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Branch circuits wire sizes are governed by the connected load amperage of the circuit. The wire size ampacity then governs the size of the breaker that is used to protect the circuit from overloading.
For general home wiring circuits the conductors used are, receptacles and lighting #14 - 15 amps, dedicated circuits load dependant, hot water tank and baseboard heaters #12 - 20 amps, clothes dryer #10 - 30 amps, range #8 -- 40 amps.
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Does the code permit the ampacity of switch legs to be less than the ampere rating of the branch circuit?
No, and here's why: the rating of the branch, determined by the overcurrent protection, is designed for the ampacity of the branch conductors so that they breaker trips before the conductors heat up enough to start a fire. If you put in smaller wires on the same branch, they will get MUCH hotter before the circuit breaker trips, if it ever does. For example, a 20A branch, protecting 12AWG wiring; add some 14 AWG rated for 15A. Something faults the switched leg at 18A; enough to burn out the wiring but not enough to trip the breaker. House burns down, insurance doesn't pay because of "faulty wiring" installed negligently by a person without proper training and credentials.
In a DC circuit must the positive and negative conductors be the same size if not how is the size difference determined?
Yes, since the current is the same through out the complete circuit. the design size of the conductor entering the circuit should be the same size as the conductor leaving the circuit.
What earth size is required for 16mm live and neutral?
Answer for USA, Canada and countries running a 60 Hz supply service.Equipment grounding conductors are not based on the size of the live and neutral conductors. Equipment grounding conductors are based on the amp rating of the circuit, which may or may not be the same ampacity of the conductors of the circuit.However, working backwards, a 16mm conductor is the same as a 3/0 conductor, which is rated for 200amps, which requires an equipment grounding conductor (earth) of at least 6 AWG copper / 4 AWG aluminum. If your circuit is rated higher (usually the breaker size) than 200 amps a larger conductor may be required.As always, if you are in doubt about what to do, the best advice anyone should give you is to call a licensed electrician to advise what work is needed.Before you do any work yourself,on electrical circuits, equipment or appliances,always use a test meter to ensure the circuit is, in fact, de-energized.IF YOU ARE NOT ALREADY SURE YOU CAN DO THIS JOBSAFELY AND COMPETENTLYREFER THIS WORK TO QUALIFIED PROFESSIONALS.
What size of wire is needed for 1500 amps?
There is no single conductor that will handle 1500 amps. For ease of handling, the conductors should be installed in parallel, triple or quad runs. For a parallel run, 2 - 2000 MCM with an insulation factor of 90 degrees C will give you a total ampacity of 1550 amps. For a triple run, 3 - 750 MCM with an insulation factor of 90 degrees C will give you a total ampacity of 1500 amps. For a quad run, 4 - 500 with an insulation factor of 90 degrees C will give you a total ampacity of 1580 amps.
What fuse do you need to run a 200 watt bulb with 230V?
The formula you are looking for is Amps = Watts divided by Volts. Once you find the amperage you can decide as to the size of a fuse you should use. Remember that fusing protects the conductors of the circuit and not the load of the circuit. A #14 wire is rated at 15 amps and can legally be loaded only to 12 amps.
Does the code permit the ampacity of switch legs to be less than the ampere rating of the branch circuit?
No, and here's why: the rating of the branch, determined by the overcurrent protection, is designed for the ampacity of the branch conductors so that they breaker trips before the conductors heat up enough to start a fire. If you put in smaller wires on the same branch, they will get MUCH hotter before the circuit breaker trips, if it ever does. For example, a 20A branch, protecting 12AWG wiring; add some 14 AWG rated for 15A. Something faults the switched leg at 18A; enough to burn out the wiring but not enough to trip the breaker. House burns down, insurance doesn't pay because of "faulty wiring" installed negligently by a person without proper training and credentials.
How do you know if the AC breaker matches the AC unit starting demand load?
