My boyfriend lives in a old farmhouse because the rent is very cheap. Of course that means the house is, how shall I say, in serious need of some upgrades. He struck a deal with the landlord for a rebate on his rent in exchange for some upgrading of the electrical wiring. An electrician friend of his replaced the fuse box with a circuit breaker, and installed some wiring for new outlets and lights. However, there’s still a lot of old wiring & outlets.
Understandably, my boyfriend tries to avoid using the old outlets as much as possible, but that leaves him short of some outlets in strategic locations. So, he has taken to running heavy duty extension cords with power strips from the new outlets. In one instance, he’s even daisy-chained a couple of power strips (although all the items plugged in here aren’t generally on at the same time). My question is - is this safe? Is he in danger of overloading the electrical system and starting a fire, or will the circuit breaker stop any problems before they get out of hand? He hasn’t had any trouble yet, but I’m a little concerned, especially with having air conditioners running on top of everything else now.
Are the power strips the type with circuit breakers?
the one I checked here has a 15amp breaker.As long as he only has one power strip per fuse it is safe because you cannot exceed the 15 amps no matter how much is plugged in.
If he is pluging one strip into the other it is still safe because you cannot exceed the first breaker.
Make sure the first breaker does not exceed the recomended fuse rating.
There’s no problem with chaining power-strips together, as long as they are rated for the same current as the breaker/fuse in the panel for that circuit. Most strips are rated at 15 amps, whether they have a circuit breaker in them or not.
Running an air conditioner off an extension cord isn’t a good idea unless the cord is rated for the air conditioner load, which could be pretty hefty. If the cord is getting fairly warm, it’s too much load.
Don’t know what the rating is for the circuits in the circuit breaker, but I’ll check the next time I’m there. I have some vague recollection of electrician buddy saying that the circuit breaker was a bit heavy duty for the average house, but I’m not sure what that ultimately means… maybe I’ve just been a worry-wort for nothing.
Th air conditioners and the refrigerator are just about the only things that are still running directly from old outlets. Since they don’t share the outlets with any other appliances, and each outlet is on a different circuit, I assume that we need not worry too much about overloading those circuits (provided the circuits they’re connected to don’t exceed the rating for the circuit, correct?).
Touch the outlet & see if it gets warm or hot. Outlets are actually pretty cheap & you can put a new one in yourself. IF you put too much load on them they can catch flambe.
I remember one day in grade school we were learning about “safety.” The teacher showed a picture of an outlet with about 5 or 6 plugs/cables connected to it (with the help of a few 3:1 adapters, of course). In a gasping voice she asked, “Is this safe?!?!” Of course, we gave her the answer she was looking for: “No. That’s an overloaded outlet, and it could burn down the house!!”
Hogwash!! All else being equal, it doesn’t matter how many appliances you have plugged into an outlet, or how many extension cords (or terminal strips) you have strung together.
So what does matter?? What WOULD compromise safety or potentially cause a fire?
You really only need to keep one thing in mind: You do NOT want to draw more current than what the ENTIRE circuit is rated for. In other words, you must first determine the current capacity of the entire circuit (in terms of amps), and then make sure your load is not pulling more than that value. (Of course, you normally go about it the opposite way: you first determine how much current your load requires, and then connect the load into a properly-rated circuit.)
Quick note: to approximate your load current, simply add up the maximum current draws of each device that’s will be powered simultaneously.
So how do you determine what your circuit is rated for? Simple: Determine the rating of EACH leg in the circuit. The rating of the entire circuit is equal to the rating of the LOWEST RATED LEG.
Here’s an example: Suppose I have an extension cord and a power strip connected together (in series) to a 15 amp wall outlet. The circuit breaker at the panel is rated at 15 amps. The power strip is rated for 15 amps, and the extension cord uses 16 awg wire. What’s the circuit rating? Answer: 12 amps. Why? Because 16 awg wire is only rated for 12 amps. If your load draws between 12 and 15 amps your extension cord should be constructed of 14 awg or heavier wire.
