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I've always wondered whyelectric plugs


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have one prong a bigger size than the other. Years ago, both prongs used to be the same size. Why was one made bigger? What advantage does it bring?

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ross549

.... because some plugs were mistakenly made with one prong larger than the other! :D :) Actually some equipment is sensitive to polarity, and only one ron in a plug is the "source" of the electricity, and the other two are just a ground.

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Guest ThunderRiver

one plug larger than the other in what way?The third probe on the plug is the ground, which is used to protect your electronic equipments against electric shock/surge.

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SonicDragon
one plug larger than the other in what way?
On the plugges with two metal things sticking out, one metal thing is fatter than the other.I don't know why they do this either.
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ok, as far as i know, one is negative, other is positive. the round 3rd plug is ground. if you have the ground, there's no way you can mix up the negative / positive plugs, but for wires that dont have ground, they made one fatter so you dont put the plug in wrong way, as some equipment is sensitive to this.then again, you have people like the previous owner of my house, who hooked up the outlet he installed himself the wrong way. :)

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SonicDragon
ok, as far as i know, one is negative, other is positive. the round 3rd plug is ground. if you have the ground, there's no way you can mix up the negative / positive plugs, but for wires that dont have ground, they made one fatter so you dont put the plug in wrong way, as some equipment is sensitive to this.
That sounds pretty good to me :)
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Stonegiant
ok, as far as i know, one is negative, other is positive.  the round 3rd plug is ground.  if you have the ground, there's no way you can mix up the negative / positive plugs, but for wires that dont have ground, they made one fatter so you dont put the plug in wrong way, as some equipment is sensitive to this.then again, you have people like the previous owner of my house, who hooked up the outlet he installed himself the wrong way.  :D
Negative and positive have no real meaning when dealing with AC (Alternating Current). One of the two parallel prongs (I forget which, but I used to know) is the "hot" prong. That's the one that has the 60/50 Hz 120 volts applied to it. When you plug something in (and turn it on as required), that completes the circuit from the hot prong, through the equipment and back to the other prong (which is normally referred to as "common"). The other prong is the return line to the power generation station. The large round prong is a ground prong. I am not entirely sure where it physically enters the ground (whether at your house or at a station designed for just that), but it does somewhere.
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Ok that last one was close.With the 2 prong type used here in America the larger one connects to the "Common" or "Neutral" line and the smaller prong connects to the 110 Volt "Hot" line. If you look outside your house you will see 3 lines comming up to your home. There is a bare aluminum stranded line that is bolted down between the pole and your house. The other 2 are 110 Volt lines off of a transformer that may be on your pole or down the street. Each pole has a Copper rod inserted into the ground as does your house. The power station also has a "Ground" rod. Between one of the "Hot" lines and "ground" or Neutral" (they are connected at the same point in the electrical box in your house" there is 110 volts (or so may be 105 to 125 depending on the area). This is all good but what about some PC servers that use 220 Volts or your A/C Electric Dryer, Stove or Water Heater? Well if you measure between the 2 "Hot" lines you will have 220 Volts. You will have a "Neutral" and a "Ground" line on these wires too. So maybe you have seen the 4 prong plug on your generator. If you were in the blackout and were lucky enough to have one you might be wondering what that plug was for. Well most likely it was a special 4 prong twist type plug. It has 2 "Hot" lines one is red and the other is black. It will have a white "Neutral" and a green "Ground" line. It is really quite interesting how this all works. All the different voltages that are possible with a few transformers and a bit of engineering. Just remember with AC Voltage the "Hot" wire always has voltage potential. Completing the circuit to ground will result in a shock. Hopefully it is in the equipment you are going to use. Otherwise it is you that will complete the circuit and be shocked.Chris

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Ok that last one was close.With the 2 prong type used here in America the larger one connects to the "Common" or "Neutral" line and the smaller prong connects to the 110 Volt "Hot" line.
OK, but this doesn't explain WHY it is this way now or what the advantage is. The old plugs with both parallel prongs the same size still work fine, even if you stick one in a new recepticle with one larger and one smaller slot.
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ross549

Some of the equipment that does not have a ground plug is "polarity" sensitive, in that the source of the power has to come into a specific side of the power supply. Thus the size is different.

