circuit with the added electrical activity. If a testing device trips the circuit protection, it means the equipment needs to be replaced or adjusted.

Calculating Loop Impedance


Why is impedance testing important? Now you know! If you have any questions about impedance testing or electrical safety, get in touch with us today. If you want to ensure your building is as safe as possible, make sure you get a FREE QUOTE for our testing services today. There’s no reason to delay. At Jim’s Test & Tag, we genuinely care about safety in your building. Let us visit your property and perform a variety of tests in one easy appointment.

Call now on 0800 454 654 or fill out the online form for your FREE QUOTE.