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The utility power supply

The ordinary power is offered by the utility power company and then connected to onsite applications. In situations where the primary power source has stopped to work, the power from a new or used generator can either be automatic or manually transferred to the onsite application using a transfer switch.

The main purpose of the transfer switch is to resupply power from the grid to a backup source of power. In this article, we are going to explain the mechanism used by the control panel to direct an automatic transfer switch.

The control panel system of a transfer switch is what enables the system to be automatic in nature. The manual transfer switches are operated using onsite personnel as well as being used in situations where the load is normally not of emergence nature as requiring quick restoration of the power supply. Using an automatic transfer switch, the power failures are identified as soon as they want to occur and the transition from the utility power to the generator power has no limitations.

The control panel task is to detect the power failure and take trigger the procedures to start the new or used generator. Once the generator has reached its exact voltage and the frequency the control unit alerts the switch to shift from the normal source of power to the generator.

The fundamental basics of the engineering behind the transfer switch are quite complicated as different components are involved in making sure it works as it is intended.

The frequency as well as the voltage

One of the major functions of the control panel involves the detection of the drop in voltage as well as a completed failure within the normal power source. Normally, all phases are being monitored. Any failure at any point is defined as a drop in voltage below the current setting upon any phase. The voltage, as well as the frequency information, is obtained and offered by the sensors to the control panel so as to determine the load existence. The minimal frequency and voltage should be attained before the transfer of the load to the new or used generator take place. This is important in making sure that the generator set is capable of accepting the load.

The time delays

The automatic transfer switches are offered in different types of time delay units. The time delay operation is a necessary feature when it comes to an automatic switch due to false alarms triggers that are caused by the normal power source from the utility company.

The common prevalent rime delay that overrides any momentary traditional outages that might cause a false engine to start and hence transfer the load. This time delay ranges from 0-6 seconds, with a single second being the common configuration.

The delay has to be short enough to bride the backup power source while complying to the city, state as well as the federal codes.

As soon as the normal power is restored, another time delay is required so as to make sure that the load is stable enough to change from the backup power. Traditionally the delay is between 0-30 minutes. The control panel should be able to automatically pass this time delay when it is returning to the normal source in a situation where new or used generator fails while the normal power source is working as required once again.

The third most common time delay includes a cool downtime for the engine. During this period the controls operate the engine unloaded before they shut it off.

Under most circumstances, it is normally desirable for the load to be moved to the backup generator as soon as the sufficient voltage and frequency have been achieved. But in some of the situations, the end-users need to sequence the different transfer switches upon the backup generator.

In case this application needs, the controls to include extra time delay that can be adjusted upon each transfer switch so that the load can be able to transfer the new or used generator in whatever desired order.

The engine control contact pint

This includes a contact point that alerts the engine control to start when normal power is supplied from the grid. In most common modern designs, this contact is normally a dry contact that closes whenever there is a failure of this normal power.

As the contact closes it, completes the circuit from the cranking batteries connecting it to the engine start control systems. In other words, these contact points open so as to shut down the new or used generator

There should be regular testing that is done upon the contact point so as to make sure that there is no failure of the circuit. When it comes to certain transfer switches there are backup contact points in copy circuits that ensure there is not any single point of failure.

The control unit testing

There should be scheduled regular testing as part of maintaining an emergency backup power system. All control units should consist of a manually operated switch so as to stimulate the normal power source when it fails. The controls that are described in this post are normally considered as the traditional/ standard when it comes to operating a transfer switch.
The guidelines that were elaborated have to be used as the minimum standard that the end-user should always depend on before making the decision to buy a transfer switch. There are quite different types of specific control units that are used in handling different applications. It is better to contact your electrical contractor so as to discuss which type of control system that will work to full fill your needs.

When you started learning how to read I am sure you were introducing to a number of signs and symbols that represented different sounds. These symbols are what is known as alphabets. The schematics, as well as wiring diagrams, are the alphabets of the motor controls. Before you can determine the logic of a control circuit, first you have to learn how to read these schematics and wiring diagrams. The problem is that there is no actual standard that is used when it comes to motor control symbols. Different companies, as well as manufacturers, use their symbols when it comes to their in-house schematics. Besides, schematics that are used in other countries may totally mean a different set of control components. Although these symbols might vary from one manufacturer to another, or from one country to another country, when you have learned on how to interpret the circuit logic, you can easily identify what the different symbols stand for no matter how they are used within the schematic. The common standardized set of symbols that are used within the United States is offered by the National Electrical Manufacturer’s Association which is commonly referred to as NEMA. These symbols will be discussed in this chapter.