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Some of the equipment that does not have a ground plug is "polarity" sensitive, in that the source of the power has to come into a specific side of the power supply. Thus the size is different.
No, that can't be it. You can take an old style plug with both prongs the same size and plug it into a new outlet straight in or 180 degrees rotated and it will power the device perfectly.
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Cluttermagnet
Some of the equipment that does not have a ground plug is "polarity" sensitive, in that the source of the power has to come into a specific side of the power supply. Thus the size is different.
No, that can't be it. You can take an old style plug with both prongs the same size and plug it into a new outlet straight in or 180 degrees rotated and it will power the device perfectly.
I can try to shed a little light here. Right, guys, it's not 'polarity' as such, as we are dealing with 60Hz AC power. That idea comes from an earlier era when one side of the AC line (neutral) was actually allowed to connect to the metal chassis of electronic gear (which sat inside wooden cabinets and so was 'insulated'). There were even some 'transformerless' designs. Long story short, this kind of stuff was _extremely_ dangerous and they outlawed it after enough folks had gotten themselves electrocuted. Well, you were supposedly safe, just as long as you had the wide prong (neutral) connected to chassis and the narrow prong (hot) going on to the power supply circuit. But what if some dummy reverses the two somewhere along the line- say by wiring his own extension cord and using the kind of plug where the two prongs are both 'skinny'. Ouch!But there was an even more important issue to be resolved, once they had broken everyone of the habit of designing potentially 'hot chassis' devices. That issue is called the "ground fault", and it alone has been responsible for many tragic electrocutions over the years. We actually had a 'ground fault' event this past winter that affected only about 4 homes served by our particular pole transformer. Having an electronics background, I quickly caught on and diagnosed it and had the power company out the same day. They found two possibly loose crimp connectors in the neutral wire and replaced both. Problem solved. The symptoms? A lot of wierd flashing of normally well-behaved table lamps, dimming of others, computer UPS's going crazy and triggering on briefly several times per hour, etc. Putting my "true rms" digital multimeter on one side of the line, I was seeing upwards of 165V at times. 125 or so is normal. And I saw as low as about 85V on the other 'phase'.What is a 'phase'? I will get to that in a minute.The appearance of the now familiar 3rd prong on US power plugs signaled the dawn of a new era of sanity. As someone else pointed out earlier, the British got it right from the start. We Americans had to kill a bunch of people before we wised up. Here is what that 3rd prong does: it connects to an entirely separate wire (green color insulation or sometimes bare within jacketed cables). That wire runs separately everywhere in your building. It is Never, Never allowed to connect to the neutral wire anywhere except right at the breaker box. The idea is to try to bring something closely resembling a 'true' ground around everywhere and connect it to the metal chassis of equipment and appliances for added safety. The whole idea is to prevent any metal housing from becoming 'hot'. It works this way only because we never draw any current through the safety ground wire. All current flows from the hot, through the device under power, and back to the neutral (reversing direction constantly, as this is AC 'alternating current').Now here is where it gets a little complicated, so try to follow along and you may come to understand 'ground faults'. Keep in mind that the transformer out on the pole is sending you 240VAC on a pair of wires. Call them L1 and L2 for line 1 and line 2. Or you can also call them phase 1 and phase 2. Then there is that 3rd neutral wire that comes along with them that is usually bare, uninsulated, stranded aluminum. Edit: The neutral is connected to a 'center tap' on the 220V transformer winding. Measure from there to either L1 or L2 and you will get 120V. Measure from L1 to L2 and you get 240V. Here it gets tricky. Bear in mind that the 3 wires from the mains feed are not quite the same as the 3 wires that come around to your normal wall outlets. How you get that 120V is you connect between, say, L1 and neutral. _And_ you bring along a 3rd wire, the 'green' safety ground, which connects to that big, bare neutral too, but _only_ at the breaker box. Very important! Of course, you can also get 120V by connecting other appliances between L2 and the neutral. In fact, when they wire your house, they try to accomplish some 'load balancing'. Say they hook your washer to one 'phase' L1 and a small room air conditioner to L2 and so on. If you manage to balance it perfectly, you get the surprising result that there is no current flowing in the neutral but plenty of current flowing in L1 and L2. But loads are dynamic- they change constantly, so usually there is at least some current flowing in the neutral. This was the big problem with the 2 prong plug systems. If there were enough of an imbalance and if the neutral were connected to the metal chassis, there would be a shock hazard if you touch the chassis with one hand and find ground with the other hand or by standing in a puddle of water, etc. Think of it this way- with perfect load balancing, the neutral has the same potential as the safety ground. But create a load imbalance and the neutral gets 'pulled' towards the voltage on L1 or L2. Neutrals can actually get quite hot with voltage, worst case.Now, a 'ground fault'- say you intentionally open (cut) the neutral coming to the house. In that case you are also 'floating' the potential on the neutral running throughout the house and the voltage across various appliances can become quite high or low, depending only on load balance. On the more heavily loaded phase, the voltage is much lower. On the lightly loaded phase, the voltage across the appliances soars. It can definitely get high enough to damage certain appliances and equipment. Edit: If the service neutral is open, current coming from L1 or L2 can no longer find its way back to the transformer center tap- but it can still travel back, completing the circuit. How? It originates in, say L1, powers appliance #1, then passes through appliance #2, then back to L2. The voltages across appliances 1 and 2 automatically adjust themselves in accordance with the ratio of load resistance of all connected appliances, combined. So, in both the case of simple poor load balance and in the case of an actual ground fault (service neutral open), the voltage on the neutral running through the house can depart significantly from 'ground'. The ground fault is more serious than just some load imbalance. But in either case, we are kept safe provided the safety ground is properly wired throughout the house, plus in every appliance requiring a 3-prong connector (plug). Although you always seem to get away with it if you use a 3-prong to 2 prong adaptor, you need to know that defeating (disconnecting) the safety ground could possibly lead to someone touching a hot chassis. Worst case, electrocutions do happen. They are rare but they do happen, believe me.So why do so many appliances get away with only having a 2-prong connector? They must be well insulated, often double insulated, but if that is done properly there is no hazard. You are never going to get a shock from a toaster or an electric drill if their cases are plastic- so a safety ground is not always needed. Bear in mind that even a plastic-cased hair dryer could still shock or electrocute someone if it fell into a bathtub full of water with them in it. That is why we have GFCI's- ground fault current interruptors, which can detect a small current flowing to ground which 'should not be there' and interrupt power. Electrical codes now mandate the use of GFCI's in kitchens and bathrooms in many jurisdictions- wherever appliances may be plugged in near sinks, tubs, and showers.There- are your eyes all glazed over? At least I left out the Ohm's Law part, which explains why these things happen. ;)
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ross549

