A landlord’s periodic inspection is the job most inspectors do more than any other. From the outside it looks like a tester moving from socket to socket. There is a sequence behind it, though, and the order you do the tests in is part of what the 2391-52 examines. It is also what keeps you safe on site.
This post follows a straightforward domestic EICR walkthrough and fills in the regulations and the safety detail that a short video skips over.
Why the inspection is being done
The purpose here is the one BS 7671 sets out for periodic inspection. In the video’s words:
“We are on a property which is basically just checking the electrical installation to make sure it’s safe for tenants.”
Regulation 651.2 puts it more formally. Periodic inspection and testing has to confirm that the installation is in a satisfactory condition for continued use. That covers protection against electric shock and burns, protection against fire and heat, whether damage or deterioration has made the installation less safe, and any defects or departures that could give rise to danger. The result goes on an Electrical Installation Condition Report (Regulation 653.1), with its Schedule of Inspections and Schedule of Circuit Details and Test Results.
The walkthrough, stage by stage
| Stage | What was checked | Where BS 7671 deals with it |
|---|---|---|
| Visual inspection | Consumer unit, sockets, switches, obvious damage | Inspection precedes testing (642.1); EICR Schedule of Inspections |
| Earthing and bonding | Main incomer, main fuse, earthing conductor, main bonding to gas and water | 411.3.1.2 (main protective bonding); 542 (earthing arrangements); 544.1 (bonding conductor sizes) |
| Zs at socket-outlets | Whether the circuit has an adequate fault path | 643.7.3; 411.4.5; maximum Zs tables (Table 41.3); Appendix 3 |
| Ze at the origin | The external earth fault loop, supply side only | 643.7.3; supply characteristics on the EICR |
Inspection comes first
The tester in the video starts at the consumer unit with a visual check before picking up an instrument, then goes round the sockets and switches looking for anything broken or obvious. That order is correct. Regulation 642.1 requires inspection to come before testing. A cracked socket front or a scorched accessory is a finding in its own right, and you want to know about it before you put a test lead near it.
The board itself looked fairly modern, with every circuit RCD protected. That is worth recording, not assuming. Regulation 411.3.3 requires additional protection by a 30 mA RCD for socket-outlets rated up to 32 A, and Regulation 411.3.4 extends that to final circuits supplying luminaires in domestic premises. Still, a device being present does not mean it works. RCDs get tested, and the integral test button only proves the mechanism, not the operating time.
With the cover off, the cables were red and black. The video handled this well:
“You can tell with it being red and black it’s not a new installation — doesn’t necessarily mean there’s anything wrong with it.”
That is the right way to think about it. Old core colours are not a defect. Condition, insulation resistance and the adequacy of protection are what count. Where old and new colours meet in the same installation, look for the warning notice required by Regulation 514.14.1.
Earthing and main protective bonding
Next come the main incomer, the distributor’s cut-out, the earthing conductor, and the main protective bonding to the incoming gas and water services. The video calls this “an important one”, and it is. Under Regulation 411.3.1.2, extraneous-conductive-parts such as metallic gas and water pipes must be connected to the main earthing terminal. Check that the conductors are present, correctly sized to Regulation 544.1.1, connected within 600 mm of the meter or point of entry where practicable, and labelled with the notice required by Regulation 514.13.1.
Missing main bonding is commonly coded C2. Undersized bonding needs a judgement based on what is actually there. The EICR coding guide works through how to reach the right classification.
The order of the tests
Once the inspection is done, testing follows the BS 7671 sequence: dead tests first, then live tests.
- Continuity of protective conductors, including main and supplementary bonding
- Continuity of ring final circuit conductors
- Insulation resistance
- Polarity
- Earth electrode resistance, where the system is TT
- Then, and only then, the live tests: Ze, Zs, prospective fault current, RCD operation, and functional checks
The reason matters. A loop impedance test pushes current round the fault path, including the circuit protective conductor. If you haven’t proved that conductor is continuous, you have no basis for assuming the path is there. If it isn’t, exposed metalwork further down the circuit can briefly rise towards line potential during the test. Dead tests make sure the live tests are done on a circuit you already know is sound. The test sequence guide goes through each step.
The video’s Zs test on sockets checks that there is “sufficient earth” on the circuit. More precisely, it confirms that Zs is low enough for the protective device to disconnect within the time Regulation 411.4.5 requires. Compare your reading with the tabulated maximum in Table 41.3. Those figures are at conductor operating temperature, so apply the 0.8 rule of thumb from Appendix 3 to a reading taken at ambient temperature.
Ze: the part the video doesn’t show
The tester then measures Ze, the external earth fault loop impedance from the origin back through the supply transformer:
“I’m going to disconnect the main earth from the fuse box so that we’re not testing any of the earths… only the one that’s outside.”
That method is correct. Disconnecting the earthing conductor from the main earthing terminal removes the parallel paths through the bonding, pipework and structural metalwork, so the reading is the supply’s own loop impedance and nothing else. The video gave no figure, only that it was a good reading.
The clip doesn’t show the isolation step, so here it is plainly. The earthing conductor must never be disconnected while the installation is energised. Once it is off, every exposed-conductive-part in the property has lost its connection to the supply earth. A fault while it is disconnected leaves nothing to clear it. The compliant method is:
- Isolate the installation at the main switch and lock it off. Don’t pull the distributor’s cut-out fuse, which is not yours to withdraw.
- Prove dead using an approved voltage indicator, proved on a known source before and after (Electricity at Work Regulations 1989, Regulations 12 and 13).
- Disconnect the earthing conductor from the main earthing terminal.
- Measure between the supply-side line terminal and the disconnected earthing conductor. These terminals are still live, so use GS38-compliant probes with minimal exposed tips.
- Reconnect the earthing conductor before restoring the supply. Check it is secure.
The safe isolation and GS38 post covers the prove–test–prove routine in full. Record Ze on the EICR’s supply characteristics, and say so if you used a figure from the distributor instead of measuring it.
Reaching the overall assessment
After inspecting and testing, every observation gets a classification: C1 (danger present), C2 (potentially dangerous), C3 (improvement recommended) or FI (further investigation required). Any C1, C2 or FI makes the overall condition unsatisfactory. You also record the agreed extent and limitations, such as floors not lifted or circuits that could not be isolated, and the recommended interval to the next inspection under Regulation 652.1.
In the exam
The 2391-52 is open book: 60 questions in 120 minutes with a 75% pass mark. That gives you two minutes a question, which is plenty if you know where to look and very little if you don’t. Before the exam, tab Chapter 41 (the maximum Zs tables), Chapter 64 (the initial verification test methods) and Chapter 65 (periodic inspection, frequency and reporting). Questions on test order and on the Ze isolation step reward knowing why the sequence exists, not just the list.
How 2391 Prep Fits Into This
2391 Inspection & Testing Pro has 556 practice questions across 7 subject areas. The ones that bear directly on an EICR walkthrough are Periodic Inspection, Test Procedures, Fault Coding, and Safe Isolation and GS38. The app’s 4 working calculators include Maximum Zs, which applies the 0.8 correction to Table 41.3 and checks a measured reading against it. Among the 15 quick reference cards, the test sequence and procedure card gives you the dead-then-live order at a glance, and the 6 field tools are built for use on site. For a free start, try the periodic inspection practice questions.
