why use a 3 wire system instead of a 2 wire system when wiring an electric heater with metal casing
So the metal casing can be "grounded" andnot aquire the potential lethal voltage if a 110 V wire inside becomes loose, wet or loses its insulation. If this happens, you could get a lethal shock just by touching the casing.
When wiring an electric heater with a metal casing, it is important to use a 3-wire system instead of a 2-wire system for safety reasons. The purpose of the additional wire in a 3-wire system is to provide a grounding path.
If a fault occurs, such as a loose, wet, or damaged wire, it is possible for the metal casing of the heater to become energized with the same voltage as the wires inside. Without a grounding path, touching the metal casing could result in a potentially lethal electric shock.
To understand why a 3-wire system is necessary for grounding, it is important to have a basic understanding of electrical circuits and grounding.
In any electrical circuit, there are three essential components: the power source, the load (in this case, the electric heater), and the conductors (wires) that connect them. Typically, the power source supplies voltage, and the load converts that voltage into the desired form of energy (heat in the case of an electric heater).
In a 2-wire system, there are only two conductors: the hot wire, which carries the voltage from the power source to the load, and the neutral wire, which completes the circuit by carrying the current back to the power source. However, there is no dedicated grounding wire.
In contrast, a 3-wire system includes an additional wire called the grounding wire. This wire is connected to the metal casing of the heater and is connected to the earth, creating a grounding path. The grounding wire provides a low-resistance path for the current to flow in case of a fault, such as a short circuit or a wire coming loose.
When a fault occurs in a 3-wire system, the grounding wire offers a direct path for the excess current to flow to the earth, bypassing the metal casing and avoiding potential hazards. This process is commonly known as "grounding" or "earthing" and helps protect against electric shock.
Therefore, when wiring an electric heater with a metal casing, a 3-wire system is necessary to ensure that the casing can be effectively grounded, reducing the risks associated with potential electrical faults.