Bağcılar

The İSTOÇ and İkitelli commercial corridor in north-west Bağcılar is dense with wholesale warehouses, print shops and textile workshops. In these businesses the high-bay lighting, forklift battery charging points, compressors and goods lifts are frequently wired onto the same phase. At the evening despatch peak that phase reaches seventy amperes while the other two sit at twenty; the main breaker trips thermally and despatch stops.

Loads are distributed symmetrically across the three phases from True-RMS clamp readings, with lighting, the charging group and motor loads placed on separate legs. The forklift charging circuit gets a 30 mA Type B residual current device able to detect DC components, because a rectifier-based charger blinds a standard Type AC unit. In the compensation panel the step contactors are replaced with the dedicated discharge-resistor type.

In Bağcılar's dense building stock a board fire is not rare: a loosening main terminal heats for weeks, the Bakelite body carbonises and eventually flame breaks past the cover. Once the fire is out, replacing the board alone is not enough, because the cable insulation has taken heat at the same time. Heat-damaged cable can look sound to the eye yet has lost its insulation resistance, and leaks again on the first heavy load.

The rebuild first measures the insulation resistance of every branch one by one with a 500 V megohmmeter and produces a damage report; any leg below 1 Megaohm goes on the renewal list. Carbonised busbars and terminals are replaced with fire-rated ceramic modular blocks and the board moved into a flame-retardant modular DIN-rail enclosure. A 10kA breaking capacity main device, a 30 mA Type A life-safety unit and a Type 2 arrester are fitted at the intake, and the report is handed over in writing for the insurance file.

In the newer residential blocks of Güneşli and Mahmutbey the load per flat has risen quickly with air conditioning, induction hobs, tumble dryers and electric vehicle charging. The shared riser in these blocks was never dimensioned for that density, so on upper floors the evening voltage falls below 200 volts; the boiler cannot ignite, LED lamps flicker and appliance boards degrade over time. Residents assume a grid fault.

Readings are taken under load at the riser head and at the top flat intake, and percentage drop calculated from run length and cross-section. Where it exceeds five percent, upgrading the riser to 4x25 mm² NYY cable is presented to the management with the measurement report. As an interim step loads are balanced across phases, and for sensitive loads such as the boiler a zero-crossing static voltage regulator is fitted inside the flat with a Type 2 arrester added to the board.

In the 1990s stock of Kirazlı, Demirkapı and Fevzi Çakmak the kitchen branch runs off a single 16 A breaker. After a renovation puts a built-in oven, dishwasher and water heater on that one leg, crackling comes from the socket back-box behind the counter at dinner time and a sharp plastic odour spreads. That odour is a definite sign the outlet has begun to melt and the socket must be taken out of service at once.

Blackened conductor ends are cut back to clean copper, the back-box replaced and an unbroken TSE-certified 3x2.5 mm² solid copper cable pulled from the board to the counter behind the skirting, using the existing trunking route without chipping the wall. A separate C16 is fitted for the oven and another for the dishwasher, with a 3x4 mm² run on a C20 for the water heater. The existing cross-section is measured with a micrometer and the breaker rating set from that.

In the older stock of Yenigün, Çınar and Yıldıztepe no protective earth was ever installed, so the neutral pin is bridged to the earth terminal inside the sockets. With that arrangement, the moment the upstream neutral loosens, 220 V phase potential energises the washing machine, dishwasher and oven chassis. Anyone touching the steel sink and the appliance together is placed directly across the mains; that is a lethal risk rather than a mild tingle, and the setup can look faultless for years.

Each socket is opened in turn, every jumper removed and the absence of any remaining bridge confirmed by measuring neutral-to-earth voltage, since one missed outlet keeps the hazard alive. Where the building has a common earth, a 16 mm² protective conductor is pulled from the flat to the main board; otherwise a solid copper electrode is driven into the garden or basement floor and its resistance measured with a digital earth tester. A 30 mA Type A device is fitted and its trip time verified by tester.