So keep these NEC ratings in mind when calculating the circuit rating:
12 awg Cu wire is rated for 20 amps at room temperature
14 awg Cu wire is rated for 15 amps at room temperature
16 awg Cu wire is rated for 12 amps at room temperature
More examples:
A 12 awg extension cord is connected (in series) to a power strip rated for 15 amps, which is then plugged into a 15 amp outlet. The circuit breaker is rated at 20 amps. What’s the circuit rating? Answer: 15 amps, because both the power strip and outlet are rated for 15 amps (the extension cord is rated for 20 amps, which is fine).
A 14 awg extension cord is connected to a 10 amp outlet. The circuit breaker is rated for 15 amps. What’s the circuit rating? Answer: 10 amps, since the outlet is rated for 10 amps.
A 14 awg extension cord is connected (in series) to a 20 amp power strip, which in turn is connected to a 20 amp outlet. The circuit breaker is 20 amps. What’s the circuit rating at the end of the extension cord? Answer: 15 amps. What’s the circuit rating at the power strip? Answer: 20 amps.
So there you have it. It does not matter how many things you have plugged into an outlet, or how many extension cords and/or terminal strips you have plugged in. The only thing that really matters is the rating of the entire circuit.
Michael Craft
Electrical Engineer
University of Dayton
Dayton, OH
Looks like the only thing not covered here is overloading.
If you plug 7 15 amp power strips in the 7 outlets that are part of a circuit protected by lets say a 30 amp fuse, the potential, Now calm down electricians, load looks like 105 amps.
Wrong!!!
You can only load the circuit with 30 amps total. The 15 amp breakers only protect from the things plugged into them.
But First
Remember that this is a old house.
It is common practice to put 30 amp fuses in to replace 20 amp fuses.
“Well I just got tired of replacing it”
That is where things get dangerous.
You have the potential,sorry I can’t think of another word,of overloading the circuit 30%.
Crafter man Welcome.I turn explaining that over to you.
Justwannano: Your analysis is correct, but Fillet said the fuse panel box was replaced with a circuit breaker panel. Under normal circumstances, this would mean that each outlet would be on a circuit protected by either a 15 A or 20 A circuit breaker.
Casdave said: “You are not thinking about disconnection times and earth impedance in such a long cable run… I personally would put in a GFCI at the source outlet, it’s just a very good idea in this situation.”
What is “disconnection time?” Are you referring to a longer tripping delay of the circuit breaker that would occur for a longer cable run? This is not a concern. In almost every circumstance, the current 99.999% the same (at nearly every instant) everywhere in the circuit. But this may not be the case for cable runs of many miles.
You also brought up “earth impedance.” Again, a difference of earth potential is rarely a concern. First of all, few appliances nowadays utilize the third ground wire. Even if an appliance does use the third ground, the electrical/electronic circuit housed within the chassis is almost always isolated from it. (By law it HAS to be!)
Finally you brought up the good 'ol GFCI (a.k.a. GFI). I am a firm believer in the safety benefits of GFI’s, so much so that I have protected almost ALL of my outlet circuits with GFI’s. While it is still possible to get electrocuted with a properly functioning GFI-protected circuit, it WILL prevent the vast majority electrocution accidents.
Now having said that, there IS one disadvantage to using long cable runs: voltage drop. Remember, the hot and neutral conductors in any AC circuit are resistors. The resistance can be quite high for long runs (as is the case when using extension cords), resulting in a significant voltage drop, ESPECIALLY for appliances that pull a lot of current. (The voltage drop is proportional to the resistance AND the current.) That’s why I ALWAYS use 12 awg extension cords - it will minimize the voltage drop, no matter what the load is.
