Calculation of wire section for devices and installations
In this topic, we explain the calculation of the air conditioning capacity in horsepower for electrical loads, and we also explain the calculation of the electric wire section for the risers of the installations, and the circuit breakers for the relevant switches.
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Calculation of wire section for electrical loads:
- The value of the wire section depends on the value of the load current, and several important things are taken into account for the type of wire:
- The quality of the metal from which the wire is made (aluminum - copper), because the electrical resistance of aluminum is higher than that of copper.
- The type of material the wire is insulated to withstand the temperature that the wire's insulator can bear. Learn more
* Before knowing the calculation of the wire section, you must know some necessary electrical terms:
Voltage: - It is known as volts and is symbolized by the symbol (V).
Current: The current is known as ampere and is symbolized by the symbol (A); It is deduced from the actual consumption of electric current
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Calculation of air conditioning power in horsepower for electrical loads:
Horse power = 746 HP
Example 1:
Formula for calculating power in watts (W), for an air conditioner with a capacity of 3 HP
3 HP ✖ 746 HP = 2238 W
* Calculation of the current intensity of the loads (amps):
Current (amps) = capacity ➗ voltage ✖ power factor (mentioned in the air conditioner) → "attached with air conditioning data from the factory source"
2238 ➗ 220 ✖ 0.80 = 13 amps
So, an air conditioner with a capacity of 3 horsepower = the value of the current (ampere) is 13 amps
* To calculate the safe wire section of the 3 HP air conditioner as follows:
The mathematical equation is relevant for a wire section
Wire cross section = current (amps) ➗ current density (3)
So, the calculation of the wire section for a 3-horsepower air conditioner:
13 A ➗ 3 (current density) “constant rated value” = 4 ms (wire cross-sectional value).
Calculate the cross section of electrical wires
Example
Calculation of the cross-section of the wire to feed a three-storey house for electric current
Calculate the section of power wires
To calculate the wire clip for a 3-storey house with 2 apartments per floor:
First: - The electrical capacity (watts w) must be calculated, and to calculate the capacity, it is necessary to know the type of electrical loads for each apartment, with the following example:
- Each apartment consists of (3 air conditioners 3 HP - microwave - washing machine - refrigerator - heater - and some other automation devices)
We estimate the capacity of 3 air conditioners in horsepower and it is estimated at 746 HP
3 HP ✖ 746 = 2238 HP
2238 ✖ 3 air conditioners = 6718 capacity of 3 air conditioners per apartment
We'll estimate the rest of the apartment loads to be 5,000 watts
The total load capacity of one apartment = 6718 + 5000 = 11718 kilowatts per apartment
The total loads of the entire property consisting of 3 floors, each floor 2 apartments = 11718 ✖ 6 apartments = 70308 watts / hour
So, it is estimated that the load of each individual apartment is approximately 70 kilowatt-hours
* Calculation of the current intensity (ampere) for the property, 3 floors per floor, 2 apartments:
Equivalent current intensity (amps)
Current = power ➗ volts ✖ power factor
Power = 70308 W Volts = 220 Power Factor = 0.9 (fixed)
220 ✖ 0.9 = 198
Current intensity (amps) = 70308 ➗ 198 = 355 amps
So, the total current intensity (amps) for a 3-storey property, each floor 2 apartments, is estimated at 355 amps. Ask us
Calculation of the wire section to feed the same property consisting of 3 floors on each floor 2 apartments:
The equation for calculating the wire section for feeding = total current intensity (amps) ➗ current density
Note: - The current density is estimated at (3) or (4) per (1) ms
In other words, the current density is estimated at 3, if the estimated distance from the public feed to enter the house is a long distance, and if the distance does not exceed 10 meters, the current density is estimated at (4).
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So the estimated wire section to feed a 3-storey property for each floor 2 apartments is as follows:
355 A ➗ 3 (remote current density) = 118
So the rated wire section of the previous property is 120mm
Advice: It is not correct to reduce the section of the neutral wire from the (hot) wire of the phase to feed the real estate risers, meaning the two ends of the wire are one section for the neutral and the phase.
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