The pushbuttons

This one of the commonly used symbols in control schematics. The pushbuttons can be represented as normally open or normally closed. Most of the pushbuttons are momentary contact appliances that they work to connect or break a connection as long as there is a connection that is applied upon them. The pressure is normally supplied to them by someone’s finger that presses the button. As the pressure is released, the button returns to its normal position. The pushbuttons consist of both movable as well as stationary contacts. The stationary contacts are fitted to the terminal screws.

The normally open button is normally characterized drawing a movable contact at the top and not in contact with the stationary contacts. As the movable contact does not touch the stationary contacts, that means there is a formation of an open circuit and the circuit will not flow from the stationary contact to the other. The way in which the symbol is drawn it assumes that the pressure has to be applied to the movable contact. As the button is squeezed the movable contacts move below and connect the two stationary contacts completing the circuit. As the pressure is released from the button, a spring returns the movable contact to its former position.

When it comes to the normally closed push button symbol it is represented by drawing the movable contact under and touching the two stationary contacts. As the movable contact touches those two stationary contacts, a complete circuit is formed and the current can flow from one stationary contact to the other. In case pressure is applied to the button, the movable contact moves away from the two stationary contacts hence opening the circuit.

The double-acting pushing buttons

This is another most used push button that you can notice throughout the industry. The double-acting push buttons consist of both the normally open as well as the normally closed contacts. When you are connecting these buttons within a circuit you have to certain to join the wires to the proper set of contacts. The double-acting push-button contains four terminal screws. There are different ways of drawing the double push button. As the button is pressed the top movable contact moves away from the surface of the two stationary contacts and the bottom movable contact connects the bottom two contacts hence completing the circuit. When the components are drawn connected by using a dashed line within a schematic diagram, it identifies that the components are connected mechanically together. In case one component is pressed, all those components that are connected by the dashed line are pressed. This is the most used method of representing several sets of push-button contacts that are controlled with a single button.

The staked push buttons

This is a common connection that involves the use of multiple push buttons. It is normally referred to as an emergency button and might be used in stopping three motors whenever needed. The push button that consists of multiple contacts is normally referred to as stacked push buttons. The stacked pushbuttons are designed by connecting multiple contact systems together which are then monitored using a single push button.

The push-pull buttons

This is also another push button that is commonly used. Some of the pull-push buttons consist of both the normally open as well as the normally closed contacts identical to a double-acting push button, but the arrangement of the contacts is different. This push-pull button is normally made to offer both the start as well as the stop operations in a single push button thus removing the need of making a second push button. As the button is pulled, the normally closed contact remains in a closed mode and the normally open contact connects the two stationary contacts completing the circuit. As the button is released, the normally open contact retains its normal position and the normally closed sections remain closed. As the button is pushed, the normally closed section then opens to disconnect the circuit while the normally open section maintains its open state. The push-pull buttons have two normally open contacts which are used to offer a run jog control within the same button. When this is achieved, the run operation is normally accomplished with the application of the control relay. 

Depending on the settings of the push-pull buttons or the mechanism in which they are used to control the circuit, they are normally used in providing the function of two different buttons within a single space. They are an ideal choice when you need to add controls within the existing control panel that might have no extra push buttons.

The lighted pushbuttons

The lighted pushbuttons are one of the examples that offer a second function within a single space. They are normally used to represent a running motor, stopped or tripped upon an overload. Most of the lighted push buttons are normally equipped with a tiny transformer that helps in reducing the control voltage to much minimal value. There are different lens caps of colors that are in existence.

How do the NEMA and the IEC design of the electromechanical motor control devices differ? When it comes to business, flexibility is an important asset. If you manage to apply either NEMA or IEC design products, that means that you have the flexibility to adapt to the local traditions as well as the product supply no matter where you are in the world. This will enable you to have the best advantage of local accessibility as well as expertise which can be a very important competitive cutting edge when it comes to the global economy. Before you decide to opt and apply one among the two, let us analyze the differences that exist between them.

They have different philosophies

The NEMA normally emphasizes many robust designs that can be used in different applications. They are easy to select and can be applied in broader applications. There are two fundamental basics within the NEMA design philosophy.

The NEMA Industrial Control Standard (ICS-2) governs the designs of NEMA motor control products. This is a formal document that consists of all the essential information regarding the design of electromechanical NEMA design motor control.

On the other hand, IEC philosophy emphasizes application and performance. To select the IEC devices, you have to have a more understanding of the application as compared to when you are selecting the NEMA devices which are general-purpose devices. For example, when you are selecting the IEC contactor you need to know the motor load, the full load current, as well as the duty cycle.

This requirement is what might bring a setback in some of the situations when it comes to clients, but for the Original Equipment Manufacturers (OEM) is an advantage. For example, an equivalent HP-rated IEC device tends to be smaller as compared to the NEMA same rated device. This is what brings a significant advantage to the OEM manufacturers. Besides, the IEC devices are cheaper as compared to the NEMA.

