How often should the test button on an RCD be pressed?

• A. Every 3 months
• B. Every 6 months
• C. Every 12 months
• D. Every 2 years

Answer: (B)

The test button on an RCD is there to check the protective function works. Pressing it creates a small, controlled imbalance so the RCD trips as it would if there were a real leakage to earth. This verifies that the device will respond to a fault and cut the circuit to protect people.

Six months is the recommended interval because RCDs can wear or drift over time, and regular testing helps ensure the protection remains reliable. If the test button doesn’t cause a trip, the RCD is faulty and should be inspected or replaced; relying on it could leave a circuit unprotected in a real fault.

Frequent testing (every six months) strikes a practical balance for most fixed installations, whereas testing more often (every three months) can be unnecessary wear, and waiting longer (twelve months or more) increases the chance of missing a failing unit.