mutant_matt Posted December 28, 2003 Share Posted December 28, 2003 Sorry for the semi-spam type post of your board but I have been searching the net and have found nowhere that can help me. I am posting on behalf of a friend who is installing a 3 phase in his garage to run a Lathe, TIG Welder and CNC Milling machine. The garage is about 50m from where the Electricity Board/Siemens are going to install the meter/distribution board/box (sorry if I get some of the terminology wrong). He has installed 4-core cable from the garage to the point where the meter will go (another garage on the edge of the property). The question is, I presume that the 4-core is wired 3 cores for the 3 phases and the 4th core for the Neutral? What about the Earth? I think that the Earth used to be wired using the outer shroud/sheilding of the cable? Is this correct? I also have heard that possibly this is no longer legal and a seperate core would have to be used for the Earth? If so, does this mean he should have installed a 5 core cable? (3 for the phases, 1 for Neutral and 1 for Earth). Siemans are coming tomorrow and he is wondering if he is ready or will he have to install another cable for the extra core? What is the difference between Neutral and Earth and is it a)important b)safe to use the outer shroud for Earth? Any help you could offer really would be most appreciated and once again, appologies for using your board to ask a non-theatre related question!! Many Thanks in advance, Matt. Link to comment Share on other sites More sharing options...
peter Posted December 28, 2003 Share Posted December 28, 2003 First of all, I really feel that 3phase is something which should only be installed by competant professionals. TPNE (Three Phases Neutral Earth) cabling should definatly consist of 5 cores. Although for permenant installation purposes, I believe single cores are permissable. You should get hold of a copy of the 16th Edition regulations regarding electrical installations, which detail exactly what is legal. I should imagine you will get more helpful replies than this one, but thought I'd get in first with what I know. As for the difference between Neutral and Earth, Neutral acts as a 0v 'marker' for the phases, whilst the Earth is for carrying any leaked current. Both are required, and cannot be combined safely. Hope some of this helps Peter Link to comment Share on other sites More sharing options...
mutant_matt Posted December 28, 2003 Author Share Posted December 28, 2003 That does help a bit, thanks <_< You should get hold of a copy of the 16th Edition regulations regarding electrical installations, which detail exactly what is legal Do you know if that is available online? Thanks, Matt :P Link to comment Share on other sites More sharing options...
Bryson Posted December 28, 2003 Share Posted December 28, 2003 Not knowing anything about Lathes, Milling machines and TIG welders I could be dead wrong, but: if the phase balance is perfect (as in, say, a motor) then you can run 3-phase power on four cores. I'd guess that that is exactly what the Lathe and the milling machine want 3-phase for. Not sure about the welder though - anyone had experience of a welders power requirements? Why doesn't he just ring Siemens and ask them? If he's shelling out for a dirty great workshops-worth of kit, they could a least offer some helpful advice. Link to comment Share on other sites More sharing options...
Matt Posted December 28, 2003 Share Posted December 28, 2003 for an earth, you can get dirty great cop;per rods that you wack about 6feet into the ground, leaving 2feet above...? as a local earth, not sure about the earth sheilding around the cable, presuming it is armoured, it it has to be by law... but I dunno about that actually being earthed itself..., I just thought that was for protection against council workers diggin up the road? Link to comment Share on other sites More sharing options...
emj Posted December 28, 2003 Share Posted December 28, 2003 Afternoon all 3-phase earth is standard wiring for a lot of motor in industrial machinery and some welders. Where the earth acts as the neutral Some machines are wired 3phase, neutral, earth but this is less common in industrial machinery. This a standard wiring format for our industry because we are braking down to single phase most of the time As for just banging in an earth rod to make an earth I would advise you to get the earth professionally tested if not the hole install The one thing to remember is that ######ing up with 3phase can damage equipment, people and kill very quickly Hope the helps a bit Regards Em Link to comment Share on other sites More sharing options...
Ike Posted December 28, 2003 Share Posted December 28, 2003 ***IMPORTANT ñ CONTACT A PROFESSIONAL BEFORE CARRYING OUT ANY ELECTRICAL WORK IF YOU ARE IN ANY WAY UNSURE*** Firstly the machinery (consisting of huge 3ph motors and not much else) should be perfectly electrically balanced which means no neutral conductor is normally required - note this is NOT the case for most theatrical applications The armour on the cable (shroud, shielding, or whatever) is normally connected to the metal casing of the fuse box, equipment or whatever it is connected to and thus is normally earthed however it should probably not be relayed on for the protective earth as its cross sectional area is often less than required. As the neutral is PROBABLY not required one of the conductors may be used for the earth, if however you are not using one of the cores of the cable as an earth you will need to have the required 'cross sectional area' of the earth conductor calculated or looked up (probably best to just ask Siemens) and if this is greater than the cross sectional are of the armour then another cable will be required. If you do use a separate earth cable ensure they run the exact same as that of the main cable and cable tie the two together every 1' or so. I dont think the wireing regs are on line but am open to corrections. EDIT: DidnÃt see the bit about the welder but IÃm pretty sure they are balanced as well. As for creating your own earth my simple advice is DONÃT. While I have done this for outdoor evens in the past they really do need testing before use with equipment you are not likely to have and creating one is not as easy as it may at first seem. Link to comment Share on other sites More sharing options...
