# Page History

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In every circuit there will be resistor(s) and generator(s), their number will the depend of the power requisites. Both components can be grouped depending on the what is required to keep constant, the current or the voltage. There are two basic ways to groups components in series or in parallel. (additional information in Connecting Batteries section)

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#### Series

The basic idea of a “series” connection is that components are connected end-to-end in a line to form a single path through which current can flow:

1. Current: The amount of current is the same through any component in a series circuit.
2. Resistance: The total resistance of any series circuit is equal to the sum of the individual resistances.
3. Voltage: The supply voltage in a series circuit is equal to the sum of the individual voltage drops.

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#### Parallel

The basic idea of a “parallel” connection, on the other hand, is that all components are connected across each other’s leads. In a purely parallel circuit, there are never more than two sets of electrically common points, no matter how many components are connected. There are many paths for current flow, but only one voltage across all components:

1. Voltage: Voltage is equal across all components in a parallel circuit.
2. Current: The total circuit current is equal to the sum of the individual branch currents.
3. Resistance: Individual resistances diminish to equal a smaller total resistance rather than add to make the total.

## Cables Sizing and Wiring

What ties all the components together in an electrical system are the cables. Cables supply the power to run appliances, and from the power sources for distribution. Unfortunately, the most common installation error is to under-size cables to the load/s or from the recharge sources.

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To better plan and size cables, please reference the cable sizing table below:

Cable sizing table is used by running across the top row until the column with the relevant amperage is found, and then moving down the left-hand column until the row with the relevant distance is reached. The color coding in the body of the table at the intersection of this row and column is the wire size. Compare this with the Cable Conversion Table to see what size cable to use.

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Also listed is a conversion chart from AWG/B&S to mm². This table gives the closest equivalent size cross references between metric and American wire sizes. In Europe and Australia, wire sizes are expressed in cross sectional area in mm².

Color Coding

While is possible to use the same cables, (as far the diameter will be the appropriate one) for AC and DC circuits, it is advisable to use different colored cables between the two types of currents, both to increase handling safety but also to make installation and repair work much faster. In existing appliances or installations have colors, logistics managers may consider replacing or standardizing them by re-color coding the wires with an external paint or marking in a method that makes sense.

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All of the aforementioned devices protect users and equipment from fault conditions in an electrical circuit by isolating the electrical supply. Fuses and MCBs only isolate the live feed; with RCDs and RCBOs isolate both the live and neutral feeds. It is essential that the appropriate circuit protection is installed ensure an electrical installation is safe.

#### Fuses

A fuse is a very basic protection device used to protect the circuit from overcurrent. It consists of a metal strip that liquefies when the flow of current through it surpasses a pre-defined limit. Fuses are essential electrical devices, and there are different types of fuses available in the market today based on specific voltage and current ratings, application, response time, and breaking capacity.

The characteristics of fuses like time and current are selected to give sufficient protection without unnecessary disruption.

#### Miniature Circuit Breaker (MCB)

An MCB is a modern alternative to fuses, and are maybe centrally located in buildings – usually called a “fuse box” or “braker box”, or attached to specific equipment. They are just like switches, turning off when an overload is detected in the circuit. The basic function of a circuit breaker is to stop the flow of current once a fault has occurred. The advantage of MCBs over fuses is that if they trip, they can be reset without having to replace the whole MCB. MCBs can also be calibrated more precisely than fuses, tripping at exact loads. Circuit breakers are available in different sizes from small devices to large switch gears which are used to protect low current circuits as well as high voltage circuits.

#### Residual Current Device (RCD)

Residual Current Devices (or RCDs) are designed to detect and disconnect supply in the event of a small current imbalance between the Live and Neutral wires at a pre-defined value - typically 30mA. RCDs can detect when a live conductor touches an earthed equipment case, or when a live conductor is cut through; this type of fault is potentially dangerous and can result in electric shocks and fires.

An RCD does not give safety against short circuit or overload in the circuit. It cannot detect – for example - a human being accidentally touching both conductors at the same time. An RCD cannot replace a fuse in function.

RCDs can be wired to protect a single or a number of circuits - the advantage of protecting individual circuits is that if one circuit trips, it will not shut down the whole building or distribution system, just the protected circuit.

#### Residual Current Breaker with Overcurrent (RCBO)

An RCBO combines the functions of a MCB and an RCD in one unit. CRBOs are a safety device which detects a problem in the power supply and is capable of shutting off in 10-15 milliseconds.

They are used to protect a particular circuit, instead of having a single RCD for the whole building

These devices are testable as well as resettable apparatus. A test button securely forms a tiny leakage condition; along with a reset button again connects the conductors after an error state has been cleared.

## Grounding/Earthing

Uncontrolled electricity can injure or even kill humans or animals. One common and effective way to control electricity is through grounding. Grounding is a physical connection to the earth that draws electric charge safely to the ground allowing a large space for electrons to dissipate away from humans or equipment. A grounding system is gives excess positive charge in electrical lines an attractive place to go – the negatively charged ground wire – eliminating the dangers of fire and electrocution.

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