100 AMP Wire Size

Technology
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100 AMP WIRE SIZE means that 100 amps wire is actually a three- wire cable. It consists of a three insulated conductors and a bare copper ground wire.

Wire

Sufficient to the amperage of the subpanel, the cable must have a wire gauge. For example, #4 copper wires are required for a 100 amp wire subpanel. Depending upon your need, the cable contains one or two hot wires.

100 amp means 100 ampere wire which consists of three wire cables. 100 amp wire also contains a wire gauge. The size of the wire depends upon the wire’s length and temperature according to it’s using.

1. What size wire do I need for a 100 amp underground 300 feet run?

I would use Aluminum direct burial 1/0-1/0-1/0-1/0 for 300 feet for 100 amps rated service. If in conduit, must still be rated underground wire and required by code also, the fourth can be as low as #4 for the ground. It cannot cut strands to make fit and also not the size wire and the breaker can handle.

:round_pushpin: What wire size do I need to go 100 feet for a 60 amp size to a workshop?

The largest conductors that will fit, is used by thumb for a service connection. If 8 AWG would work, then 6 AWG fits, then use it. A larger service conductor provides a better power factor (cooler wires), so your workshop will eventually grow to have more power loads, I also know it is only a 100 foot run.

2. How do you size a wire?

American Wire Gauge system (AWG) is used to measure the size of wire. Rated with a numerical designation that runs opposite to the diameter of the conductors, wire gauge refers the physical size of the wire. It is noted that, the larger the wire diameter, the smaller the wire gauge number.

:round_pushpin: Can you run a 100 amp sub panel off a 100 amp main panel?

According to my best understanding, to run a 100A subpanel of a 100A main panel, there is no code issue. So, installation is correct, as long as the wire size. You need a four wire service for a subpanel. You also need two hot, a neutral and an equipment ground.

:round_pushpin: What is better 100 Amp or 200 amp service?

For a home of less than 3000 square feet, a 100-amp service is good. It does not have electric heat or central air-conditioner. 200-amp service is used for a home larger than 2000 square feet. It has larger electric heat and central air conditioner.

3. Is a 100 amp service enough?

When installing central air, a heavy upgrade from a 100-amp electrical service is often recommended. Even it is not absolutely necessary, but it can be a good idea. The service loaded up with 240-volt major appliances even before air-conditioning is installed, many houses with 100 amp services have this type of service. 100 amp service is enough for transferring wire

:round_pushpin: How many circuits can you have on a 100 amp service?

100 amp services are enough large or powerful enough to power a simple moderate sized home’s general branch circuit it is according to some electricians. It has also power to power one or two electrical appliances, such as range, water heater and cloth dryer.

:round_pushpin: How much it cost to go from 100 amps to 200 amps?

It cost $750 to $2000 for upgrading an electric panel from 100 to 200 amps. This cost does not include the change of wiring for additional circuits. If the cost of running new wiring for additional circuits include, then a high price is also require for that purpose.

100 amp wire

4. What does a double 100 amp beaker mean?

When you say it has double 100 amp beakers, then it depends upon what you mean. If you mean that a beaker has 2 strands or handle which are tied together, then these handles are of 100 amps. But, if you mean that a beaker has 4 handles tied together, then it is consider be of 200 amp service.

:round_pushpin: What are the normal amps for the house?

Up to 100 to 200 amps are used in some homes for electrical services. The measurement of the volume of electricity flowing in wires is called Amperage. In very old homes, this measurement can vary in 30 amps. In a very large home, for extensive electric heaters 400 amps can be used.

:round_pushpin: How much does a 100 ampere service cost?

$1200 to $1600 is the average price to install a new 100-amp service. But, if the service panel needs to replace, then $850 to $1100 are required. Most modern homes required 200-amps because of the electric heaters, etc. But, most old or middle homes require only 100-amps with minimal use of electricity.

:round_pushpin: How to Install 100 AMP wire?

100 amp wire installation is shown by a video from which you can understand the working better. Here it is;

5. What size generator do I need for 100 amps?

You can use 8-12 kW Gen Set, if you have a 100 amp service panel. But if you have an air conditioner, then use larger generator. You can also use 15-20 kW Gen Set, if you have a 200 amp service panel. But again if you have air conditioner or large well pump etc. then use large generator.

:round_pushpin: How many watts are 100 amps?

  • If we have 70 amps then power is 8400 watts and voltage is 120 volt.
  • If we have 80 amps then power is 9600 watts and voltage is 120 volt.
  • If we have 90 amps then power is 10800 watts and voltage is 120 volts.
  • If we have 100 amps then power is 12000 watts and voltage is 120 volts.

:round_pushpin: Can I run a 100 amp subpanel?

You could run a subpanel of up to 200 amps, because the total can be twice the amperage of the box. So, you can run a 100 amp subpanel off a hundred amp main panel. You should not overload the service panel and you should connect the subpanel safely and correctly to the main panel.

:round_pushpin: What is a 100 amp subpanel?

