When walls grow tea stains, plumbers narrate masonry. When MCBs dance nightly but paint stays dry, log the electromagnetic subplot.
| Symptom cluster | Hypothesis bias |
|---|---|
| Trip only during squall gusts open terrace door | Wet gland or outdoor isolator cap seal |
| Trip at compressor start every humid Tuesday | Inrush + weak C-curve folklore; corroded contact resistance |
| Whole-flat RCCB twitch while kettle + TV + charger stack | Leakage budgeting; EMI caps failing on cheap SMPS fleets |
| Sparks audible near meter during tank overflow | Water route into service cutout — escalate immediately |
If you smell overheated PVC alongside puff paint, escalate both electrical isolation and civil moisture tracing — sequencing matters for safety.