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A home’s electrical system and its components are often taken for granted. Coming home late at night and flipping a switch to guide your way through a dark house involves more maintenance than just changing a light bulb. Ensure that your electrical system and components are up to date and up to performance. Browse the topics on the right to keep your home burning bright.


Service Voltage
The service voltage can be determined by counting the number of wires connected to the mast or weather head. A 2-wire drip loop indicates a single-phase, 120-volt electrical service. A 3-wire drip loop indicates a single-phase, 240-volt electrical service. A 4-wire drip loop indicates a 208 or 240-volt three-phase service. Three-phase electrical systems are typically found commercially, such as in a supermarket or someplace with commercial refrigeration equipment. Two-phase services have 5-wire drip loops and are typically found in industrial applications. A licensed electrician should evaluate three and two phase systems.

Typical Service Entrance Cables
Note that some commercial and industrial systems do not carry standard 240-volt services, and may not be compatible with ordinary 240-volt household appliances.

Service Entrance Amperage
The service entrance amperage is sometimes difficult to determine. The amperage can be derived from the size of the service entrance cable (SEC) by: (a) looking for the size printed on the cable insulation; or (b) comparing the cable sizes to the chart listed below, using a gauge to determine size.

Electric Meter
Although the meter is usually owned by a service power company, it should be checked for defects. The following are some areas that should be evaluated.

Look for broken meter seals, or other evidence of tampering. Check to make sure all openings for the meter are properly closed and sealed to keep moisture out.

Check that the meter and meter box are properly secured to the building. Evaluate the location of the meter installation. Provisions should be made to prevent damage from cars, etc. 

Check for rust at the bottom of the meter socket box/enclosure, which is typically located on the exterior of the house. When the service entrance cable enters at the top of the meter box, and the seal is not water tight, water may cause rust that is evident at the bottom of the box. 

If the service entrance cable enters at the top of the meter socket/box and the cable that services the main panel comes out of the bottom of the meter socket/box, there is a possibility that water may follow the SEC from the meter box to the main panel. Check the main panel for rust at terminals inside the box and especially on the bottom of the panel.

Service Disconnect Inspection
When the service disconnect is located on the exterior of the structure, the following areas should be closely evaluated:

  • Check for excessive rust or corrosion on the interior and exterior of the box. 
  • Check for rust or corrosion at the terminals on the inside of the box. 
  • Ascertain that the enclosure is a proper, approved, weather-tight box and  is suitable for exterior installation. 
  • Check to determine that the meter box is properly secured to the building.

Service Panel Inspection
After locating the main disconnect, main service panel and sub-panels that may be present, remove the covers very carefully and evaluate the interior components for the following items:

Check for signs of corrosion on both the panel and all of the interior connections. Corrosion on the interior of the panel may indicate water penetration via the service entrance cable or a condensation problem in the area.

Look for circuit breakers/fuses that have more than one electrical conductor attached to them. Double or triple tapping is normally prohibited, both by local jurisdictional requirements and the National Electric Code (NEC). 

Splices are allowed only to extend the lengths of the wire inside the panel. Splices are never allowed for the connection of more than one line to a circuit breaker/fuse. · Anti-corrosive gel should be found on aluminum cable connectors. 

  • Check that branch circuits are not wired before the main service disconnect. 
  • Circuit breakers or fuses without conductors may lead someone to believe that the panel has more circuits than it actually has. 
  • Low voltage transformers are usually not allowed inside the service panel due to the heat that they create. 
  • Check for loose and unattached conductors inside the panel. All conductors inside the panel must be properly terminated. 
  • Check the two-pole (240-volt) circuit breakers. Two-pole breakers must trip together, so that they provide total safety for the circuit. The use of nails or pins to hold two breakers together is not acceptable. A properly designed connector should be utilized. 
  • All ground wires should be properly secured to the ground wire or the neutral/ground buss, depending on the panel. 
  • Neutral wires should be properly secured to the neutral wire buss. · Check wires for signs of arcing, charred metal, or burnt wire insulation. 

Evaluate all cables entering the panel box to ensure that they are properly protected and secured. BX or metal armor cables must have special plastic bushings inserted between the conductor and the outer shield of the cable to protect the wiring. Wire retainers should secure non-metallic wire. Check all the wiring sizes and their respective fusing. Make sure all the wires are properly sized for the respective fuse or breaker to which they are attached.

Openings in the panel that may present a shock hazard · Check for single conductor aluminum wire sizes smaller than #8. Such wiring needs special consideration, since it has been known to pose fire hazards even when properly installed.

  • All panels must have their interior connections covered to prevent shock. 
  • Check that the main disconnect for the service is marked “main.” 
  • Report inaccessible electrical service panels. 

The NEC requires a minimum headroom of 6'6" at the service panel, and 30" around the panel area, as well as a 36-inch clear area in front of the panel for servicing. (Known as the "Working Rule".)

  • The panel must be securely attached to the wall or other structural components. 
  • There should be no missing screws in the panel cover. The screws should be blunt-ended. 

There must be either a single means of disconnecting the electrical service system, or there must be no more than six disconnects in order to shut down the entire electrical system. (Six finger pulls or hand throws) Modern systems will have a single means; older split buss panels may have 6 disconnects. 