Through the double pole breaker, it connects. And the role of the 100 amp subpanel is that cannot exceed the amperage of the main panel. It is important that the breaker will be correctly sized, for the feeding of sub-panel. Depending on the requirements, up to 100 amps a 100 amp subpanel is connected by the breaker.

:writing_hand: Summary

100 amps wire is actually a three- wire cable. It consists of a three insulated conductors and a bare copper ground wire. I would use Aluminum direct burial 1/0-1/0-1/0-1/0 for 300 feet for 100 amps rated service. A larger service conductor provides a better power factor (cooler wires), so your workshop will eventually grow to have more power loads, I also know it is only a 100 foot run. Depending on the requirements, up to 100 amps a 100 amp subpanel is connected by the breaker. American Wire Gauge system (AWG) is used to measure the size of wire.

:gear: Frequently asked questions

100 amp wire size is a wire which contains three wire cable. Some people also ask following questions about 100 amp wire size. Here are these;

:one: Can I put 50 amps breaker in a 100 amp panel?

Use a 30 amp to be code worthy, because it does exceed the rating of the receptacle. The circuit will run with a 30 amp breaker and a #8 Romex, because the circuit will not draw more than about 22 amps. But if the 10-30 is obsolete than a 14R-30 is used and it will be fine. On- off switch is also used to run the function of live wire.

:two: How do I know if my electrical panel is overloaded?

There are three signs from which you can indicate that your electric panel is overloaded.

  • First big indication of the overloaded electric panel is that the frequently trip of the breaker.
  • Second big indication of overloaded is the excessive amounts of current caused by the breaker, wiring and other electrical components can cause overheat or creating a fire hazard.
  • The overload can create sparking and buzzing.

:three: How many amps are in a volt?

Electromotive force or electric potential is defined as ‘’the potential difference between the two points of the current carrying wires of 1 ampere, when the power dissipated between these points is equal to 1 watt. Hence a ‘’Volt’’ is a unit of electric potential or EMF.

:four: Can you feed a 100 amp subpanel with a 60 amp breaker?

It is of less amperage so it is not violate anything for a main breaker. It will be okay, if it is used for lights. The max rating that you can feed it is actually the 100 amp rating of the subpanel. So, it is clear that it can be used for fans, lights, or anything which carry low load. For high load, or larger things, 200 amps is used.

:five: Is 100 or 150 amps enough for a house?

Instead old homes, new homes have 150-200 amp service. But, very large houses may have a 400 amp service. With the number of new electrical appliances, over the years there is the increase in amps. The amperes on the main breaker will determine the maximum amount the house can safely use.

:white_flower: Conclusion

100 amps wire size is actually a three- wire cable. It consists of a three insulated conductors and a bare copper ground wire. A larger service conductor provides a better power factor (cooler wires), so your workshop will eventually grow to have more power loads. The measurement of the volume of electricity flowing in wires is called amperage. In very old homes, this measurement can vary in 30 amps. In a very large home, for extensive electric heaters 400 amps can be used. If we have 100 amps then power is 12000 watts and voltage is 120 volts.

:sagittarius: Related Topics

Wire

Live Wire

On-Off Switch

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very useful and Informative post indeed, I like it

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100 AMP wire.
Why would you need add a Sub-panel?
There are various circumstances in which you need to add up a sub-panel. A few such circumstances are cited below:
1) Running out of space on main panel:
Houses are built in a way to meet current needs. Plans regarding installation of panels does not differ to planning regarding building house. So if your main panel runs of space for circuits you may want to install a sub-panel to create some space for the additional circuits needed.

2) Proximity:
Running wires all the way from the main panel to ■■■■ and corner of the home not only makes a mess of the house but also causes a drop in voltage. The best way to avoid these issues is installation of a sub-panel. Additionally it assists you create many circuits in your desired location if you add a sub-panel.

3) Tripping the breaker:
Typically circuits draw too much current against that desired for amperage rating of circuit breaker so the circuit breaker trips. While wiring aggravates the situation in such event, installation of sub-panel placate by providing you ease as you can easily access the target sub-panel and reset it there.

4) Cost-saving:
The set-up costs substantially decrease in installing a sub-panel. Additionally usage costs are also lesser in setting up a sub-panel as power wastage due in wire is more than that in the panel.

Caution:
Your safety is a primary concern!
It is always recommended to consult a professional when working with electricity because of inherent dangers and threats posed by accidents and minor mistakes.

Setting Up sub-panel:
For any of the above reasons or some other reason you are committed to setting up a sub-panel, the next important step is the calculation of load which the sub-panel will draw. You just need to add all the inputs that will connect to the circuits on the sub-panel. In case it is given to you in watts, divide it by voltage given on service boards to convert it into amps since the main panel and sub-panel are measured in amps. Make sure that the amperage of sub-panel exceeds the load of required for all circuits and appliances which will be connected to the sub-panel.

Size of the wire:
The length and width of the wire connecting the main panel to the sub-panel is the next main consideration when setting-up a sub-panel. It is advised to use a 4-wire cable consisting of a brace of hots, a neutral and a ground wire; the last of which is to minimize risks in the event of any mishaps as it provides a safe, low resistance passage when any fault occurs in the system.

