Sizing the neutral: Sec. 220-22. You must size the neutral conductor to carry the maximum unbalanced current in the circuit (i.e. the largest load between the neutral and any one ungrounded phase conductor). You calculate the first 200A of neutral current at 100%.
The “neutral” wire should ALWAYS be the same size as the “hot” wire. That said, that isn’t alway true either, as there is the case of a 220/120 vac appliance, such as an electric stove/oven. The cord on those will have a smaller neutral.
Furthermore, what size neutral is required for a 200 amp service? It really depends on the electrical codes in your area. 200 A services are usually #3/0 copper. Sometime you can use a reduced neutral, sometime codes prohibit it.
Also know, can you downsize a neutral wire?
It is possible to downsize a feeder or service neutral according to the calculations in the National Electrical Code here: 220.61 Feeder or Service Neutral Load. (A) Basic Calculation. The maximum unbalanced load shall be the maximum net calculated load between the neutral conductor and any one ungrounded conductor.
How do I calculate wire size?
Divide the voltage running through the cable by your target current. If, for instance, 120 volts will act on the cable, and you want 30 amps to run through it: 120 / 30 = 4. This is your target resistance, measured in ohms. Multiply the cable’s length by its material’s resistivity.
Does current flow through the neutral wire?
Normal circuit currents flow only in the neutral, and the protective earth conductor bonds all equipment cases to earth to intercept any leakage current due to insulation failure. The neutral conductor is connected to earth ground at the point of supply, and equipment cases are connected to the neutral.
Why is there no neutral wire in 3 phase?
A neutral wire allows the three phase system to use a higher voltage while still supporting lower voltage single phase appliances. In high voltage distribution situations it is common not to have a neutral wire as the loads can simply be connected between phases (phase-phase connection).
Why is neutral wire thinner?
The returns for all three phases are combined together to form the neutral wire. So result is that the net current in the neutral is usually smaller than the currents in the live wires. If the current is smaller then the resistance can be increased by using thinner wires without too much of a loss of energy.
Why is the neutral wire needed?
The reason that one of the power wires is named “neutral” is because it is connected directly to the building ground connection at the circuit breaker panel. The grounding of the neutral wire is not related to the operation of electrical equipment but is required for reasons of safety.
What is the difference between ground and neutral?
Ground refers to the physical ground or earth. Neutral refers to the star point of a STAR connected load. This does not apply to DELTA connected loads. Kirchhoff’s current law says that in any three phase STAR connected system any imbalance in current or voltage is carried by/in the neutral.
What is the difference between phase wire and neutral wire?
Phase and neutral are both conductors. The load circuit receives (so to speak) power from the phase conductor, and returns (so to speak) power back to the neutral conductor. The only difference between phase and neutral is that neutral is grounded at the distribution panel.
Why does 240v not need a neutral?
The grounded (neutral) conductor is connected to the center of the coil (center tap), which is why it provides half the voltage. Therefore, if a device requires only 240V, only two ungrounded (hot) conductors are required to supply the device.
Why are neutral and ground tied together?
The reason that one of the power wires is named “neutral” is because it is connected directly to the building ground connection at the circuit breaker panel. Therefore it is connected directly to the grounding (third) wire.
How do you determine neutral current?
To calculate the neutral current flowing in a three phase star connected system (Sinusoidal load)… If the three phase currents are equal to one another, then the neutral current is zero. If one of the phase currents is different (higher or lower) than the others, then the neutral current is equal to the difference.
What is an unbalanced neutral?
ANS) Neutral wire is a return path for unbalance current. Electrically neutral is zero potential with respect to live potential. It provides a low impedance path for the fault current to flow to the ground, instead of our body and thus saving us from dangers of electrocution.
How many amps does a neutral carry?
That way, the amperage of the two circuits cancel each other out when the power returns to the utility on the neutral. In this case, the current on the neutral would be 1 amp: 8 – 7 = 1. If both appliances pulled 8 amps, the current on the neutral would be 0.
What is neutral load?
Load (usually black, sometimes red): is a continuation of line and goes out to downstream devices. Non-GFCI circuits will not have a load. Neutral (usually white): completes the AC circuit and carries excess current to ground. Ground (bare): carries any inadvertent current away from the circuit in case of a fault.
What size wire do I need for a 200 amp service?
So, for a 200-amp service, you would still be allowed to choose a 4/0 AWG aluminum or 2/0 AWG copper, but you would choose it from the 75 degree C column in Table 310.15(B)(16).
What size ground wire do I need for a 200 amp service?
The minimum size equipment grounding conductor for this 200-ampere feeder is a 4 AWG copper conductor. The answer is based on NEC-2008, Sections 250.122, Table 250.122, and Chapter 9, Table 8 (conductor properties).