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Old 03-19-2010, 04:40 PM  
rosborn
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Default electrical problem

Okay . . . . .

I am not an electrician and, therefore, haven't a clue as to how to attack this problem.

Here is the scenario -

Our house was built in 1973. A week ago we lost power at an outlet which led to a complete circuit failure. I don't know how electrical circuits are set up in typical houses but our circuits are set up to power various outlets and power sources throughout the house. This one in particular powers an outlet in our family room, an outlet in the living room (not the same room), a ceiling light in the laundry room, etc.

Thinking it was a failed breaker I replaced said breaker today. I flipped the switch on the breaker and . . . . . . nothing.

Did I say that I am not an electrician?

So . . . . where do I go from here?

Any and all help would be GREATLY appreciated.

Thanks,

Rob



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Old 03-19-2010, 07:56 PM  
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Rob:

Are any of the outlets that have been affected GFCI's? (Groundfault Circuit Interrupter's) That is, do any of them look like this:



If so, then the problem is most likely that someone pushed the black "Test" button on the GFCI when pushing a plug into the GFCI. In that case, the red "Reset" buttom would have popped out, and you can restore power to the affected outlets by pushing the red Reset button back in.

If you can't find any GFCI's in your house (look in the kitchen and bath first, and then look everywhere else, even in the garage), or pushing the Reset button on any GFCI's you find doesn't help, then read on...

The first step would be to buy a digital multimeter so that you can confirm that there's 110 volts AC at the screw terminal on the circuit breaker.

Here is a blurb I wrote up years ago explaining how house wiring is typically set up. You would do well by reading it and asking any questions to straighten out any confusion.

Welcome to Basic Household Wiring: (this write up is longer than 10,000 characters, so I had to break it into two posts)

The wires that run overhead to your house carry 220 volt power. That 220 volt power is delivered via two power lines and a neutral wire. In practice, the two power lines will have black and red insulation on them, and the neutral wire will have white insulation on it. You will probably also encounter "ground" wires which have either no insulation or green insulation.

The two power lines each carry 110 volts AC, but they are "out of phase" by 180 degrees. That is, when the black power line is at +110 volts with respect to the white neutral wire, the other red power line will be at -110 volts with respect to the white neutral wire, and vice versa. So the voltage you would measure between each of the two power supply lines and the white neutral wire would be 110 volts AC, but the voltage you would measure between the black and red power lines would be 220 volts AC.

The standard 110 volt circuits for the ceiling lights or electric outlets in your house are made by connecting those lights or outlets between the white neutral wire and EITHER the red power wire OR the black power wire coming into your house. All of those connections are made in your electrical panel and a fuse or circuit breaker is provided for each such circuit in your house. So, some of the 110 volt circuits in your house that go to lights or electric outlets or fans are powered by the red wire, and some are powered by the black wire. As long as the circuit is between the red wire and the white wire, or between the black wire and the white wire, you have a 110 volt AC circuit. If you put a 15 amp fuse or breaker on that 110 volt circuit in the panel, then you have a 110 volt 15 amp circuit, and normally household circuits are in fact 110 volt 15 amp circuits. Newer houses often use 20 amp breakers for the electrical outlets in the kitchen because these outlets often have high demand appliances plugged into them, like toasters, microwave ovens, electric frying pans, etc.

So, if you look at a typical circuit going to a ceiling lamp (say), then you would have a 15 amp fuse or breaker on one side of the electrical panel or the other. The 12 or 14 gauge two conductor cable that goes to the ceiling light will have a black and white wire inside it. The black wire will connect to the 15 amp fuse or breaker and the white wire will connect to the "neutral bus bar" inside the panel. So, even if the fuse connects that black wire to the red voltage source, the wire will still have black insulation on it, so never presume that wires with the same colour of insulation are connected to the same voltage source. The cable with that black and white wire will go to an electrical box with a switch in it. The black wire will connect to a screw on one side of the light switch, and the white wire will terminate inside the electrical box. Another cable with a black and white wire in it will go from the switch to the light fixture. One end of the black wire in that second cable will be connected to the switch and the other end will be connected to the light fixture to supply power to the light bulb. The white neutral wire from that second cable will also be connected to the light fixture, to allow power to flow out of the bulb and back to the generating station. The other end of that white wire will connect to the white wire from the first cable that terminated in the switch's electrical box. So electrical power might come in the red wire from the generating station, go into a 15 amp fuse and then go along a black wire to a switch. That switch would stop or allow power to flow through another black wire to the light bulb, and then the power would flow back to the neutral bus bar in the electrical box via the white wire.