The other main factor affecting the performance of the panel is the temperature ratings of the insulation system. Friction in the wire and resultant heat generated in the wire as more current flows pushes these systems to limits. Of the multiple temperatures listed on the equipment, use the lowest one for your safety.

The last consideration is thickness of the wire. Higher temperatures ratings require a high gauge wire to minimize resistance and consequent heat to support same capacity and vice-versa for lower temperature ratings.
When deciding on the length of the wire it is advisable to use next gauge, thicker wire to accommodate greater travelling distance and avoid voltage drops. The recommended distance for this increase is when the length of the cable exceeds 50 feet.

The surroundings of the wire:
The surrounding temperatures of conductors also affect them and their ampacity. For example if the conductor works in a surrounding temperature of 85F you will need a thicker wire to support the same amperage. Usually the environmental temperatures are not significant consideration in this matter but if the conductors are in proximity of other conductors emitting heat, you either need to create some distance between them or shift to lower gauge.

Consult an Electrician:
When working with electricity, safety of the human life is utmost consideration. Even minor mistakes can be fatal not only for the operator but also for others. It is highly recommended to consult professional for accomplishing the task safely and well.

Summing-up:

Various factors affect the installation of a sub-panel including but not limited to thickness, length, surrounding temperatures and required load. The average wire gauge for in ordinary circumstances is 3AWG, subject to alteration in changed circumstances.
Hence it is important to consult a professional when working on the panels.

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When it comes to the wiring of the house the work should be conducted on sheer safety rules. None of the amateurs are supposed to be handling the task because a slight mistake can cause short circuiting thus leading to fire. The choice of words is very important because if you choose a wire that is capable of carrying alller intensity of current for a bigger ampere then it will lead to overheating of the wire and burning the equipment or erupting fire. In any case thorough analysis of equipment required is necessary so to avoid any damage.

Sub panels

Sub panels are the secondary service panel which gives 100 amp of service. The system for most homes is that it takes the service from the municipality and it is directed to master panel which is further divided into one or two sub panels. For connecting the master panel with the secondary ones a 2-guage electrical cable with non-metallic sheathing should be used to carry full 100 amp. The cable should also have two hot wires, one for grounding and other neutral wire. The standard colour of the sheath is usually yellow while the wire should be of 2-guage size.

Wire length

Length of the wire also greatly defines the guage wiring to be used. Much of the current is lost due to the resistance in electrical wires. So if the wire is long it will have more resistance since it will need more power to reach the outlet. Therefore a suitable wire is of 2-guage if the length of the wire is to be kept up to 2 feet.

If there is a confusion between two guage sizes for a 100 amp line then be at the cautious side. If the guage sizes are too large then there is money to be spent and if the sizes are small then the performance of the circuits will not be good posing risk of fire. So its better to go for bigger guage.

Precautions required

Switch off the main power line before dealing with electrical panels. If required you can call the service provider to cut off the electricity from the main. Also involved a licensed electrician who will check the work afterwards when you are done with 100-amp lines.

Electrical work needs alot of care because it involves risk of electric shocks as well. So follow the precautions.

  • · Avoid the contact with water. Water conducts electricity immediately so just a slight but if contact will be enough to play havoc. So keep it dry all the time.
  • · Use sound equipment. Avoid broken plugs, damaged insulations or flawed cords.
  • · Turn off the main switch
  • · Wear gloves or use insulated tools while working.
  • · Use tester to check that the equipment is reenergized and then work with it
  • · If you have to work at poles then use a wooden ladder instead of steel or aluminum.
  • · You should know the codings of wire in your country.
  • · Know about the modern requirements like the Ground Fault Circuit Interuppter GFCI which is used to cut off power and used mostly in kitchens and bathrooms where it is damp area.
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Electrical Wire Sizing Calculation

Introduction

The proper sizing of an electrical (load bearing) cable is important to ensure that the cable can:

:black_small_square: Operate continuously under full load without being damaged
:black_small_square: Withstand the worst short circuits currents flowing through the cable
:black_small_square: Provide the load with a suitable voltage (and avoid excessive voltage drops)
:black_small_square: (optional) Ensure operation of protective devices during an earth fault

General Methodology

All cable sizing methods more or less follow the same basic six step process:

  1. Gathering data about the cable, its installation conditions, the load that it will carry, etc
  2. Determine the minimum cable size based on continuous current carrying capacity
  3. Determine the minimum cable size based on voltage drop considerations
  4. Determine the minimum cable size based on short circuit temperature rise
  5. Determine the minimum cable size based on earth fault loop impedance
  6. Select the cable based on the lowest of the sizes calculated in step 2, 3, 4 and 5

:writing_hand: Step 1: Data Gathering

The first step is to collate the relevant information that is required to perform the sizing calculation. Typically, you will need to obtain the following data:
Load Details

:writing_hand: The characteristics of the load that the cable will supply, which includes:

