Where Bright Ideas

Earth Fault Loop Impedance

Earth Fault Loop Impedance

A little known piece of information for home and property owners is something called Earth Loop impedance.

When an electrician visits your home, for any electrical work which includes extending circuits, Fuse board upgrades, and the Periodic Inspection / Electrical Installation Condition report (EICR)  The electrician will carry out an Earth loop Impedance Test amongst other testing of the circuits.

Why is earth fault loop impedance testing important?

It is carried out to make sure that, should a fault occurs in an electrical circuit, the electrical fault current will be strong enough to set off the circuit protection. If this fault current is left undetected, circuits can overheat and catch on fire.

With electricity it takes the path of least resistance to the ground.  Different properties in towns, villages, or even out in the country side have different “Earthing arrangements.  So too do Shops / Offices / Warehouses / factories etc.   Through these the Electrical earth wiring arrangement in buildings are often connected to the ground. In electrical terms this will be  referred to as an earth return circuit. The earthing cables / earthing rods are  there for electrical current to pass through when a short circuit happens.

Earth fault loop tester

The electrician will measure with their equipment the resistance of how an electrical current to assess the earthing by its path. The resistance in the earthing cable / arrangement needs to be low so that the fault current can travel down into the ground without causing damage to the system.

In some cases the resistance of this earth return circuit is too high.  The electrician will find that the earth  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.

Circuit protection by the means of Circuit Breakers, and RCD’s will detect issues along the earth wires – often called Circuit Protective Conductor (or “c.p.c” which is a system of conductors (cables)  joining up all together all exposed conductive parts, which includes earthing Conductors equipotential Bonding, sockets / Switches & light fittings.   The Circuit Protection devices  will switch off should, and when the current is detected.

What if the earth loop impedance be too high?

However should the resistance is too high, the circuit protection may not operate at all. As a user of electrical items you may not notice any issues, however over a period of time your equipment around you my start to deteriorate (stop working or catch fire).  Often we can be called out when a property has fluctuations in current – the light flicker, appliances start to go wrong, or don’t even work.

Why is the earth fault loop impedance testing Important?

If you care about your home / property, you care about the safety of your family, or employees, you should care about the ongoing quality of the electric circuits,

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 electrical testing & inspection..

Earth fault loop impedance for your home / Property

An impedance check is essential for ensuring safety in your home / property. Overheated circuits and damaged wiring are a real recipe for disaster. If your leave the circuits unchecked, you could be having a fire in the near future, wondering where you went wrong.

Why is it important at home to have  impedance testing ?

Short circuits can occur in any type of dwelling.  So should you be a homeowner, landlord, or letting agent, we encourage thorough electrical testing throughout you’re the property. Electrical Safety is nothing to mess around with – whether you’re at home or at work, and the testing carried out by a trained, & Qualified Electrician – not a DIY Novice who has bought a cheap multi-meter off the internet.

What happens during an earth fault impedance test?

During a resistance test, the Electrician will use a specialised calibrated testing meter, to inspect the earth return circuit. The Electrician will do this by plugging the testing machine into a power socket or supply source.

The Electrician will carry out 2x earth fault loop Impedance measurements. 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 (Positive / +) conductor resistance, and the earth conductor (c.p.c / Green and yellow cables) resistance.

Bright Spark Electricians use electrical testing devices that operate a with a low electrical current. The electricians take their readings at this level so that we don’t trip the RCD attached to your circuit with the added electrical activity.  However should at  testing device trips the circuit protection, it could mean equipment needs to be replaced or alterations to the circuits may be required.

Will the electricity have to be switched off?

Some of our testing is carried out with the power on, however all the equipment will be needed to be unplugged, from the wall sockets.   Other parts of the testing requires the electricity to be switched off as we don’t want our electricians carrying out the testing to be electrocuted.

Depending on the size of the property, and distribution boards, the electricity may be off from around an hour to a number of hours. 

Do we need to provide access?

When testing we need clear access to the Consumer unit / fuseboard so we can open it up, and get to it comfortably as our electrician may need to have their hands in there for quite some time.

Our electrician will also need access to the electricity meter and the big Black fuse where the cable comes into the property.

Our electricians will also need access to Sockets, and switches, so if there are cupboards / Cabinets filled with items,  or lots of ornaments on the top, these will be needed to be able to move away with your assistance. If we find we are left to move ornaments, we lay these down on soft furnishings near by to avoid any damage, but do not actually log the original positions of the items on the furniture.

Do we have to turn off & unplug things such as Fridges / Freezers / computers / Television recording devices?

In simple truth YES, some items can be left plugged in until the essential tests are carried out, and as soon as the tests completed can be plugged back in.  Althouogh our electricians are brilliant, they cannot always remember which of a multitude of plugs were plugged in or even switched on as unfortunately testing up to 2-3 properties a day, all plugs look the same after a while.

Should you have any questions about impedance testing or electrical safety, please do not hesitate to get in touch with us today. If you want to ensure your Home or Property is as safe as possible, call us for your FREE QUOTE for our testing services.

The costs for Testing are calculated from the number of circuits / fuses / Circuit breakers in you Consumer unit, so a photograph of one of these is usefull for us to provide a FREE QUOTATION

If you are unsure then there no reason to delay. Bright Spark Electrical services genuinely care about safety in your Property, so please contact us to visit your property and perform a series of tests in one easy appointment.

Telphone: 01892 531728

Or

Email:  karen@brightsparkelectrian.co.uk