RCD standing leakage budget
How much standing leakage one RCD can carry.
Reads AS/NZS 3000:2018 and AS/NZS 3760:2022. Tables checked 1 Oct 2026.
Try a job 4
Each job fills in example values. Replace them with your values.
- Check the leakage on a home office RCDWhether a heat pump, four computers and a fridge stay within budget.
- Find why a workshop RCD tripsFour Class I tools at their test limit against a 30 mA RCD.
- Split an office over RCDs by leakageHow many RCDs six computers and six monitors need.
- Check a 10 mA RCD for childcareWhether a heat pump and chargers fit one 10 mA RCD.
Inputs
Worked example with the default inputs. The live calculator replaces it when the page loads.
- Country
- New Zealand
- Rated residual current
- 30 mA
- Protects socket-outlets
- Yes
- What the RCD supplies
- 3 rows
Standing leakage
7.3mA
- Leakage on this RCD
- Within the one-third budget
- Budget, one-third of the rating
- 10mA
- Share of the rated residual current
- 24.3%
- RCDs to keep each within the budget
- 1
This result is a design aid. Verify it against the current standard.
Calculation steps
- Heat pump: 1 × 3.5 mA measured3.5mA
- Computers: 3 × 1 mA measured3mA
- Fridge: 1 × 0.8 mA measured0.8mA
- Standing leakageResult7.3mA
- Budget, one-third of the rating10mA
AS/NZS 3000:2018 Cl 2.6.2.1 Note 1
- The RCD may operate above15mA
AS/NZS 3000:2018 Cl 2.6.2.1 Note 1
- Share of the rated residual current24.3%
- Leakage on this RCDWithin the one-third budget
AS/NZS 3000:2018 Cl 2.6.2.1 Note 1
- RCDs to keep each within the budget1
AS/NZS 3000:2018 Cl 2.6.2.1
About this calculator
How this is calculated
Every item on a circuit leaks a little current to earth in normal use, through its insulation and through the filters on its supply. An RCD cannot tell that current from a fault. On one RCD the leakage of everything it supplies adds up, and enough of it trips the RCD with nothing wrong. AS/NZS 3000 asks for circuits to be split so the leakage expected in normal use is unlikely to trip the device. This tool adds up the leakage on one RCD and checks it.
You list what the RCD supplies. For each item you type a measured or maker's leakage, or you take the in-service test limit for its class from AS/NZS 3760: the most a Class I or Class II item may leak and still pass its test. The class limit is a worst case. Most items leak much less, so a measured figure gives a truer total.
The total is checked against two points of the clause's first note. The leakage should not pass one-third of the RCD's rated residual current, and an RCD may operate at any residual current above half of it. Past one-third the tool warns that unwanted trips are likely, past half that the RCD may trip, and at the rating it fails, because the RCD is made to trip there. It then places the items, largest first, on the fewest RCDs that keep each within the one-third budget, without splitting an item.
| Step | Table or clause | What it decides |
|---|---|---|
| Leakage of a Class I or Class II item | AS/NZS 3760 Table 2.1 | The worst-case leakage of an item with no measured figure |
| The duty to split circuits | AS/NZS 3000 Cl 2.6.2.1 | That normal leakage must not trip the RCD |
| The budget and the point it may trip | AS/NZS 3000 Cl 2.6.2.1 Note 1 | One-third and one-half of the rated residual current |
| Socket-outlets on one RCD | AS/NZS 3000 Cl 2.6.2.1 Note 2 | A reminder that plugged-in items add leakage |
| A 10 mA RCD in New Zealand | AS/NZS 3000 Cl 2.6.3.3.2 Note 3 | Fewer socket-outlets on one 10 mA RCD |
Worked examples
- A home office: a heat pump, three computers and a fridge leak 7.3 mA in total. That is within the 10 mA budget of a 30 mA RCD, so 1 RCD keeps it in budget.
- Four Class I power tools at their test limit could leak 20 mA, over half the rating, where the RCD may trip. Spread over 2 RCDs, each stays within its 10 mA budget.
- An office: six computers and six Class II monitors leak 15 mA, over the 10 mA budget. They need 2 RCDs.
- A heat pump and four chargers on a 10 mA RCD leak 6 mA, over half of 10 mA. The budget is 3.33 mA, so 2 RCDs keep each within it.
- An Australian laundry: washing machine, dryer and freezer leak 8.5 mA, within the 10 mA budget on 1 RCD.
Limits
The tool adds standing leakage, the current that flows all the time. It does not model the short surges as filters charge at switch-on, leakage from a frequency drive at its switching frequency, or a fault. Type F and Type B RCDs, and where each is needed, are for the RCD selection tool.
The class limits are the most an item may leak and still pass. A measurement with a leakage clamp on the circuit gives the real figure.
See also: RCD selection, RCD arrangement and Test and tag.
Questions
Each answer describes what this tool calculates. The result is a design aid. Verify against the current standard.
Why does an RCD trip with nothing faulty?
Every connected item leaks a little current to earth in normal use. On one RCD the leakage adds up. An RCD may operate at any residual current above half its rating, so 15 mA of normal leakage can trip a 30 mA RCD.
How much leakage can one 30 mA RCD carry?
AS/NZS 3000 Cl 2.6.2.1 Note 1 says the leakage should not pass one-third of the rated residual current: 10 mA for a 30 mA RCD. The tool adds the items and checks the total against that.
Where do the leakage figures come from?
Type a measured or maker's figure for each item. Where you have none, the tool can use the AS/NZS 3760 in-service limit for the item's class: 5 mA for Class I and 1 mA for Class II. Those are the most a passing item may leak, so they are a worst case.
How many RCDs do I need?
The tool places the items largest first on the first RCD with room under the one-third budget. An item is not split between RCDs. The count is the fewest that keep each RCD within the budget.
What items leak the most?
Items with filters on their supply, such as computers, drives, heat pumps and LED drivers, and heating elements as they age. Measure them where you can: the leakage of one model differs from another.
Clauses and tables this tool reads
- AS/NZS 3000:2018 Cl 2.6.2.1Leakage on an RCD
- AS/NZS 3000:2018 Cl 2.6.2.1Standing leakage on an RCD
- AS/NZS 3760:2022 Table 2.1, 2.2, 2.3In-service test limits for electrical equipment
Every clause and table, with how each was verified
Tables last checked on 1 Oct 2026.
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