On 10 Oct 2006 12:04:36 -0700 snipped-for-privacy@mail.croydon.ac.uk wrote: | snipped-for-privacy@ipal.net wrote: | |> It's probably a lot more about the common practices. Electrons don't care |> about the color of insulation. But installation practices sure do in both |> countries. And the colors are different. Old habits might die hard. You |> might have to watch out for grounding that blue wire. | | Are you aware that our colours have recently changed? Red, yellow and | blue have now become brown, black and grey (don't blame me, I didn't | choose the colours!) black has become blue. That means that what used | to be a phase colour (blue) is now neutral, and what used to be neutral | (black) is now a phase. A special warning label, I don't know the | exact wording, has to be placed on any installation where both old and | new colours are found together.
Well, then I was right, at least with respect to the new colors. I just don't know if the OP worked with the new colors or the old ones. If he did work with the new ones, he might well bond the blue wire to ground, which would be wrong here, but right there.
| I'm not an electrician, but I'm amazed at how much difference the is | between the two countries; It's difficult to find things that are the | same. With the exception of the new European harmonised colours it | does seem to me that things are much simpler here than they are over | there, where things really do seem over-complicated. To start with, | take Voltage; over here, unless you're running something really big, | like a steelworks or an electric railway, it's 415 phase to phase, 240 | phase to neutral (I should call it 400 and 230 now, but old habits die | hard, and nothing's really changed). Over there it's 120, 208, 240, | 277, 347, 480 or 600; have I missed any out? It can be wye (we would | call it star) or delta. If it's delta it can be that strange | centre-grounded system where two of the wires are 120 to ground, and | the third is 208, so the three phases are not all the same. Then what | on Earth is open delta? I've heard of it, but I've never found anybody | who can tell me what it is.
Open delta is delta with one of the windings missing. You still get the same voltage at the same phase across the points with the missing winding, but you are getting it from the other two windings. One advantage of open delta is it won't backfeed. But then, that's an advantage wye/star, too. You have to derate open delta because all three phases are pulling from just
2 windings.
Yes, it is a complex mess of voltages over here. Some old guy that was messin' with light bulbs over 100 years ago decided to split the circuit in half at 110 volts because it made his bulbs last longer. He could have used the 127 volts that was there in the star 220/127 volt systems, except for the fact that he was dead set on using DC instead of AC.
I'd be just as happy if they would switch all the power here to 480/277. Of course doing that today would be such a mess. They wouldn't be able to get rid of the 120 volt stuff for many decades. But at least incandescent lights could be run on 12 or 24 volts very effectively, and fluorescent could be run on 277 directly.
The 208 volt thing is a messy issue. Many offices, as well as apartments in large buildings, have that instead of 240. Unless you change out the burner elements, expect it to take a bit longer for the water to boil at the highest temperature (though at lower settings, it's thermostat driven, so it just changes how long the element stays on).
BTW, if you took a transformer designed for 480 or 277 volts at 60 Hz, and wanted to run it at 50 Hz, guess what the voltage would then have to be. Yup, 400 or 230. I bet that's not a coincidence.