Read the literature for the ac condensing unit, or the tag on the outside of the unit. Minimum circuit ampacity= minimum breaker, wire and fuse size. Maximum circuit ampacity= the maximum size. Your circuit breaker, wire size and disconnect fuses should all be at or between those 2 numbers.
Is it better to have a high or low resistance across a circuit breaker?
A circuit breaker is supposed to protect the more valuable component the circuit is connected to. Too low a resistance, a minor glitch (spike) will break the circuit and stop the device from working. Too high a resistance, no glitches, no matter how large (a child sticking a paper clip into the wall sockets, for example), will break the circuit and the device (child) may get damaged. Each circuit will have a purpose (power load), and the circuit breaker should be chosen for that purpose with some tolerance. A free standing closed circuit breaker should have no resistance across its internal contacts. The main purpose of a circuit breaker is to protect the conductors that supply the load. If the current going to the load becomes greater that the amperage rating of the wire the circuit will open thereby saving the conductors from damage. Once the load current is below the wire rating ampacity, the breaker can be reset for normal operation.
Why conductors in circuit are covered with insulators and why insulators should be always kept dry?
So that it's nice!
Why conductors in circuit are covered with insulators and why insulators should always be kept dry?
So that it's nice!
What causes the main breaker to trip from a fault current from a twenty amp branch circuit?
If the fault was on the 20 amp branch circuit, the branch circuit breaker should have tripped, not the main breaker. Call a qualified electrician to check out your wiring.
How are Branch circuit protected?
Branch circuits are protected by the circuit breaker found in the electrical panel. Each circuit should have its one breaker. The breaker should be rated to protect the insulation of the wire, so you can determine the breaker size based on the circuit conductor size Example #14-2 should be protected by a 15 amp breaker
In a DC circuit must the positive and negative conductors be the same size if not how is the size difference determined?
Yes, since the current is the same through out the complete circuit. the design size of the conductor entering the circuit should be the same size as the conductor leaving the circuit.
If you're installing a circuit that will contain receptacles in an industrial area and the first receptacle is more than 50 feet (15.24 meters) from the load center you should?
Connect the circuit to the appropriate size circuit breaker to meet the required amperage of the circuit. Turn the breaker on and use the circuit. Unless the circuit is of a very high ampacity, plus 200 amps, don't worry about voltage drop over 50 feet.
Will a rcd detect live to neutral fault?
No. An RCD operates by detecting fault currents on the circuit protective conductors(earth). An MCB(mini trip) should operate with a live to neutral fault(over-heating the circuit).
What earth size is required for 16mm live and neutral?
Answer for USA, Canada and countries running a 60 Hz supply service.Equipment grounding conductors are not based on the size of the live and neutral conductors. Equipment grounding conductors are based on the amp rating of the circuit, which may or may not be the same ampacity of the conductors of the circuit.However, working backwards, a 16mm conductor is the same as a 3/0 conductor, which is rated for 200amps, which requires an equipment grounding conductor (earth) of at least 6 AWG copper / 4 AWG aluminum. If your circuit is rated higher (usually the breaker size) than 200 amps a larger conductor may be required.As always, if you are in doubt about what to do, the best advice anyone should give you is to call a licensed electrician to advise what work is needed.Before you do any work yourself,on electrical circuits, equipment or appliances,always use a test meter to ensure the circuit is, in fact, de-energized.IF YOU ARE NOT ALREADY SURE YOU CAN DO THIS JOBSAFELY AND COMPETENTLYREFER THIS WORK TO QUALIFIED PROFESSIONALS.
How is the rating of the branch-circuit protective device affected when conductors used are of a larger size than called for by the code?
The branch circuit circuit breaker or fuse protects the wire and devices that make up the circuit. If you have a 15 A breaker the wire size must be at least 14 AWG. You could have a larger wire size like 12 AWG, but not a smaller size like 18 AWG. Note as the number decrease the wire size is larger in cross sectional area. All the receptacles and switches should be rated equal to or greater than the branch protection device.