:black_small_square: Load type: motor or feeder
:black_small_square: Three phase, single phase or DC
:black_small_square: System / source voltage
:black_small_square: Full load current (A) - or calculate this if the load is defined in terms of power (kW)
:black_small_square: Full load power factor )

:black_small_square: Locked rotor or load starting current (A)
:black_small_square: Starting power factor ()
:black_small_square: Distance / length of cable run from source to load - this length should be as close as possible to the actual route of the cable and include enough contingency for vertical drops / rises and termination of the cable tails

:writing_hand: Cable Construction

The basic characteristics of the cable’s physical construction, which includes:

:black_small_square: Conductor material - normally copper or aluminium
:black_small_square: Conductor shape - e.g. circular or shaped
:black_small_square: Conductor type - e.g. stranded or solid
:black_small_square: Conductor surface coating - e.g. plain (no coating), tinned, silver or nickel
:black_small_square: Insulation type - e.g. PVC, XLPE, EPR
:black_small_square: Number of cores - single core or multicore (e.g. 2C, 3C or 4C)

Installation Conditions

:writing_hand: How the cable will be installed, which includes:

:black_small_square: Above ground or underground
:black_small_square: Installation / arrangement - e.g. for underground cables, is it directly buried or buried in conduit?
for above ground cables, is it installed on cable tray / ladder, against a wall, in air, etc.
:black_small_square: Ambient or soil temperature of the installation site
:black_small_square: Cable bunching, i.e. the number of cables that are bunched together
:black_small_square: Cable spacing, i.e. whether cables are installed touching or spaced
:black_small_square: Soil thermal resistivity (for underground cables)
:black_small_square: Depth of laying (for underground cables)
:black_small_square: For single core three -phase cables, are the cables installed in trefoil or laid flat?

Step 2: Cable Selection Based on Current Rating

Current flowing through a cable generates heat through the resistivity losses in the conductors, dielectric losses through the insulation and resistivity losses from current flowing through any cable screens / shields and armoring.

The cable components (particularly the insulation) must be capable of withstanding the temperature rise and heat emanating from the cable. The current carrying capacity of a cable is the maximum current that can flow continuously through a cable. It is sometimes also referred to as the continuous current rating or ampacity of a cable.
Cables with larger conductor cross -sectional areas (i.e. more copper or aluminium) have lower resistivity losses and are able to dissipate the heat better than smaller cables.
Therefore a 16 mm2 cable will have a higher current carrying capacity than a 4 mm2 cable.

Base Current Ratings

:writing_hand: International standards and manufacturers of cables will quote base current ratings of different types of cables in tables such as the one shown below. Each of these tables pertain to a specific type of cable construction (e.g. copper conductor, XLPE insulated, etc) and a base set of installation conditions (e.g. ambient temperature, installation method, etc). It is important to note that the current ratings are only valid for the quoted types of cables and base installation conditions.

Reference Installation Method
Reference installation method mentioned in above table is explained below:

Method A

:black_small_square: A1 - Insulated single core conductors in conduit in a thermally insulated wall
:black_small_square: A2 - Multicore cable in conduit in a thermally insulated wall

:writing_hand: This method also applies to single core or multicore cables installed directly in a thermally insulated wall (use methods A1 and A2 respectively), conductors installed in molding, architraves and window frames.

Method B

:black_small_square: B1 - Insulated single core con ductors in conduit on a wall

:black_small_square: B2 - Multicore cable in conduit on a wall

:writing_hand: This method applies when a conduit is installed inside a wall, against a wall or spaced less than 0.3 x D (overall diameter of the cable) from the wall. Method B also applies for cables installed in trunking / cable duct against a wall or suspended from a wall and cables installed in building cavities.

Method C

:black_small_square: C - Single core or multi -core cable on a wooden wall

:writing_hand:This method also applies to cables fixed directly to walls or ceilings, suspended from ceilings, installed on unperformed cable trays (run horizontally or vertically) and installed directly in a masonry wall (with thermal resistivity less than 2 K.m/W).

Method D

:black_small_square: D1 - Multicore or single core cables installed in conduit buried in the ground
:black_small_square: D2 - Multicore or single core cables buried directly in the ground

Method E
:black_small_square: E - Multicore cable in free -air
:writing_hand: This method applies to cables installed on cable ladder, perforated cable tray or cleats provided that the cable is spaced more than 0.3 x D (overall diameter of the cable) from the wall. Note that cables installed on unperformed cable trays are classifies d under Method C.

Method F

:black_small_square: F - Single core cables touching in free -air

This method applies to cables installed on cable ladder, perforated cable tray or cleats provided that the cable is spaced more than 0.3 x D (overall diameter of the cable) from the wall. Note that cables installed on unperformed cable trays are classified under Method C.