Very, very useful information, clutermagnet..... I am an electronics technicion (sp?), and that explained a lot.From what you said, you have two problems creating shock hazards-1. load imbalance2. ground faultJust want to make sure I understand this...... :) P.S.- go ahead- delve into ohm's law ;)

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*APPLAUSE FOR CLUTTERMAGNET*impressive!all i know is how to install plugs (connect white wire to silver screw, and black wire to gold screw, and hook up ground to green screw)... or is that the other way around? i always forget ;) quick question since theres a good electrical thread going on here...i'm hooking up a 2 year old central air unit i got thru a real good deal ($500 CAN). a friend knows how to do silver brazing so he'll do all the welding and hooking up freon lines.my question is about the power. at first i got a 40 AMP fuse, thinking naturally all A/C use 40 AMPs and thick 10 gauge wire, 2 phase wire. but the guy i bought the A/C from game me all lines and wires, and there is just a 1 phase 12 gauge wire with it. i was about to get thicker wire, but i checked the A/C panel and its a high-efficiency unit. it says needs 12.6 amps, delay fuse 15amp, max fuse 20amp, 1 phase, 230 volt.i sort of understand it, but have a couple questions: how much more efficient is a 230 volt 1 phase A/C than a standard 120 volt 2 phase 40 amp a/c? also, i have spare 15 amp breaker. can i hook it up, or will it keep tripping? do you recommend a 20 amp breaker, or see how it runs on 15 amp breaker first?

