An RCD sees leakage to earth. An MCB sees overload and short circuit. Neither reliably sees a low-current series arc at a loose terminal, which is exactly the condition that produces heat inside an accessory. AFDDs are designed to detect that signature.
Where they help most
Circuits with many terminations and older accessories, bedroom circuits, and premises where escape would be slow. Anywhere a smouldering connection would have time to develop unnoticed.
Why they are not everywhere
Cost per circuit is significantly higher than an RCBO, and board space is finite. For most domestic installations, correctly torqued terminations, quality accessories and periodic inspection remain the primary defence — AFDDs are an addition, not a replacement.
Our position
We will price AFDDs on request and explain where we think they add most value in your particular property. What we will not do is present them as mandatory for a standard domestic board when they are not.
Common questions
- Can AFDDs be added later?
- Yes, if there is board space and a compatible device range.
- Do they nuisance trip?
- Modern devices are considerably better than early generations, but some appliances can cause operation.
- Do they replace RCBOs?
- Combination devices exist that provide both functions in one module.
- Are they required in homes?
- Their use is risk-based in dwellings; we advise per property rather than by rule of thumb.
If you want AFDDs considered, say so at quote stage and we will show the cost per circuit.
Related guides
- RCD vs RCBO: What the Difference Means at HomeThe difference is not protection quality — it is how much of your house goes dark when something leaks.
- Surge Protection Devices in a Domestic BoardAn SPD protects connected equipment from transient voltage spikes — not from every electrical mishap.
- Burning Smell From a Socket or SwitchThis is the one symptom on this site where our advice is to stop using the circuit today.