Electrical Safety Information

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Whether you are working on electrical equipment or working on other do-it-yourself projects, there are some rules that apply to all situations.

  1. Use the proper tools for the job.

  2. Remove clutter as much as possible...keep the work area clean to avoid tripping over items that could have been removed.

  3. Wear proper footwear, dust masks, eye protection, hearing protection, gloves, etc. to suit the job.

  4. Make sure ladders are in good repair and do not stand on the top or second from the top step.

  5. Be aware of who is near you. This is especially important if young children are near you. Do not leave power tools where a curious child may decide to play with them. When working on ladders be aware of what is happening below.

  6. Be aware of the risks present when chemical solvents or flammable liquids are present. Ensure that there is proper ventilation and make sure chemicals are always out of reach of children. If you must smoke, take a walk outside if there are flammable liquids inside (or fumes).

  7. Work at a sensible pace. On many projects, especially where mixed material such as cement, grout, etc. begins to dry, people panic and try to work faster. In the case of mixed material, try not to mix batches larger than you can work with safely. For electrical work, keep in mind that you will need light to work by. If you start a job too late in the day it may be dusk with the power still off. Plan ahead and have another source of light to work by.

  8. Avoid awkward or heavy lifting. Ask for help with the heavy stuff such as drywall. Also, avoid awkward stretching that can twist your back. This happens a lot when people are on a ladder that is not properly positioned for the job.

  9. Do not be afraid to ask for help. Especially when using ladders it is common for people to risk injury by trying to do it all on their own. If you need somebody to hold a ladder you should wait until there is somebody available to help. In the case of an extension ladder, you may just need somebody to steady the ladder while you climb up and tie it securely. When the work is done you may need help again for a few minutes to move the ladder so ask for help. The hospitals have too many heroes already. I have lost count of the number of times I've seen somebody lose control of an extension ladder. In some cases, other people have been injured by the falling ladder. In other cases, there are no injuries but significant property damage.

Electrical Safety

Electricity can certainly kill you. Before you attempt an electrical project you should keep in mind that electricians require years of practical training and months of classroom work. The actual training time varies in different states and in different provinces, but 4 years is usual, with about 8 months of this spent in classrooms and the rest working full time on job sites. After the 4 years, the electrician is regarded as qualified (Journeyman), but he/she will always be learning. Nobody knows it all. As a Master Electrician with 32 years of experience, I don't know it all.

Don't expect to be able to work as fast as a qualified electrician. The work is physically demanding. You will spend a lot of time climbing ladders and moving ladders. You need to be able to stand comfortably on a ladder while leaving both hands free to do the work.

After a day of climbing ladders while wearing a tool belt you may wish that you had left the job to an electrical contractor.

Tripping Breakers And Blowing Fuses

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If you have read the information on the Electrical Terminology page, you will understand that a reduction in circuit resistance will cause an increase in current flow in that circuit and also in the upstream feeder and main service. To try to understand what goes on when a breaker trips or a fuse blows, we can consider a practical situation. We will use a normal 15 Amp circuit at 120 Volts as an example. If this circuit has a load present that would normally draw 12 Amps, (like a kettle) we could conclude that the effective circuit resistance is 10 Ohms. We divided Voltage by Current to find this Resistance.

Of this 10 Ohms, about 9.9 Ohms is in the kettle, while the cable for the circuit has about 0.1 ohms. Therefore, if the cord connecting the kettle to the receptacle were to develop a fault that allowed current to pass from one wire to the other without passing through the kettle element (commonly known as a short circuit), this would cause the current to reach a value that could be 1200 Amps. This time we divided the Voltage by the cable resistance to find the current. As the cable size increases (gets thicker) to carry more current, the cable resistance decreases....and the available fault current increases. You may see a 10,000 Amp fault on a 100 Amp circuit breaker if the fault occurs on the main cables.

If 1200 Amps appears on a 15 Amp circuit breaker, the circuit breaker should trip instantly. However, we must remember that the 1200 Amps is also present on the main circuit breaker for the panel. This may be a 100 Amp circuit breaker. In such cases you may find that the main circuit breaker trips more quickly than the 15 Amp circuit breaker.

The same can be said for fuses. In some cases, the main fuse operates near it's maximum value for a long period of time and becomes "tired" or "stressed". In such cases the "tired" fuse may blow before the 15 Amp fuse.

So, how do you find the cause of tripping breakers or blowing fuses? You should start by paying attention to which circuit breaker tripped. If it is only the 15 Amp breaker that tripped you have already isolated the problem to that circuit.

If the main circuit breaker has tripped, you need to find out which individual circuit caused the problem. Ideally, you will have a megohm meter to test each circuit. If you rely on resetting the breaker to find the problem, this could create more damage so this should be avoided. You should begin by switching off all of the individual circuit breakers and ensuring that the main circuit breaker is completely OFF. Test the main bus of the panel for a fault to ground and also for a fault between the two "live legs" (red to black). With all breakers off, the megohm meter should show infinity. With this done, you know that the main breaker can be turned on. So switch it on to make sure it doesn't trip with all individual breakers off.

Assuming that the main circuit breaker stayed on, you now know that the problem is in an individual circuit....but which one? You now test each circuit looking for a very low resistance. Some of the circuits may have a low resistance due to the nature of the load. For example, lamps may have a very low resistance when cold. so begin by finding those circuits that have relatively high resistance. By switching on these circuits you may get some light to work by since you will likely be working by flashlight at this point.

Eventually, through the process of elimination, you will get to the offending circuit.