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Some of the equipment that does not have a ground plug is "polarity" sensitive, in that the source of the power has to come into a specific side of the power supply. Thus the size is different.
No, that can't be it. You can take an old style plug with both prongs the same size and plug it into a new outlet straight in or 180 degrees rotated and it will power the device perfectly.
I can try to shed a little light here. Right, guys, it's not 'polarity' as such, as we are dealing with 60Hz AC power. That idea comes from an earlier era when one side of the AC line (neutral) was actually allowed to connect to the metal chassis of electronic gear (which sat inside wooden cabinets and so was 'insulated'). There were even some 'transformerless' designs. Long story short, this kind of stuff was _extremely_ dangerous and they outlawed it after enough folks had gotten themselves electrocuted. Well, you were supposedly safe, just as long as you had the wide prong (neutral) connected to chassis and the narrow prong (hot) going on to the power supply circuit. But what if some dummy reverses the two somewhere along the line- say by wiring his own extension cord and using the kind of plug where the two prongs are both 'skinny'. Ouch!
I'm sure the answer to my questions is somewhere in what you wrote, but I'm clearly not smart enough to see it. Could you simplify this [quite] a bit? :blink: To paraphase what has gone before:1. Forget the ground prong.2. Modern electric sockets have a big slot and a smaller slot.3. Modern electric plugs have a matching big prong and a small prong. 4. Older electric plugs have both prongs the same size.5. Older electric plugs work fine in newer recepticles/sockets.So what did the different size prongs bring to the table???? Why was the change made? How does it help anything? Is there any exposure to using older style electric plugs?
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cluttermagnet gets the "UNCLUTTERED MIND" award! Woooohoooo!That was so good and clear that I DARE anyone to ask him to clarify the following question:Why the "AC_High" side wiring is BLACK in color and the "AC_Neutral" side wiring is WHITE in color (per UL code)?The "AC_Protective" side wiring being GREEN makes perfect sense as it is/should be tied to "Earth_Ground" (sooner or later)!This color coding is ALL wrong if you ask me and does NOT follow the convention of DC wiring in the world over! {High=RED >> Return=BLACK}I think that this problem actually causes more SAFETY issues in the long run! And have seen mis-wiring from people that attempt to follow logic (not knowing UL code)! :blink:I need a double shot of SAFETY please! :blink:

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from what i gathered, the older style (prongs same size) led to 'greater' chance of accidental ZAPPING if there was load imbalance between the 2 prongs, and/or certain electronics are very picky with load imbalance / polarity / whatever you wanna call it, so everyone standardized on Big Prong / Small Prong design to give more safety to the consumer (i.e. less deaths) :blink: if you have an older electrical device with prongs same size, it shouldnt matter using it either way as the device probably has safety designed into it since it was made back in the day of same size prongs. newer devices all have the big / small prong, and if more safety is needed, 3 prongs

