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IEC 60364-4-417 min read

Worked Example: Touch Voltage from an Unbalanced Neutral/Earth Current

A modest 15 A imbalance current through a 2 Ω ground path produces a touch voltage that comfortably clears the IEC 60364-4-41 dry-location limit.

Scenario

Neutral/earth imbalance current15 A
Ground path impedance2 Ω
Touch factor1.0 (worst case — full ground potential rise appears across the body)
EnvironmentDry / normal (50 V limit)

Step-by-step calculation

Step 1: Compute the ground potential rise (GPR)

GPR = Iimbalance x Zground
15 x 2
GPR = 30 V

Step 2: Apply the touch factor to find actual touch voltage

Vtouch = GPR x touch factor
30 x 1.0
Vtouch = 30 V

Step 3: Compare against the IEC 60364-4-41 conventional touch-voltage limit

Vtouch ≤ UL?
30 V ≤ 50 V (dry/normal locations)
Passes, with 20 V of margin

Step 4: Estimate the resulting body current for context

Using the commonly-cited IEC 60479-1 reference body resistance of 1000 Ω.

Ibody ≈ Vtouch / Rbody
30 / 1000
≈30 mA (informational only, not itself the pass/fail check)

Result summary

CheckRequirementActualStatus
Touch voltage vs. dry-location limit≤ 50 V30 V✓ PASS
At 30 V, this scenario's touch voltage stays under the 50 V dry-location limit with a reasonable margin — but the same 15 A imbalance current in a wet or conductive location (25 V limit) would fail outright.

Key insight: The touch-voltage limit itself is environment-dependent, not just the touch voltage being checked against it — the exact same electrical fault (15 A through a 2 Ω path) is a comfortable pass in a dry office and a clear fail in a wet or conductive location, which is why IEC 60364-4-41 sets two different limits rather than one universal number.

Try it with your own numbers

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Frequently asked questions

What does the touch factor of 1.0 actually represent?

A touch factor of 1.0 is the worst-case assumption — that the full ground potential rise appears directly across the body (hand to feet, or hand to hand). In practice, the geometry of where a person stands relative to the earthing point, and any additional resistance in the contact path, often reduces the fraction of GPR that actually reaches the body — but assuming the full value by default is the conservative, safety-first starting point.

Would this same fault pass in a wet location?

No — the wet/conductive-location limit is 25 V, and 30 V exceeds that. This is exactly the kind of case where the environment classification, not just the raw electrical numbers, determines whether a design is acceptable — the same physical installation might need additional bonding or a lower-impedance ground path specifically because of where it's located.

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