İstasyon, Tuzla

Tuzla's İstasyon Mahallesi is the old centre fabric around the Marmaray line, and part of its building stock is over forty years old. In these buildings cloth or lead insulated copper conductors still run inside concealed steel conduits; the insulation turns brittle and cracks, two cores touch and arcing starts inside the junction box. A crackling sound from the wall and a faint burnt odour are the first signs, and because the arc is invisible it is usually noticed late.

The circuit is measured with a 500 V megohmmeter; where insulation resistance falls below 1 Megaohm the cable is not patched but pulled anew through the existing conduit route in Low-Smoke Zero-Halogen cable. If the steel conduit has narrowed or been crushed the route is first tested with a draw wire, since otherwise the insulation strips during the pull. All junctions are closed with Wago 221 lever terminals, old twisted and taped splices removed, and an arc fault detection device plus a 30 mA Type A unit added to the board.

In the older stock of İstasyon a ceramic screw-in fuse board still sits in the hall cupboard. These boards contain no residual current device at all, so protection against electric shock is zero; the fuse melts and welds into its base under overload, fails to clear a short circuit and the body carbonises over time. The sockets usually have no earth either, with the neutral pin bridged to the earth terminal.

The old board is removed entirely and a flame-retardant modular DIN-rail enclosure installed: an independent Type C breaker per room, dedicated circuits for kitchen and bathroom, and a 30 mA Type A residual current device plus a Type 2 surge arrester at the intake. Flat sub-boards use a minimum 6kA breaking capacity and building intakes 10kA. Where a İstasyon address has no earth, a solid copper electrode is driven, its resistance measured with a digital earth tester and the socket jumpers removed one by one.

In İstasyon a washing machine, tumble dryer, dishwasher and electric heater often feed from a single outlet through a multi-way extension block. Once the current through one 2.5 mm² run approaches thirty amperes the cable insulation chars, the socket box blackens and warmth is felt through the wall; the extension block body itself begins to melt. A True-RMS clamp meter measures that current with the appliances running together, leaving nothing to guesswork.

The fix is splitting the circuit rather than upsizing the breaker, because a larger breaker leaves the cable unprotected and raises the fire risk. Continuous loads such as a dryer or heater get 3x4 mm² on a C20, the washing machine 3x2.5 mm² on a C16, and each run is pulled unbroken from the board. Charred cable is never patched but renewed back to the board, with the existing cross-section measured by micrometer so the breaker rating matches.