Method G

:writing_hand: When the ed inst lltinnditins differ from the Conditions, derating or correction) factors can e applied to the ase current ratings to obtain the actual installed current ratings.
International standards and cable manufacturers ill provide derating factors for a range of installation conditions, for example ambient /soil temperature, grouping or bunching of cables, soil thermal resistivity , etc. he installed current rating is calculated by multiplying the base current rating each of the derating factors, i.e.

here is the installed current rating A)

is the base current rating A)
are the product of all the berating factors or example, suppose a cable had an ambient temperature derating factor b = and a grouping debating factor of kg = . , then the overall derating factor d =
. x . = . . or a cable ith a base current rating of A, the installed current rating would be Ic = . x =
When si ing cables for loads, the upstream protective device fuse or circuit breaker) is typically selected to also protect the cable against damage from thermal overload. he

protective device must therefore be selected to exceed the full load current, but not exceed
the cable’s installed current rating, i.e. this inequality must be met:

Where is the full load current A)

is the protective device rating A)
is the installed cable current rating A)

A cable’s conductor can be seen as an impedance and as a result, he never current flows through a cable, there will be a voltage drop across it, derived by Ohm’s law i.e. V = IZ).
he voltage drop will depend on two things:

Current flow through the cable the higher the current flow, the higher the voltage drop

Impedance of the conductor the larger the impedance, the higher the voltage drop

Cl Impedance

The impedance of the cable is a function of the cable cross-sectional area) and the length of the cable. cable manufacturers will quote a cable’s resistance and reactance in /km.

Calculating Voltage p or AC systems, the method of calculating voltage drops based on load power factor is commonly used. ull load currents are normally used, but if the load has high startup currents e.g. motors), then voltage drops based on starting current and power factor if applicable) should also be calculated.

Where is the three phase voltage drop V)
is the nominal full load or starting current as applicable A)
is the ac resistance of the cable /km) is the ac reactance of the cable /km)
is the load power factor )
is the length of the cable m)

Where is the single phase voltage drop V)
is the nominal full load or starting current as applicable A)
is the ac resistance of the cable /km) is the ac reactance of the cable /km)
is the load power factor pu)
is the length of the cable m)

Where is the dc voltage drop V)

is the nominal full load or starting current as applicable A)
is the dc resistance of the cable /km) is the length of the cable m)

Maximum Permission Voltage Drop:
Maximum voltage drops across a cable are specified because load consumers e.g. appliances) will have an input voltage tolerance range. This means that if the voltage at the appliance is lower than its rated minimum voltage, then the appliance may not operate correctly.
In general, most electrical equipment will operate normally at a voltage as low as nominal voltage. or example, if the nominal voltage is VAC, then most appliances will run at VAC. Cables are typically for a more conservative maximum voltage drop, in the range of at full load.

Calculating Maximum Cable length due to Voltage drop
:writing_hand:It may be more convenient to calculate the maximum length of a cable for a particular
conductor si e given a maximum permissibly voltage drop e.g. of nominal voltage at full
load) rather than the voltage drop itself. or example, by doing this it is possible to construct tables showing the maximum lengths corresponding to different cable si es in order to speed up the selection of similar type cables.
The maximum cable length that will achieve this can be calculated by re-arranging the voltage drop equations and substituting the maximum permissible voltage drop e.g. of V nominal voltage = . V).

Where is the maximum length of the cable m)
is the maximum permissible three phase voltage drop V) is the nominal full load or starting current as applicable A)
is the ac resistance of the cable /km)
is the ac reactance of the cable /km) is the load power factor )

Where is the maximum length of the cable m)
is the maximum permissible single phase voltage drop V) is the nominal full load or starting current as applicable A) is the ac resistance of the cable /km)
is the ac reactance of the cable /km) is the load power factor )

Where is the maximum length of the cable m)
is the maximum permissible dc voltage drop V)
is the nominal full load or starting current as applicable A)
is the dc resistance of the cable /km) is the length of the cable m)

Step 4 Short circuit temperature

during a short circuit, a high amount of current can flow through a cable for a short time. This surge in current flow causes a temperature rise within the cable. high temperatures can trigger unwanted reactions in the cable insulation, sheath materials and other components, which can prematurely degrade the condition of the cable. As the cross-sectional area of the

cable increases, it can dissipate higher fault currents for a given temperature rise. Therefore,
cables should be si ed to withstand the largest short circuit that it is expected to see.

Minimum Cable Size use to Short Circuit Temperature
The minimum cable due to short circuit temperature rise is typically calculated with an equation of the form:

Where is the minimum cross-sectional area of the cable mm2)
is the prospective short circuit current A)
is the duration of the short circuit s)
is a short circuit temperature rise constant

The temperature rise constant is calculated based on the material properties of the conductor and the initial and final conductor temperatures. if international standards have different treatments of the temperature rise constant, but by way of example, IEC -5-54 calculates it as follows:

Initial and Final Conductor Temperatures

:writing_hand: The initial conductor temperature is typically chosen to be the operating temperature of the cable. The final conductor temperature is typically chosen to be the limiting temperature of the insulation.

Short Circuit Energy

:writing_hand: The short circuit energy is normally chosen as the maximum short circuit that the cable could potentially experience. we over for circuits with current limiting devices such as C fuses), then the short circuit energy chosen should be the maximum prospective le-through energy of the protective device, which can be found from manufacturer data.