The features and benefits of NEMA

The easy selection is the basic advantage when it comes to the NEMA design starter. To choose a NEMA design device you only need to know the horsepower as well as the voltage of your motor.

The NEMA products are easily serviceable as compared to the IEC products. Besides they provide front access to the internal components easily. Unless there is a need for replacing the entire device, contacts, and coils of different sizes can be repaired easily without having to remove the device from the panel.

Besides the reserve capacity is among the things that make the NEMA products to be among the most considered. They are normally designed to work widely across different applications. That is why they are normally referred to as the general-purpose devices as opposed to the IEC devices which are designed for specific applications.

The NEMA design devices consist of interchangeable heater elements. In fact, different ranges of thermal units are available for different overloads. This is what makes the NEMA product so attractive on most of the construction applications where there is ultimate motor use or when the actual motor nameplate cannot be identified.

The motor control center (MCC) or the enclosed package solution is the tradition of NEMA. Normally most of the NEMA devices are sold in the form of starters in either open design or in different enclosed designs.

The features and benefits of IEC

The wide number of IEC contactor sizes enables the user to be able to closely match the contactor to the application or load. Different from the NEMA where the available sizes are standardized throughout the industry, the number of different contactor size ratings varies with the OEM.

Normally the IEC starter is half the size of the same ratings of its counterpart (NEMA). This means the physical differences between the IEC and the NEMA are significant.

The IEC devices are so modular as they can snap within a 35-mm or within larger sizes, such as a 75-mm DIN rail. This removes the need of drilling holes and mounting each component independently. That is why installing them into the panel is quite simple.

As compared to the NEMA starters which are normally sold as fully assembled, the IEC starters are normally sold as components allowing you to assemble them yourself. You have a chance of selecting only the parts that you need and connect them together without a need for using tools.

Besides, as compared to the NEMA starters, the IEC thermal overload relays normally consist of fixed thermal elements which have an adjustment range that might need replacing the entire overload relay in case of a significant motor FLC changes due to application needs.

Most of the IEC contactors are used in group installations, as well as NEC 430-53 handles this application facet. But this is not identical to IEC contactors as you can install any starter via using this method.

The IEC products are normally sold to OEMs, and then they are installed within the application where many devices are needed to handle different operations of the machine.

The type 2 coordination refers to the IEC standard that can be used to a NEMA design product as well.

The type 2 protection makes sure that there is a use of the correctly rated and a class of fuse with the contactor or starter. This protection type needs that, after the occurrence of a short-circuit condition testing, the starter or contactor must be capable of being reused without having to replace any component or part. Besides, no significant alteration is allowed within the operating time-current features of the overload relay. This is known as a coordinated protection standard when it comes to short-circuit protective components, contactor, or the overload relay. 

The rules are entirely the same for both the NEMA and the IEC design devices. For the type 2 coordination, the traditional higher withstanding rating of the NEMA design starter offers a wide selection of short circuit protection appliances. The type 2 coordination having the IEC style devices will offer identical coordination as well as the degree of protection, but the selection of the fuse classes might be more limited. For the short circuit currents of u to 5000 A. The Type 2 protection when it comes to the IEC rated motor starter would need Class RK5, J, CC, or RK1 fuses. For the short circuit currents that can go to up to 100Ka, CLASS RK1, as well as the CC fuses, are needed.

In comparison to the NEMA design devices, the IEC style devices are more disposable as compared to NEMA devices which are more serviceable. The fact is the IEC devices that are below 100A are normally considered as being disposable as they can be isolated from the DIN rail and thrown away while being replaced with a new product in a matter of few minutes.

The self-protected starters are the new category that involves starters as defined in a UL 508-E. normally that kind of a starter has a contactor, a short-circuit, and an overload relay protection. The device also undergoes a unique procedure, one that moves beyond that of a conventional combination of the motor controllers. This procedure is responsible for testing the starters at different fault levels, hence verifying that coordinated protection that is identical to Type 2 is offered.

The training

Training is the basic difference that exists between the NEMA and the IEC design products. This is due to their application-specific styles. The IEC devices need a more understanding of the application performance when it comes to the device selection process. But when it comes to NEMA you do not need many of the variables that are needed when selecting the IECs devices.

This does not mean that you will need to have extensive training before you can select an IEC product. It only means that your training should be specific in nature. To select an IEC products needs more time as well as knowledge to make sure that the selection complies with the application.

Once you have selected the exact device, then everything will go as intended. Remember that both the IEC and NEMA design devices will produce identical outcomes.

