1. The Core Concept: Wire Gauges & MCB Matching
Think of electrical wires like water pipes. A thicker pipe can carry more water without bursting. Similarly, a thicker copper wire (measured in square millimeters or sq. mm) can carry more electrical current (Amperes) without overheating. When an appliance consumes electricity, it draws current. Heating and cooling appliances like Geysers, Irons, and Air Conditioners draw massive amounts of current compared to a TV or a lightbulb.
If you connect a heavy 2000-watt Geyser to a thin 1.0 sq. mm wire meant for a lightbulb, the wire will act like a resistor. It will heat up, melt the plastic insulation around it, and eventually start a house fire. This is where the MCB (Miniature Circuit Breaker) steps in. The MCB is your home's security guard. Its job is to monitor the current and trip (turn off) BEFORE the wire can melt. Therefore, placing a large 32A MCB on a thin 1.5 sq. mm wire is highly dangerous—the wire will burn before the MCB realizes there is a problem.
| Wire Thickness | Safe MCB Rating | Standard Usage (Appliances) |
|---|---|---|
| 1.0 sq. mm | 6A - 10A | LED Lights, Ceiling Fans, Doorbells |
| 1.5 sq. mm | 10A - 16A | Standard Room Sockets (Mobile, TV, Laptop) |
| 2.5 sq. mm | 16A - 20A | Power Sockets: Geyser, Fridge, Washing Machine, Iron |
| 4.0 sq. mm | 20A - 25A | Heavy Loads: Air Conditioners (AC 1.5T+), Heavy Heaters |
2. Room-by-Room Planning: Applying the Rules
Now that you understand wire sizes and MCBs, you must plan your switchboards to accommodate modern living. A lack of foresight here leads to dangerous tangles of extension cords spanning across your living room floor.
🛋️ Living Room (Baithak)
The living room is a hub for entertainment devices that don't draw much power, but require many individual plug points.
Sockets & Wiring
- TV Unit: 4 Sockets (10A) wired with 1.5 sq.mm for TV, Router, Setup Box, Soundbar.
- AC / Heavy Heater: 1 Power Socket (16A/20A) wired with 4.0 sq.mm on a dedicated MCB.
- Convenience: 2-3 Sockets (10A) in low corners for vacuum cleaners or floor lamps.
Lighting (Wattage & Type)
- Ambient Light: 4 to 6 LED Panels (12W - 15W each) in Warm White (4000K).
- Accent Light: Concealed LED Strip Lights (COB 10W/meter) inside the false ceiling.
🍳 Kitchen (Bhansa)
The kitchen is the most power-hungry room. Heating elements (Induction, Microwave, Kettle) require thick 2.5 to 4.0 sq.mm wires on separate circuits to prevent tripping.
Sockets & Wiring
- Heavy Appliances: 3 Power Sockets (16A) for Fridge, Microwave, and Induction/Chimney.
- Countertop (Working Area): 3 Sockets (10A) for Mixer grinder, Rice cooker.
- Water Purifier: 1 Socket (6A) below or near the sink area.
Lighting (Wattage & Type)
- Main Task Light: 2 to 4 LED Panels (15W - 18W) in Cool White (6500K) for high visibility.
- Under-Cabinet: LED Strip or Profile Light (5W - 10W/m) to remove shadows from the chopping counter.
🛏️ Bedrooms & Bathrooms
Bedrooms focus on convenience (like two-way switches), while bathrooms focus on absolute safety (waterproofing and dedicated geyser lines).
Bedroom Setup
- Bedside: 2 Sockets (10A) one on each side for mobile charging, 30 inches from the floor.
- Two-Way Switches: Essential for turning off main lights from the bed.
- AC Point: 1 Power Socket (16A) wired with 4.0 sq.mm wire.
Bathroom Setup
- Water Heater (Geyser): 1 Power Socket (16A) placed near the ceiling, away from shower spray. MUST have 2.5 sq.mm wire.
- Mirror Light: LED Wall Sconce (5W) mounted right above the mirror.
3. Standard Switchboard Heights (Ergonomics)
All electrical heights are measured from the Finished Floor Level (FFL)—the level after your floor tiles or marble are fully laid. A common mistake is Mistris placing switch boxes based on the raw concrete slab, resulting in switches being too low once the flooring is complete.
- Main Room Switch:48 inches (4 feet) from FFL. Easy to reach for adults and kids.
- Bedside Sockets:30 inches (2.5 feet) from FFL. Just above standard bedside tables.
- Kitchen Counter:44 to 46 inches from FFL (Approx 8-10 inches above the granite slab).
- AC / Geyser Point:84 to 96 inches (7 to 8 feet) from FFL, keeping wires safely out of reach.
4. The Mandatory Color Coding Rule
A professional Mistri must always follow standard color coding. This ensures any electrician can safely repair your home in the future without getting electrocuted.
- Phase (Live): Red, Yellow, or Blue wire.
- Neutral: Black wire.
- Earth (Ground): Green wire.
5. The 5 Biggest Wiring Mistakes Mistris Make in Nepal
Even with the best materials, poor workmanship can ruin your electrical system. Keep an eye out for these common shortcuts taken on construction sites.
❌ 1. Skipping the Earthing Wire (Green Wire)
To save money, some contractors do not run the green earth wire to every socket. If a Geyser or Washing Machine short-circuits without an earth wire, the metal body becomes electrified, leading to fatal electric shocks.
❌ 2. Ignoring Two-Way Switches for Stairs & Bedrooms
A two-way switch allows you to turn a light on from the bottom of the stairs and off from the top. Mistris often install standard one-way switches, forcing you to walk back down in the dark.
❌ 3. Using One Single Color Wire for Everything
If a Mistri uses red wire for Phase, Neutral, and Earth just because 'it was left over', future maintenance becomes a guessing game, drastically increasing the risk of a short circuit.
❌ 4. Plastering Over Junction Boxes Completely
Circular junction boxes are placed in walls to pull wires. Painters or plasterers often completely cover them up. If a wire ever burns out, you will have to physically hammer and break the wall to find the hidden box.
❌ 5. Forgetting Outdoor Waterproof Sockets
Homeowners often forget they need power on the terrace (Chhat) for washing machines or festive Tihar lights. Running extension cords from inside the house is dangerous. Install IP65 rated waterproof sockets outdoors.