Simple enough, right? Well, household circuits can be that simple, but most often they aren't. That's because for a purely resistive load like an incandescent light bulb, Volts X Amps = Watts. So, in our circuit we have 110 volts delivered to a 60 watt light bulb, and according to that formula, our circuit is only carrying six elevenths or an amp, or 0.54 amps. Since the circuit breaker or fuse will allow up to 15 amps through that circuit, we have plenty of capacity in that circuit to power other things. So, typically there will be more than just a single light bulb on a household circuit. Other circuits (to electrical outlets or a ceiling fan, say) might connect to our circuit at the electrical box where the switch is.

220 volt circuits for the house's electric stove and electric clothes dryer are made by connecting the circuit between the main black and red wires at the electrical panel. Both the red and black wires carry 110 volts AC with respect the the white neutral wire, but because they're 180 degrees out of phase, there's 220 volts AC between the red and black wires. So, if you connect a circuit between the main black and main red wire going into the house, then you have a 220 volt circuit. If you're wiring a range, you normally need a 50 amp circuit, which requires a 50 amp breaker on BOTH the red and black wires going to the range. That means, you have to have a 50 amp breaker on the black wire going to the range and a 50 amp breaker on the red wire going to the range. And it also means you have to trip BOTH breakers before there's no power in the range, so you can work safely on it. If you're wiring an electric dryer, you need a 30 amp circuit, so that means you must have 30 amp breakers on both the red and black wires going to the dryer. On appliance wiring diagrams for 220 Volt AC appliances, like stoves and electric clothes dryers, the two power lines will typically be called "L1" and "L2" for "Line 1" and "Line 2".

When you open a typical electrical panel you'll notice that the fuses or circuit breakers are typically arranged in two vertical rows; one on each side of the panel. Do not assume that one side of the panel is for tapping off the red power line and the other is for tapping off the black power line. The buss bars inside the electrical panel determine what gets connected where, and often breaker positions above one another on the same side of the panel will be connected to opposite voltage sources. This is done so that the circuit breakers can be "ganged together" so that you can't flip the breaker off to one power line going to a stove or dryer without turning the power off to BOTH power lines at the same time. In Manitoba, where I live, the electrical code requires that circuit breakers for 220V appliances be "ganged" together in this way for safety reasons.

The technically incorrect but easiest way to think about this is that the power comes "in" on the red and black wires and goes "out" on the white wire. Obviously it doesn't because AC voltage is power that's flowing one way and then the other every 120th of a second, but that way of thinking about it will at least help you better understand house and appliance wiring and the reasons behind doing certain things certain ways.

For example, there is a standard wiring convention when wiring 110 volt electrical outlets and plugs. You will notice that the screw connections on one side of the duplex receptacle will be chrome plated, whereas those on the other side will be bare brass. Always connect the light coloured wire (the white neutral wire) to the light coloured screw (the chrome plated screw), and the dark coloured wire (the red or black wire) to the dark coloured screw (the bare brass screw).

Similarily, on 110 volt three prong plugs, you'll notice that the screw for the wider prong is chrome plated and the screw for the narrower prong on the plug is bare brass. You follow the same convention when wiring a plug as you do a receptacle. The light colour wire goes to the light colour screw and the dark colour wire goes to the dark colour screw (and the ground wire goes to the round prong). Remember this next time you're fixing an extension cord. If you mix things up when replacing the end on an extension cord, then the wiring convention doesn't help keep you any safer whenever you use that extension cord.



