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Comment No. 1 Is it ok to place a neutral and ground wire under the same lug in a panel or sub-panel?
Mike's Answer: No, see 408.20.
Comment No. 2 I don't understand the reasoning for not allowing multiple neutral conductors on the same lug in a panel. The neutrals are all linked to one bar so what difference does it make. Please enlighten me about this.
The following is extracted from my textbook, Understanding the National Electrical
Author's Comment: If two grounded (neutral) conductors were connected to the same terminal, and someone removed one of them, the other might unintentionally be removed as well. If that happens to the grounded (neutral) conductor of a multiwire circuit, it could result in excessive line-to-neutral voltage for one of the circuits. See 300.13(B) for details. Figure 408-16
300.13 Splices and Pigtails
Author's Comment: The opening of the ungrounded (hot) conductors, or the grounded (neutral) conductor of a 2-wire circuit, during the replacement of a device doesn't cause a safety hazard, so pigtailing of these conductors isn't required [110.14(B)].
CAUTION: If the continuity of the grounded (neutral) conductor of a multiwire circuit is interrupted (open), the resultant over- or undervoltage could cause a fire and/or destruction to electrical equipment.
Example: A 3-wire, 120/240V circuit supplies a 1,200W, 120V hair dryer and a 600W, 120V television. If the grounded (neutral) conductor of the multiwire circuit is interrupted, it will cause the 120V television to operate at 160V and consume 1,067W of power (instead of 600W) for only a few seconds before it burns up. Figure 300-32
Step 1. Determine the resistance
of each appliance, R = E2/P.
R of the Television = 120V2/600W
Step 2. Determine the current
of the circuit, I = E/R.
Step 3. Determine the operating
voltage for each appliance, E = I x R.
Voltage of Television = 6.7A x 24 ohms
WARNING: Failure to terminate the ungrounded (hot) conductors to separate phases could cause the grounded (neutral) conductor to become overloaded, and the insulation could be damaged or destroyed by excessive heat. Conductor overheating is known to decrease insulating material service life, which creates the potential for arcing faults in hidden locations and could ultimately lead to fires. It isn't known just how long conductor insulation will last, but heat does decrease its life span. Figure 300-33
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