EICR codes explained

The four codes at a glance

The rule is simple: any C1, C2 or FI makes the whole report unsatisfactory. C3s never do, however many there are.

C1: danger present

C1 means someone could be hurt right now: exposed live conductors you can touch, a smashed socket with live parts showing, a metal light fitting that's live because it lost its earth. An inspector who finds a C1 should make it safe before leaving, usually by isolating the circuit or removing the accessory, and tell the person responsible straight away. You'll see C1 items listed with a note of what was done to make them safe.

C2: potentially dangerous

C2 is the most common reason a report fails. It means the installation is not dangerous at this moment, but would become dangerous if a fault occurred, or if someone did something entirely normal. Typical C2s include:

• socket outlets that could be used for equipment outdoors, with no RCD protection;
• no main protective bonding to incoming gas or water pipes;
• an earth fault loop impedance too high for the breaker to disconnect quickly enough;
• signs of overheating at terminals or accessories;
• a consumer unit with missing blanks or damage that leaves live parts reachable with a finger.

FI: further investigation required

FI is used when the inspector has seen something that may be dangerous but can't confirm it within the time or access available. An example is a circuit that tests as having low insulation resistance, where finding the cause means lifting floors. An FI isn't a polite way of saying "we don't know": it should describe a specific concern that needs checking without delay. Once investigated, it either becomes a C1, C2 or C3, or it's cleared.

C3: improvement recommended

C3 marks something that doesn't meet the current edition of BS 7671 but isn't dangerous. Plenty of older installations were built to earlier rules, and they're not unsafe just because the rules have since changed. A common C3 is a distribution board mounted too high to reach easily: it's inconvenient, not dangerous. On one commercial report we reviewed, that was the only observation across seven boards, and the result was correctly satisfactory.

C3s are worth planning for, especially when you're doing other work, but they don't need fixing for the report to pass, and a landlord isn't required to fix them within 28 days.

Section by section: reading the rest of the report

The codes get the attention, but the other sections tell you how much the report is worth.

Reason for the report and details of the installation

Who asked for it, the date, the type of premises and the estimated age of the installation and of any alterations. If "evidence of alterations" says yes, expect more observations.

Extent and limitations

This is the section most people skip and the one that matters most. It records how much of the installation was actually inspected. On large or occupied premises, inspectors sometimes agree to test a sample, for example "25% of installation", and exclude roof spaces, floor voids or accessories above a certain height. That can be reasonable, but a satisfactory result then only applies to what was looked at. If a landlord's report covers a quarter of the house, ask why.

Summary and recommended next inspection

The overall Satisfactory or Unsatisfactory result, and the date the inspector recommends for the next inspection. For rented homes, the date on the report becomes your legal deadline, even if it's sooner than five years.

Supply characteristics and earthing

The earthing arrangement (TN-C-S, TN-S or TT), the external earth loop impedance (Ze), the prospective fault current, the main switch, and the size of the earthing and bonding conductors. Missing bonding to gas or water shows up here.

Schedule of inspections

A long checklist with a tick, a code, N/A or LIM against each item. A lot of LIMs (limitations) here, for example on concealed cables or accessories, should match what the extent and limitations section says.

Schedule of circuit details and test results

One line per circuit, for every distribution board. This is where you can see whether the inspector really tested the installation. A report with descriptions but no test readings tells you very little.

Understanding the test results

You don't need to be an electrician to sanity-check the numbers:

• Insulation resistance: should be at least 1 MΩ. Healthy modern circuits usually show ">200" or similar. Readings in single figures on an old installation are worth asking about.
• Ring final circuits (r1, rn, r2): the line and neutral readings should be almost identical. For standard 2.5/1.5 mm² cable, the earth reading is about 1.67 times higher. Big differences can mean a broken ring.
• Measured Zs: should be below the maximum Zs listed for the protective device on that line. If it's above, the breaker may not trip fast enough in a fault.
• RCD trip times: a 30 mA RCD must trip within 300 ms at its rated current. Most trip in 15–40 ms. Each RCD should also have its test button confirmed.

Lots of "N/A" or blank boxes against circuits that clearly exist, with no matching limitation, is a sign of a light-touch inspection.

What to do next

If your report is satisfactory, file it and note the next inspection date. Landlords must give a copy to tenants within 28 days. If it's unsatisfactory, get the C1, C2 and FI items quoted and fixed, then keep the certificates for the remedial work with the report. Our guide on what to do when an EICR fails covers this in detail, or book an EICR with us.