A residential electrical service drop is the final stage of delivering power from the utility to a home. It consists of the overhead wires, weatherhead, conduit, cables, meter, and main service panel that connect the home to the utility power lines. Understanding the components and installation of a proper service drop is essential for safety, efficiency, and meeting electrical code requirements.

Overview of a Residential Electrical Service Drop

A residential service drop typically consists of:

Utility power lines – The utility company runs overhead power lines along streets and alleys near homes. These lines carry electricity from power plants to neighborhoods.
Weatherhead – This is an enclosure mounted on the roof or exterior wall near the service panel. It prevents moisture from entering the conduit.
Conduit – Rigid metal conduit runs from the weatherhead, down the side of the house, and over to the service panel. It protects the service entrance wires.
Service entrance cables – These large, insulated wires run through the conduit from the weatherhead to the main service panel. They carry power from the utility lines into the home’s electrical system.
Electric meter – Mounted on the exterior wall, the meter measures electricity usage for billing by the utility provider.
Main service panel – The service panel (or breaker box) receives power from the meter and distributes it throughout the home through circuit breakers and neutral/ground bus bars.

Proper installation by a licensed electrician ensures the service drop meets code requirements for capacity, materials, grounding, and safety. The service drop’s amperage capacity must match the home’s electrical needs.

Utility Requirements for Residential Service Drops

The utility company provides specifications for the service drop attachment point and components they will connect to. Common utility requirements include:

Service drop attachment – The utility specifies where on the home the service drop will attach, usually 18-24 feet above ground. This clears typical vehicle heights.
Weatherhead location – Positioned close to the service drop attachment point, within utility specs for location and height.
Meter housing – Provided by the utility, a meter base approved for the service voltage. Mounted in an accessible location per utility standards.
Service entrance conductors – Service cables must be sized and insulated for the delivered voltage, typically 120/240V single phase.
Service panel size – The main breaker amp rating and bus bars must match the service drop capacity.
Grounding – A ground wire or rod must be installed per utility grounding procedures.

Coordinating with the utility helps ensure the service drop connection point meets their requirements. They will not complete the hookup if their standards are not met.

Electrical Code Requirements

The service drop and all components must be installed to meet National Electrical Code (NEC) standards and local jurisdictional codes. Key requirements include:

Conductor sizing – Service entrance wires must be sized for the dwelling’s calculated load based on NEC procedures, with margin for future expansion.
Voltage drop – NEC limits acceptable voltage drop to 2-3% between utility attachment and service panel. Larger wires reduce drop.
Conduit fill – Cables must not exceed allowable fill percentage for the conduit size per NEC.
Protection from damage – Conduit and cables run from weatherhead to service panel must be secured, protected from weather, and at least 10 feet above ground.
Service panel – The main service panel must meet all code requirements for ratings, grounding, and overcurrent protection.
Overcurrent protection – The service disconnect (main breaker) must match the service amperage rating and provide protection from overloads.
Bonding – The main panel must have a grounded (neutral) bus bar properly bonded to the grounding electrode system.

Inspection and Approval

The local building department will inspect the service drop and connection point on the home before the utility completes the hookup. The inspector will check for proper materials, installation, and compliance with electrical code.

Service Drop Installation Process

Installing a new residential electrical service drop involves several key stages:

1. Load Calculation

The electrician first calculates the home’s electrical load requirements to determine the required service capacity. This accounts for lighting, outlets, appliances, future expansion, and NEC demand factors. A 200 amp, 120/240V single-phase service is typical for a medium-sized home.

2. Coordinating with the Utility

The utility is contacted to set up new service and provide their requirements. Their specs for attachment point, meter housing, and any other needs are obtained.

3. Setting the Service Attachment Point

A secure point for the overhead service drop wires to attach to the home is established. This is commonly an eye-bolt lag screwed into a rafter tail or other structural member 18-24 feet above ground.

4. Installing the Weatherhead

A weatherhead matching the size of the conduit is mounted on the roof eave or exterior wall near the attachment point using a conduit strap or other secure fasteners.

5. Running the Conduit

Rigid metal conduit is run from the weatherhead to the meter and service panel location. All bends are made with sweeping elbows for ease of wire pulling.

6. Installing the Meter Housing

The meter base provided by the utility is securely mounted in the approved location. This readies the home for the meter installation.

7. Pulling Service Entrance Wires

Properly sized copper or aluminum service conductors are run through the conduit from the weatherhead to the main service panel.

8. Installing the Main Service Panel

The main service panel is installed with suitable bus bar capacity for the incoming service wires. A main disconnect breaker sized to match the service rating is connected.

9. Grounding Electrode System

Ground rods, ground ring, or other grounding electrodes are installed per NEC requirements and connected to the service panel ground bus.

10. Utility Hookup

After inspection approval, the utility crews connect the service drop wires to the attachment point and meter. Power can then be supplied to the home.

11. Testing and Finishing

With the utility hookup complete, the electrician confirms proper energization, voltage, and grounding to finish the service drop installation.