Once you have isolated the problem to an individual circuit, you need to look at how many receptacles, lights, etc. are on that circuit. In the case of the kettle example, you would unplug the appliance to see if this clears the fault. If the fault clears, this means that the kettle has a problem. In the case of a circuit with several lights, you should switch off individual room lights. Again, through the process of elimination, you will get to the source of the problem. If there are receptacles in the circuit and portable items plugged in, you should unplug all of these and inspect each of them.

If you follow these steps, you should get to the root of the problem. As with most things, you will work more quickly as you gain experience.

If you need to replace a circuit breaker, a light fixture, a switch, etc. to solve the problem, remember that you should avoid used equipment. With used electrical products, you have no way of knowing how reliable these will be and this could present safety concerns.

The process above deals with a short circuit. However, in some cases a circuit breaker will trip or a fuse will blow due to an overload condition. With an overload, there will be a period of time between each breaker tripping or fuse blowing episode. Usually, the overload will be on an individual circuit but it can also happen on a main circuit breaker or a main fuse. You can use a clip on ammeter to test the current being drawn on the main circuit breaker. This can often take some time to do, especially if heating loads are present. For example, it may happen only at meal times on cold days so you need to pay attention to the circumstances present when the problem occurs. You solve the overload by re-distributing the load on individual breakers and by upgrading the service if the main breaker is overloaded.

You can help solve problems by taking time to clearly lable your electrical panel to identify each circuit. When you have some spare time, use it to write down in a notebook, which breaker controls each light, receptacle, etc. By doing this you can avoid overloads by not using an already loaded circuit to plug the steam iron (air conditioner, etc)into.

Troubleshooting Information - The Three Wire System

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North American Homes make use of a three wire supply that has many good points when installed and maintained correctly properly. However, there are problems with this system, especially when work is done by "do-it-yourself" individuals. There are two basic problems.

In North America, the supply of electricity comes to the home as three wires. A ground connection is created right at the home by use of driven ground rods, buried plates or a metal water line. The third wire is bonded to this ground connection. The three wires come from the "center tapped" secondary winding of a transformer. Two outer legs have 240 volts across them. The third wire is the center tap so there are 120 volts between this wire and either of the other two wires. The third wire carries only the unbalanced load and not the full load current. The center tap is connected to a grounding conductor at the transformer. The frequency is 60 Hertz.

Since there are two "Live" wires, there are two main fuses or, more usually, one Double Pole circuit breaker. There is no doubt that the North American system attempts to provide more safety than the European system. Portable appliances and light bulbs use 120 volts. Fixed appliances and heavy heating loads use 240 volts. In Europe, light bulbs and portable appliances use 240 volts at 50 Hertz on a two wire system.

What are the problems with this system?

Well, the first problem comes because we need to use double-pole circuit breakers for the fixed load circuits. If this is done properly there is no problem. However, there are cases where two single-pole circuit breakers are used instead of one double-pole breaker. If one of these single pole breakers is tripped or switched off, the appliance stops working. The appliance is still "Live" because the second circuit breaker is still on. Trained people know how to test for this and avoid a shock. The do-it-yourself individual may receive a shock. If the correct circuit breaker is used, both poles will trip and there is no problem. This is one of those cases where "making it work" does not mean "making it safe"

A typical situation may involve a person who has decided to move an electrical baseboard heater (perhaps to install new carpet or tile). This person may lower the setting of the thermostat to the lowest setting. This will stop heat from being produced but there is still one live wire at the heater. Most untrained people would assume that there are no live wires present just as would be the case at a light fixture that is switched off. If you look at a 240-volt thermostat you will notice that it probably does not have an OFF position marked. This is because it must completely disconnect the heater if it says OFF. In other words, it must be a 2 pole thermostat. Most thermostats are only a single pole.

The second problem is caused by a poor neutral (third wire) connection. The severity of this problem depends on where the poor connection is located. For example, if it happens at a receptacle (plug) in the kitchen you may destroy a small appliance. This is how it happens. Remember that we have 240 volts available. In a kitchen plug, each half of the duplex receptacle is on a different "live" leg and they have a common neutral (3 wires).

If the neutral wire is disconnected or has a poor connection, we have two 120 volt appliances plugged in to form a series circuit. Suppose that we have a clock radio plugged into the bottom outlet and a kettle plugged into the top outlet. The clock-radio has a resistance that is about 30 times (and maybe more) that of the kettle. When the neutral is removed from the circuit, we have a series circuit and the current is common to both appliances. The voltage drop across each appliance will be the common current multiplied by the resistance. If the clock-radio has 30 times the resistance, it will have most of the 240 volts across it. We will get something like 8 volts across the kettle and 232 volts across the clock-radio. Guess what happens to the clock-radio.

The U.S.A. has dealt with the kitchen receptacle problem by using 20 Amp 120 Volt two wire circuits, whereas Canada still allows 3 wire circuits for the kitchen with the option of using 20 Amp 120 Volt circuits.

If the poor connection is back at the main panel and on the incoming supply, many devices that draw low current can be destroyed. This includes a lot of expensive computer equipment, sound equipment, telephone equipment, etc. If you have a large load on one "live" leg and a relatively small load on the other "live" leg there will be damage. If your light bulbs seem to burn out too quickly, this could be the cause of the problem. The problem is more common in homes that use Aluminum wire. More on aluminum wiring later.

Many untrained individuals do not fully understand how important the grounding connection is to the system. People have been known to remove a main grounding wire while gardening because they thought it was not important (only a ground).