1.      How does a reversing contactor operate?

A reversing contactor refers to the contactor that reverses a 3-phase motor using contactors. You have to run a single set of wires straight via a single contactor, and a parallel set of wires via another contactor where you interchange one set of wires. As the motor is started, the motor rotates in a single way, and when the contactor is started, the motor turns in the opposite direction.

2.      What is the mechanism of reversing motor starter?

The reversing motor starter is created in such a way that it reverses the shaft rotation of a 3 phase motor. This is achieved by interchanging any among two line conductors that deliver the motor load. The reversing magnetic motor starter includes a forward and reverse starter as components of the assembly. The electrical, as well as the mechanical interlocks, are offered only the forward or the reverse starter can be applied at any given time but they cannot be engaged at the same time.

3.      What does a reversing starter refer to?

This refers to a 3 phase starter motor controller that consists of two motor contactors. It does not use the contactor to open and close the power circuit so as to turn the motor on and off, but it uses a forward and reversing contactors in controlling the motor directions.

4.      What does an auxiliary contactor do?

Contactors are normally classified in load and auxiliary contactors. The load contactors consist of extreme switching capacity. These are normally used as the main contactors as they can handle loads of up to 600 A /AC1. The auxiliary contactors are just designed for switching currents which are lower ratings to up to 6 A. Among the auxiliary contactors count are the timer relays and the safety relays. Basically, an auxiliary contactor is a normal low power relay but designed like a normal contactor and when used in combination with another contactor it is referred to as auxiliary contactor to imply that it is not used to switch loads but it is used to activate or deactivate or control the operation. The auxiliary contactors normally consist of contacts and have no main contacts.

5.      What is the main operation of a contactor?

The load contactors are normally with extreme switching capacity which normally is used as the main contractor. It is installed to handle loads of up to 600 A /AC1.

6.      Why should I use an auxiliary contactor?

Normally an auxiliary contactor is a normal contactor just like a low power relay if it is used in combination with another contactor is known as an auxiliary contactor in order to identify its use as it is not used for switching loads but it is used for activating and deactivating or controlling function. This means that auxiliary contactors consist of only auxiliary contacts and have no main contacts.

The standards have to simply live for the control panel designers by providing the guidelines to which the products can be safely installed within their designs and panels. But sometimes these guidelines lead to confusion such as during a situation where two standards offer different guidelines for the same type of product.

This is what occurs in the industrial motor control devices that comply with standards from the National Electrical Manufacturers Association (NEMA) for the US or the International Electrotechnical Commission (IEC) for Europe and the rest of the world. This is not a new case as it dates back in the ’80s even though some of the customers are still confused about their differences, and they do not know when to use one vs the other. In this post, we will be discussing so as to clear up this confusion.

First of all, as mentioned earlier, NEMA is common for North American standards whereas the IEC devices are for Europe and the rest of the world. There are exceptions to heavy industries with American influence such as the oil fields in the Middle East where you can find NEMA controllers being commonly used

Second is that their difference is more technical in nature especially for tiny controllers that make up a large percentage of the majority of those sold which are the NEMA sizes 00, 0, 1, and 2.

Besides their different starts with the device configuration. The NEMA style contactors, as well as the starters, are normally purchased in fully assembled within casings. In case the customer or contractor is in need of a NEMA size 2 contactor, he/she will be able to pick one off the shelf from one of the many suppliers and he/she will be sure that it will suit the rated motor. The NEMA size unit consists of an extra reserve capacity inbuilt which allows the same size contactor to be used for many different applications.

When it comes to the IEC design contactors, they are sold much as components that can be installed within the panel. These are far more application-specific meaning that they are normally rated to be used in specific motors and for a specific purpose. In case you have two motors of the same size, but one of them will be turned off while the other will not, you are likely to use different sizes of IEC design contractors where each will be ideally designed for a specific purpose. The OEMs like that way as they can easily match contactors to the load than when it comes to the NEMA, which can help in saving space and money.

The NEMA design f contactors and starters normally allow for more maintenance, when it comes to specific parts that can be easily replaced if needed. With their inbuilt reserve capacity, they are also designed to be used for long life, typically around a million operations or a lot more than any motor starter.

When it comes to the IEC, their focus is on performance for the expected lifespan of the equipment which they control. As there are more modular in nature and component-based, it is easier to replace if there is any failed component as they normally slide into a DIN rail type mounting mechanism in the smaller sizes.

A common thing when it comes to all the products is that they are all required to be UL/CSA listed and should undergo UL testing which is the same for both the NEMA and the IEC design of products. This aims at assuring customers that neither of these products sacrifices anything from the safety point of view.