Finally, note that a voltage drop is not normally a dangerous situation; it usually just constitutes an inefficient set-up. But it must be realized that in some cases too much of a voltage drop WILL cause the appliance to become damaged, malfunction, overheat, or simply not operate.
Michael Craft
Electrical Engineer
University of Dayton
Dayton, OH
Are you sure about that? Most appliances with a three-wire plug connect the chassis to the earth ground (the “third wire”). My PC is one example.
In fact, this was required by UL when we’ve submitted products for UL approval (under UL standard 1244). All exposed metal had to be connected to earth ground, which was the ground terminal on the plug.
I don’t think appliances that are double insulated need this, but not all are double insulated.
Arjuna34 said: “Are you sure about that? Most appliances with a three-wire plug connect the chassis to the earth ground (the “third wire”). My PC is one example. In fact, this was required by UL when we’ve submitted products for UL approval (under UL standard 1244). All exposed metal had to be connected to earth ground, which was the ground terminal on the plug. I don’t think appliances that are double insulated need this, but not all are double insulated.”
I understand that appliances with a three-wire plug connect the chassis to the earth ground (the “third wire”). My point was that the electrical/electronic circuit housed within the chassis is almost always isolated from it.
Let me take a little more time to explain this. First some background stuff…
For most residential services there are exactly three wires coming off the secondary of the step-down transformer that’s hanging on the utility pole: Two hots (lets call them hot1 and hot2) and a center tap. The differential voltage between hot1 and the center tap is nominally 115 VAC rms. The differential voltage between hot2 and the center tap is nominally 115 VAC rms. To make matters more complicated, hot1 and hot2 are 180 degrees out of phase (both referenced to the center tap). And because they’re 180 degrees out of phase, the differential voltage between hot1 and hot2 is around 230 VAC rms. (If they were in phase, there would be no differential voltage between hot1 and hot2!) Also keep in mind that the secondary of any transformer, if left alone, is a “floating voltage,” sort of like a battery. (A 1.5 volt battery has a differential voltage of 1.5 volts between the “+” and “-” terminals, but the voltage between either terminal and earth ground is not defined UNLESS YOU FORCE IT TO BE SOMETHING.)
O.K., are you with me so far?
The “hot” on your typical 115 VAC, 15 A outlet is connected to hot1 OR hot2 (never both!). The neutral on the same outlet is connected to the center tap.
Still with me? O.K. Now the above scenario would work O.K. to power your computer, except it has some potentially lethal problems:
While we know the (differential) voltage BETWEEN the hot and neutral is around 115 VAC, we do not know what the voltage of the hot (or neutral) is relative to earth ground; it’s not “defined.” If the transformer’s isolation is extremely good, the voltage may be low. However, if the transformer’s isolation is bad, the secondary voltage of the transformer could easily “float up” to over 10,000 volts, or whatever the transformer’s primary winding is at. Not good, not good, not good…
What if a device has a metal chassis? And what if a hot wire inside the chassis broke loose and touched the chassis? Answer: You’ll get shocked.
So how do we fix these problems?
To fix problem #1, we simply tie the transformer’s center tap to earth ground. This will guarantee that neither hot1, hot2, or the center tap will ever be greater than 115 VAC with reference to earth ground. It also means the outlet’s neutral is tied to earth ground at the breaker box.
There are two ways to fix problem #2. Since the outlet’s neutral is tied to the center tap, and thus to earth ground, you could tie the neutral to the appliance’s chassis. But this not a good idea. (i.e., Don’t do this!!!) First of all, you have to use a polarized plug, and assume the plug and outlet were wired correctly. Secondly, there could be a voltage on the chassis relative to earth ground, even though it is tied to earth ground at the panel. This could happen for a variety of reasons: voltage drop along the neutral wire between the outlet and breaker box, bad connection along the neutral wire, differences in ground potentials, etc. A BETTER idea is to have an independent “third” wire. Like the neutral, this wire would connect to earth ground at the breaker box. Unlike the neutral, however, this wire would NOT carry any current under normal operation. It would simply connect to the appliance’s metal chassis. If a hot wire were to break loose inside the appliance, or there was some leakage, the chassis would conduct the current to earth ground and throw the circuit breaker. At the very least, it will keep you from getting zapped.
