WTA.05 Two Way Conduit Lighting

To begin this job I had to learn a whole new set of skills. I started by receiving instruction from my tutor on techniques of pipe bending. This was done using a pipe bending machine. The outcomes of the task were to:

Bend a 900 bend in 20mm metal conduit Use a die and cast to create a threaded conduit end piece Attach the conduit to a Consumer Unit (CU) using the correct fittings Create a "kick" bend to the C.U Attach the assembly to the wall using the correct fittings

After being shown the above tasks by my tutor, I proceeded to the WTA.05 project.I started by making sure my work area was clean and tidy, free from materials and equipment. I gathered the tools I would need for the job, and collected a components basket from the store. I also collected separately, one length of 20mm metal conduit. The first task was to mark out the job on my work board. This included the component locations and the conduit layout. This was done to the layout diagram in my practice book.First FixI next proceeded to mark out and cut the 20mm steel conduit to the correct lengths, I would need 4 lengths for this job. Each piece of conduit was threaded, this was done with a stock and die. I first secured the pipe lengths in a pipe vice. This keeps the tubing steady whilst work is being carried out. I started by putting the die on the end of the tubing, and making a small turn to start the threading process; after this the die was removed. I proceeded to apply a small amount of cutting lubrication to the conduit end. This would help give me a smooth thread cutting and prevent damage to the tubing. The threading was carried out by turning the die 3 times, then going back over 3 times. This continued until I had a thread of roughly 20mm. This process was carried out on each conduit length (excluding large length for bending.)The next step was to put the 900 bend in the large length of conduit. This was done using a pipe bending machine. After bending the pipe and checking it for square; I proceeded to thread the ends of this length as done before. On the top of the 900 bend the threading was made longer. This was to incorporate a running coupling joint. The threading was made the length of a full coupler, plus 5mm. I began attaching the conduit to the work board.

Firstly I attached the inspection elbow to the CU (Fig.3). This was done with a threaded gland (Fig.2). The gland was tightened with a bush spanner. I then attached the first length of conduit, this was done by screwing the conduit into the inspection elbow. I then drew lines down each side of the conduit so I could place a conduit saddle in the center (Fig.1). The conduit was then removed so I could fit the saddle to the back board with a 20mm woodscrew. The conduit was attached again, this time with the lamp holder metal back box attached to the end. The saddle had the top piece screwed in to secure the conduit and another 20mm woodscrew fixed through the lamp holder back box.

. Fig.1 Fig.2 Fig.3

The same process was repeated from the underside of the lamp holder back box to secure the first metal clad switch. This left the attachment of the second switch and the 900 conduit bend.To connect this piece of conduit I would have to complete a running coupling. I started this process by attaching a locking ring and a coupler to the end of my elbow. I then cut and threaded a small piece of conduit to be threaded inside the lamp holder back box. These 2 pieces were butted together and the coupler turned in place. This connected the conduit to the lamp holder back box, and the locking ring behind the coupler secured the pieces together. A saddle was attached on the vertical piece of tubing, as well as another lighting switch back box. Back boxes were secured with 20mm woodscrews. This ended the first fix of the project.

Second FixThe wiring of the conduit system began with cutting 1 length of blue/neutral/rn wire, 4 lengths of brown/line/r1 wire, and 2 lengths of green yellow/earth/r2 wire. These were all single wires 1.5mm. I removed the cover on the inspection elbow and threaded the neutral wire first. I then threaded 1 line wire from the CU to switch 1; two line wires from switch 1 to switch 2; and a final line wire from switch 2 to the lamp holder. Earth wire was threaded from the CU, to the lamp and from the lamp to switch 1 and 2. This would act as the circuit protective conductor (CPC). All wires were stripped to the cores at the ends ready for terminating. In the lamp holder back box, I connected the rn wire to the neutral terminal on the lamp holder. Also the line wire from switch 2 connected to the line terminal on the lamp holder. Switch 1 connected the common terminal to the consumer unit (B16 MCB), whilst the two remaining line wires connected in terminals L1 and L2. (L1 and L2 terminal wires were marked accordingly on installation, so easy identification would be possible at this stage.) All circuit protective conductor (CPC) wires were connected in the earth terminal, including the CPC wire from the metal switching box. Switch 2 had a line wire from the common to the lamp holder. Terminals L1 and L2 were connected with L1 and L2 from switch 1.At this stage, all switch covers were attached to the back boxes. The lamp holder and CU wires were left accessible for testing.

Dead TestContinuity testing was done with a multi-functional tester (MFT). I used pin connections from the MFT, connected to the positive and negative ports on the back of the unit. The unit was set to ohms. Placing the pins on the lighting rose terminals, I took readings for R1-R2, R1-Rn, and R2-Rn. (Whilst taking the readings, the corresponding connections were made within the consumer unit, using terminal blocks.)The rn was tested from the neutral terminal in the ceiling rose, the r2 from the earth terminal, and the r1 from the loop live terminal. When testing through the line connection, switches 1 and 2 were switched to test the functionality. Insulation resistance was also carried out with the MFT, using the crocodile clip connections, again in the positive and negative ports of the MFT. I connected the clips to paired wires in the consumer unit, (R1-R2, R1-Rn, and R2-Rn) the unit was set to 500v. Whilst the wires were connected I held down the test button on the unit; this puts 500v through the circuit to test for any damage to insulation or toughing wires. When testing for continuity, by testing all three wires paired together, (R1-R2, R1-Rn, and R2-Rn) this proves polarity in the circuit.

Live testAfter all my dead test was completed, I moved onto the live test. This was carried out under the supervision of a tutor. The consumer unit was first connected to live power. The master switch and MCB were switched on, providing power to the circuit. The switches were pressed simultaneously to test the functionality of the switches working. All tests came back correct.