The selection remains within the customer’s point of view. In case you are looking for a simple device you can just pick off a chart and install it quickly, while being sure that it will last for the entire lifetime of the motor, then go for NEMA. In case you need a contractor that is more specific and is matched to the application as well as the equipment that you have in mind, thus saving panel space and money, the IEC is the best option for you.

But there might be other reasons that might lead you to choose one instead of the other. For example, Ford Motor Co. has dozens of final assembly plants all over the globe for its focus model. Despite the company being connected to the use of NEMA products, but its Michigan plants, when it came to the Focus model wanted it to have the same standard around the world so decided to use the IEC controllers in each plant.

In case you are having a problem with getting your motor to start this can be caused by a number of reasons. In this article, we will go through different techniques that will help you identify the problem that prevents your motor from starting. Besides we will offer some simple solutions too.

When the motor fails to start, there are a few things that you should keep into consideration so as to determine what might be the cause of the problem. In case it is a new installation and has never been started, then it is so important that you check the wiring diagram in order to determine and make sure that all the wires are properly connected. In case it is an older installation and has worked before, that means that it should be wired properly unless there were some changes that took place recently that might have caused any problem within the wiring. Here is a quick guide to troubleshooting the magnetic motor starter:

The visual inspections

First of all, inspect the terminals and cables to identify any signs of corrosion, burning, cable insulation cracking or any damage of any sort. In case you identify any visual evidence of any damage, switch off the power and have a licensed electrician review the components, installation as well as the wiring. If there is not any visual sign of the problem, then proceed to the following step.

The motor overload tripped

The most common motor problem and which can be easily fixed is that the motor overload might have tripped. The overload is designed in such a way that it protects the motor in case the current exceeds the maximum load amperage. This is just like resetting or checking the circuit breaker in your breaker box. In order to reset the overload, just push the red button that is found on the overload, or in case you have an external reset button, then press it. This is also an ideal time to ensure that the reset is configured in a manual mode.

Overload failure

In case the resetting of the overload did not solve the problem, then you can do a quick check so as to identify if the overload has failed. Make sure that you verify if the power is disconnected, the lockout the circuit in case there is a need for that. Then use an ohmmeter measure the continuity that is between the Normally Closed (NC) terminals on the overload. The exact resistance measurement is not important as you are trying to identify if there is continuity. If the Ohm meter indicates OPEN then the overload is damaged and has to be replaced.

The overload indicates continuity

In case the overload indicates continuity between the two NC terminals, then you will have to explore further. Record the information from the motor plate. It is critical that you know the voltage, phases as well as the maximum load amperage (FL) of your motor. With this kind of information, things can easily go smoothly.

Verify the overload configurations

Now you have to verify the overload configuration and make sure that it is set to maximum/full amperage from your motor’s nameplate based upon the supplied line power of the motor.

Verify the 3 phases

Once you have identified the needed input voltage, using a digital multimeter, verify that all the 3 phases of electrical potential are all working. In case it is a single-phase, make sure that the single-phase voltage is into existence. It is ideal to check this upon the cable that is moving within the contactor at terminals L1, L2, and L3. In case if there is a disconnect switch, check the incoming wires along with the disconnect. Measure between the legs L1, L2, and L3 to make sure that you have full voltage in accordance with the input line power of your motor.

Disconnecting the line power

In case you are missing one or more phases while the circuit consists of fuses, disconnect the line power and use your multimeter to measure for continuity over the fuses.

The blown fuse

In case one of the fuses is blown, then you will have to replace it. Sometimes the fuse holders might be corroded and this might prevent continuity. Therefor inspect to identify any corroded fuse holder and in case there is one, clean it using electrical contact cleaner together with a toothbrush.

In case you followed the above steps and yet nothing worked, then it might be the right time to call a licensed electrician for more help.

The generator interlock kit is a device that is designed in allowing safe powering of the home using a portable generator when there is a power outage. It is a cheap alternative as compared to installing a dedicated transfer switch. The kit attains the same operation by applying an external interlock upon the existing breaker panel. this enables the main breaker to be switched on or a particularly designated load breaker to be switched on. But it prevents both breakers from being on at the same time. The interlock load breaker is used as the backfeed breaker, as the generator is directly connected to this breaker or can be connected to it via an inlet.

Under normal conditions, the main breaker is always on, allowing power from the external mains to flow into the panel, and the backfeed breaker is off, breaking the generator off from the circuit. The external mains always feed the panel while the panel cannot backfeed the generator. There should never be any backfeed to the generator as it has no need and it might damage the generator.

When the generator is running, the backfeed breaker comes on allowing power from the general to flow into the panel, and the main breaker is switched off blocking the external mains. The generator works to feed the home by backfeeding the panel while the panel cannot backfeed the external mains. Backfeeding the external mains is risky and illegal as it can lead to electrocution of line workers, start a fire as well as overload or damage the generator. 