Brian Posted December 28, 2003 Share Posted December 28, 2003 As for creating your own earth my simple advice is DONÃTGood advice. Depending on the type of installation it may cause problems if you provide your own earth, for example if the supply is going to be a PME system. As far as Neutral goes you will almost certainly need one since I assume you will want lights and ordinary 13A power points in the area. IEE wiring regs are not available on-line. This is one of those cases where if you need to ask how to do it then you shouldn't be doing it. Sorry if that sounds harsh, it's not meant to be, it's just that the money saved by doing it all yourself is not worth your life. For instance do you know if Siemens are providing a TN-C system or a TN-S system or a TN-C-S system or a TT system or a IT system? What provision they are making to terminate the PE or PEN conductor? (These questions are simply to point out that it ain't that simple). Link to comment Share on other sites More sharing options...
Drew Posted December 28, 2003 Share Posted December 28, 2003 Can anyone point me in the direction of a brief guide to three phase electrics? I'm familiar with the working of single phase mains, as you would find in a home. Thanks Link to comment Share on other sites More sharing options...
Ike Posted December 28, 2003 Share Posted December 28, 2003 For instance do you know if Siemens are providing a TN-C system or a TN-S system or a TN-C-S system or a TT system or a IT system? What provision they are making to terminate the PE or PEN conductor? (These questions are simply to point out that it ain't that simple).I, perhaps incorrectly, assumed it would be a TN-S earthing system with the supplier making provision for the termination of the PE conductor. After giving it more thought I have realised that I was wrong to take assumptions when it comes to subjects of such severity and I strongly suggest you contact a professional electrician before continuing. I also failed notice that it was not a dedicated machinery circuit and will probably be running lighting etc which will not be balanced 3 phase appliances. Yet another point I didnÃt pick up on was the fact that the cable run may be underground or in harsh conditions which may make my comments about adding a separate earth inappropriate. Ike Link to comment Share on other sites More sharing options...
mutant_matt Posted December 28, 2003 Author Share Posted December 28, 2003 Thanks for the help so far guys. As I said before, this is purely for the Lathe, Welder and CNC machine. There is already a seperate lighting and ring main, supplied from the house for the garage. Any further help, most appreciated. Thanks, Matt <_< Link to comment Share on other sites More sharing options...
themadhippy Posted December 29, 2003 Share Posted December 29, 2003 yep you can use the aurmouring for the earth conductor,its wot those key ring thingys in the gland kit are for but you need to know the length of run,size of cable,type and rating of protective device being used and the earth impedance at the point of supply to ensure its up to the job.Also depending on the type of incoming supply will dictate how you provide the earthing connection.Best and safest option is to get a spark in.As for neutrals best to put in,not olny for lighting and genral power,but also the machine control circuitry may require one Both are required, and cannot be combined safelyquack quack oops,<_< it is allowed,but not used very much these days after the head,(main fuse) it is however a very common way of providing the incoming supply3-phase earth is standard wiring for a lot of motor in industrial machinery and some welders. Where the earth acts as the neutralaye?????? Link to comment Share on other sites More sharing options...
Rob Posted December 29, 2003 Share Posted December 29, 2003 TN-C system or a TN-S system or a TN-C-S system or a TT system I've just hit this stuff on the C&G course I'm doing. Any chance of a dummies guide to the above from any of you wise men? Link to comment Share on other sites More sharing options...
Brian Posted December 29, 2003 Share Posted December 29, 2003 TN-C system or a TN-S system or a TN-C-S system or a TT system I've just hit this stuff on the C&G course I'm doing. Any chance of a dummies guide to the above from any of you wise men? For pictures see inside the IEE wiring regs. TN-C. Neutral and Earth share the same conductor throughout the installation. TN-S. Separate Neutral and Earth conductors, separate Neutral and Earth terminal supplied by electricity company. What you might regard as the 'normal' way to do things. TN-C-S. aka PME. Separate N & E conductors through installation. N & E are joined at the point of entry into the building. Electricity company supply a combined N & E incoming wire. TT. Separate N & E conductors through installation. Local earth electrode independent of earth at sub-station. IT. No incoming N feed. Star point of sub-station connected to earth via impedance or not at all. Local earth electrodes. Of the above the most common is TN-S, you will come across TN-C-S and TT is the old way of doing it with local earth rods. Link to comment Share on other sites More sharing options...
themadhippy Posted December 29, 2003 Share Posted December 29, 2003 if my memory correct T=earth, N= neutral,S=seprate and C= combined,cant rember the corect term for I but think its independant?, the first bit is the incoming supply arangment and the second bit the arragment of conductors within the instalation Link to comment Share on other sites More sharing options...
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