Bağcılar is terraced and very densely built, with short gaps between buildings and thin walls. Using a drill or breaker after 22:00 is therefore not neighbourly or practical, and fault location is done entirely by silent means. Branches are separated one by one at the board and measured with a megohmmeter, while the route is followed from the surface with an inductive cable tracer and a FLIR thermal imager.

Once the faulty leg is isolated, the refrigerator, boiler and lighting are restored within the first ten minutes and the rest of the home runs safely. If the concealed run is permanently broken, a temporary safe line is installed overnight on the surface in fire-retardant trunking and the noisy permanent work booked for the next working day. Because narrow streets can lengthen the walk from where the van parks, the arrival time is given to the customer honestly.

Every terminal inside the board is tightened with a calibrated screwdriver to the torque printed in the manufacturer catalogue, between 2.5 and 3.5 Nm. Hand tightening leaves an invisible slackness and residual contact resistance; current crossing that resistance carbonises the copper surface, resistance climbs further and a thermal runaway chain begins. As the chain advances the terminal passes 200 degrees, melts cable insulation and ignites the Bakelite enclosure.

On completion the whole board is swept with a FLIR thermal imager, not just the replaced component but every breaker, the residual current device and all busbar links. Latent hotspots above seventy degrees are located and re-torqued, which stops the customer facing the same fault again a few days later. The sweep is carried out under load, because heating is invisible in a de-energised board and the fault stays hidden. In older boards containing aluminium conductors the terminals are diarised for a further check after six months, since aluminium cold-creeps and works loose again over time.

In buildings with no protective earth, bridging the neutral pin to the earth terminal inside a socket is known on site as bootleg grounding. The moment the upstream neutral loosens or breaks, full 220 V phase potential energises the washing machine, dishwasher and oven chassis, and anyone touching the steel sink or appliance is placed directly across the mains. Such a setup can look faultless for years, then kill after a single loosened screw.

Our intervention removes every jumper one by one, drives a solid copper earth electrode, adds an earth busbar to the main board and commissions a 30 mA Type A residual current device whose trip time is verified in milliseconds with a dedicated tester. Removal of every jumper is additionally proven by measuring neutral-to-earth voltage at each socket, since one missed outlet keeps the hazard alive. Chassis continuity on metal-bodied appliances such as washing machines and dishwashers is also measured to confirm they are genuinely bonded to the protective conductor.

In a Güneşli apartment block the flat intake board caught fire and, once extinguished, the whole flat was left without power. On arrival our crew found the Bakelite body completely carbonised and the main neutral busbar melted. Rather than simply swapping the board, the insulation resistance of every branch was measured one by one with a 500 V megohmmeter; the living room and kitchen legs read between 0.2 and 0.4 Megaohm, proving those runs had taken heat. Both heat-damaged branches were renewed from board to outlet, the carbonised busbar replaced with fire-rated ceramic modular blocks, the board moved into a flame-retardant modular DIN-rail enclosure and a 10kA main device, a 30 mA Type A unit and a Type 2 arrester fitted at the intake. All measured values were handed over as a written report for the insurance file.

On this callout the root cause was recorded with photographs and a thermal image, each step of the work written onto the service report and handed over against the customer's signature. Labour carries a 1 year guarantee.

At a wholesale warehouse in İSTOÇ the main breaker was reported to trip repeatedly at the evening despatch peak, leaving forklift charging unfinished. True-RMS clamp readings showed phase one drawing 68 amperes against 24 and 19 on the others; the high-bay lighting and two forklift chargers had been wired onto the same phase. Loads were distributed symmetrically across the three phases, the charging group separated from lighting and fed by its own NYY run from the board, and that circuit fitted with a 30 mA Type B residual current device able to detect DC components. In the compensation panel a welded step contactor was replaced with the dedicated discharge-resistor type, and the panel handed over after a thermal sweep under load.

On completion socket earth continuity and loop impedance were measured, the residual current device tested twice via its own button and an external instrument, then the system was safely re-energised.