The operation

A generator interlock kit is connected on the floor cover upon the home’s breaker panel. It has two sliding steel or plastic plates that are held together using three bolts depending on the brand. When they are moved down the plates prevent the generator backfeed circuit breaker while allowing the main breaker to maintain its ON position. While when it is moved up, the generator backfeed breaker might be turned on, and the main circuit breaker is switched off. The generator backfeed circuit breaker is the connected to the generator inlet that is connected to the exterior of the structure. There is a short cord connecting the generator to the casing inlet normally via a twist-lock as well as the socket.

The advantages

• Just like the transfer switch, the interlock kit allows the generator to power the panel and all of its entire circuits depending on the generator’s maximum load capacity; and not just the corded appliances only.
• The interlock kit does not need an independent panel to function, it can be connected directly on the home’s main breaker panel so long as it has any unused double pole breaker slot that is available.
• The generator interlock kit which is sometimes referred to as a transfer switch removes the need for using extension cords in powering the appliances.

The disadvantages

• Although most of them are test by an independent lab to meet the UL standard, they normally have no UL Listing mark. This means some electrical inspectors reject the use of these interlock kits.
• To remove the electrical panel’s cover might enable the generator backfeed breaker to switch on while the main is still on, this will energize the power lines or overload the generator in case the generator is connected.
• In some of the applications, connecting an interlock kit needs drilling holes within the panel cover, and this means that once it is installed it cannot be isolated.
• Due to the fact that the main breaker is switched off, he homeowners have no way of identifying when the utility power is restored unless you manually turn the generator’s breaker off while the main breaker on. But there is at least a single device that can produce an audible alert that indicates that the utility power has been restored.
• To install an interlock kit needs two or more spaces within the existing panel.

A lot of lights and appliances in a traditional home run on 120-volt electricity, but a few of them consume too much power for that and are should be supplied with 240-volt electricity. Examples of these include water heaters, dryers, and furnaces. Every single 240-volt appliance should be on its dedicated circuit that is controlled using a breaker that is rated for the current specifications for that particular appliance which is specified on its attached label. A room air conditioner is a good example of the appliance that will need a 30-amp breaker.

The breakers that can control 240-volt circuits is known as the double pole breaker. Each one is made up of two separate breakers which are permanently connected together. One breaker contacts one of the two 120-volt hot buses within the panel and the other breaker contacts the other hot bus. When you join the wire to one of the breakers and the other hot wire to the second breaker, the voltage that is generated by both wires is 240 volts.

A double-pole breaker is not a tandem breaker

There is a certain confusion that can be seen between a double –pole breaker and a tandem breaker, which also is made up of two breakers that are connected together. The difference that exists between the two is that a tandem breaker such as the QO tandem that is manufactured by Square D which is a leading manufacturer of breakers and panels is, in fact, a pair of a single-pole breaker. It is designed in such a way to occupy a single slot panel and can act as double independent 120-volt breakers. A tandem breaker offers a way to get more operations from a panel that is almost full. Tandem breakers are normally rated to handle 15 or 20 amps, which is the number that is marked on the front. When it comes to double-pole breakers these are normally rated to handle less than 30 amps.

The basics of a 240-volt wiring

Electricity normally enters the panel using a pair of hot wires having a voltage of 240 volts where each holds 120 volts. Each of the two wires is connected to a bus bar, and 120-volt circuits take power from one or the other among these bus bars, and this means a 120-volt circuit breaker is designed to connect a single bar. The bars are forged in an S-shape making the successive breakers contact each one alternately. 240-volt breakers take two slots within the panel by contacting both bus bars.

A 240-volt circuit requires a 3 – conductor cable which has a minimum wire gauge of 10 AWG. The cable consists of two hot wires, which are colored black and red, and contain a neutral and ground wire which is not considered as a conductor. Every single hot wire is joined to one of the two terminals upon the double-pole breaker, whereas the neutral wire gets connected to the neutral bus in the panel as the ground wire is connected to the ground bus.

Connecting a 30-amp double pole breaker

The circuit breakers are not interchangeable as they cannot be installed from one different panel model to another. Make sure that when you purchase a breaker you have to get one from the same company that manufactured your existing panel.

The cable that is powering the circuit has to be securely clamped in order to access the port. After stripping an inch of insulation from each of the wire in the cable, connect the white wire to an available plug upon the neutral bus within the panel and then connect the ground wire to a ground bus. Besides, connect the red wire to the lug on one of the breaker terminals and this does not matter as whatever wire you connect will not have any problem. Then connect the black wire to the other terminal. The breaker usually snaps or hooks within a chosen slot. Not that you will need two adjacent slots to connect them to a double pole breaker. Once the breaker is installed in place and you have turned it on, the circuit is already energized.