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Cluttermagnet
cluttermagnet gets the "UNCLUTTERED MIND" award!  Woooohoooo!That was so good and clear that I DARE anyone to ask him to clarify the following question:Why the "AC_High" side wiring is BLACK in color and the "AC_Neutral" side wiring is WHITE in color (per UL code)?The "AC_Protective" side wiring being GREEN makes perfect sense as it is/should be tied to "Earth_Ground" (sooner or later)!This color coding is ALL wrong if you ask me and does NOT follow the convention of DC wiring in the world over!  {High=RED >> Return=BLACK}I think that this problem actually causes more SAFETY issues in the long run!  And have seen mis-wiring from people that attempt to follow logic (not knowing UL code)! :blink:I need a double shot of SAFETY please! :ph34r:
Some thing are hard to explain. I can't defend having the Hot the Black wire and the Neutral the White wire. It seems counterintuitive. With DC electronics, and even with the old tube gear, we usually chose brighter colors to mean more danger, for example Red="B+", the high 'plate voltage' supply for vacuum tubes, Orange='screen grid' supply, a lower 'high voltage'. But even here they were not consistent. For example, the relatively safe 6.3 VAC filament voltage went through Green wires (!). And a higher DC voltage, say a -120V negative bias supply might be in some light tan or even slate or blue wires. And yes, during the transition from tube to solid state gear, there were units that had both green filament wires and the green safety ground, both in the same chassis. :blink: Some folks get in trouble when they try doing their own electrical work. Yes, we occasionally see where some one has interchanged the black and white, so at some point you are going to find a black wire joining a white wire! Or maybe you just have a situation where the skinny socket slot is the neutral and the wide one is the hot. OTOH, there are some valid situations, such as with 3-way wall switches, where white and black wires do connect together legitimately. That I have seen many times.Regarding the wide prong issue, think of it as a holdover from the transitional era when houses were wired with 2-prong outlets. We still have a few of those in out 1960 vintage house. Wide supposedly enforced polarization in the sense that it supposedly insured that the neutral and not the hot got connected to metal chassis. But it was so easy to screw up, and occasionally such screwups cost lives. I guess they kept the wide prong partly as a reminder that it is the neutral side. Today we even see wide/skinny on, say, a table lamp. The theory here: it is safer to put the neutral on the relatively large threaded base your bulb screws into. That way, if you slip while you have a failed bulb out of the socket, you are touching a conductor much closer to earth potential compared with the 120V hot conductor. The hot gets routed through the switch and then on to that little contact way down in the bottom of the socket, where human contact is far less likely to happen.
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Stonegiant
There- are your eyes all glazed over? At least I left out the Ohm's Law part, which explains why these things happen.  :blink:
What, no Kierchoff's Voltage and Current Laws? :ph34r: I was an Electronics Technician in the US Navy so they didn't go into that kind of detail for us. We learned ship specific stuff. 3 phase, 120v/240v/450v/4160v ungrounded systems.I'm currently looking for a Electronics Tech job (out of the navy :lol: ).
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Cluttermagnet