Step 5: Earth Fault loop Impedance
:writing_hand: Sometimes it is desirable or necessary) to consider the earth fault loop impedance of a circuit in the cable. Suppose a bolted earth fault occurs between an active conductor and earth. during such an earth fault, it is desirable that the upstream protective device acts to interrupt the fault within a maximum disconnection time so as to protect against any inadvertent contact to exposed live parts.
Ideally the circuit will have earth fault protection, in which case the protection will be fast acting and well within the maximum disconnection time. The maximum disconnection time is chosen so that a dangerous touch voltage does not persist for long enough to cause injury or death. or most circuits, a maximum disconnection time of 5s is sufficient, though for portable equipment and socket outlets, a faster disconnection time is desirable i.e. < s and will definitely require earth fault protection).
we Over for circuits that do not have earth fault protection, the upstream protective device
i.e. fuse or circuit breaker) must trip within the maximum disconnection time. In order for the protective device to trip, the fault current due to a bolted short circuit must exceed the value that will cause the protective device to act within the maximum disconnection time. or example, suppose a circuit is protected by a fuse and the maximum disconnection time is 5s, then the fault current must exceed the fuse melting current at 5s which can be found by cross-referencing the fuse time-current curves).
By simple application of ohm’s law:

Where is the earth fault current required to trip the protective device within the minimum disconnection time A) is the phase to earth voltage at the protective device V) is the impedance of the earth fault loop ) It can be seen from the equation above that the impedance of the earth fault loop must be sufficiently low to ensure that the earth fault current can trip the upstream protection.

The Earth Fault loop

The earth fault loop can consist of various return paths other than the earth conductor, including the cable Armour and the static earthing connection of the facility. we over for practical reasons, the earth fault loop in this calculation consists only of the active conductor and the earth conductor.

The earth fault loop impedance can be found by:

Where is the earth fault loop impedance )
is the impedance of the active conductor ) is the impedance of the earth conductor )
Assuming that the active and earth conductors have identical lengths, the earth fault loop impedance can be calculated as follows:

Where is the length of the cable m)
and are the ac resistances of the active and earth conductors respectively /km) and are the reactance of the active and earth conductors respectively /km) Maximum Cable length
The maximum earth fault loop impedance can be found by re-arranging the equation above:

Where is the maximum earth fault loop impedance ) is the phase to earth voltage at the protective device V)
is the earth fault current required to trip the protective device within the minimum disconnection time A)
The maximum cable length can therefore be calculated by the following:
Where is the maximum cable length m) is the phase to earth voltage at the protective device V) is the earth fault current required to trip the protective device within the minimum disconnection time A) and are the ac resistances of the active and earth conductors respectively /km) and are the reactance of the active and earth conductors respectively /km)
that the voltage at the protective device is not necessarily the nominal phase to earth voltage, but usually a lower value as it can be downstream of the main bus bars. This voltage is commonly represented by applying some factor to the nominal voltage. A conservative value of = 0. can be used so that:

Where Vn is the nominal phase to earth voltage V)

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100 Amp wire Size:

For a 70 amp, the most secure wire size is a check 3. For 80 amp, the most secure wire size is measure 2. The dependable guideline for 100 amp is that you go with a wire size measure 1. 125 amp requires a wire size 2/0. For 150 amp, the correct wire size is 3/0. For 200 amp, you will need a wire size 250 kcmil. For 300 amp, the correct wire size is 500 kcmil. 400 amp administration requires a wire size of 1,000 kcmil. For 600 amp administration, we suggest a wire size of 1,750 kcmil

Wire Sizes for different amp amount:

On the off chance that you are uncertain of which kind of material you are managing, or you don’t have a clue about the correct temperature, we generally recommend deciding in favor alert, why the section to the correct shows you the least number in the various segments. It’s in every case better to pick a greater wire in the event that you are uncertain about any of the conditions that could impact the exhibition.
60 amp

As for 60 amp, you will truly need a 6 check wire size, and in case you’re more careful, a 4 measure. That is, obviously, expecting the correct conditions like temperature.
80 amp
In case you’re working with 80 amp power, you need a check 4 copper wire, though it would should be a size 2 on the off chance that you are going for aluminum all things being equal.
100 amp
For 100 amp, you are looking to either get a measure 1 wire size made of aluminum, while a check 3 can do it when made of copper.
125 amp
To play it safe, you will need to ensure you’re either utilizing a check 1 copper wire or a 2/0 aluminum wire for 125 amp of administration.
150 amp
For 150 amp, according to the graph underneath, you’re taking a gander at a 3/0 wire measure made of aluminum, though a 1/0 is the littlest size you can go with when taking a gander at copper.
200 amp
200 amp requires a wire size 250 made of aluminum or a 3/0 size when made of copper.

