Periodic Requirements
13%of exam
Safety Management
5%of exam
Periodic Inspection
17%of exam
Periodic Testing
65%of exam
Quick Facts
- Qualification
- City & Guilds 2391-51
- Award
- Level 3 Award
- Scope
- Existing electrical installations
- Mandatory unit
- 2391-501
- Online test
- 2391-051
- Online items
- 40 multiple-choice questions
- Online time
- 90 minutes
- Online condition
- Open book; invigilated
- Online pass
- Approximately 75%
- Pass adjustment
- Reliability adjusted
- Visual task
- 30 minutes
- Practical task
- 150 minutes
- Short-answer task
- 60 minutes
- Guided learning
- 41 hours
- Total time
- 55 hours
- Entry profile
- Experienced electrotechnical candidates
- BS 7671 edition
- Check live assessment materials
Report Pack
Report, inspections, circuits, results, recipient guidance.
EICRInspection scheduleCircuit scheduleTest resultsRecipient guidance
2391-51 vs 2391-50
2391-51
- Existing installations
- Periodic condition reporting
- EICR focus
2391-50
- New or altered work
- Initial verification
- EIC focus
Match award to installation stage
Assessment Reference Picker
- Taking online test→Paper references only
- Taking visual Task A→No references
- Performing practical Task B→No reference materials(During testing)
- Confirming Task B results→Permitted references(After testing)
- Taking short-answer Task C→Permitted paper references
- Using calculations→Non-programmable calculator
- Selecting publication edition→Follow assessment instructions
- Adding navigation aids→Use compliant page tabs
Qualification Map
- 2391-51
- Periodic inspection awardExact scope
- 2391-501
- Mandatory unitPass required
- 2391-051
- Online multiple-choice testPass required
- Assessment
- Online test plus assignment
- Qualification level
- Level 3
- GLH
- 41 guided hours
- TQT
- 55 total hours
- Candidate profile
- Experienced electrical practitioner
- Newcomers
- Qualification not suitable
Assignment Tasks
Visual thirty; practical one-fifty; written sixty.
Task A visualTask B practicalTask C short-answer
2391-51 vs 2391-52
2391-51
- Periodic pathway only
- Existing installations
2391-52
- Combined pathway
- Initial plus periodic
Do not borrow combined content
Online Blueprint
- Requirements
- 5 questions13%
- Safety management
- 2 questions5%
- Periodic inspection
- 7 questions17%
- Periodic testing
- 26 questions65%
- Online total
- 40 questions
- Online duration
- 90 minutes
- Online format
- Multiple-choice
- Online result
- Pass or fail
- Indicative pass
- Approximately 75%
Extent vs Limitation
Extent
- Planned coverage
- Agreed before work
Limitation
- Restricts planned coverage
- Reason must be recorded
Do not disguise reduced scope
Source Hierarchy
- EAWR
- Workplace electrical safety law
- Health-safety law
- Statutory duties
- BS 7671
- National wiring standard
- Guidance Note 3
- Inspection-testing guidance
- GS38
- Electrical test equipment guidance
- Existing records
- Planning evidence
- Previous certificates
- Installation history
- Manufacturer data
- Equipment-specific criteria
Scope Planning
- Purpose
- Continued-service safety assessment
- Extent
- Agreed inspection coverage
- Limitation
- Recorded excluded access
- Sampling
- Representative inspection selection
- Defects found
- Expand sampling appropriately
- Operational constraints
- Plan disruption controls
- Records review
- Identify installation history
- Client agreement
- Confirm extent beforehand
- Inspector duty
- Record accurate findings
EICR Documents
- EICR
- Condition assessment report
- Inspection schedule
- Inspected-item record
- Circuit details
- Circuit identification schedule
- Test results
- Measured-values schedule
- Recipient guidance
- Report-use instructions
- Extent entry
- Coverage clearly stated
- Limitations entry
- Restrictions clearly justified
- Next inspection
- Recommended interval recorded
Assessment Materials
- Online test
- Paper references permitted
- Online references
- BS7671 OSG GN3
- Electronic references
- Not permitted online
- Visual Task A
- No references
- Practical Task B
- Confirm results only
- Short-answer Task C
- Paper references permitted
- Calculator
- Non-programmable scientific permitted
- Personal notes
- Not permitted
- Highlighting
- Permitted
- Page tabs
- Paper markers permitted
- Short cross-references
- Permitted
- A4:2026
- Published current amendment
- A3:2024
- Valid through 15 October 2026
- Installation transition
- Either edition through 15 Oct 2026
- Assessment edition
- Follow live City & Guilds materials
Isolation Sequence
Identify, inform, isolate, secure, prove, test, reprove.
