Godown Wiring Diagram (3 and 4 Lamp), Tunnel and Hospital Wiring

Godown wiring diagram: the short answer

A godown wiring diagram shows a row of lamps switched one after another, so that a person walking through a long store room lights the next lamp and puts out the one behind with a single switch. For three lamps it uses one 1 way switch at the entrance and two 2 way switches, chained together in the phase.

It is a standard practical of the ITI Electrician trade, taught alongside staircase, corridor and hospital wiring.

We make the switches, holders, MCBs and line testers used on these boards at our works in Marol, Andheri East, Mumbai; every MRP below is from our current catalogue. Practise under your instructor; wiring in a building is a job for a licensed electrician.

Godown wiring vs tunnel wiring: is it the same circuit?

In most ITI practical files, classroom notes and videos, godown wiring and tunnel wiring mean exactly the same circuit: lamps lit one at a time as you walk, each switch lighting the lamp ahead and putting out the lamp behind. The NIMI theory book used in ITIs separates them: godown wiring keeps one lamp on, tunnel wiring keeps at least two on, because a tunnel is darker.

So read the job sheet first. Godown wiring one lamp glows at a time and the others are off. Tunnel wiring (NIMI) at least two lamps glow while you move, and every switch is a 2 way switch. Corridor wiring and hostel wiring sit in the same lesson but are different circuits.

If the 2 way switch and its COM, L1 and L2 terminals are new to you, read our 2 way switch wiring diagram for the staircase circuit first. Here the 2 way switch is a changeover: its COM goes either to a lamp or on to the next switch.

Godown wiring diagram 3 lamp: how the circuit works

In a 3 lamp godown wiring diagram the phase goes through the 1 way switch S1 to COM of the 2 way switch S2; L1 of S2 feeds lamp 1 and L2 of S2 feeds COM of S3; L1 of S3 feeds lamp 2 and L2 of S3 feeds lamp 3, while the neutral goes straight to all three lamps.

Godown wiring diagram, 3 lamps: one 1 way and two 2 way switches

Drawn by us. As drawn, S1 is on and S2 sits on L1, so only lamp 1 glows. Earth is not shown; it goes to any metal box or fitting. Wire colours vary; a tester confirms which wire is which. Tap the diagram to open it full size.

Walk in: S1 on at the door lights lamp 1. At lamp 1, flip S2 to L2: lamp 1 goes out and lamp 2 lights. At lamp 2, flip S3 to L2: lamp 2 goes out and lamp 3 lights. There is only one path from the phase to any lamp, so one lamp at a time is built into the wiring. Some books write the 2 way positions as OFF and ON instead of L1 and L2.

Godown wiring diagram 4 lamp: adding a lamp

To wire four lamps, add one more 2 way switch to the chain: L2 of S3 now goes to COM of a new switch S4 instead of to a lamp, L1 of S4 feeds lamp 3 and L2 of S4 feeds lamp 4, so four lamps need one 1 way switch and three 2 way switches.

Godown wiring diagram, 4 lamps: one 1 way and three 2 way switches

Drawn by us. As drawn, S2 and S3 sit on L2 and S4 on L1, so only lamp 3 glows: the walker is in the third section. Wire colours vary; a tester confirms which wire is which. Tap the diagram to open it full size.

The rule for any length: N lamps need N switches, that is one 1 way switch at the entrance and N − 1 2 way switches, each fixed where its lamp section ends.

Walking out runs the chart backwards. At the far end, flip S4 back to L1: lamp 4 goes out and lamp 3 lights. Flip S3 back at lamp 3, then S2 at lamp 2, and finally switch S1 off at the door, which puts out everything whatever the other switches show.

What conditions must godown wiring meet?

A godown wiring practical is passed when the circuit meets five conditions: only one lamp glows at a time, each switch lights the next lamp and puts out the one behind, the sequence reverses on the way out, S1 puts out everything, and every switch breaks the phase, never the neutral.

1. One lamp only: no switch position may light two lamps together.
2. Forward step: one flip lights the lamp ahead and puts out the lamp behind.
3. Return step: the same switches, flipped back in reverse order, light the way out.
4. Master off: S1 at the entrance cuts the whole chain.
5. Phase only: switches in the phase; the neutral runs to every holder unbroken.

Examiners also check tight terminals, the earth at any metal box, and that on a screw-type holder the switched phase goes to the centre contact.

Tunnel wiring theory: when two lamps stay on

Tunnel wiring, as the NIMI theory book defines it, is the version of the circuit in which at least two lamps stay on while a person moves through, so that he lights the lamps ahead and puts out a lamp behind with one switch; all its switches are 2 way switches.

The book attaches a caution to that circuit: it is not in accordance with the IE rules, because the phase and the neutral come to the same switch, so it must be wired with care. We do not draw that version here; if your job sheet asks for it, follow your instructor’s drawing.

For the one-lamp version, the godown diagrams above apply unchanged. In Hindi classrooms the rule is often said as “aage ki batti jalao, peeche ki bujhao”: light the lamp ahead, put out the lamp behind.

Hospital wiring diagram: bright, medium and dim

Hospital wiring is the ITI practical in which two lamps are controlled by a 1 way switch and a 2 way switch so that a ward can have full light for the doctor, medium light, or a dim night light: wired in series both lamps glow dim, and in parallel both glow bright.

Hospital wiring diagram: two lamps, a 1 way and a 2 way switch

Drawn by us. As drawn, S1 is off and S2 is on phase, so the two lamps are in series and both glow dim. Wire colours vary; a tester confirms which wire is which. Tap the diagram to open it full size.