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Old 03-19-2010, 07:57 PM  
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The reason for this wiring convention is safety. If homeowners, electricians and appliance manufacturers all follow this wiring convention, that will ensure that the on/off switch for 110 VAC appliances will always be on the power supply wire (that is, the red or black wire) that delivers power to the appliance, NOT on the white wire that allows power to flow out of the appliance. And, this is important from a safety perspective because it ensures that the on/off switch will always allow or prevent power from going into the appliance, not from coming out of the appliance.

Before both electrical plugs and receptacles were "polarized", both of the prongs on a plug and the slots in a receptacle were the same size. So, you could plug a 110 VAC appliance into a receptacle with the plug either right side up or upside down. The appliance would work equally well either way. However, in one of these positions the on/off switch of the appliance would be on the power supply wire and would control power going into the appliance. In the other position, the on/off switch would be on the white wire and would allow or prevent the power from flowing out of the appliance. So, if there were a short circuit in the appliance, having the plug upside down meant that you could get a shock from the appliance anytime it was plugged in. It wouldn't have to be "on" to give you a shock. Thus, if you happened to be turning a faucet off while you were handling a faulty toaster, you could end up getting 110 volts at 15 amps across your heart even if the toaster was off at the time.

So, by sticking to this dark screw/dark wire wiring convention, we always end up with the on/off switch to an appliance on the power supply line, and that keeps things safer. If we follow that convention, then we can never get a shock from a faulty appliance unless it's turned on.

There is also a standard wiring convention used when wiring the plugs, receptacles and terminal blocks of 220 volt appliances, all of which will have provision for connecting THREE wires as well as a ground wire. Normally the ground wire terminal will be easy to identify because it will be grounded to the electrical box by an electrical conductor, and the remaining three connection points for the red, white and black wires will be arranged in an obvious ROW. The wiring convention is that the white neutral wire is ALWAYS connected to the middle terminal in that row of three connection sites, and the red and black wires are connected on either side of it. It doesn't matter which side you connect the red or the black wires to, as long as the white is in the middle and the red and black are on the outside, you're good to go. If your stove or dryer doesn't come with a cord and you want to connect one to the terminal block of the appliance, the same rule applies, namely "white in the middle, black and red on the outside". If you're wanting to wire a receptacle for a stove or electric dryer, then again, the same rule applies. First identify the ground wire terminal, and the remaining three connection points will be in a row, and the white wire always goes to the middle connection point with the red and black wires on either side. So, if it's 220 Volts AC, look for a visible row of three connection sites and always connect the white wire to the middle of those three sites and the red and black on either side of the white. This point has now been officially hammered into your head; for 220 Volt, white in the middle, black and red on either side.

Every dryer cord will have 4 prongs sticking out of it. The straight ones are for the red and black wires, the "L" shaped one is for the white wire and the round one is for the ground wire. Range cords also have 4 prongs, but they will use 3 straight prongs for the red, black and white wires and a round one for the ground wire. Configuring the plug and receptacle differently (with an "L" shaped prong instead of a straight one) is done so you can't stick a 30 amp dryer plug into a 50 amp range receptacle or vice versa.

The heating elements in both electric dryers and stoves require 220 volt power, but you still need to run the white wire to the stove or dryer. The reason why is that there will be circuits within the stove or dryer that require only 110 volt power. For example, the electric motor that turns the dryer drum or the light bulb inside an oven will both require 110 volt AC power, not 220 volt power.