So here’s the moral of the story: Under normal circumstances, EVERYTHING inside an appliance (transformers, motors, circuit boards, wires, connectors, switches, etc.) is electrically isolated from earth ground. By the same token, everything is isolated from the metal chassis. The metal chassis is hard-wired to earth ground via an independent wire tied to earth ground at the breaker box. If something were to come loose inside the appliance and touch the chassis, you would always be safe, since the chassis is tied to earth ground.
Oh, one more thing: sometimes it is important to tie a chassis to earth ground for reasons other than safety. For example, a sensitive instrument may require shielding from EMF.
Michael Craft
Electrical Engineer
University of Dayton
Dayton, OH
Disconnection time = Time for a protective device to operate when a fault occurs.
All devices such as fuses and circuit breakers will operate faster with a high excess current than with a low excess current.
For example a rewirable fuse of say 5amp will take 5seconds to disconnect with a fault current of 13amp.
The same fuse with 45amp will take 100 milliseconds to disconnect.
But a fault current of 10 amps would take 100seconds to go.
And yes the tables do err on the side of caution.
So now you have your explanation of disconnection time.
Although I am looking at charts based on a 220v system the current ratings will still have the same effect but the amount of current in a given circuit will be less on 110v.
The differance of a few tenths of an ohm can be very important so I’m afraid you are wrong in that.
Just because many devices do not have an earth does not make it irrelevant to take it into consideration.There will come the time that such an appliance is connected.
More explaining - If a fault such as a short-cicuit or a ground fault occurs then swift diconnection is of extreme importance, especially if we are talking about hand-held appliances.The maximum time for disconnection allowed in the UK(on 120v systems) for portable apliances is 800 milliseconds and since people are largely the same I would expect a US figure somewhere in that order.
Basically if you are holding the appliance you and it earths out you want the juice to turn off ASAP.
What determines disconnection time?
The supply voltage-the size of the fault current-the type of protective device.
The larger the fault current the faster the cicuit will disconnect.
There is also another reason why you want the power off quickly but I will leave that for a moment.
For those not in the know I =V/Z
That is I=Current V=Voltage Z=Total Impedance
At mains frequency reactive elements are not usually a major factor.
Any source of supply has a source impedance a typical one in the UK would be between .2 to 1.7 ohms.Pick a lower range one at .4 ohms.
Lets us imagine we have an extension lead and that it add .2 ohms(and in experience that a is fair figure)
Put in the numbers 110v/(.4+.2) and the current is 183 amps.
When I look up the charts for a 15 amp rewirable fuse it would take 100millisecs to clear the fault and using our regulations that would be legal.
Now put in another three extension cords each of 0.2 ohms lets see what happens.
And if I look up the chart for that I find the disconnection time is 400 millisecs. In the US that would be legal but in the UK with our 220V you are only allowed a max of 400 millisecs and that is too near to the bone, especially when it is reasonable to expect impedance to rise slightly due to aging of contact surfaces.
I would not rather be connected to a faulty appliance at all but 800 millisecs (which is allowed in the UK on120v cicuits)is a long time to be getting an electric shock.
Remember that the impedance of the extension leads includes both live with neutral or earth.
I can improve the disconnection time dramatically by using a differant protective device, if I used a circuit breaker that disconnection time would fall to around 20 millisecs.
Over in the UK a cicuit breaker is not the same as a GFCI, if it is the same in the US then changing for one is a good idea.
Earlier I in this post I said there was another reason why you want power removed quickly, here we go then –
As long as an overcurrent is flowing the cables have to take it without deterioration ie Melting.