Working in the panel is so dangerous as the hot bus bars are normally energized. Due to this danger, it is better that you let a professional licensed electrician do the work.

There is normally a confusion when it comes to the use of tandem circuit breakers within the panelboards. This confusion also faces electricians and electrical inspectors too. In this post, we want to explain things into detail and make sure that you will no longer be confused.

A summarized definition

A tandem circuit breaker is referred to as a double circuit breaker that occupies the space of a single circuit breaker or panelboard. You might have heard some electricians calling it a duplex, twin, half-height, slimline, wafer breaker, half-inch or double depending on where you come from. While the tow-pole circuit breaker is connected to two poles, a tandem breaker doesn’t.

A tandem circuit breaker allows you to connect two circuits on a panelboard by occupying a single circuit breaker space. They are normally applied after the panel has been filled to its maximum capacity with standard circuit breakers. Due to this, they are normally called cheaters.

Does this mean that installing them is cheating? No, it is not. The installation of tandem circuit breakers is just an acceptable practice as long as the panelboard is designed to be used for tandem circuit breakers and they can be installed in any locations that are mounted with panelboards.

How does a home inspector determine if the tandem circuit breaker is allowed into the panelboard that they are inspecting? There are several ways to do so.

The class CTL panelboards

The panelboards should comply with the UL standard 67, which needs all lighting and appliance panelboards to comply with Class CTL (Circuit total Limiting). There is an old formula that is used to determine the number of circuits that can be installed in the class CTL panelboard that is being inspected. This formula is essential to use when you are inspecting an older electric panel that has no proper labeling inside the panel. You will have to take the amperage of the panelboard and multiply it with the number of poles, and then divide it by 10. This sounds a bit complicated but it is just simple. Let us take an example so that you can understand.

Let us use 100 amp panelboard as an example that will make you understand

100 Amp X 2 Poles = 200 then 200/10 = 20

As based on this formula the maximum number of circuits that can be used in a 100-amp 120/240-volt panelboard is 20. When it comes to panelboards not manufactured as lighting and appliance panelboards there are totally no limits to the number of circuits breakers that are allowed. Note that this formula is no longer applicable in today’s panelboards.

There is a confusion that is created by the 2008 National Electrical Code (NEC). The previous versions of the NEC were limiting the maximum number of circuits in a lighting and appliance panelboard to 42. The 2008 edition of the NEC dropped the lighting and appliance panelboard section, but the NEC 408.54 states that “A panelboard must be offered with physical means in order to prevent the installation of extra overcurrent devices than the specific number which the panelboard was designed, listed and rated to handle.

The manufacturers still specify the maximum number of circuit breakers that are allowed and should also offer the rejection feature so it has to prevent the application of tandem circuit breakers where they are not allowed.

The class CTL panelboards have different ways of preventing class CTL tandem circuit breakers from being applied in locations where they are not meant to. This is what is known as the rejection feature.

The tandem circuit breakers are manufactured like this so as to prevent people from improper use although this does not stop everyone from doing so.

When it comes to panels that were manufactured before the adaption of the class CTL standard, the non-Class CTL tandem circuit breakers are accepted to be connected as replacement circuit in breakers only. The non-Class CTL tandem circuit breakers are not designed with a rejection feature, unlike the Class CTL breakers. As it is clearly labeled on the side of all circuit breakers, such circuit breakers that were manufactured before the adaption of the class CTL standard are not allowed. Sometimes it is difficult for home inspectors as the markings are not usually visible after being installed, and the home inspectors cannot pull out the breakers to try to figure it out.

Does the panelboard accept tandems?

Now as we have discussed the general guidelines for tandem circuit breakers, let us now look at the means that home inspectors or electrical inspectors use to determine when the tandem breakers are accepted in different panelboards.

The version of the panelboard                             

The version or part number of the electric panelboard normally shows whether or not the electric panelboard is designed in a way that it can allow tandem breakers and how many of them can be used. Here are some few examples:

• The G3040BL1200 contains 30 spaces and allows a total number of 40 circuits. You can use up to 10 tandem circuit breakers.
• The G3030BL1150 has 30spaces and 20 circuits are accepted. You can use up to 8 tandem circuit breakers.
• The BR1212B100 consists of 12 spaces and has a total of 12 circuits that are allowed. No tandem circuit breakers are allowed.
• The HOMC20U100C consists of 20 spaces and has a total of 20 circuits that are allowed. No tandem breakers that are allowed.

This will help you as it has simplified the pattern.

What is the major concern when it comes to circuit breakers?

