generally, 1 sqmm copper wire carries 10-15a we take as 10a 1.5 ton ac 1600w/230v= 7amps then why 4 sqmm wire recommed.
But electirclian use 2.5A for copper and 1.5A for alumunium which 60% lower than copper wire.
AC’s current draw is correct for its rated power, there are several crucial factors that necessitate a larger wire size (like 4 sqmm) for a 1.5-ton AC, even if a simple calculation suggests 7 amps could be handled by a smaller wire.
Here’s why 4 sqmm wire is typically recommended for a 1.5-ton AC:
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Starting Current (Inrush Current): This is the most significant factor. When an AC compressor starts, it draws a much higher current for a brief period (milliseconds to a few seconds) than its continuous running current. This “inrush current” can be 5 to 7 times the running current. For a 7A running current, the starting current could easily be 35A or more. A 1 sqmm wire, rated for 10-15A, would experience a significant voltage drop and could even be damaged by this surge.
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Voltage Drop: Longer wire runs, even with appropriate sizing for continuous current, can experience significant voltage drop. A 1.5-ton AC needs a stable voltage to operate efficiently. Excessive voltage drop can lead to:
- Reduced efficiency of the AC unit.
- Overheating of the AC’s motor.
- Premature failure of the AC unit.
- Overheating of the wire itself. Even if the current is only 7A, a smaller wire might not maintain the required voltage over the distance.
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Future Load/Safety Margin:
- Appliances aren’t always run at their exact rated power: Factors like ambient temperature and system efficiency can cause slight variations.
- Future Upgrades: While not directly applicable to a fixed AC, in general wiring, it’s good practice to allow for some future expansion.
- Safety Factor: Electrical codes and recommendations always build in a safety factor to prevent overheating, fire hazards, and equipment damage. This accounts for unforeseen circumstances, environmental factors, and variations in manufacturing.
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Heat Dissipation and Ambient Temperature: Wires generate heat when current flows through them. The ability of a wire to dissipate this heat depends on its cross-sectional area, insulation type, and the surrounding ambient temperature. In warmer climates or enclosed spaces, a larger wire is needed to prevent excessive temperature rise.
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Circuit Breaker Sizing: The wire size must be appropriate for the circuit breaker protecting the circuit. If you have a 15A or 20A breaker (common for AC units), the wire must be able to safely carry that current continuously without overheating, even if the AC’s running current is lower. If you use a 1 sqmm wire on a 20A breaker, and there’s a fault drawing 20A, the wire could overheat before the breaker trips.
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Insulation Type and Installation Method: Different types of insulation have different temperature ratings. The way the wire is installed (e.g., in conduit, open air, bundled with other wires) also affects its current-carrying capacity (ampacity). Electrical codes provide tables that factor in these conditions.
In summary, while calculation for continuous running current is a good starting point, the recommendation for 4 sqmm wire for a 1.5-ton AC takes into account the crucial factors of starting current, voltage drop, safety margins, heat dissipation, and compliance with electrical codes, all of which are essential for safe and efficient operation.
Always consult with a qualified electrician and refer to local electrical codes (like the National Electrical Code in many countries, or IS 732 in India) for specific recommendations and requirements for your region.
1.5 AC rated 1600w Starting current vs running
inrush current, Typically, the starting current can be 2-6 times the running current. For a 1.5-ton AC, this could mean a starting current of 30-40 amps or even higher, compared to a running current of around 6-8 amps
