Service entry wiring (C) Carson Dunlop AssociatesElectrical Service Entry
Wire & Service Ampacity Inspection

  • SERVICE ENTRY WIRING & AMPACITY - CONTENTS: How to inspect the electrical service entry wiring for components that limit the electrical service ampacity available to the building - a 200 Amp main panel does not itself assure that 200A is available. How to determine electrical service ampacity - how much electrical power do we have at a building? Electric meter defects that can be determined by visual inspection
  • POST a QUESTION or READ FAQs about electrical service ampacity determination for buildings
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Electrical service entry wiring, service entry cabling (SEC), & the electrical meter: how to inspect for & report service ampacity, service entry defects & hazards.

Carson Dunlop's sketch at page top shows where the electrical inspection starts at a residential property.

Green links show where you are. © Copyright 2017, All Rights Reserved.

Inspecting the Electrical Service Entry Wiring bringing electrical power to the electric meter

Service entry wiring (C) Carson Dunlop Associates

This article series discusses procedures for safe and effective visual inspection of residential electrical systems including electrical panels and other components, when the inspection is conducted by trained building inspection professionals, home inspectors, electrical inspectors, and electricians.

[Click to enlarge any image]

Our photo (left) illustrates an unstable and improper passage of electrical service wiring over the roof of a private home

. In this case the house was being used to support electrical wiring that was in turn bringing power to a separate home located nearby.

Examples of electrical service defects that can be spotted outdoors at the electrical service entry

Unsafe outdoor electrical service entry cables at a mobile home (C) D Friedman S Vermilye

A study by the author (Reporting Extent and Sources of Rust and Corrosion in Electrical Panels, HOLM Conference) showed that very common sources of water leaks into and damaging electrical panels include frayed SEC, leaks at the top of the meter, and leaks at the building wall where the SEC passes from the bottom of a meter pan into the building electrical panel.

How to Determine Residential Electrical Service Ampacity

Readers of this section should see AMPS & VOLTS DETERMINATION for a detailed article on how to determine the amps and volts of a building's electrical service.

Do not rely on the ampacity printed on the main fuse or breaker, though that information is important. Examine the following:

So what determines the actual service ampacity at a building?

A General Table of Electrical Service Ampacity vs. Service Entry Cable Sizes

AMPS Copper Aluminum
30 10* 8*
60 6* 6*
70 6* 4*
100 4 2
125 2 1/0
150 1/0 2/0
200 2/0 4/0

Ampacity of an Electrical Service - Details of how to determine electrical service ampacity and voltage by visual inspection and/or safe use of test instruments.

Electrical Service Ampacity Defects

Electric Meter Defects

Obsolete electric meters (C) Daniel Friedfman


Question: short circuit & current leaks at electrical service entry wiring

2016/09/06 I am hoping to get some suggestions.

I power cleaned a drain and felt mild electrocution in my hands. I further discovered the ground from the outlet in the home had current. I flipped the main breaker and ground still has current as does the panel box itself. The city has an old wiring system where neutral is ran back through the power line.

Ground to neutral is not allowed. Home has 200 amp service ran through 2/0 stranded copper SEC. However city line is aluminum half as thick. Main transformer blew power to the block when I started pulling close to full 200 amps.

What do I do? - Anonymous by private email


This SEC wiring damage case report has been moved to ELECTRICAL SERVICE ENTRY DAMAGE


Continue reading at XAMPS VOLTS DETERMINATION or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.


Articles on Building Electrical Service Wiring - SEC Cabling


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SERVICE ENTRY WIRING & AMPACITY at - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.


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