So, in an electric stove the heating elements will be connected between the red and black wires because they need 220 volts, but the electrical outlets provided for convenience on the stove console will be connected between the white wire and either the red or black power wires because the convenience outlet(s) is intended to provide 110 volt power to small kitchen appliances which run on 110 VAC. And, this is also why you will often see TWO convenience outlets on a stove instead of just one. One of those convenience outlets will be powered by the black wire, and the other one by the red wire. But, wait a second... since the main black and red wires going to a stove are fused at 50 amps each in the electrical panel, any circuit between the red and white OR black and white wires inside the stove will give you a 110 volt 50 AMP CIRCUIT. Such a circuit probably won't stop pumping out the electricity if there's a short somewhere in a kitchen applicance plugged into a convenience outlet on the stove, and 50 amps going through wiring rated at 15 amps is a great way to start a fire. That's why for each of the electric outlets provided for convenience on range cooktops, there will be also be a 15 amp fuse right in the range somewhere that fuses the convenience outlet down to 15 amps.
If you have two cooktop plugs, one will be driven by the red wire and one by the black wire, and each will have a separate fuse that limits the power coming out that convenience outlet to 15 amps.

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Old 03-19-2010, 08:16 PM  
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Rob:

Check of tripped GFCI's in your house first. If you don't find any, or any that are tripped, then buy a cheap multimeter (about $10 or so) and post again.

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Old 03-19-2010, 10:59 PM  
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Originally Posted by Nestor_Kelebay View Post
Rob: The first step would be to buy a digital multimeter so that you can confirm that there's 110 volts AC at the screw terminal on the circuit breaker.
Nestor,

Got it. Thank you for the very informative reply. I have to admit, I did not know much of that. I also have to admit that I did not know about the chrome screw for the light wire and the brass screw for the dark wire. Very good info.

So, confirming 110 volts AC at the screw terminal on the circuit breaker will tell me if the circuit is/is not complete? Isn't it interesting that the whole circuit was working one minute and not the next?

Thank you for your help.

Rob
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Old 03-19-2010, 11:00 PM  
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Originally Posted by Nestor_Kelebay View Post
Rob:

Check of tripped GFCI's in your house first. If you don't find any, or any that are tripped, then buy a cheap multimeter (about $10 or so) and post again.
We don't have any GFCI's in our house.
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Old 03-20-2010, 02:22 PM  
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So, confirming 110 volts AC at the screw terminal on the circuit breaker will tell me if the circuit is/is not complete?
No, confirming 110 volts AC at the screw terminal on the circuit breaker will tell us whether or not power is even getting into the circuit at the circuit breaker. It could be a bad circuit breaker, or it might not be installed correctly, or not making proper contact with the bus bar.

Measure the voltage between the screw terminal of the circuit breaker and the neutral bus bar in the electrical panel. If you get 110 volts AC, then you know that the circuit breaker is providing power to the circuit.

The next step would be to check for continuity at the affected receptacles.

One way to do this would be to flip the circuit breaker off, plug a long extension cord (like a lawn mower extension cord) into one of the affected receptacles and take the female end of the cord to the electrical panel. Then check for continuity (using the ohm meter scale) between the screw terminal on the turned off circuit breaker and each of the slots on the female end of the extension cord.

It's rare for there ever to be a break in the wire inside the wall (since the wire doesn't move), so if you haven't got a long extension cord, we can also just check for voltage at each of the affected receptacles.

Now, are you certain that the circuit breaker that you replaced was for the two electrical outlets and lamp? The reason why I ask is that if we have power at the breaker's screw terminal but we don't at the coloured wire going to each of the receptacles, then we've got a difficult problem because that means there has to be a break in the wire somewhere.

My hunch is that there's no break in the wire inside the wall. Most likely it's just that a wire in one of the electrical boxes became disconnected.
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Old 03-20-2010, 02:34 PM  
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Originally Posted by rosborn View Post
Thank you for the very informative reply. I have to admit, I did not know much of that. I also have to admit that I did not know about the chrome screw for the light wire and the brass screw for the dark wire. Very good info.
None of this stuff is complicated. It's just a matter of learning it, understanding it, and then applying common sense to figure out what's wrong.

If you read throught that write-up and understood half of it, then you already know more than most homeowners about the wiring in your home.


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