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Powering the lights in a powercut...
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<blockquote data-quote="tapfit2004" data-source="post: 247620" data-attributes="member: 189049"><p>i am an electrical contractor based in ireland, but i have done the city and guilds exams iee 16th edition.</p><p></p><p>most lighting circuits are not wired in a ring, i have never come across one in 15 years. socket circuits in kitchens would be, as it effectively doubles the size of the cable to each point (2.5 mmsq from each side = 5 mmsq) which allows an increased fuse/mcb protection.</p><p></p><p>when connecting a ring circuit to a fuse board/consumer unit you would always bring the two ends of the circuit directly back to the fuse/mcb as if you joint them before hand and only bring 1 cable back you defeat the purpose of running in a ring circuit in the first place.</p><p></p><p>the way you explain that your house is wired with lives going to the switches and neutrals going directly to the lights is the old way of running in lighting circuits, used because it uses less cable and cable was more expensive than labour costs years ago (new way of wiring is quicker but uses a lot more cable)</p><p></p><p>you will need a live and neutral to charge your ups so you will only be able to install it at a point where you have a live and neutral present. the best place would be beside your consumer unit. before starting turn off the main switch/fuse, and make sure that your neutral bar is not live. (i have come across this a couple of times where the elecrticity companies tails have been swapped so be warned)</p><p></p><p>the easiest way to connect would be to remove the lighting circuit live and neutral from the fuse board/consumer unit and connect them to the output of your ups, then run two new live and neutral cables from your fuse board/consumer unit to the input of your ups. if your fuse/mcb value is 10amps (as in most lighting circuits) you should change the fuse/mcb down to 6 amps or put in a fused spur unit fed from the existing 10a fuse/mcb with a 5 amp fuse in it. alternatively you could just put in a socket and plug in the ups, but by the regs this socket should be protected by an rcd.</p><p></p><p>if your lights are on two different fuses/mcb's, make sure that there is a different neutral wire coming back from the light in the cellar (you should have 2 lighting neutrals at the fuse board/consumer unit if fed from two different fuses/mcb's). if there is 2 lighting neutrals then no need to read the next section as it gets a bit complicated and i might not have explained it fully (its nearly 2am and i need some sleep)</p><p></p><p>if there is only 1 lighting neutral and your supply to the ups is broken without all the power going off (ie the fuse blows or mcb trips on your ups protected circuit) you could end up with the neutral being live at the output of your ups. (this would happen if the light in the cellar was switched on and the fuse/mcb for the ups supplied lights was blown/tripped.) see diagram below</p><p></p><p></p><p>[fuse 1]-----live------[ ups ]---L--(switch)--(light)--|</p><p>{neutral bar}----neutral--[ box ]X--N---------------------|</p><p>[fuse 2]-----live-----------------(switch)--(cellar light)-|</p><p></p><p>--- & | are wires</p><p></p><p>X is the point which would be live as the ups would have cut off the neutral rerurn to the neutral bar because it would see no power coming from fuse 1(tripped or blown) and power coming from fuse 2 through the bulb in the cellar light would have no return path either thus it would become live at the neutral connection on the ups. easiest way to cure this is to run a seperate neutral to the cellar light.</p><p></p><p>hope this helps. if you have any questions or think i need to explian better post back but it might take a few days for me to respond as my internet connection is on the blink so i dont get online that often. regards, tf</p></blockquote><p></p>
[QUOTE="tapfit2004, post: 247620, member: 189049"] i am an electrical contractor based in ireland, but i have done the city and guilds exams iee 16th edition. most lighting circuits are not wired in a ring, i have never come across one in 15 years. socket circuits in kitchens would be, as it effectively doubles the size of the cable to each point (2.5 mmsq from each side = 5 mmsq) which allows an increased fuse/mcb protection. when connecting a ring circuit to a fuse board/consumer unit you would always bring the two ends of the circuit directly back to the fuse/mcb as if you joint them before hand and only bring 1 cable back you defeat the purpose of running in a ring circuit in the first place. the way you explain that your house is wired with lives going to the switches and neutrals going directly to the lights is the old way of running in lighting circuits, used because it uses less cable and cable was more expensive than labour costs years ago (new way of wiring is quicker but uses a lot more cable) you will need a live and neutral to charge your ups so you will only be able to install it at a point where you have a live and neutral present. the best place would be beside your consumer unit. before starting turn off the main switch/fuse, and make sure that your neutral bar is not live. (i have come across this a couple of times where the elecrticity companies tails have been swapped so be warned) the easiest way to connect would be to remove the lighting circuit live and neutral from the fuse board/consumer unit and connect them to the output of your ups, then run two new live and neutral cables from your fuse board/consumer unit to the input of your ups. if your fuse/mcb value is 10amps (as in most lighting circuits) you should change the fuse/mcb down to 6 amps or put in a fused spur unit fed from the existing 10a fuse/mcb with a 5 amp fuse in it. alternatively you could just put in a socket and plug in the ups, but by the regs this socket should be protected by an rcd. if your lights are on two different fuses/mcb's, make sure that there is a different neutral wire coming back from the light in the cellar (you should have 2 lighting neutrals at the fuse board/consumer unit if fed from two different fuses/mcb's). if there is 2 lighting neutrals then no need to read the next section as it gets a bit complicated and i might not have explained it fully (its nearly 2am and i need some sleep) if there is only 1 lighting neutral and your supply to the ups is broken without all the power going off (ie the fuse blows or mcb trips on your ups protected circuit) you could end up with the neutral being live at the output of your ups. (this would happen if the light in the cellar was switched on and the fuse/mcb for the ups supplied lights was blown/tripped.) see diagram below [fuse 1]-----live------[ ups ]---L--(switch)--(light)--| {neutral bar}----neutral--[ box ]X--N---------------------| [fuse 2]-----live-----------------(switch)--(cellar light)-| --- & | are wires X is the point which would be live as the ups would have cut off the neutral rerurn to the neutral bar because it would see no power coming from fuse 1(tripped or blown) and power coming from fuse 2 through the bulb in the cellar light would have no return path either thus it would become live at the neutral connection on the ups. easiest way to cure this is to run a seperate neutral to the cellar light. hope this helps. if you have any questions or think i need to explian better post back but it might take a few days for me to respond as my internet connection is on the blink so i dont get online that often. regards, tf [/QUOTE]
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