Gauge Wire:

The gauge wire is the size of the wire width, essentially. Its size decides how much electrical flow it can securely convey. In the event that you have at any point been to the electrical part of a home improvement shop, you will see wires come in a few sizes.
Rather than alluding to it utilizing its real thickness, individuals would allude to it utilizing its check size, 6 measure wire, 4 check wire, three measure size, two check wire, one check wire, 1/0 measure wire, 2/0 check wire, 3/0 check wire, and 750 measure wire.
The check size is conversely relative to the measurement, which implies the higher the size, the more modest the distance across. On the off chance that the size isn’t in the actual wire or is hazy, you can utilize a thickness check to decide it. Getting the correct measurement is significant in light of the fact that it decides the greatest current it can securely deal with. Utilizing a wrong wire could prompt significant issues over the long haul. So prior to choosing which measure size to purchase, first check how much electrical flow the wire will deal with by recognizing the gadgets you intend to utilize.
The United States, alongside 65 different nations, utilize the American wire check as the unit of measure. Different nations utilize the Imperial Standard Wire Gauge, which was characterized by the British Board of Trade.
Right size of wire:
A wire typically consumes in the event that you utilize the mistaken size. It is prudent to realize the right wire size to keep this from occurring. Interestingly, a great many people don’t know that size has an effect. Individuals frequently make the actual associations without speaking with or calling an authorized circuit tester. It could prompt major issues when done inaccurately. At the point when the arrangement includes the electrical switch, you should play it safe. Introducing the correct parts will extraordinarily keep regular issues from occurring. Much of the time, issues emerge as a result of an inaccurate wire measure. The measure and breaker should be viable with one another. In the event that you have a 60 amp electrical switch for your water warmer, garments dryer, or forced air system that you have no clue about which wire measure size you need, read through the following segment as we control you in understanding the rudiments.
What happened when you choose wrong wire size:
It is a typical confusion for individuals to believe that as long as the closures of the wire fit a connector, there will be no issues. It isn’t the situation for circuit breakers. Individuals who are unconscious of their significance frequently utilize too little measure wires to associate their circuit breakers. More modest wire checks are less expensive than the greater ones, which is the reason individuals who are uninformed frequently go for the less expensive one, thinking it won’t have any effect. Unfortunately, it is simply going to set them back additional over the long haul.Utilizing a bigger wire for your electrical switch is regularly the most ideal approach. The solitary adverse consequence this has is on your spending plan, which will set you back more forthright. When picking a bigger one, you wind up spending more than what you may require. Nonetheless, it won’t make any harm your electrical switch. All things being equal, it can more readily deal with the electrical flow moving through it.

Effects of choosing wrong wire size:
It can light a fire
A consuming wire that prompts lighting a fire is the most pessimistic scenario. Albeit present day circuit breakers have their security measures, it may not be sufficient if the heap is excessively. For instance, a typical security measure for present day circuit breakers is the outing component. At the point when the electrical switch encounters an over-burden, it will outing to carve the flow from going through, keeping any harm from occurring. Notwithstanding, having an excursion instrument doesn’t keep a fire from occurring.

Wires that have softened
A little wire can deal with less current, which makes them more impervious to the progression of energy. Notwithstanding, if the wire measure is route more modest for your electrical switch, the flow coursing through the wire is beyond what it can deal with. Because of high opposition, heat produces and will in the long run lead to the wire softening.

Harm to the hardware :

Beside ■■■■■■■■■ drop issues and the chance of lighting a fire, utilizing a more modest wire check may harm your gear over the long haul. At the point when the stockpile of force isn’t steady, it might bust your hardware.

A drop in ■■■■■■■■■

On the off chance that you associated machines to an electrical switch utilizing a check wire that is excessively little, accomplishing top proficiency might be outlandish. The apparatuses can just get a piece of the energy it needs to work at top ■■■■■■■■■. Basically, your apparatuses will be probably not going to accomplish their ideal exhibition.
FAQS:
Can a size 8 or 10 gauge wire handle 60amp?
Suppose you have a 8-check wire and a 10-measure wire lying around at home, and you need to know whether you can utilize these with a 60 amps electrical switch. How about we take each measure wire each in turn. For the 8-check wire, it can’t deal with a 60 amp electrical switch. For the 10-measure wire, it can’t deal with a 60 amp electrical switch too.
What size I need for 100 amp ?
The size wire viable with a 100 amps electrical switch relies upon the wire’s material and the surrounding temperature. For a 100 amps electrical switch, you can utilize a 3-check copper wire at a surrounding temperature of 167°F, a 2-measure aluminum wire at an encompassing temperature of 194°F, or a 1-check aluminum wire at a surrounding temperature of 167°F.
Can you run a 100 amp sub panel off a 100amp main panel?
To the best of my arrangement, there is no code issue running a 100A subpanel off a 100A primary board, insofar as the wire size is right, and the establishment is right. For a subpanel, you need four wire administration (two hots, an impartial, and a gear ground).
Can you put 50amp breaker in 100amp panel?
As the board is evaluated at 100 amps the 50 amp breaker can be utilized for any circuit in the board.On the off chance that you need more amperage you should add a circuit. I unequivocally deter property holders from introducing anything like this. Assuming you have gear you need to supply with 50 amps, you should contact a circuit tester.
Conclusion:
Above mentioned is the detail information about choosing the correct wire size,if you don’t choose correct wire size it may have many sideffects.So carefully read the information given above and choose the correct wire size for your any purpose.

