Operational Sequence WTA.04 (Octopus Circuit)

Before starting any work, I carried out a risk assessment. I then gathered the tools required, and inspected them for any damage. I also collected my work basket from the workshop store, and compared the list of components in my basket, to the practice book list of components required for the job.

After preparing, I began to mark out my work area. As advised from previous assignments, When marking out; I followed the practice booklet diagram exactly, and kept dimensions to an easily workable area. I positioned the junction box to the right of my consumer unit, and parallel to the top. The four switch positions were marked out below, and the three lighting positions positioned above. All were level with one another and of an equal distance apart. One problem I have had is the spirit levels not being very accurate, because of this, I have measured and used my best judgement to keep components level.

After marking out I began the first fix of the Octopus Circuit. I first screwed the junction box to the back board with three 20mm woodscrews, the one in the middle also attached a 12 bar terminal block, to the center of the metal junction box. The next components were the switch box's. I started with the third switch, the metal clad switch. This was because my Steel Wire Armored cable for the connection, was already cut; and the switch box had to sit at exactly that level from the junction box. ( I took this into consideration when marking out my components.) Attaching the metal clad switch required me to attach the SWA cable to the junction box, and the switch first. This was done by placing the screwed flange through both components, and attaching with a hex nut. When the switch box was positioned correctly, it was attached to the work board using two 20mm woodscrews.

Example SWA cable connection

Following the third switch installation, switch box's one, two and four were mounted on the back board with two 20mm woodscrews each, in parallel to switch number three. Switches one and two on the left, and switch four on the right.

The next components to attach were the lamp holders back box's. These were affixed above the junction box. One directly above, one 30cm to the left, and one 30cm to the right; all level with one another.

After all the components were fixed to the work board, I started to fix the cables for each component. I started by checking the practice booklet for cable types to be used, as there are a lot of different cables to be used in the circuit. From the consumer unit to the junction box, and from the junction box to all three lamps, I was to use 1.5mm2 T/E cable. I laid this out to all three lamps, and the consumer unit from

the junction box; making sure to follow all pre-drawn cable routes. After making sure there was enough cable in each component, and cutting the cable to length, I proceeded to clipping the cable. This was done with 1.5mm cable clips. I kept all spacing between clips at the same length, and all bends to an acceptable radii. Switches one and four, were to be connected with 3 core-Earth cable. The same as before I laid the cable to the pre determined routes, and clipped using 5-7mm cable clips. The second switch was to be wired using 1.5mm flex cable. This was a new cable to me, and comprised of a white flex with 3 wires inside, live, neutral and earth. I cut the wire to the right length as the others, ensuring to leave enough cable at each end for terminating. This was clipped with 1.5mm round cable clips, as the cable was round as opposed to flat. The final cable was already laid previously, (SWA cable to switch three) but just needed a single cleat to secure the cable to the work board, This was attached with a 30mm woodscrew.

At this stage of the job, all components are in place and all cables connecting the components are laid out and clipped to the work board.

I commenced stripping the cables in each component. The1.5mm2 T/E cable was stripped of the grey outer sheath, and then each individual wire (Live, Brown, R1 - Neutral, Blue, RN) Was stripped 5-10mm from the end. This was done at all three lamps, the three ends at the junction box, the consumer unit, and the end at the junction box again. Also the copper earth core had earth sleeving applied at all ends of the cable. The 3 Core and Earth cable at switches one and four, was stripped in the same way, but with different colored wires (Black, Grey, Brown). The SWA cable was already prepared from the previous job. The flex cable was stripped differently. This had a white outer sheath. This was scored gently from where I wanted to remove the sheath, then I bent the cable back and fourth to completely remove the outer white sheath. The three core wires were then stripped at the ends ready for termination.

For switches two and three, the live/brown/r1 wire was connected to the common, the blue/neutral/rn wire was connected to the L1 terminal and the earth wire was connected to a spare terminal block. Switches one and four had the live/brown/r1 wire connected to the common, the grey wire connected to L1 terminal and the black wire connected to the L2 terminal. (Grey and Black wires had brown sleeving applied as all wires would be potentially live at any given time)

All ceiling rose's were then attached to the lamp holder back box's, ensuring the wires from the cable came through the center for termination. Earth/yellow:green/r2 wires were connected to the earth terminal at the top; live/brown/r1 wires were attached to the loop live terminal, where the live wire for the lamp connection was located: and finally the neutral/blue/rn connection was made to the neutral terminal.

After all component termination was complete, (excluding the junction box) I screwed all lamp holders into place and all switch faces were attached, securing with socket screws.

The final step was to terminate the junction box.

I began with all the earth connections. These were attached together in the first 3 terminals. I used earth wire to make links between the terminals, ensuring that all components were earthed properly. I then attached the live wire from the consumer unit to the fourth terminal, and linked it to the fifth. Terminal four then had switches 1 and 2 attached through the live wire, and terminal 5 had switch 3 attached.

(Switch 4 does not need a live supply as this is connected to switch 1.) I used terminal 6 and seven, to attach each of the wires from switch 1 to switch 4; grey to grey, and black to black (Brown sleeving applied, as these may be live.) Next I attached the switches to the lamps. I used the blue neutral wires from switch 2 and three (applied brown sleeving) and attached each to terminals 8 and 9, which would be attached with the live wires from lamps 2 and 3. Terminal 10 was used to attach the live from switch four, to the live on lamp 1. Finally all neutral wires were attached in terminals 11 and 12; these were linked together and connected back to the neutral from the consumer unit. This completed all connections in the junction box, I screwed the front of the box back on.

In the consumer unit I attached the earth wire to the earth terminal bar, and the neutral wire to the neutral terminal bar. The live connection was made to a MCB06. The consumer unit cover was replaced. This completed m y circuit ready for dead testing.

Dead Test

To dead test my circuit, I would use a multi-functional tester. The first test to carry out was continuity. This was done by connecting my wires in pairs at the consumer unit. (R1-R2, R1-Rn, R2-Rn). With each pair connected. I tested each on the three lamps in the circuit. I set the MFT to ohms, and used the pin connections in the positive and negative ports in the back of the unit. I used the pins to test between each of the terminals in the lamp holder, corresponding to which connection was made in the consumer unit. E.g when testing R1-R2 I would use the pins on the live and earth terminals in the lamp. This was done for all three lamps, and the highest reading was used. At first I was getting very high readings, and it turned out I had a faulty MFT. After switching MFT's, I got very low readings of under 0.1. This was the results I was looking for. Also, when testing and pair with r1 in the pair, I would turn the switches off/on for the corresponding lamp. This was to test the polarity and functionality of the circuit. When the switches would turn the lamp off, the readings would jump to 999<.

The next test I would carry out would be insulation resistance. I would carry this test out by testing the wires in pairs again at the consumer unit, (R1-R2, R1-Rn, and R2-Rn). I connected the wires to the MFT using the crocodile clip connections. These were again used in the positive and negative ports on the back of the MFT. The MFT was set to 500v (volts) this time. When pressing and holding the test button on the MFT, 500v would be sent through my circuit. Because I did not want a connection between the different wires, the correct reading I was looking for this time would be 999<. This is the reading I got for all tests.

Live Testing

Live testing on my circuit was done with a tutor present. I first secured all component covers, screwed the lamps back to the ceiling roses, and put light bulbs in all three lamp holders. The consumer unit was then plugged into the live supply. Switches 2 and 3 were pressed to turn on/off lamps 2 and 3. Switches 1 and four were pressed in sequence to turn lamp 1 on and off with alternative switches. This proved functionality of all switches, and that the circuit was wired correctly.