Components of a Residential Service Drop

The key components that make up a typical overhead residential electrical service drop include:

Weatherhead

Mounted on exterior wall or roof eave near service drop attachment
Made of cast aluminum or PVC
Has threaded hubs for conduit connections
Provides weatherproof seal around service entrance cables

Conduit

Rigid galvanized steel or intermediate metal conduit
Runs from weatherhead to service panel
Protects wires from damage
Threads directly into weatherhead and panel

Service Drop Cables

Insulated copper or aluminum conductors
Rated for 600 volts
Sized based on service capacity (ex: 2/0 AWG for 200A service)
Most often 3 wires (2 hots, 1 neutral)

Meter Housing

Provided by utility
Mounted in accessible exterior location
Consists of socket enclosure and jaws to secure meter
Allows utility to access meter for installation/replacement

Main Service Panel

Receives incoming service drop wires
Main disconnect breaker matches service rating
Panelboard distributes power through branch circuit breakers
Bus bars sized for service capacity
Neutral/ground bus bars appropriately bonded

Service Drop Installation Tips

Here are some helpful tips for a successful residential service drop installation:

Always coordinate with the utility early in the process to meet their requirements.
Choose the largest conduit size that wire fill permits – it allows easier wire pulling.
Use sweeping elbow conduits for all bends – this eases wire pulls around corners.
Clamp conduits securely – expansion/contraction can push through weak clamps.
Pull wires carefully, using proper lubricant – kinking or scraping damages wires.
Double check that wire sizes can handle the calculated service load.
Verify the grounding electrode system meets all NEC sizing and bonding requirements.
Have the inspector see the service drop before the utility hookup to catch any issues.
Let the utility crews do the hot work of connecting the service drop wires.
Take photos at each stage of the installation for permit and insurance purposes.
Test voltages and ground continuity once the service is energized.

Following code diligently and paying attention to details such as these will ensure a problem-free residential electrical service drop installation.

Common Service Drop Mistakes to Avoid

Some common mistakes seen on residential service drops lead to hazards or code violations if left uncorrected:

Underrated wiring – Service entrance wires undersized for the home’s calculated load.
Excessive voltage drop – Wires too long or small cause low voltage in the home.
Inadequate wire protection – Cables loose or exposed and subject to damage.
Damaged wires – Kinked or scraped cables from poor pulling technique.
Poor weather seal – Gaps around conduit allow moisture into wires at weatherhead.
Insecure attachment – Loose eye bolt or other inadequate means of securing service drop.
Wrong conduit type – Using flexible conduit instead of rigid conduit for service wires.
No sweep elbows – Sharp conduit bends make wire pulling difficult and strain conductors.
Overfilled conduit – Too many conductors crammed in exceeds allowable fill percentage.
No grounding electrode – Lack of ground rod or other grounding electrode to service panel.

Careful planning, checking code requirements, and competent installation will avoid these mistakes and their potential hazards.

FAQs About Residential Service Drops

Some common questions that arise concerning residential electrical service drops include:

How close can the service drop attachment be to the roof?

The NEC requires at least 3 feet of clearance from the roofline. The attachment point must allow this clearance so the service drop can be safely connected.

Does the service drop attachment point require special hardware?

Yes, an eye bolt or other fitting rated for overhead service drop support must be used. Lag screws alone do not provide adequate strength.

Can the conduit bend or offset to avoid roof obstacles?

Yes, as long as only sweeping elbow conduits are used to avoid kinking the wires. The straighter the conduit route, the better.

What size conduit is needed for a typical 200 amp residential service?

2-inch rigid metal conduit is usually adequate based on the 3 service entrance wires and standard wire sizes.

Should spare conduit runs be installed for future use?

Yes, installing some spare conduits from the weatherhead to the panel provides for easier expansion later.

How is an underground service drop different than an overhead one?

Underground service has no exterior wires – it runs from the utility pole or transformer to the home underground through buried conduit. The wiring, meter, and panel requirements are similar.

Can a homeowner install their own electrical service drop?

Typically not. Most jurisdictions require a licensed electrical contractor to install the service due to the specialized knowledge and safety requirements involved.

How much does a new 200 amp residential service drop installation cost?

The average price range is $2000 – $4000 depending on the complexity of the house wiring upgrade and locality. Bigger services with longer wire runs cost more.

How long does it take the utility company to connect the service drop?

After proper inspection approval, the utility can usually hook up the service within a week or less. The overall project duration depends on the electrician’s work to upgrade the home’s wiring.

Conclusion

Installing a proper residential electrical service drop requires coordination with the utility, meeting NEC requirements, and competent workmanship. While the process is complex, taking it step-by-step with attention to detail will result in a safe, code-compliant service drop that reliably delivers power to the home for years to come. Planning the project around utility needs, securing necessary permits, and hiring a qualified electrical contractor is key to success. With some background knowledge of the components and installation process, homeowners can be informed participants and help enable a smooth service upgrade.

Summary of Key Points:

The service drop delivers electricity from the utility lines to the home’s main panel through overhead wires, weatherhead, conduit, cables, and meter.
Early coordination with the utility ensures their requirements for attachment, metering, and other specs are met.
NEC rules for capacity, voltage drop, conduit fill, wire protection, and grounding must be followed.
Typical installation steps include load calc, utility coordination, mounting attachment hardware, running conduit, pulling wires, installing the meter and panel, grounding, and utility hookup.
Mistakes like underrated wires, kinked cables, inadequate grounding, and other issues can cause hazards or code violations.
Homeowners hiring a qualified electrician and understanding the basics helps ensure a properly installed service drop.

Residential Electrical Service Drops: What You Need to Know