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How to Select a Electrical Wire or Cable

When selecting a cable for your specific application, a number of variables require attention. These are

(a) Wire Size and type of load to be supplied
(b) Permissible voltage drop
(c) Prospective fault current
(d) Circuit protection
(e) Environmental conditions of installation

strong text Load to be supplied

In order to select the appropriate cable, it is necessary to know the voltage
and the load current in amps. This information will be available either
directly in amps or as kW or kVA.

The following formulae apply:

I_FL = (KW ×1000)/(√3×V ×cos∅) Amps if we know KW, voltage, as well as power factor

I_FL = (KVA ×1000)/(√3×V) Amps if we know the KVA rating as well as the voltage

Use this value of current to determine the Electrical Wire or cable size by reference to the Relevant tables given in Section 4 (Paper insulated), Section 5 (XLPE insulated Medium voltage) or Section 6 (PVC and XLPE insulated low voltage) For Copper or Aluminum conductors.
A slightly larger conductor size may be chosen for safety aspects, and to provide for the higher than usual current which may be experienced during starting of electric motors.

Example of Cable selection for low Voltage:

Suppose it is required to supply a 3 phase, 400 volt, 100kW motor connected
in star/delta, over a distance of 50m buried direct in ground. The
motor load is known to have a power factor of 0,9 lagging. The full load line
current, IFL can be calculated as follows:

I_FL = (100×1000)/(√3×400 ×0.9) = 161 Amps

We now refer to table 6.2 on pg 38 and note that the smallest copper conductor, PVC insulated cable , that can supply a current of 161 amps in the ground, is a 50 mm² rated area cable. This cable can carry 169 amps continuously if installed under standard conditions.

Permissible Voltage Drop

Calculate the highest current drawn by the load, by multiplying the current as calculated in 1.1 by an appropriate factor. If a Star/Delta motor starter is used on a motor, this factor is 3. If the motor is started direct on line, then use a factor of 6. Where the load is resistive heating, lighting or a transformer, it is not necessary to increase the current as calculated in 1.1.

Calculate the volt drop which will be experienced at the load terminals by reference to table 6.2 or 6.3 on pg 38 or pg 39. The maximum volt drop allowed by SANS 10142-1 during full load running condition. There is no hard and fast rule as to the allowable volt drop under starting conditions. Depending on the type of load to be started, there is the possibility that the torque may be compromised during starting, if the motor is subjected to difficult starting conditions. A reasonable volt drop should be chosen in these cases

The volt drop may be calculated in two different ways:

(a) Multiplying the current by the impedance of the length of cable. Calculate the percentage volt drop by reference to the phase to earth voltage.
(b) Multiply the current by the length of cable, and then multiply the result by the volt drop per amp per metre figure as given in table 6.2 or 6.3 on page 38 or page 39, depending on the type of conductor.

Starting Current = 3 x Running Current
= 3 x 161Amps
= 483Amps

Impedance of 50m of 50mm² Cable (Table 6.2) pg 38

= 0.4718/1000×50

= 0,02359 ohms

Volt Drop = 483 x 0,02359

		= 11.394/230×100/1

= 4,95% (Acceptable)

Using Method (b)

Starting Current = 3 x 161Amps
= 483Amps
Volt Drop per amp per metre = 0,817 mV/A/m (Table 6.2) pg 38
Volt Drop = 0,817 x 10 x 483 x 50
= 19,73 volts

Percentage Volt Drop = 19.73/400×100/1

= 4,93% (Acceptable)

Not:- It often happens on long runs of electric cable that a larger conductor than that calculated in 1.1 is required for volt drop reasons.

Example of Cable section for medium Voltage (11KV)

We wish to supply a 2MVA 11kV transformer from an Eskom supply point which is 3km away. We are to use an underground paper insulated, copper conductor cable. The depth of burial of the cable is 1,25m. Ground thermal resistivity is 2K.m/W. The ground temperature is 25°C and there are no other cables in the trench. Short circuit level may be assumed to be 250MVA, and the earth fault level 100 MVA, and it may be assumed that a fault will be cleared in half a second.

I_FL = 2000000/(√3×11000)

   = 105 Amps before derating for non standard conditions

Derating factor for Depth of Burial at 1,25mis 0,96.
Derating factor for Soil Thermal Resistivity at 2 K.m/W is 0,84.
Derating factor for Ground Temperature of 25°C is 1,00.

Total Derating = 0,96 x 0,84 x 1,00
= 0,8064

= 105/(0.8064)

= 130Amps

Table 4.2 on pg 28 shows that a 35 mm² Copper conductor cable would be capable of carrying this load (130A). This is confirmed by reference to the Paper Insulated Cable brochure (Page 13).

The cable size required is thus 35 mm² Copper conductor, 3 Core General purpose belted cable. (Table 17 SANS 97).