We answer some of your common questions centered around bad circuit breaker symptoms and other related topics, such as : How does a circuit breaker work? How to replace circuit breaker, what causes a fuse to blow, fuse Box vs circuit breaker, Circuit breaker will not reset and much more.
Circuit breakers are essential when it comes electrical safety. This is your first line of defense, protecting you from an electrical fire. They also prevent damage to your appliances when an electrical fault is detected.
When the first symptoms of a bad circuit breaker are detected, you should address the situation without delay. But how do know if a circuit breaker is faulty? Why does a circuit breaker keep tripping? This article is going to discuss circuit breakers in depth. From a how a circuit breaker works, to all you all need to know about circuit breakers, fuses, and how to keep your electrical wiring safe.
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Bad Circuit Breaker Symptoms
Few us pay much attention to the electrical panel in our homes. When a breaker trips, we reset it and hope that this sorts the problem out. It’s only when a breaker won’t reset, that we start to take things seriously. This an obvious inconvenience. In general, people don’t realize the dire potential hazards relating to bad circuit breakers. Then again, a faulty breaker may not be the cause of our frustration. So let’s start by examining how a circuit breaker works. With this understanding we’ll be able to move to more pressing issues, like why a circuit breaker keeps tripping, or why it won’t reset.
A Multi-meter might be necessary for some problems
How does a circuit breaker work?
A circuit breaker is used to automatically interrupt an electric circuit when an overload or short circuit is detected. Designed as more practical solution to the conventional fuse, which needs to be replaced after each use, the idea of a mechanical circuit breaker was first conceived by Thomas Edison in 1879. High current circuit breakers were first introduced for large scale electrical distributors. Smaller, more economical units later became available for domestic use and are now the standard method of electrical protection in homes and commercial buildings.
A circuit breaker works by detecting an electric fault, using thermal or magnetic properties. A thermal-magnetic circuit breaker uses heat to detect a circuit overload and the magnetic field to detect a short circuit. The thermal effect makes use of a bimetallic strip and the magnetic effect makes use of an electromagnet. Both components are equally important.
A bimetallic strip is simply two metals, joined in layers. The principal is to use two metals that expand and contract at different temperatures. A bimetallic strip used for circuit breakers will usually be a strip of copper and a strip of steel, welded or riveted together. Because these metals react differently to heat, the strip will bend when heated. The bimetallic strip is connected to a spring activated lever that opens the circuit when the strip bends. The electric current that supplies the circuit is conducted through a coil. As the current increases, the coil generates heat. This is calibrated to bend the plate a calculated amperage. A 10A circuit breaker will generate enough heat to bend the plate once the current passing through the coil reaches 10A.
A short circuit is an unintentional flow of an electric current along an abnormal path. In conventional AC electric circuits, this usually happens when the hot conductor makes direct contact with the neutral. Because there is little resistance (electrical impedance) between the two conductors, excessive heat is produced. This will cause the insulation around the conductor to melt. Often the conductor may melt. An electric short may even cause an explosion if the amperage is high enough. We can see this a runaway current. With no resistance the current simply cascades, with ever-increasing energy being delivered.
To prevent a short circuit from causing damage, the electromagnetic field created by the increasing current is utilized. Part of the circuit breaker consists of an iron core, with wire coiled around it to from an electromagnet. An armature, positioned close to the electromagnet, rotates with the magnetic force, causing the trip bar to open the circuit. Under normal load, the current passing through the coil does not generate enough magnetic force to move the armature. As the “runaway” current, caused by a short circuit, increases, so does the electromagnetic field. This happens rapidly, fast enough to break the circuit before the heat generated by the short circuit can cause any harm.
When you consider that, within a small circuit breaker, there is so much going on, you should realize how important it is to ensure that these mechanisms function correctly. A circuit breaker should remain reliable for a long time. But this will depend on the quality of the components and the amount of times the breaker opens and closes. There are other factors too, like heat generated from high loads and arcing. All this will be discussed in more detail as we continue.
What causes a circuit breaker to trip?
We know, from discussing how a circuit breaker works, that it will trip when there is too much current flowing through the breaker (current overload). We also know that a circuit breaker will trip in the event of a short circuit. Now it’s time to examine the causes behind these situations.
Current Overload
This is the most common reason why a functioning circuit breaker can trip and there can several causes for a current overload. I’m going to list these and then discuss how to diagnose and correct the situation.
High current electrical equipment
Lawnmowers, welders, and large power tools may require more current than the circuit is capable of conducting. This is often a result of startup load for inductive motors. A lawnmower with a 1,000W electric motor can require as much as 3,000W to start, sometimes more. At 110V, this is 27A. Although the lawnmower will require around 9A when running, the initial inrush current will be much higher. If you try to use this mower on a 20A circuit, it will trip when you pull the lever to start it.