If the is a large current through a resistance, even a small one the heating effect can be swift.We are talking here of fault currents that can easily peak at over 200 amps.
Even if we have no earth fault because the appliance is double insulated this is still true since a short cicuit in mains flex is common enough to think about.The best situation is for the power to be removed before there is an explosion-usually at or very near to the fault.
A large tripping current ensures that this is so.
My advice to Fillet is use GFCI and use the largest gauge cable possible for the extension leads.
Thicker cables tend to be mechanically more sound and thicker cables reduce the circuit impedance, thus increasing the fault current, thus decreasing the disconnection time.
FTR sources of information are –
16th Edition Wiring Regulations for Electrical Installations
and
The Institute of Electrical Engineers(IEE) On Site Guide
casdave> All devices such as fuses and circuit breakers will operate faster with a high excess current than with a low excess current. For example a rewirable fuse of say 5amp will take 5seconds to disconnect with a fault current of 13amp. The same fuse with 45amp will take 100 milliseconds to disconnect. But a fault current of 10 amps would take 100seconds to go. And yes the tables do err on the side of caution.
You’re correct. (Guess I gotta brush-up on my electrical safety terminology). And the same goes for circuit breakers. Here’s something else to ponder: while circuit breakers are convenient, they aren’t as fast as fuses. It typically takes a number of power line cycles to throw a circuit breaker, while many fuses can blow in less than one PLC.
You also explained the relationship between disconnection time and load resistance. I’ll have to admit I had never really given it much thought, but your analysis and conclusions are correct. However, in most situations a typical homeowner would encounter, it is probably only a 2nd order concern.
For example, let’s assume the equivalent source impedance is 0.2 ohms at a particular 115 VAC outlet. A dead short at the outlet would result in a current 575 A rms. Now lets say Joe Homeowner plugs a wimpy 25 foot, 16 awg extension cord into this outlet. 16 awg copper wire at 20 Celsius is 0.004 ohms per foot. Thus the extension cord adds 2250.004 = 0.2 ohms, and the equivalent source impedance is now 0.4 ohms. A short at the end of the extension cord will now result in 287.5 amps, or half the current.
In either case the breaker will throw quickly, so I wouldn’t worry about it. Not only that, but it must be stressed that we cannot make exact calculations when something shorts out for a variety of reasons, including:
The current vs. disconnection time of a circuit breaker has a fairly wide tolerance
The source impedance is probably non-linear (i.e. it’s probably a function of current), and probably unpredictable during a short
Conductors and connectors will rapidly heat up in the few milliseconds between when the short occurs and the circuit breaker opens (though this will have the effect of increasing disconnection time)
The contact resistance of the short itself will probably be significantly higher than the source impedance (possibly swamping out the effects of long extension cords)
So here’s the bottom line: I wouldn’t worry too much about disconnection time unless you’re running hundreds of feet of small gage extension cable. Furthermore, it should be noted that short circuits usually don’t result in anyone getting electrocuted; instead, their biggest danger is catching wiring on fire.
Michael Craft
Electrical Engineer
University of Dayton
Dayton, OH
Fillet: You asked about Ground Fault Circuit Interrupters (GFCIs, a.k.a. GFIs).
GFIs are very cool devices. Basically, a GFI can “sense” if there is a current leak to ground, and break the circuit if it is above a certain threshold. Most GFIs that protect against electrocution will open the line if it senses a current of more than 3 to 5 mA (0.003 to 0.005 amps).
To understand why a GFI is important, you must first understand how most people are electrocuted.
To get electrocuted, there must be some minimum voltage between (at least) two points on your body. (The source impedance must also be below a certain value, but we won’t get into that.)
