Beatrice Lang
In electrical terms, a 'leg' refers to one of multiple hot conductors in a circuit. For instance, a 240-volt circuit may feature a neutral wire and two hot legs, with 240 volts to each other and 120 volts each to the neutral. When a circuit breaker is removed while an appliance is running, it can cause problems with the legs of the circuit, resulting in the need for an electrician to fix the issue.
| Characteristics | Values |
|---|---|
| Definition | "Leg", as in "hot leg", refers to one of multiple hot conductors in a circuit. |
| Example | 240-volt circuits feature a neutral and two hot legs, 240 V to each other, and 120 V each to the neutral. |
| Circuit breaker box | A leg of current may be missing from a circuit breaker box. |
| High-leg service | Not all high-leg services are open delta. Some 3-phase services have 3 transformers on the pole feeding a high-leg service, also known as a "closed delta". |
| Nominal voltages | 240-volt delta 3 phase, 120/240 single phase, and 208 volts to ground high leg. |
| Color | High legs are typically marked orange or red. |
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What You'll Learn
- 'Leg' refers to a ''hot leg'' or one of multiple hot conductors in a circuit
- A 220v a/c has two legs, each supplying 110 volts, and a third neutral wire
- A 'dead leg' is when a wire is unable to get energised
- A 'red leg' panel is a type of high-leg service
- A 'high leg' can be marked as orange instead of red
'Leg' refers to a ''hot leg'' or one of multiple hot conductors in a circuit
In electrical terminology, a "leg" refers to a hot leg or one of several hot conductors in a circuit. A hot conductor is any conductor that is connected and has electric potential relative to the electrical ground or neutral. In 110/220-volt systems, hot conductors are typically black or red and, in some cases, blue. These conductors terminate on brass-coloured terminals.
For example, a 240-volt circuit features a neutral wire and two hot legs, each with a voltage of 240 V to each other and 120 V to the neutral. This configuration allows for a split-phase electrical power distribution system, where the two legs of the circuit are 180 degrees out of phase with each other, resulting in a voltage of 240 V between the legs.
In a three-phase system, each of the three conductors carries a voltage that is one-third of the total system voltage. These systems are often used in industrial applications and can be configured in various ways, including wye (Y) and delta (Δ) configurations. In a wye configuration, the neutral point of the system is connected to ground, while in a delta configuration, the three conductors are connected directly to each other without a neutral point.
It is important to note that issues with a circuit breaker box can result in a "missing leg of current," as described in a user's account. In this case, an electrician is usually required to resolve the issue, as it may involve complex voltage checks and repairs.
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A 220v a/c has two legs, each supplying 110 volts, and a third neutral wire
In electrical terms, a 'leg' refers to one of multiple hot conductors in a circuit. For instance, a 240-volt circuit features a neutral wire and two hot legs, each with 240 V to each other and 120 V each to the neutral.
A 220v a/c, therefore, has two legs, each supplying 110 volts, and a third neutral wire. This third wire is sometimes referred to as the common wire. The two legs are typically red and black, and the neutral wire is white. The voltage between the two legs is 220v, and the voltage from either leg to the neutral wire is 110v.
In a single-phase, 3-wire residential electrical system, one leg to neutral may have 110v, while the other leg to neutral may have 130v. This voltage imbalance is likely caused by a "neutral issue".
It is important to note that if a breaker is removed while the a/c is running, there is a risk of arcing across the breaker contacts and the lugs, which are the main supply wires to the bus bar. This can cause one leg of the current to be missing, as described in a user's account of their A/C unit no longer running after the breaker was pulled out.
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A 'dead leg' is when a wire is unable to get energised
In electrical terminology, a 'leg' refers to one of multiple hot conductors in a circuit. For instance, a 240-volt circuit features a neutral wire and two hot legs, with 240 volts to each other and 120 volts each to the neutral wire. These legs are the two sides of where the power comes in that the breakers then draw power from.