*APPLAUSE FOR CLUTTERMAGNET*impressive!all i know is how to install plugs (connect white wire to silver screw, and black wire to gold screw, and hook up ground to green screw)... or is that the other way around?  i always forget  ;) quick question since theres a good electrical thread going on here...i'm hooking up a 2 year old central air unit i got thru a real good deal ($500 CAN).  a friend knows how to do silver brazing so he'll do all the welding and hooking up freon lines.my question is about the power.  at first i got a 40 AMP fuse, thinking naturally all A/C use 40 AMPs and thick 10 gauge wire, 2 phase wire.  but the guy i bought the A/C from game me all lines and wires, and there is just a 1 phase 12 gauge wire with it.  i was about to get thicker wire, but i checked the A/C panel and its a high-efficiency unit.  it says needs 12.6 amps, delay fuse 15amp, max fuse 20amp, 1 phase, 230 volt.i sort of understand it, but have a couple questions:  how much more efficient is a 230 volt 1 phase A/C than a standard 120 volt 2 phase 40 amp a/c?  also, i have spare 15 amp breaker.  can i hook it up, or will it keep tripping?  do you recommend a 20 amp breaker, or see how it runs on 15 amp breaker first?
Questions about air conditioner efficiencies are beyond my areas of competence. I can tell you that you can run more powerful units only from 240V because you are limited as to how much current you can draw from 120V lines. The general rule of thumb is that 12 gage wire allows a 120V branch to be fused at 20 amps. The older 14 gage (thinner) wire was only allowed to run off of a 15 amp fuse. Actually we mostly use circuit breakers today.Your high efficiency unit is within the capabilities of your 120V lines. You should think carefully before fusing any existing 120V line at 20 amps at the unit. You have no idea what wires join up within your walls. If there is any 14 gage in that branch, your limit is 15 amps. I would suggest a 15 amp circuit breaker. BTW breakers provide delay before opening for overloads, just like a delay fuse (slow blow fuse). With that unit on that 120V branch line, you can expect to start popping breakers if you plug much more in parallel with it. But no harm is done, so you can run other stuff from that branch in the winter. You are safe anyway because of your breaker. Run that air conditioner and your entire computer setup from the same branch and the breaker will likely pop. But then you simply move your other things to a different branch line. The best you can do is to find which of your 120V lines are served by 20 amp breakers at the breaker box. Choose one of them for your air conditioner, but still go with a separate 15 amp breaker at the unit. You should best avoid choosing any branch served by a 15 amp breaker to power your unit, though in theory it is OK to do so.I suppose some big central units might draw 40 amps at 240 or perhaps 120V- but that would require a special line to be installed. I think they use either #8 or #10 gage wires, I'd have to go look it up. With the really heavy wire, you could indeed end up with a 40 or perhaps 50 amp breaker on that one line. I doubt they do that at 120V, anyway, 240V would be a much better choice so as to avoid big load imbalances.Regarding 'phases', this can cause a _lot_ of confusion. Suffice it to say that it is highly likely that you only have 'single phase' service coming into your home. My previous comments about 'phase 1' and 'phase 2' only means that L1 and L2 reach their highest voltage peak at alternating times, i.e when L1 hits that peak value on the sinusoidal voltage curve, L2 is 0 volts at the same moment. Needless to say, you cannot connect them together (L1 and L2 ). This would amount to shorting out your entire 240V service, and a big breaker would quickly pop. I doubt there is any such thing as a 2 phase 120V air conditioner. These units are either going to run from single phase 120V or more powerful ones need to run from 240V single phase. Only if you happen to want to run an electric welder or something that uses great amounts of power would you need '3 phase' service. In that case, you could ask your power company to run a separate 3 phase 440 volt line, and pay them for it. Very few folks are ever going to need 3 phase power for their home. BTW there should be no such thing as a 120V air conditioner that draws 40 amps. No standard home wiring could safely deliver 40 amps. But you can get the same power safely by running a 240V 20 amp unit.
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btw: I live in an apartment building built in the 50's. All the wall sockets are two slots only and there doesn't appear to be any green (ot third) wires for grounding. All the wall sockets have only 2 wires connected. What's up with this?