In a vast majority of electrocution cases, the person is already touching earth ground at some point on their body. They’re either standing barefoot on the ground, or touching something that has a relatively low impedance path to ground. Now you must understand that being grounded constitutes ONE point. Now you just need ANOTHER part of your body to come in contact with a voltage significantly higher (or lower) than earth ground and you’ll get electrocuted. A common candidate for this “second point” is the hot conductor in your AC house wiring, since it always maintains a relatively high voltage with reference to earth ground. (At any instant it is somewhere between +162 V and -162 V, as referenced to earth ground.)
O.K., now let’s talk a little bit about leakage current in an appliance (don’t worry, this will all make sense in the end).
Under normal circumstances, the current in the hot conductor and the current in the neutral conductor will be very, very close in value, at every instant, for just about anything you plug into the outlet. I say “very close” because some appliances, particularly those that have a ground plug, or are always in contact with earth ground, or have AC line filters & surge protectors, will have a little bit of leakage current. What is happening in these cases is that a little bit of current goes directly from the hot conductor (or somewhere else in the circuit) to earth ground, and thus does not “show up” in the neutral conductor. Naturally this is frowned upon by the safety folks, since they would prefer that no current is leaked to ground. But it has been established that a leakage current of 0.5 mA or so won’t hurt anything. (Unless it’s a medical instrument.)
Time for an example:
Let’s say you plug a toaster into an outlet and you turn it on. Before you turned it on, there was no current in the circuit. After you turned in on, 3.1235 amps flowed in the hot conductor while 3.1231 amps flowed in the neutral conductor. This means that the toaster is “leaking” 0.4 mA (0.0004 amps) of current directly from hot to earth ground, which is considered safe. Now let’s say you grab the kitchen faucet with your right hand and you stick your left middle finger into the toaster. Assuming your body is a 1000 ohm resistor (quick note: it’s usually higher than that), the hot conductor will now draw 3.2385 amps while the neutral conductor will still have 3.1231 amps on it. We now have a leakage current of 0.1154 amps: Of this value, 0.0004 amps is the toaster’s leakage current (which is always present), and the rest of it (0.115 amps) is flowing through you!! Not good, not good, not good…
So this is where the GFI comes in. The GFI is constantly “monitoring” the DIFFERENCE between the current in the hot conductor and the current in the neutral conductor (with the use of a “differential transformer”). If the GFI detects a difference of more than 3 to 5 mA current it will open the circuit. Pretty cool, huh?
But contrary to popular belief, you can STILL get electrocuted with a GFI-protected circuited. How? Now this is for instructional purposes only; DON’T DO THIS:
Isolate yourself from ground (i.e. wear rubber-soled shoes and don’t touch anything around you)
Touch the hot conductor in an outlet. Notice that if you do this you will NOT get shocked, since this is only “one point” (see above).
Touch the neutral conductor. Zap.
Notice the GFI DID NOT TRIP.
So why didn’t the GFI trip? Well, why should it? Since your body is isolated from ground, all of the current in the hot conductor shows up on the neutral conductor. Your body looks like a clock radio!
But the above example doesn’t happen often because (as explained earlier) people are usually electrocuted by touching the hot conductor, while another point on their body is in contact with earth ground.
Michael Craft
Electrical Engineer
University of Dayton
Dayton, OH
Mike Craft explained what they do. To install one, you can either change the breaker in your panel to a GFI breaker (assuming you’ve got breakers and not fuses in your panel), or install a GFI receptacle in the circuit. A GFI receptacle protects all receptacles downstream in the circuit also, so it’s good to put it early in the circuit (first if possible). You can also buy a GFI extension cord, which is a normal extension cord with a GFI receptacle on it. They’re not real easy to find though, but you can make your own in a pinch.
Of course, if the circuit doesn’t have a ground wire with it, the GFI isn’t going to help much, since the whole point is to sense ground current.
Like many things in the electical/electronic industry there are lots of ways of achieving certain ends depending on the exact circumstances.
Fuses will disconnect faster than circuit breakers is true up to a point.
Rewirable fuses of the type found in homes should in theory outperform miniature circuit breakers(MCB) but for one or two reasons they don’t always, mostly to do with people.