A dead leg is when a wire is unable to get energised, resulting in a loss of power to certain areas. This can be caused by a fallen tree limb knocking one of the wires loose, or by an issue with the electrical panel or meter. In the case of a dead leg, the electrical utility should be called, as it may be their problem to fix. If they determine that it is not their responsibility, then an electrician should be contacted.
If you are experiencing a dead leg, it is important to turn off all the big appliance breakers, such as the AC/Heat pump, dryer, stove, and water heater, as these appliances need 240 volts to operate and will try to operate on 120 volts with an open return path, which can be dangerous.
Until the issue is resolved, you can use appliances that run on 120 volts by turning the electric oven on high. This will allow the 120-volt appliances to work until the electrician arrives.
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A 'red leg' panel is a type of high-leg service
In electrical terms, a "leg" refers to one of multiple "hot" conductors in a circuit. In a 240-volt circuit, for instance, there is a neutral wire and two hot legs, each with 240 volts to each other and 120 volts to the neutral.
A red leg panel, also known as a "high-leg" panel, is a type of high-leg service. It is marked as "3-Phase Red Leg, 208-v to ground" and contains various 20-amp, 60-amp, and 100-amp 3-phase breakers, as well as 20-amp, 120-volt breakers. This type of service is beneficial to power companies as they can supply it using two single-phase transformers instead of three.
The high leg in a red leg panel is typically labelled as "B" phase, but it can also be labelled as "A" or "C" phase, depending on local practices and conventions. In some cases, the high leg may not be clearly marked, which can lead to confusion and potential issues, as seen in an example where a building owner installed new lights that kept frying the ballast because they were connected to the high leg without their knowledge.
The high-leg delta service provides a unique advantage by offering a line-to-line voltage higher than the standard 208 V found in most three-phase services. Additionally, it provides a line-to-neutral voltage on two of the phases, making it suitable for connecting appliances and lighting. This configuration allows large equipment to draw less current, requiring smaller wire and breaker sizes.
In summary, a red leg panel, or high-leg panel, is a specific type of electrical service that offers advantages in voltage supply and equipment connectivity. It is an important concept in electrical engineering and power distribution.
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A 'high leg' can be marked as orange instead of red
In electrical terminology, a "leg" refers to one of multiple "hot" conductors in a circuit. A "hot" conductor is any conductor that has electric potential relative to electrical ground or neutral. In 110/220 volt systems, the hot conductor is either black or red, and sometimes blue.
A high leg, on the other hand, is a term used to describe a type of electrical service configuration, specifically a three-phase transformer (or three single-phase transformers) with four wires coming out of the secondary. Three of these wires are the three phases, and the fourth is a neutral connected as a centre-tap on one of the windings.
The high leg can be marked with an orange colour, instead of red, to indicate the presence of a neutral. This is a common practice, but not the only way to identify a high leg. Other colours like purple, yellow, or even other means such as tags, can also be used. The National Electrical Code (NEC) requirement 110.15 specifies that high legs should be marked with an orange finish, but utilities providing electrical supply are not bound to follow the NEC and may use other colours.
The use of orange to mark a high leg is especially relevant in a 4-wire, delta-connected system where one phase winding is grounded. In such a system, only the conductor or busbar with the higher phase voltage to ground should be marked with an orange outer finish or by other effective means.
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Frequently asked questions
In electrical terms, a "leg" refers to one of the multiple hot conductors in a circuit. For example, a 240-volt circuit has a neutral wire and two hot legs, each with 240 volts to each other and 120 volts to the neutral.
A "hot leg" refers to one of the multiple hot conductors in a circuit. In a 220V system, there are two hot legs, each supplying 110V, and a third neutral wire.
A red leg panel refers to a high-leg service, which is a type of electrical service where one phase has a higher voltage than the others. The high leg is typically marked in a specific color, such as red or orange, to indicate the higher voltage.
A dead leg refers to a loss of power or voltage in one of the legs of a circuit. This can occur when a wire is not energized or there is an issue with the power supply.
If you suspect a missing or dead leg, it is important to contact a licensed electrician to diagnose and fix the issue. They will be able to perform voltage checks and ensure that your electrical system is safe and functioning properly.