Identify sourceInform usersSecure isolationProve-test-reprove
Dead vs Live Tests
Dead tests
- Supply securely isolated
- Continuity and insulation
- Prove dead first
Live tests
- Supply energised
- Loop and prospective current
- Additional controls required
Never energise dead-test instruments
Safe Isolation Path
- Work area confirmed→Identify every source
- Affected users identified→Inform before isolation
- Correct circuit confirmed→Operate isolation device
- Circuit isolated→Lock against reconnection
- Warning needed→Attach caution notice
- Tester selected→Prove on known source
- Tester proven→Confirm conductors dead
- Dead confirmed→Reprove voltage indicator
- Alternative source possible→Repeat source controls
Safe Isolation
- Identify
- Correct supply and circuit
- Inform
- Notify affected persons
- Isolate
- Disconnect every relevant source
- Secure
- Prevent reconnection
- Prove tester
- Verify before testing
- Test conductors
- Confirm dead safely
- Reprove tester
- Verify after testing
- Stored energy
- Discharge and control
- Alternative supplies
- Identify every source
Calibration vs Before-Use Check
Calibration
- Periodic accuracy assurance
- Traceable maintenance record
Before-use check
- Immediate condition check
- Required each use
One never replaces the other
Instrument Control
- Correct function
- Match intended measurement
- Measurement category
- Match electrical environment
- Voltage rating
- Suit expected system voltage
- GS38 leads
- Protected probes and leads
- Before-use check
- Inspect instrument condition
- Calibration
- Maintain verified accuracy
- Known source
- Prove voltage indicator
- Instrument identifier
- Record traceable details
- Live measurement
- Apply additional controls
Code Order
Danger, potential, improve, investigate—code actual risk.
C1 = dangerC2 = potentialC3 = improveFI = investigate
EICR vs EIC
EICR
- Reports current condition
- Uses classification codes
- Periodic inspection output
EIC
- Certifies installation work
- Initial verification output
- No condition codes
2391-51 centres on EICR
Observation Code Picker
- Danger exists now→C1(Immediate action)
- Potential danger exists→C2(Urgent remediation)
- Safety improvement advised→C3(Recommendation)
- Danger possibly concealed→FI(Investigate promptly)
- Only C3 observations→Satisfactory(No C1 C2 FI)
- Any C1 found→Unsatisfactory(Danger present)
- Any C2 found→Unsatisfactory(Potential danger)
- Any FI found→Unsatisfactory(Risk unresolved)
Inspection Evidence
- Visual inspection
- Observe accessible condition
- Touch
- Check looseness or heat safely
- Hearing
- Detect abnormal operation
- Smell
- Detect overheating evidence
- IP suitability
- Match environmental exposure
- Damage
- Assess safety significance
- Deterioration
- Assess continued service
- Alterations
- Check safety impact
- Accessibility
- Record genuine restrictions
- Inspection first
- Inform test selection
C1 vs C2
C1
- Danger present
- Immediate action required
C2
- Potentially dangerous
- Urgent remedial action
Distinguish present from potential
Sampling and Limitation Picker
- Scope is negotiable→Agree extent first
- Sampling is proposed→Choose representative sample
- Defect appears→Increase sample appropriately
- Access is impossible→Record genuine limitation
- Shutdown is restricted→Record operational limitation
- Test risks damage→Adapt test method
- Test must be omitted→Document exact reason
- Evidence remains insufficient→Consider FI coding
EICR Codes
- C1
- Danger presentImmediate action
- C2
- Potentially dangerousUrgent action
- C3
- Improvement recommendedAdvisory
- FI
- Further investigation requiredWithout delay
- Unsatisfactory
- Any C1 C2 FI
- C3 only
- May remain satisfactory
- Code basis
- Actual safety risk
- Observation
- State defect precisely
- Recommendation
- Match identified risk
C3 vs FI
C3
- Improvement recommended
- Risk already assessable
- Can remain satisfactory
FI
- Risk unresolved
- Investigation required promptly
- Makes report unsatisfactory
Uncertainty about danger means FI
Inspection vs Testing
Inspection
- Uses senses
- Finds visible condition
- Guides test selection
Testing
- Uses instruments
- Produces measured evidence
- Confirms electrical performance
Inspect before choosing periodic tests
Test Evidence
Predict, measure, compare, interpret, record.
