Proper grounding of a residential electrical system is a critical safety requirement that ensures electricity flows safely and properly throughout a home. Grounding protects from electrical shocks, overloads, and fire hazards by providing a path of least resistance for stray electrical energy. Homeowners should have a solid understanding of the key grounding requirements for residential services to ensure their electrical systems are code-compliant and reduce risks.

Overview of Grounding in Electrical Systems

Grounding refers to connecting specific parts of an electrical installation to the earth via low resistance paths. This provides protection in several key ways:

• Fault current path – If a short circuit or other issue occurs, the excess current travels safely into the earth instead of remaining in the wiring system. This protects wiring from overheating and reduces fire risks.
• Equipment grounding – Connecting exposed metal parts to ground prevents shocks if a person contacts the part while a wire is energized. The current flows harmlessly to the earth.
• Overvoltage protection – Lightning strikes or power surges often overload a system with excess energy. Grounding dissipates this safely without damaging connected equipment like appliances.
• Noise reduction – Electrical noise interference from appliances and devices gets directed into the earth as well. This minimizes disruptions to sensitive electronics like audio systems.

Residential services are required to have specific grounding and bonding connections for optimal safety per the National Electrical Code (NEC). This ensures stray currents have an intentional, low-resistance path to earth to operate overcurrent devices and prevent hazards.

Key Grounding Requirements for Home Electrical Services

Grounding a residential service involves both the system grounding electrode and equipment grounding conductors. The main requirements mandated by the NEC include:

System Grounding Electrode

The grounding electrode connects specific parts of the electrical system to the earth itself. Key requirements for the electrode are:

• Rod electrodes – At least two ground rods driven at least 8ft into the earth and spaced 6-8ft apart. Rods must be at least 5/8″ diameter.
• Supplemental electrodes – A metal underground water pipe within 5ft of grade level must also be bonded to the grounding electrode system, if present.
• Concrete encased electrode – When present, a concrete encased electrode consisting of at least 20ft of either steel reinforcing bars or bare copper conductor must also be used.
• Resistance – Total resistance to ground measured at the main panel cannot exceed 25 ohms. Additional ground rods may be necessary.
• Main bonding jumper – The grounded neutral circuit conductor and equipment grounding conductors must be bonded together at the main panel.
• Size – Grounding electrode conductor wire must be sized adequately, usually #4 or #6 AWG copper minimum.

Equipment Grounding Conductor

The equipment grounding conductor provides the critical connection between exposed metal appliance parts and the grounding system. Key requirements are:

• Continuity – The path to ground must be permanent, continuous, and able to carry fault current.
• Insulation – Green or bare copper conductors must be used. Regular wire insulation isn’t sufficient.
• Sizing – Equipment grounding conductors must be sized based on the rating of the overcurrent device protecting the circuit.
• Bonding – All exposed metal parts of electrical equipment must be bonded to the grounding system. This includes boxes, conduits, motors, ranges and more.

Inspecting Key Grounding Locations

When evaluating an existing electrical system or troubleshooting issues, there are several key points that should be inspected for proper, code-compliant grounding:

Main Service Panel

• Neutral and grounding bars are bonded together properly.
• An adequately sized main bonding jumper connects the bars.
• Grounding electrode conductor is connected to the ground bus.
• Bare copper wire is used for all grounding conductors.

Receptacles

• Equipment grounding conductor makes full contact with outlet box and receptacle ground screw or clip.
• GFCI outlets are installed properly and functioning (trip when tested).
• polarity tester shows proper wiring.

Light Switches

• Equipment ground wires attached securely to switches via ground screws or clips.
• Metal switch boxes properly bonded to ground.

Appliances

• All exposed metallic appliance parts are bonded to equipment grounding conductor.
• Appliance cords have sufficient ground wire and prongs.
• Grounding type receptacles used for appliance circuits.

Outside

• Ground rods driven fully into earth and spaced properly (8ft down, 6-8ft apart).
• Grounding electrode conductor continuous from main panel ground bar to rods.
• Water lines and other electrodes properly bonded to grounding system as applicable.

Frequently Asked Questions

What size ground wire do I need for a 15A or 20A circuit?

For standard 15 and 20A branch circuits, #14 AWG copper wire is sufficient as the equipment grounding conductor. The NEC permits reduced sizing compared to the phase conductors.

Can I use the ground wire as a neutral?

Absolutely not! The equipment ground must provide a safe, dedicated path for fault currents only. Using it as a neutral conducter could present a severe shock hazard.

Do all outlets and lights need a ground wire?

Yes, the NEC mandates that all receptacles and lighting fixtures must be grounded to protect against shocks upon contact with exposed metal parts. GFCI outlets provide some protection but are not a substitute for proper grounding.

Can I clip the ground prong off a plug to fit an old outlet?

Removing the ground prong defeats the safety benefits of appliance grounding and may create a shock hazard. You should replace ungrounded outlets with grounded versions instead. Never remove ground prongs.

Do CSST gas lines need bonding?

Yes, corrugated stainless steel tubing (CSST) gas piping is considered an electrical conductor. The NEC requires it must be bonded to the grounding electrode system. This is a critical precaution against damage and fires if lightning strikes.

How often should I test my home’s grounding?

Testing grounding resistance yearly is advisable. Resistance should not drift too much but it’s prudent to verify it stays under 25 ohms at the main panel. Higher resistance reduces effectiveness of the grounding path.

What should I do if I get shocked by touching an appliance?

Frequently getting shocked points to poor appliance grounding. You should immediately disconnect the appliance by unplugging it or shutting off the circuit breaker. An electrician should diagnose and fix any grounding conductor issues before using the appliance again.

Why is proper grounding important if I have GFCIs?

While GFCIs are crucial for protection against shocks, they operate by detecting current leakage and opening the circuit. Proper grounding provides a dedicated path for dangerous currents, keeping them out of the body in the first place. The two systems complement each other.

Can I use the earth itself as a ground in remote areas?

The NEC does permit using the earth directly as a grounding electrode if other sources like ground rods aren’t feasible. However, proper testing must show the earth has resistance under 25 ohms to qualify. Driving additional rods may still be easier than testing remote earth locations.

Conclusion

Grounding forms the backbone of electrical safety for any home. Don’t take grounding lightly – ensuring your home’s electrical system is properly grounded to the earth can prevent shocks, fires, and save lives. Follow NEC guidelines closely for system electrodes, equipment grounding conductors, and accurate resistance measurements. Inspect key points inside and out to catch any compromised grounding before it becomes a hazard. If in doubt, hire a qualified electrician to evaluate your grounding and suggest improvements. Safe grounding is well worth the investment in your family’s safety.

Summary of Key Points

• Grounding provides critical protection against shocks, overloads, and fire hazards in electrical systems.
• Code mandates ground rods, supplemental electrodes, proper conductor sizing, and total resistance under 25 ohms.
• All receptacles, switches, and exposed metal parts must bond securely to the grounding system.
• Annual inspections should cover the main panel, outlets, appliances, and ground rods.
• Never remove ground connections or use ground wires improperly.
• GFCIs complement but don’t replace proper system grounding.
• Hire an electrician immediately if you experience repeated electrical shocks in your home.