The connections: lamp 1 runs from the neutral to a midpoint M, lamp 2 from M to COM of S2. L1 of S2 takes the phase and L2 takes the neutral. S1 joins the phase to M.

Why dim? In series two equal lamps share the 230 V supply, so each gets about half and glows dim. With S1 on, M is at phase, so lamp 1 always gets the full supply and glows bright.

What are the hospital wiring conditions?

The hospital wiring practical must give four states from two switches: off, dim with both lamps in series, medium with one lamp, and bright with both lamps in parallel, using two lamps of the same wattage, with no switch position that joins the phase straight to the neutral.

Same wattage: with unequal lamps the voltage splits unequally in series, and one lamp glows while the other barely shows. Filament lamps: the practical is set with ordinary filament lamps, because an LED lamp has a driver inside and two in series do not share the voltage predictably; the dim step may flicker or stay dark. Phase and neutral in S2: as with NIMI’s tunnel circuit, treat it as a training-board circuit. In the medium position lamp 2 is off but both its terminals sit at phase, so never change a lamp on this board with the MCB on.

For a hospital wiring diagram 3 lamp version the principle holds (series dim, full supply bright), but the switch arrangement changes, so follow your instructor’s drawing. A nurse-call bell is a separate circuit; for that we make the VIZA V1290 hospital bell indicator, ₹282 MRP.

Components list for godown and hospital wiring practicals

A 3 lamp godown board needs one 1 way switch, two 2 way switches, three lamp holders and lamps, an MCB, wire and a tester; a 4 lamp board adds one 2 way switch and one holder; a hospital board needs one 1 way switch, one 2 way switch and two holders with lamps of the same wattage.

Switches: on a conventional training board, our VIYONA 101 1 way switch is ₹22 and the VIYONA 102 2 way switch ₹36 MRP, both from the VIYONA 6 A Deluxe range. In modular form, the KEMPS K101 10AX 1 way switch is ₹65 and the KEMPS K102 10AX 2 way ₹105.

Holders: the VIYONA 202 batten holder and 201 angle holder are ₹26 each in our Deluxe skirt holder range. MCB: the VIYONA 401 single pole MCB, 6 to 32 A, is ₹145 in our 10kA MCB range; how an MCB trips is a guide of its own. Wire: 1.5 sq mm is common practice for lighting, such as our VIYONA house wire. Add a screwdriver, stripper, tape and a multimeter.

Godown wiring practical: step-by-step wiring with the MCB off

Wire the board in a fixed order: isolate and prove dead, mount the parts, run the phase chain through the switches, run the neutral to every holder, then check continuity before any supply is connected.

1. Isolate. MCB off, and prove the board dead with a multimeter or voltage tester; a neon tester alone does not prove dead.
2. Lay out. Mark S1 at the entrance end, then S2, S3 and so on beside lamps 1, 2 and 3. Fix boxes and holders.
3. Phase in. From the MCB to S1 only. S1’s other terminal to COM of S2.
4. Chain. L1 of each 2 way switch to its lamp; L2 to the next COM. On the last switch, L2 goes to the last lamp.
5. Neutral. Loop the neutral to the second terminal of every holder, never through a switch.
6. Earth. To any metal box or fitting.
7. Check dead. With a meter on continuity, step through the position table and confirm one lamp path per row.
8. Power. Only with your instructor present, MCB on, then walk the table in and out.

How do you test godown and hospital wiring?

Test with the supply off first: use a multimeter on continuity to check each switch position against the table and confirm that no position joins phase to neutral, then switch on the MCB with your instructor present and walk through every row of the switch-position chart.

With power on, a line tester shows where the phase is: in godown wiring each holder should show no glow when its lamp is off (in hospital wiring, the unlit lamp in the medium position is still at phase). We make the VIYONA line tester 811 (code 198) at ₹36 and 812 (code 199) at ₹42 MRP. A neon tester only shows that a phase is present, so no glow is not proof of dead; confirm with a meter.

Many institutes also use a series test board before the first switch-on; follow your instructor’s method. For hospital wiring, look for equal dim glow in the series position: unequal glow means unequal wattages or a loose joint.

Common mistakes in godown, tunnel and hospital wiring

Most failures in these practicals come from five mistakes, and the switch-position table finds four of them.

COM on L1 or L2: the chain wire lands on a switched terminal, so two lamps light together or a lamp never lights. Switches in the neutral: the lamps still change, but every holder stays live. Last switch wrong: L2 of the last switch left empty, so the last lamp never lights. Unequal lamps in hospital wiring: the dim step looks like one lamp on. Loose terminal: flicker and heat at a switch.

The rule behind the first two, phase to the switch and neutral to the load, is explained in our phase, neutral and earth guide; our switch board wiring diagram draws a full board, and 1 way vs 2 way switch shows how to tell the switches apart.

Viva questions on godown and hospital wiring

Questions examiners often ask after the practical, with short answers to put in your own words.

Why is S1 a 1 way switch? It only connects or cuts the phase to the whole chain; a 2 way switch with one terminal unused also works. How many switches for N lamps? N: one 1 way and N − 1 two way. Why can only one lamp glow? The chain gives one path from phase to lamp.

Why do lamps in series glow dim? Two equal lamps share 230 V, about 115 V each. Which hospital position gives medium light? S1 on, S2 on phase. Why must the switch be in the phase? So the holder is dead when the lamp is off. Does a neon tester prove a circuit dead? No; use a meter.