Rewirables seem to have a greater tolerance to low overcurrent than MCBs and the reason they often take longer to go might be to do with the way they heat up the air surrounding the fusewire.
Human nature being what it is if there is persistant blowing of fuses people will fit heavier duty wire or if they don’t have any handy then they might use a few strands of copper flex to about the same diameter or anything that looks likely.
I had had to replace an entire box because one intrepid individual decided he’d had enough of fuses going so he used thicker wire.When a fault occurred it not only did not blow the fuse but so much metal material had evaporated onto the inside of the carrier that it acted like part of the circuit and there was effectivly no protection at all.(A few working colleagues have had to do the same so it isn’t that rare)
Using enclosed fuses filled with quartz(we call them high rupturing capacity-HRC) you will outdo the MCB any day.When it says 32amp on them it means that and no more.People are reluctant to spent the few extra dollars for them but they are standard industrial fare.
The advantage of the HRC fuse is that when it goes the quartz melts and forms glass which prevents secondary arcing which can occur in high current situations, it is also why they can be made smaller than their equivalent rewirables.
The fastest circuit breakers I have worked on are the vacuum breakers which we use on some older plant that uses 3.3kV.These things cut off in less than 30 degrees(no I’m not gonna bother with radians today) of a cycle.
A friend I was at college with now works for Merlin-Geraint who manufacture switchgear for grid at 275kV and more.Their SF6 breakers are unbelievably small for such high voltages(the older ones were literally the size of a walk in wardrobe) but the cutoff times are incredible less than 10 degrees per cycle which in itself causes problems such as current chopping.Here the supply is broken so rapidly that a back e.m.f larger than the supply voltage can develop.The insulation at these working voltages as you can imagine is very good.The upshot of this is that the SF6 breaker had to be redesigned to increase the disconnection time for certain grid applications.
Here’s a story I heard but it might be a UL, maybe you can comment.
It seems that a Swedish engineer was contracted to design and oversee the installation on the overhead power network for the South African railway system.
Early on relations were poor(some versions of this say that he disliked the apartheid system) but he was held to his contract.
The system was installed and tested in parts as it became ready but not the whole network at once.
Happy that things had proceeded as planned the Engineer was paid off and the rest of the work was completed according to design.
The big day arrived and the whole network is made live-briefly- and all the protection shut the lot down.
After much time and scratching of heads it was determined that the network could be run but with chunks of it not active.
The ground capacitance of the complete network was such that the leakage across it blew all the protection.
There was no cheap or easy way of correcting this and it cost the SA government a fortune to put right.
True or not - no idea but beermat calculations indicate that there would have to be a minimum of around 5000 miles of overhead cable to achieve this and there is the problem of substations.So unless we were wrong I would tend to doubt it.(could this be a Cecil question?)
Casdave: Very interesting! And I guess I’m from the old school… I trust fuses MUCH more than circuit breakers! Except for that nasty characteristic of secondary arcing.
Arjuna34: You’re description of how to install a GFI, and the varieties they come in, is exactly correct.
What to hear something else interesting? Our house was built in 1960. They installed 115 V / 10 amp receptacles when they built the place. As we all know, these receptacles don’t have the third “ground” connection, so I decided to replace all the outlets with 115 V / 15 amp receptacles. Well guess what? They didn’t run ground wires!
Simply swapping-in a 15 amp receptacle when there’s no ground wire is big no-no, or so I thought. According to later revisions of the NEC, you CAN install a 15 amp receptacle and NOT hook a ground wire to the receptacle’s ground terminal if it is GFI-protected (and labeled as such). It was then just a matter of figuring out which outlets were wired “nearest” to the breaker box for each circuit; replacing these outlets with GFI outlets allowed the other outlets “downstream” to all be protected. After doing so, I replaced all the rest with 115V / 15 amp outlets, and never worried about the ground wires.