The solution is to use a 30A circuit for the lawnmower (or any high-current appliance). Though a common rookie mistake is to simply change the existing breaker for one with a higher amp rating. This is extremely dangerous. A circuit breaker is installed in accordance with the gauge of the wiring it supplies. A 20A circuit will use a 12-gauge wire to supply the outlets. For a 30A circuit, you need to install 10-guage wire. If you require a circuit capable of supplying 30A (or more), and don’t have a 30A circuit on your breaker box, a new circuit, with the correct gauge wire needs to be installed. This should be done by a qualified electrician, knowledgeable in the electric code and local regulations.
Multiple startup for several appliances
Sometimes a circuit breaker may trip, seemingly at random. Most of the time every thing’s fine and then, for no apparent reason, the circuit trips. You go reset the breaker, and all is well. Some time later that breaker trips again, so you reset it again.
This situation is usually a result of two appliances, requiring a high inrush current, starting simultaneously. If, for example, you have a refrigerator and an air conditioner running on the same circuit, the combined startup current of both appliances may exceed the amperage that circuit can supply. Since both these appliances cycle, using a thermostat, you never know when they could start.
If one appliance is running and the other starts, the circuit won’t trip, since only one appliance requires the additional current to start. It is rare, but sometimes both the AC and refrigerator will start at the same time. Since both require a high startup current (up to three times their normal running current), the load will be extremely high. For a brief period, the power required to start both the AC and refrigerator will be 5 – 6 times more than if they were both running.
The solution is to sperate the two appliances. Basically, you don’t want them to use the same circuit. A properly wired house will have several circuits in the same room. In other words, different outlets will be supplied by different circuit breakers. Simply unplug the air conditioner and plug it into an outlet that’s on a different circuit.
Faulty Appliances
If you switch an appliance on and the circuit trips, you can be sure that the appliance has a fault. This could be damaged insulation, a faulty capacitor, or water in the appliance. Sometimes, in the case of a water heater or refrigerator, you may not realize it is the appliance that is causing the breaker to trip. This is because these appliances switch on and off automatically.
The only way to diagnose automatic appliances is to disconnect each appliance one by one. When you discover the faulty appliance, the circuit will stop tripping. The faulty appliance then needs to be repaired or replaced.
If your water heater keeps tripping the breaker, there can be a number of reasons why this is happening. Usually, you need to check the heating element as this is the most common cause. The thermostat may also be faulty. In both cases, it’s simply a matter of replacing the faulty component. Another reason, especially in older houses, could be burnt or damaged wiring supplying the water heater. New wires would need to be installed. Finally, the breaker may be faulty. I’ll be discussing circuit breaker faults, diagnosis, and replacement later. So keep reading.
Short Circuit
A short circuit can happen because of damaged wiring, a faulty appliance, a damaged outlet, or water. It can sometimes be difficult to diagnose a short circuit. The best way to do this is to use a multi-meter set to detect continuity.
A faulty appliance is the easiest to sort out. If you disconnect the appliance and the circuit stops tripping, you’ve found the culprit. A damaged outlet can often be diagnosed visually. If the there is any kind of visible damage, liked cracked plastic or signs of burning, replace the outlet.
If there are no visible signs of damage to the appliance, outlet, or wiring, the only way to find the fault is to use a multimeter. Set the multimeter to “continuity”. Most multimeters will have an alarm that beeps when there is a continuous electric current. Always conduct a continuity test on the main wiring with the circuit with breaker switched off. If you’re testing an appliance, make sure it is disconnected. Hold one point of the multimeter to the hot wire or terminal and the other to the neutral. If you detect continuity, it means there is a short circuit between hot and neutral. Do the same test between hot and ground, then neutral and ground, to check for a short to ground.
Sometimes there can be exceptions to this. Testing an electric motor will always display continuity, even when there is no short circuit. Testing neutral to ground with a closed GFCI will also display continuity when there is no short circuit. This may require disconnecting the ground wire or switching the GFCI breaker off.
Circuit breaker will not reset
All of the above examples assume that the circuit breaker is good working order. If your circuit breaker keeps tripping and will not reset, first eliminate wiring, outlet, or appliance faults as described above.
If, after eliminating all these factors, the breaker still will not reset, it means the breaker is faulty. The only solution left is to replace the breaker.
What causes a circuit breaker to fail?