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btw: I live in an apartment building built in the 50's.  All the wall sockets are two slots only and there doesn't appear to be any green (ot third)  wires for grounding.  All the wall sockets have only 2 wires connected.  What's up with this?
how can you run your computer without a 3-prong cable?
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btw: I live in an apartment building built in the 50's.  All the wall sockets are two slots only and there doesn't appear to be any green (ot third)  wires for grounding.  All the wall sockets have only 2 wires connected.  What's up with this?
yes that is vintage wiring. There is no ground. This does not meet todays code. There are actually only 2 wires going to each plug not 3. If you value your computer equipment you should add a grounded outlet. How? you can get a good ground from any (metal) cold water line. Just buy a clamp at home despot and run a 12 Gage wire from it to your new outlet.Cluttermagnet:Most houses have 2 phase into the house. I work on Highline motorhomes and we use single phase. Single phase means although you have L1 and L2 if you read across them you will read 0 volts. 2 phase you will read 240. The 2 hot legs are actually the same phase in my application not 180 degrees out.
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How much more efficient is a 230 volt 1 phase A/C than a standard 120 volt 2 phase 40 amp a/c? also, i have spare 15 amp breaker. can i hook it up, or will it keep tripping? do you recommend a 20 amp breaker, or see how it runs on 15 amp breaker first?
This is where Ohm's law would come in handy.Basically if an appliance is running on 120VAC like our PC's and it draws 600 Watts when it is powered on then the circuit will have a 5 Amp load on it. Or take your 1750 Watt hair dryer, when on full blast it is drawing 14.6 Amps.Now let's say your PC is now connected to a 230/240 VAC line (L1+L2 in Cluttermagnet's illustration) at 600 Watts on a 240VAC circuit it will only be drawing 2.5 Amp's. While this might not be much in the way of amperage if you add 10 more PC's to the mix like server farm would there would be need for roughly 1/2 the circuts than the 120VAC would need. Appliances like your stove may run on 120VAC and 240VAC at the same time depending on the model. It may use the 120VAC to run the light and the fan but step up to 240 for the heating elements. My GE Range is protected by a 40 Amp breaker. Total possible current draw would be 9600 Watts before the breaker blew. I doubt I would ever run it up that high but 8000 Watts is not out of the question. Electric motors would use the 240VAC advantage because the line offers more voltage pressure than 120VAC offers. This will allow more powerful motor's. 120VAC is limited to about 7 effective horse power before a 20A circuit will blow. While 240VAC offers motor's that are much more powerful. After a certian HP rating though 3 phase power is needed to smooth out the waveform for more even HP.Well I got more but Dinner is ready.Chris
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ross549
There- are your eyes all glazed over? At least I left out the Ohm's Law part, which explains why these things happen.  <_<
What, no Kierchoff's Voltage and Current Laws? :unsure: I was an Electronics Technician in the US Navy so they didn't go into that kind of detail for us. We learned ship specific stuff. 3 phase, 120v/240v/450v/4160v ungrounded systems.I'm currently looking for a Electronics Tech job (out of the navy ;) ).
I have 4 years left as an ET in the Navy. You may want to try usajobs.com. Most of the "ET" jobs start at about the GS-7 level. Worth a look!
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btw: I live in an apartment building built in the 50's.  All the wall sockets are two slots only and there doesn't appear to be any green (ot third)  wires for grounding.  All the wall sockets have only 2 wires connected.  What's up with this?
how can you run your computer without a 3-prong cable?
It's plugged into a UPS. The UPS is plugged into a high quality surge protector. Haven't had any problems yet. Here in CA, we don't get much in the way of lighting storms and the power in this area is pretty steady.
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Stonegiant
There- are your eyes all glazed over? At least I left out the Ohm's Law part, which explains why these things happen.  :lol:
What, no Kierchoff's Voltage and Current Laws? :P I was an Electronics Technician in the US Navy so they didn't go into that kind of detail for us. We learned ship specific stuff. 3 phase, 120v/240v/450v/4160v ungrounded systems.I'm currently looking for a Electronics Tech job (out of the navy :D ).
I have 4 years left as an ET in the Navy. You may want to try usajobs.com. Most of the "ET" jobs start at about the GS-7 level. Worth a look!
Awesome. Thanks
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Cluttermagnet
btw: I live in an apartment building built in the 50's.  All the wall sockets are two slots only and there doesn't appear to be any green (ot third)  wires for grounding.  All the wall sockets have only 2 wires connected.  What's up with this?
yes that is vintage wiring. There is no ground. This does not meet todays code. There are actually only 2 wires going to each plug not 3. If you value your computer equipment you should add a grounded outlet. How? you can get a good ground from any (metal) cold water line. Just buy a clamp at home despot and run a 12 Gage wire from it to your new outlet.Cluttermagnet:Most houses have 2 phase into the house. I work on Highline motorhomes and we use single phase. Single phase means although you have L1 and L2 if you read across them you will read 0 volts. 2 phase you will read 240. The 2 hot legs are actually the same phase in my application not 180 degrees out.
