Question 1

Which size conduit pipe is used in house wiring?

Accepted Answer

20 mm and 25 mm PVC conduits carry most light and socket circuits in homes; 25–32 mm suits main runs, risers and circuits with several heavy wires. When in doubt go one size up — it makes pulling wires easier and leaves room for later.

Question 2

What are light, medium and heavy gauge conduits?

Accepted Answer

They're grades of wall thickness and crush strength. Light gauge suits protected runs in walls; medium is the common all-rounder; heavy gauge is for slabs, floors and anywhere concrete is poured or the pipe may be stepped on or buried.

Question 3

How many wires can go in one conduit?

Accepted Answer

Keep the total cross-section of the cables (with insulation) to about 40% of the conduit's inside area so wires pull easily and stay cool. As a rough guide, a 20 mm conduit takes around five or six 2.5 sq mm wires; use 25 mm if you need more.

Question 4

Can I use plumbing PVC pipe for electrical wiring?

Accepted Answer

No. Electrical conduit is made to electrical standards — self-extinguishing, the right wall thickness and smooth inside — with matching bends and boxes. Plumbing pipe isn't designed for fire behaviour or for pulling cables.

Question 5

How should conduit be laid in a roof slab?

Accepted Answer

Use heavy gauge conduit, tie it to the reinforcement so it doesn't float or crush when concrete is poured, cap open ends and boxes to keep concrete out, and place fan boxes at the right spots before the pour. Leave a draw wire in each run.

Question 6

What is a fan box?

Accepted Answer

A fan box is set into the roof slab before casting, with a hook or rod to hang the ceiling fan and room for the connections. It must be strong and well anchored — the fan's weight and wobble hang on it.

Question 7

What are junction boxes used for?

Accepted Answer

Junction boxes give an accessible, closed space where conduits meet and wires are joined or branched, and they act as draw points on long runs. Fit covers so the joints are protected but can be reached later.

Question 8

How many bends can a conduit run have?

Accepted Answer

Keep it to about two right-angle bends between boxes. More than that makes wires hard to pull and can damage insulation; add a junction or inspection box instead.

Question 9

What is casing-capping?

Accepted Answer

Casing-capping is a PVC channel fixed on the wall surface with a snap-on cover, used for surface wiring — in renovations, rented spaces and where cutting walls isn't possible. It's quick and neat but less protected than concealed conduit.

Question 10

What is corrugated (flexible) conduit for?

Accepted Answer

Flexible corrugated pipe bends by hand without fittings, so it's used above false ceilings, behind panels and for short drops to light points. Use rigid conduit in walls and slabs where strength matters.

Question 11

Why leave a draw wire in conduit?

Accepted Answer

A draw (fish) wire left in an empty or part-filled conduit makes it easy to pull new cables through later — for an extra circuit, TV or internet — without breaking walls.

Question 12

Should I choose concealed or surface wiring?

Accepted Answer

Concealed wiring (in conduit inside walls and slabs) is neater and better protected, but must be planned before plastering. Surface wiring in casing or conduit is cheaper and easier to change, and is the practical choice for renovations.

Question 13

What conduit fittings are there?

Accepted Answer

Bends and elbows for corners, tees for branches, couplers to join lengths, reducers between sizes, saddles and clips to fix surface conduit, and inspection bends and boxes to reach the wires. Use fittings from the same system so they fit tightly.

Question 14

Is PVC conduit safe in a fire?

Accepted Answer

Electrical PVC conduit is made self-extinguishing: it doesn't keep burning once the flame is taken away. It still gives off smoke when it burns, which is why low-smoke cables are used in public buildings.

Question 15

When is metal conduit used instead of PVC?

Accepted Answer

Steel (GI) conduit is used where wiring is exposed to knocks or heat — factories, plant rooms, parking areas and outdoor exposed runs — and where the building's specification calls for it. It must be earthed.

Question 16

Should power and data cables have separate conduits?

Accepted Answer

Yes. Run TV, internet and CCTV cables in their own conduits and boxes, away from power wiring, to avoid interference and keep low-voltage systems separate from mains.

Question 17

Why do metal boxes rust, and what can I do?

Accepted Answer

Damp walls, leaks and bathrooms rust ordinary steel boxes. Use galvanised (GI) boxes or PVC boxes in damp places, fix leaks first, and keep boxes covered during plastering and curing.

Question 18

How deep should switch boxes be set in the wall?

Accepted Answer

Flush with the finished plaster surface, so the plate sits flat. Set boxes at the right depth before plastering and use spacers or adjustable boxes where the plaster is thick.

Question 19

How is conduit run underground?

Accepted Answer

Use heavy gauge conduit (or HDPE pipe) at a safe depth, with draw pits where runs are long or change direction, and warning tape above it. Seal the ends where they rise into buildings so water and insects don't follow the pipe in.

Question 20

How do I fix surface conduit neatly?

Accepted Answer

Use saddles or clips at regular intervals (closer near bends and boxes), keep runs straight and level, and use proper bends instead of heating and bending the pipe. Plan the route so it follows edges and corners.

Question 21

What is a deep junction box?

Accepted Answer

A deep box gives more room for joints, connectors and loops of wire — useful above false ceilings, for fan and light points with several circuits, and anywhere many conduits meet.