In most cases, a circuit breaker will stop working due to old age. However, there can be external factors that may cause a circuit breaker to fail prematurely:
- Consistent high current. When a circuit is close to its maximum load continuously, it will always operate at a high temperature. This will cause the insulation to become brittle and shorten the lifespan of the circuit breaker. It’s a good idea to try spread the load evenly over all circuits. In other words, try not to use too many appliances on a single circuit.
- Continuous tripping. If a circuit breaker trips regularly, over a prolonged period of time, wear on the springs and contacts will eventually cause the circuit breaker to fail.
- Arcing usually occurs when a circuit breaker opens or closes under load. The higher the load, the more likely and the more severe the arc will be. This is a spark between the contacts and will cause them to burn over time. Regular tripping, or constantly switching the breaker on and off under load will cause arc damage. Remember, a circuit breaker is not a regular switch and not should be used as one. Often, people switch equipment, like pumps, on and off using the breaker. This damages the breaker. A switch, designed for this purpose, should be installed.
- Water damage is a common problem for all electrical equipment. Frequent exposure to water or damp will damage a circuit breaker.
Replacing a Circuit Breaker
While it is recommended that only a qualified electrician replace circuit breakers, DIY cowboys, or those with enough experience, can do this. It’s important to work safely and methodically to avoid electrocution or a fire risk.
For those brave enough to attempt this themselves, here’s a step by step guide to replacing a circuit breaker:
- Before you begin, make sure you have the correct circuit breaker. It should be of the same amp rating and brand as the one you’re replacing. Often two breakers may look identical, but don’t fit the panel in the same way. You will also need an insulated screwdriver and a multimeter. You may require a wire cutter as well as wire stripper.
- Start by switching off all branch breakers, followed by the main breaker.
- Remove the breaker cover and test for voltage. Make sure there is no current on the breaker to be replaced.
- Disconnect the wire from the affected breaker and check for damage. In some instances, the load wire may be burnt, or the insulation damaged. If you observe any damage, cut away the affected portion of the wire and strip away only enough insulation to ensure proper contact with the load terminal of the breaker.
- Pry away the old breaker, making sure not to damage the panel or adjacent breakers.
- Slot the new breaker into position and connect the load wire. Ensure that the screw securing the terminal fully tightened.
- Replace the panel cover and switch the main breaker on, followed by the branch breakers.
A replacement circuit breaker can cost anything from $35 – $60 for a 15A – 60A breaker. A main breaker will cost around $40 – $100.
Replacing an electric panel.
If your house is old, you may want to replace your existing panel or upgrade to a higher amperage to allow for increased power needs. The modern home generally uses more electricity than people expected in the past. For this, you will need to get a certified electrician for the job. They are required to sign off on the installation. If you don’t use an electrician with the requisite qualifications, your insurance will not be valid and you may face penalties, in the form of a fine, from your local authority.
- Cost
to install a new panel:
- 100A – $1,200 – $1,600
- 200A – $1,800 – $2,500
- 400A – $2,000 – $4,000
- Cost
of upgrading your existing panel:
- From 60A to 100A – $850 – $1,100
- From 100A to 200A – $1,300 – $1,600
- From 200A to 400A – $2,000 – $4,000
- Cost will vary depending on the electrician and the number of circuits required.
Fuse Box vs Circuit Breaker
Circuit breakers have become the norm because they are less hassle and can be safer for the homeowner. However, in some instances a fuse box can be the only option if space is limited. Fuses are much smaller than circuit breakers. Fuses are also used for sensitive equipment as they are more precise and not easily affected by changes in current.
Fuse Box
Pros:
- Cheaper than circuit breakers.
- More compact.
- Easy to replace.
- Sensitive to current changes.
Cons:
- Need to be replaced every time there is an overload.
- Typically lower amp ratings than circuit breakers and may not be sufficient for some modern equipment.
- Risk of injury when replacing. The main power supply must be switched off when changing the fuse.
Circuit Breakers
Pros:
- Quick and easy to reset.
- Can be used with GFCI.
- Meets modern electrical requirements.
Cons:
- More expensive to replace.
- More complicated to replace, requiring a qualified electrician.
- Not as sensitive to current changes.
What causes a fuse to blow?
A fuse is the most simple way of protecting a circuit. It is simply a thin piece of wire that will melt at a certain temperature. The type of wire used, and it’s thickness, determines when the fuse will melt. This is calculated by the heat generated by a circuit at a determined amperage. When we talk about a fuse “blowing” it is really that the metal conductor in the fuse melts, thereby breaking the circuit. When the current flowing through the circuit exceeds the amp rating for that fuse it will blow. The causes for a blown fuse will be the same as those that trip a circuit breaker, an overload or short circuit.