Hi, Scott-Welcome aboard! Hope you find Scot's Forums as enjoyable as I have.Hmmm, well that's a little different, your motorhome service entry scheme. I assume you can still get 240V from some connection? Or is no 240V used in this situation? I think the way to do what you are describing would involve having two separate, isolated, 120v secondaries in the transformer. Then you could hook them up either in phase or out of phase between L1 and L2, your choice. I would like to see a schematic of such a setup. I have no experience with those animals. The 'normal' residential presentation is of course from a single 240V, center tapped secondary winding.Well, most homes have electrical service better described as "single phase", as I understand it, even though there is a 180 degree difference looking at L2 with respect to L1 (or vice versa). A true multi-phase setup, almost always 3 phases, consists of 3 different 'hot' connections plus a neutral, and if you took a look at the waveforms with a multi trace oscilloscope, you would see that each of the 3 phases differs from the others by ±120 degrees. And it will be sourced from special 3 phase transformers, i.e. 3 different secondary windings with 3 separate hot leads plus a common return lead. This stuff is starting to get way too technical for a computer forum, however, so I will stop here. It can be confusing because we have been using the notion of phase two different ways in this thread- but it is safe to say that if a building is receiving all of its power from a single transformer secondary winding, that is single phase service. I may be on shaky ground so far as terms used in your industry, however, as they may differ a little. But I am at least certain of the soundness of the principles I am trying, however poorly, to describe. :lol:
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Cluttermagnet
btw: I live in an apartment building built in the 50's.  All the wall sockets are two slots only and there doesn't appear to be any green (ot third)  wires for grounding.  All the wall sockets have only 2 wires connected.  What's up with this?
yes that is vintage wiring. There is no ground. This does not meet todays code. There are actually only 2 wires going to each plug not 3. If you value your computer equipment you should add a grounded outlet. How? you can get a good ground from any (metal) cold water line. Just buy a clamp at home despot and run a 12 Gage wire from it to your new outlet.
I'm a little concerned to hear about the use of water pipes as part of an electrical safety ground scheme. The reasons behind this get a bit complicated but it boils down to two problems- (1.) I don't think the NEC (National Electrical Code) permits this sort of connection, although I would have to research that point, and (2.) those water pipes may get 'earthed' ('grounded') at more than one point, allowing there to possibly be some considerable potential difference (voltage) under unusual ('fault') conditions between the water pipe ground and, say, the neutral- or the safety ground. There is a better way. Even in the old days of 2-prong outlets, the jacketed cables ("Romex", etc.) already had a 3rd wire included. It was usually a skimpy, bare, 16 gage, copper wire, but it did serve as a sort of primitive safety ground. Open up one of your 2-prong outlets and you are likely to spot that small wire, probably hooked around a cable clamp screw to connect it to the metal utility box.Now mind you, I'm not giving advice here, and you should consult the NEC and youir local codes and ordinances and have all work performed by a licensed electrician. There, I'm politically correct. But you could change out the old connector for a new 3-prong one and add 2 copper pigtails to the small copper wire. They get tightly twisted together, then a crimp ferrule clamped around them all. Local code may allow the use of a wire nut over the tightly twisted ground wires. Then one new pigtail back to the utility box clamp screw and the other one to the green screw on the connector. Oh, and if you have two different jacket cables meeting inside the box, then you would be twisting 4 pigtail wires together- cable 1 safety ground, cable 2 safety ground, green screw on connector housing, and metal utility box. It is important that the safety wire be continuously connected together inside every box, and that every cable has its grounds connected, no exceptions. And most important, the safety grounds definitely _should not_ randomly connect to other grounds like water pipes, etc. if it happens to run near them. The only place that ground wire string should connect back to should be the neutral bus in your breaker box. Only in that one place should the safety ground string and the service neutral/ premises neutral all come together. If one wanted to tie in a cold water pipe to this system ground, the _only_ logical place to make that connection would also be at the neutral bus inside the breaker box- but this may not be permitted by NEC and I certainly do not see any compelling reason to do it anyway. Note that this may or may not bring your premises 'up to code', but if the safety wire is present in every jacketed cable, and connected together everywhere without exception, and only connects to neutral in your breaker box, then you are 'up to date' and have safer outlets. Remember, the 2-prong and 3-prong outlets are functionally equivalent. I have no doubt that ibe is running his computers just fine that way. The only real difference is that important safety margin you may need if something goes wrong inside equipment. Rarely, components inside can break down in such a way that the line voltage could appear on a metal cabinet. If you happen to be touching that cabinet at the time, and also touching something grounded with another hand or foot (water pipe perhaps?) you might get a nasty shock. But ground that same cabinet with a safety ground, and there is some chance of avoiding injury. Maybe a GFCI protected outlet pops, or your circuit breaker pops, or any number of other things happen or don't happen, but usually you are going to dodge the bullet because of that all important safety ground. That is why it is there. Normally, you don't need it. But when things go wrong, they can go badly wrong in a split second. Having or not having a safety ground connection to the metal cabinet you happen to be leaning across at that moment could literally make a life or death difference.One final thought- if all equipment is entirely in plastic enclosures, shock hazards are pretty slim and a 2-prong plug should be fine. The entire safety issue centers around the shock hazard from metal enclosures, and only during unusual ('fault') conditions. The only exception to this is the obvious danger posed by any electrical appliance dropping into a full sink or tub when a person is immersed in that water. And the answer there is switch to GFCI outlets.
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