RCD Selection
Check if an RCD is required and test the trip time.
Questions
Each answer describes what this tool calculates. The result is a design aid. Verify against the current standard.
What does the RCD selection tool do?
The tool reports whether a final subcircuit needs additional protection by an RCD, the maximum rated residual current for the duty, and the maximum trip times. It also compares a measured trip time at the rated current and at five times the rated current with those limits.
Which clause and regulation does it use?
The requirement comes from AS/NZS 3000:2018 Clause 2.6.3.3 in New Zealand and Clause 2.6.3.2.3.3 in Australia. Clause 7.9.3 covers electric vehicle circuits in New Zealand only; Australian ones take Clause 2.6.3.2.3.3. The trip limits come from Electricity (Safety) Regulations 2010 regulation 24. Disconnection times come from Clause 5.7.2.
What are the RCD trip time limits in New Zealand?
For shock protection at 30 mA or less the limits are 300 ms at the rated residual current and 40 ms at five times the rated current. For property protection the limits are 0.5 s and 0.15 s, with a rated residual current up to 300 mA.
Why does a 40 amp circuit show no requirement?
The Australian clause applies to final subcircuits with a rating of 32 A or less. Above that rating the clause states no requirement, so the tool reports none. The New Zealand residential clause sets no rating cap, so it still applies.
Does the tool cover medical and patient areas?
Only in part. It reports the 10 mA patient limits from regulation 24. Medical locations also follow AS/NZS 3003, which AmpSize does not hold. Amendments 2 and 3 to AS/NZS 3000 revised Clause 2.6.3 and are not on hand, so check the current edition.