| Then there are the plugs and sockets. Our normal 13A one is BS1363, | and they're all the same. For industrial use, there's what was BS4343, | which now has a EN number which I can't remember. They come in 16, 32, | 63 and 125A versions, are colour coded for Voltage, and have three, | four or five pins, but in each case a higher current one is like a | lower current one, except that it's larger. Over there you seem to | have the same things, called pin and sleeve devices, but rated at 20, | 30, 50 and 100A for some reason. You also have orange ones for | combined 120/240V and grey, which I think are 480V, which we don't have | here. Before BS1363 we had BS456, which had round pins, there were | four ratings, 2, 5, 15 and 30A. Again, they were all similar, except | for size. They are little used now, excepr the 5 and 15A ones for | stage lighting. | | Over there you have the NEMA range; where do we start with those, it's | truely bewildering. Obviously, you need many different versions for | the various Voltages in use there, but then look at the current | ratings: 15, 20, 30, 50 and 60A. Here there is generally a difference | of 2-3X between sizes; there you have five ratings just to cover a | range of 4:1. Then there seems to be little pattern to the various | versions. Take the 15A ones; the 5-15 has vertical pins, increase the | Voltage and the 6-15 has horizontal ones. If you need 277V the 7-15 | has them at an angle, between those of the 5-15 and the 6-15. Then | look at the 20A ones, why have two ratings so close together? The 5-20 | logically ought to look like a 5-15, but larger. It doesn't of course, | the neutral pin is turned horizontal. the 6-20 doesn't look like a | 6-15 either, the neutral pin is turned vettical, so the 5-20 and the | 6-20 each have one horizontal and one vertical pin, but the opposite | way round, so the orientation of the pins sometimes indicates Voltage, | and sometimes current. The 20A receptacles have 'T' slots, so they can | also take 15A plugs, except in Canada, where they don't. I've never | seen a 7-20, but I believe it's similar to a 7-15, but with one pin | slightly wider. I don't think my brain can cope with the 30-60A ones, | with their 'L' shaped pins etc. Then there are the locking range, | which are totally different, not to mention the various non-Nema ones. | | Then consider the number of pins on a plug; over here it can be: | | 2 pin L,N (shavers and toothbrushes only). | 3 pin L,N,E. | 4 pin L1,L2,L3,E | 5 pin L1,L2,L3,N,E. | | over there they can be: | | 2 pin hot, neutral or hot, hot. | 3 pin hot, neutral, ground or hot, hot, ground or hot, hot, neutral | or hot, hot, hot. | 4 pin hot, hot, nuutral, ground or hot, hot, hot, neutral or hot, | hot, hot, ground. | 5 pin hot, hot, hot, neutral, ground. | | I think that's covered all the possible combinations, with each having | it's own NEMA configurations of course. | | The whole thing just seems to be incredibly complicated; there must be | an awful lot to learn to be an electrician over there.
Wow, you covered the mess quite effectively.
About the only consistency I have seen in the NEMA plug patterns is that a 6-15 plug will fit into a 14-15 outlet with the correct wiring. But they didn't seem to do that with any other amperage.
Personally, I don't really like the BS1363. I would prefer the Schuko over either what is in UK or US. OTOH, if I were to design it, I'd have a plug with a metal shroud that doubled as ground, with the neutral being a round pin in the center, and each phase in three phase systems being a pin at 120 degrees around a circle. Outlets with only single phase would only have openings at the center and one end if they were L-N, and just the two ends if they were L-L. Plugs could match the load and be able to fit any outlet with the correct type of phases available. A higher voltage would be a large plug with pins further apart. I'd probably use blades rather than round pins for the phase lines, and make the blades wider (not thicker) for higher amps (and only in L-L).
I would definitely have chosen 60 Hz or even higher if I were to have designed the system. I would keep a higher voltage, but require incandescent lights be run on 32 volts or less.
| A couple of things you might be able to tell me: | | What colours are used for a three phase installation over there?
208Y/120: HOT: black, red, blue NEUTRAL: white
480Y/277: HOT: brown, orange, yellow NEUTRAL: gray Grounding: green Isolated ground: green/yellow combination
The colors are not all in the NEC. Neutral and ground are, as is the one higher voltage wire of that center tapped delta 240 system (2 hots are 120 volts at 180 degrees from each other, and one more hot is 208 volts at 90 degrees, forming a delta) has to be orange. Some other rules exist about using distinctive colors for phases, but the exact colors are not specified. Some local areas do specify specific colors and those are not always the same. For example in Austin Texas, 480Y/277 uses purple for one of the colors
| I believe a fairly large customer, say a shopping mall or a large | office building, or large railway station for example would be likely | to have a three phase 480/277V supply. I assume that large plant, | HVAC, elevators etc. would probably be driven by 480V three phase | motors, and I know that large discharge lighting installations are | often 277V, but they would also need 120V for things like office | equipment, and small lighting. Obviously you cannot get this by | connecting directly to the 480/277V supply. Does the electricity | company provide them with a separate 120V supply, or does the customer | just get 480/277, and they provide their own step-down transformer? In | either case is it centre-tapped 120-0-120V, as in a domestic | installation, or just a simple 120V?
The customer or landlord usually provides a transformer to step down from
480/277 to get 120. But it is usually done as a 208/120 three phase step down to keep the loads balanced on the phases. But in smaller cases, that step down could just be single phase, taking 480 to a transformer and getting 120/240 (120-0-120) out. The simple 120 volt 2-wire system is very rare. Voltage drop is worse on 120 volts than on 240 volts. But by splitting the loads across 2 phases like that, you cut the current in half and the impact of voltage drop is reduced.