When tandem circuit breakers are applied in areas where they are not accepted, they could lead to an improper physical connection with the connection bar within the panelboard which can lead to a fire outbreak. The tandem circuit breakers also raise the total load upon the bus bars within the panelboard; this requires the home inspectors or electricians to use their common sense.

In case home inspectors or electricians identify tandem circuit breakers that are installed in an improper location, they will normally recommend repairs to be made. In case the bus bars of the panelboard has been destroyed or altered in any way to allow the installation of tandem circuit breakers, the panelboard must be replaced. There is absolutely no way that can help the home inspectors determine if the bus bars have been destroyed without having to remove the circuit breakers. This is something that they are not allowed to do.

The National Electric Code (NEC), as well as all local building codes, need GFCI which is a ground fault circuit interrupter protection for most of the outlet receptacles in an entire home as well as in outdoor areas. The requirements are installed to protect the user from being exposed to shock in case there is a ground fault, a situation in which electrical current can accidentally flow beyond the created circuit. This protection is normally needed whenever an outlet is in contact with the earth or to water sources that can lead to the development of a direct path to the earth.

This needed protection can be offered either by the GFCI circuit breaker or sometimes by the GFCI receptacles. There are pros and cons to each of the two approaches depending on their installation. Besides you have to keep in mind that you must also adhere to the local electrical code that you must follow in order to pass electrical inspections as they might have their special requirements to how they should provide GFCI protection in your jurisdiction.

Traditionally, a GFCI circuit breaker handles the same thing as the GFCI receptacle and therefore to make a proper choice needs you to measure different cons and pros of each.

The GFCI circuit breakers are ideal for protecting the whole circuit

The GFCI circuit breakers are just simple. When you install one within the service panel, it enables the GFCI protection to the entire circuit which includes the wiring as well as all the devices and appliances that are in connection with the circuit. When an AFCI protection is also needed, there is a dual function AFCI/GFCI circuit breaker that can be applied.

The GFCI circuit breakers are more practical in conditions where the entire circuit outlets need to be protected. For example, when you are installing a receptacle circuit to your garage workshop or a huge outdoor patio base. Due to these receptacles you need a GFCI protection, this means that in order to have maximum efficiency you need to wire the circuit using a GFCI breaker so that all the appliances and devices which are connected to the circuit are protected.

Besides the GFCI receptacles are generally applied instead of a traditional outlet receptacle to provide protection to a single outlet area. But the GFCI receptacles can be wired in two identical ways to provide two identical levels of protection. Single location protection provides GFCI protection at a single receptacle point. While the multiple location wiring offers protection to the first GFCI receptacle and each receptacle that is downstream of it including the traditional receptacles within the same circuit. But it does not offer protection to the part of the circuit that is between the main service panel and itself. For example, in case the GFCI receptacle that is wired for multiple location protection lies as the fourth receptacle on the line within the circuit that contains seven outlets, then the first three outlets will never be protected.

The GFCI receptacles should be installed in easily accessible locations

In case the GFCI breaker trips you will have to reset the service panel as you are able to reset it at the receptacle location. The National Electrical Code (NEC) needs the GFCI receptacles to be in locations that are easily accessible so that to ensure there is easy access when you need to reset the receptacle in case it trips. Therefore, GFCI receptacles cannot be installed behind appliances or furniture. In case you have receptacles that require GFCI protection over these locations, install the GFCI breaker.

To reset a receptacle is traditionally more efficient than having to go all the way to the service panel in order to reset a breaker, but not that in case you wire a circuit for multiple-location protection from a single GFCI receptacle, whereas that particular receptacle controls everything that is downstream. In case there is any wiring problem below, you will need to backtrack so as to identify the GFCI receptacle so as to reset it.

The GFCI receptacles are so easy to install

Sometimes what to install depends on the question of efficiency. For example, in case you want a GFCI protection for a single or double receptacles let’s say, for a bathroom or laundry room, it will probably be sensible to install GFCI receptacles at those locations. Besides if you are a do it yourself type and you have no experience working on a service panel, installing a receptacle will not be an issue as it simple and safer as compared to installing a circuit breaker.

Other factors to consider

• The GFCI receptacles have wider bodies as compared to the traditional receptacles, so in some conditions, the physical room within the wall box affects your choice of selection. When it comes to the standard boxes there might be insufficient room to install a GFCI receptacle safely thus making the GFCI circuit breaker an ideal choice.
• The cost can also be a factor when it comes to decision making. A GFCI breaker might be expensive costing around $40 to $50, as compared to $4 to $6 for a standard breaker. In case money is a problem you will have to protect only a single location, and the GFCI outlet might be an ideal choice as compared to the GFCI breaker.
• The last one is the local electrical code which might have specific GFCI requirements that are identical to those which are recommended by NEC. You will have to consult your local building code department in order to have proper details and guidelines.