Expected valueActual valueCurrent criterionReasoned conclusion
Ze vs Zs
Ze
- External loop impedance
- Measured near origin
Zs
- Complete circuit loop
- Includes circuit conductors
Calculated Zs uses Ze plus R1R2
Periodic Test Picker
- Verify protective paths→Continuity test(Dead test)
- Verify ring conductors→End-to-end tests(Dead test)
- Detect insulation damage→Insulation resistance(Protect electronics)
- Verify conductor identity→Polarity checks(Context controls)
- Verify electrode resistance→Earth electrode test
- Measure external loop→Ze test(Live precautions)
- Measure complete loop→Zs test(Live precautions)
- Find prospective current→PFC test(Record highest)
- Verify RCD performance→RCD instrument(Apply current criteria)
- Verify three-phase rotation→Phase sequence tester
- Verify device operation→Functional test
- Assess voltage drop→Measured conductor resistance
Continuity Polarity
- Protective continuity
- Verify protective conductor paths
- Main bonding
- Confirm continuity
- Ring line
- Measure end-to-end continuity
- Ring neutral
- Measure end-to-end continuity
- Ring CPC
- Measure end-to-end continuity
- Cross-connections
- Reveal ring irregularities
- R1 plus R2
- Circuit protective path
- Polarity
- Confirm correct conductor connection
- Dead continuity
- Never test energised
R1+R2 vs r1+r2
R1+R2
- Circuit protective path
- Point-specific value
r1+r2
- Ring end-to-end sum
- Whole ring conductors
Capital and lowercase differ
Insulation Resistance
- Purpose
- Detect insulation deterioration
- Dead test
- Isolate before testing
- Sensitive equipment
- Protect before test
- SPDs
- Disconnect when practicable
- Connected equipment
- Prevent test damage
- Separated circuits
- Verify required separation
- Parallel paths
- Interpret measured resistance carefully
- Test voltage
- Select current standard value
- Result
- Compare current permitted criteria
Earthing Loop Fault
- Earth electrode
- Measure electrode resistance
- Ze
- External loop impedance
- Zs
- Complete circuit loop impedance
- Zs relationship
- Ze plus R1 plus R2
- PEFC
- Prospective earth fault current
- PSCC
- Prospective short-circuit current
- PFC
- Highest relevant prospective current
- Loop test
- Live-test precautions required
- Result comparison
- Use current permitted limits
RCD Functional Phase
- RCD instrument test
- Verify disconnection performance
- RCD test button
- Functional operation only
- RCD type
- Select compatible test method
- Fault protection
- Verify applicable criteria
- Additional protection
- Verify applicable criteria
- Phase sequence
- Confirm correct rotation
- Functional testing
- Operate controls and devices
- Isolation devices
- Confirm effective operation
- Manufacturer instructions
- Apply device-specific guidance
Test Selection
- Fixed sequence
- Not recommended periodically
- Inspection findings
- Drive test choices
- Installation condition
- Adapt testing safely
- Installation use
- Consider operational risk
- Extent
- Apply agreed coverage
- Limitations
- Document constrained testing
- Omitted test
- Record reason clearly
- Temperature
- Correct affected results
- Conductor length
- Interpret resistance proportionally
- Parallel conductors
- Account for parallel paths
- Connected load
- Prevent false readings
- Nulling
- Compensate test leads
Results Interpretation
- Expected result
- Predict before testing
- Measured result
- Record actual value
- Permitted limit
- Use current assessment reference
- Unexpected value
- Investigate before coding
- Temperature correction
- Apply where relevant
- Parallel path
- May lower resistance
- Voltage drop
- Use measured conductor resistance
- Circuit load
- Include design conditions
- Documentation
- Transfer results accurately
Common Traps
Universal Test Sequence
Memorised fixed order ≠ Risk-selected periodic testing
Age-Based Coding
Old installation automatically defective ≠ Code actual safety risk
C3 Outcome
C3 automatically unsatisfactory ≠ C3-only may be satisfactory
RCD Test Button
Button proves disconnection time ≠ Instrument verifies performance
Reference Access
Same rules every task ≠ Task-specific material permissions
Electronic Books
Electronic references online ≠ Paper references online
C1 and C2
Both mean immediate danger ≠ Present versus potential danger
Inspection Timing
Test everything first ≠ Inspect then select tests
Calibration Assurance
Calibration replaces checks ≠ Check condition before use
Prospective Fault Current
Record lowest reading ≠ Record highest relevant value
Limitations
Silent exclusions acceptable ≠ Record and justify restrictions
Award Identity
2391-51 equals wiring exam ≠ 2391-51 assesses periodic work
Last Minute
- 1.Confirm 2391-51 periodic scope
- 2.Testing carries 65% online
- 3.Requirements carry 13% online
- 4.Inspection carries 17% online
- 5.Safety carries 5% online
- 6.Carry permitted paper references
- 7.Check live assessment edition
- 8.Remove prohibited personal notes
- 9.Know task-specific reference rules
- 10.Visual Task A forbids references
- 11.Prove voltage indicator twice
- 12.Lock isolation against reconnection
- 13.Identify every possible supply
- 14.Inspect before selecting tests
- 15.Record agreed extent and limitations
- 16.Increase sampling after defects
- 17.Use suitable instrument category
- 18.Check leads meet GS38
- 19.Record instrument identifiers
- 20.Verify calibration status
- 21.Classify actual safety risk
- 22.C1 means danger present
- 23.C2 means potentially dangerous
- 24.C3 means improvement recommended
- 25.FI requires further investigation
- 26.C1 C2 FI mean unsatisfactory
- 27.No universal periodic test sequence
- 28.Document adapted or omitted tests
- 29.Compare results using current criteria
- 30.Complete every EICR schedule
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