Use the calculator as a pre-check, not a certificate
Treat the output as an early review. Final values still need proper design, inspection, testing and current BS 7671/manufacturer data.
Electrical calculator · insulation resistance / IR test / megger / fault finding
Insulation Resistance Test Triage
Turn L-N, L-E and N-E insulation-resistance readings into practical next-step notes for damp circuits, appliances and fault finding.
For electricians reviewing low or borderline MΩ readings without treating a web tool as certification.
Field notes
Field notes for IR test triage
Practical checks to run before this calculator result turns into a site decision.
Compare against the actual protective device
Device type, rating, breaking capacity, curve, RCD type and correction factor assumptions can change the conclusion. Do not rely on a generic label.
Write down the assumptions
If the result is used in a job discussion, record Ze/Zs, cable data, correction factors, supply voltage and any reason for accepting, splitting or investigating the circuit.
FAQ
IR test triage FAQ
Short answers for UK temporary electrical and HVAC planning.
What is the IR test triage used for?
Turn L-N, L-E and N-E insulation-resistance readings into practical next-step notes for damp circuits, appliances and fault finding. It is mainly for UK electrical review work, especially where a quick pre-check is needed before selecting equipment or changing a temporary setup.
Can this replace BS 7671 design, inspection or testing?
No. Treat it as a pre-check for the conversation or job file. Final decisions still need current BS 7671 requirements, manufacturer data, inspection, testing, risk assessment and the actual site conditions.
What should I verify before acting on the result?
Check current BS 7671 values, manufacturer device data, measured results, earthing arrangement, correction factors and site installation conditions. If any assumption is uncertain, use the result as a prompt to investigate rather than as clearance to switch on.
What does an amber or red result usually mean?
It normally means the margin is weak, an assumption is missing, or the load should be split, staged, moved closer to the supply, reduced or checked by a qualified electrician before use.
Next tools in this workflow
See job flows
Calculator · BS 7671 / voltage drop
HVAC voltage drop envelope
Estimate voltage drop over long leads for heaters, air movers, dehumidifiers and portable AC, with compressor start warnings.
Calculator · PFC / PSCC
PFC / fault current
Estimate PSCC or PEFC from Ze and voltage, compare against device breaking capacity, and draft a quick test-sheet note.
Calculator · max Zs / MCB
Max Zs checker
Check a measured Zs value against an entered device limit, with optional 80% rule headroom and clear pass/check wording.
Calculator · CPC / adiabatic
CPC adiabatic
Use the adiabatic equation shape to compare fault current, disconnection time, k factor and CPC size as a planning aid.