Why Does Neutral & Ground Short Together in AC Circuits?

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SUMMARY

The discussion addresses the critical issue of why neutral and ground wires are shorted together in AC circuits, particularly in older installations. It emphasizes that current standards dictate that neutral and ground should only be connected at the main service entrance, while subpanels must maintain separation. The conversation references the IEC 60364 standards, which outline three grounding systems: TN, TT, and IT, each designed to protect against insulation faults. For further insights, participants are encouraged to explore resources like Electrical Riddles.

PREREQUISITES
  • Understanding of AC circuit design and installation standards
  • Familiarity with grounding and bonding principles in electrical systems
  • Knowledge of IEC 60364 grounding system classifications
  • Experience with electrical panel configurations and subpanel installations
NEXT STEPS
  • Research the differences between TN, TT, and IT grounding systems
  • Study the National Electrical Code (NEC) regulations regarding grounding and bonding
  • Learn about the implications of improper neutral-ground connections in electrical safety
  • Explore resources on electrical installation best practices and troubleshooting
USEFUL FOR

Electricians, electrical engineers, safety inspectors, and anyone involved in the installation or maintenance of AC electrical systems will benefit from this discussion.

monus76
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hi there
need help

i just need to know why ground and neutral ( A.C CIRCUITS) short together on the body of machine chassis or panels.i found this in one oil heating unit ,with high wattage of heating element.

who ever can reply ,highly appreciated

with thanks
 
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It depends on when the installation was done. New installations should never have the neutral and ground hooked together except in the main service entrance. Any subpanel, disconnect for a furnace, air conditioner, etc. must keep the neutral and ground separated. In the past, the neutral and ground were allowed to be shared or connected in subpanels. Search physics forums for this sort of thing. It's been discussed before.
 
In low voltage systems, the three main grounding system are used as defined in IEC 60364:

- Exposed-conductive parts connected to neutral -TN-
- Earthed neutral -TT-
- Unearthed (or impedance-earthed) neutral -IT-

The purpose of these three systems is identical as regards protection of persons and property mastery of insulation fault effects. For choosing the best grounding system, it is important to know our requirements and resources.

For more information you can refer to Grounding riddle No.21 in http://electrical-riddles.com
 
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