Electrical Testing

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Domestic 240 volt house installations

Modern housing has PVC sheathed cables. Barn and chapel conversions may have wires coated in mineral wool, rubber, cotton-pitch, who knows? Old farmhouses can have many outbuildings with power. Pools, garages, stables, kennels, water features, a variety of buildings can house many strange things that run on electric power.

This broad diversity means that there is no single recipe to follow when deciding if an installation is safe. It's up to the electrician to make that call, based on experience more than decree.

Electrical Installation Condition Report (EICR)

This is a 5-year cyclic test defined and introduced in the late 2000 era and it became mandatory for rented domestic properties in England in 2001-2. It is now difficult to sell any property in England without getting an EICR first. The report has to be written and signed by the Tester, who must belong to a recognised trade body, such as NECEIC or NAPIT

Preparing for an EICR

If you live in or rent out a normal domestic home, from a studio flat to a family house, there are some issues you should know about before you book an electrician to make the tests.

  • The test takes upwards of 2 hours usually. One man for simple jobs, two men for large rambling houses where there may be a lot of walking up and down stairs between the switch panel, known as the Consumer Unit, and the electrical outlet under test.
  • The result comes on many pages of a pre-printed form, many tick-boxes and several value entries. It will be signed by the Tester.
  • The outcome is one of two : satisfactory, or unsatisfactory. This is enlarged by a list of findings which are given failure categories : C1 C2 C3 F1
  • There is no ongoing obligation for the Tester to stay and fix anything, or return. Job done, he's gone.

To prepare yourself, you can make some initial visual checks and get the easy stuff fixed, either by quote from an electrician or DIY.

  • Do you have a modern consumer unit with three kinds of switch in it? A Main switch, one or two ELCB, a row of MCBs. If not, it may cause a problem. You'd need a very lenient tester. Best to upgrade first.
  • Are there any light switches, sockets, lamp-holders etc. that are cracked? Or burnt? Get them replaced.
  • Can you see any coloured wires anywhere? red-black-blue-brown-yellow? Exclude green and green/yellow, those are earth wires. All wires must be double-sheathed until inside their terminating unit, so only the grey outer sheath should be visible. The consumer unit also. Any long exposed wires should be covered by plastic electrical trunking. That can be bought at any DIY store; it's a 2-part click-together item.
  • Have you done any DIY fitting of showers, concealed lighting, dimmers, or motion detectors? It's worth revealing such to your chosen EICR tester before he visits, he can quickly tell you if you've violated any safety rules so you can fix them before the test.
  • Have you removed or painted over any labels near the consumer unit? Or any earth-bonding strips around pipes? Those usually have a metal tag on them stamped "do not remove". Have you boxed in any such strips so they can't be seen? If you covered the ugly pipes then you need to unscrew enough for a visual inspection. Or maybe find a pre-prettying photograph of them?

The test procedure

Your Tester will have several bits of gear. He will unscrew a number of "terminations" at random - sockets and light fittings mostly, to check the quality of the wiring behind. There will be a lot of back-and-forth, so keep the access clear by the consumer unit. You will be without power for several periods, so don't start cooking.

Your first hurdle is when he doesn't find bad any regulation violations. No problems with lights, fans or sockets too close to a bath, shower or sink. He may find a lack of labels or lack of identifying sleeves on switch-wires, but these are code-3 (C3) faults for which you just get a warning. No MCBs fuses or cables the wrong size.

Your second and major hurdle is the test results : continuity and insulation resistance. Continuity problems are broken wires and bad, dirty, burnt connections. Insulation is the long build-up of grease and nicotine behind switches, sockets and light fittings. Dust sticks to this, so do dead spiders and wood-lice. Slugs electrocute themselves, mice chew cables, so do squirrels I hear (not confirmed, may be a liabel).

This is your night-mare. The fault may be behind any bit of plastic. Or behind all of them because of old-age. The latter means a full re-wire perhaps?

The aftermath

If you have a low insulation resistance fault, you could try pleading. There's an absolute no-no below 1.megohm. a big concerned look below 10, a worried grunt below 50. It depends. A new-ish clean house with no outbuildings should be over a hundred megohms. It's the inspector's call.

So if you've been left with an unsatisfactory EICR with either a continuity or insulation fault, it's now a detective scene. DIY is possible.You can buy a cheap insulation tester for £20-30. It generates a 240-500-1000 volt signal at a tiny current from a 9-volt battery and measures resistance in megohms. It can't kill you, maybe give a tingle if you touch the terminals. For a continuity tester an ordinary multi-meter should do.

Look for the obvious culprits : old pendants, disused bell transformers, sockets near the cooker or in a damp area. Sockets with neons wired the wrong way round (neons show as 60.megohms? might be wrong on this). If you have a ring of sockets, break it half-way and check each half, then quarter it, go on until you find the bad socket.

Light fittings are daisy-chains not rings, work back from the last one. Maybe take the opportunity to modernise some fittings.

You have to hope it IS a fitting and not a wire in the wall with a nail through it. Or a wire stretched to breaking. Or one crushed under a floorboard. Or a rat's dinner.

Good luck.

The re-test

A new EICR test is not usually necessary unless you make major changes or decide to use a different electrician. The "remedials" can be an added inspection note to the original EICR. But some electricians won't sign off DIY work, so it's often easier to start again.