Check the compatibility of the service entrance cable to the rating of the main panel enclosure box. If the service entrance cable is rated for 100 amps maximum and the main service panel contains a 200-amp main disconnect, it poses a potential fire hazard. 

Adequacy of the electrical service should be determined. By today’s standards, 100-amp service is considered minimal service. 

Identify the materials used for branch circuit wiring inside the service panel. Copper is preferred wiring material for all circuits 30 amps and under.

Check for circuit breakers that are not properly secured or are loose. Some circuit breakers are not compatible with the box they are installed in, and some of the older Federal Pacific panels had this problem with the prescribed breakers. In these cases, the panel cover may be holding some of the breakers in place. Arcing is common with this situation, but it may not be readily visible until the insecure breaker is removed

Check the outside of the panel to see if it is warm or hot. This should be a cause for immediate concern. 

Do not operate any breakers, main disconnects or fuses to check operation. However, be aware of corrosion rust evidence of previous condensation that might indicate operation problems.

Bonding of Service Equipment
Noncurrent-carrying metal parts and equipment, such as the panel, service cable, armor or sheath, equipment enclosures, meter boxes, and fittings are required to be bonded to the metal enclosures which are enclosing electrical components. They may be bonded with approved connectors or locknuts. Bonding jumper size is based on the size of the over-current protection device. They are the same size as the equipment grounding conductors. Other systems with current-carrying potential (i.e., water and gas piping) should be bonded back to ground. Sub-panels should be bonded to the main panel box to ensure a single, low impedance ground. Bonding should be provided where necessary to ensure electrical continuity and the capacity to safely conduct any “fault current” that is likely to be imposed. Equipment and/or piping that may become energized should be bonded to the service equipment, the grounding conductor at the service, the grounding electrode conductor where it is of sufficient size, or to one or more grounding electrodes.

Systems and circuit conductors are grounded to limit voltages due to lightning, line surges, or unintentional contact with higher voltage lines, and to stabilize the voltage to ground during normal operation.

Equipment grounding conductors are bonded to the system grounded conductor to provide a low impedance path for fault current that will facilitate the operation of over-current devices under ground fault conditions.

The protective devices should be selected and coordinated to permit the circuit protective devices that are used to clear a fault without the occurrence of extensive damage to the electrical components of the circuit (i.e., circuit breakers, GFCIs, proper grounding and bonding). Grounding should:

  • Be permanent and continuous
  • Have the capacity to safely conduct any fault current that is likely to be imposed on it; and
  • Have sufficiently low impedance (resistance) to limit the voltage to ground and to facilitate the operation of the circuit protective devices.

Driven rods are the typical choice for grounding conductors when a plastic water service pipe is present, since plastic does not conduct electricity.

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How do you tell the exact size of an electric service?
The size of the electric service is dictated by the smallest of the following three items:

  • Size of the main disconnect breaker or fuse (100amps, 125amps, 150amps, 200amps)
  • Rating of the service cable (#4, 2/0, 4/0, etc.)
  • Rating of the panel (printed on a label) Example: If the cable is rated 100 amps, the disconnect is 150 amps and the panel is rated 150 amps, then the size of the electric service is 100 amps (the smallest of the three qualifying items).

Is my electrical service grounded?
Grounding of your main electrical service is usually done one of three ways. There is also redundancy installed in many homes so you may have multiple grounds. Service grounding can be achieved with wire attached from the main service panel to the home's main water service pipe, or wire attached to an 8-foot metal rod driven into the ground in the vicinity of the main panel, or a wire attached permanently to rebar within the concrete foundation, commonly referred to as UFER ground.

How does a ground fault circuit interruptor (GFCI) work? 
A GFCI senses the balance of current in the circuit. As long as the same amount of current that leaves the circuit breaker or supply buss returns to the neutral, the GFCI will remain closed. If there is any current leakage in the circuit for any reason, the GFCI will sense the difference and open the circuit. A typical GFCI will open if there is .5 miliampere of current loss. (A unit of current equal to one thousandth of an ampere "amp.") Electricity moves at the speed of light (186,000 mps). This allows approximately 1/40 of a second for the GFCI to react.

GFCI circuit breakers are safety devices designed to prevent electrocution when one comes into physical contact with water and electricity at the same moment.

What is an Arc Fault Circuit (AFCI)?
Arc Fault Circuit Interrupters, or AFCI, are circuit breakers designed to 'trip' when arcing electricity has the potential to start a fire. For example, a damaged electrical cord with a broken conducter that 'arcs' when power is supplied.

Arc Fault Interrupters are very sensitive devices and may trip under normal usage. They currently are found in the circuits of new construction in bedrooms, but discussion is ongoing regarding the future of AFCI to be placed in all rooms.

How hard is it to upgrade the electric service in my house?  
Upgrading the electric service is an involved procedure that will include one or all of the following: replacement of the service entrance cable; upgrade and possible replacement of the main disconnect panel; installation of an additional branch circuit over current devices (commonly known as fuses and circuit breakers); and rewiring the branch circuit connections at the main disconnect panel. This is a question that you could ask an inspector and receive advice that may help you determine a reasonable plan of action. Anytime repairs are performed on or within the electrical system and its components, a licensed electrician should be contacted to make these repairs.

What is a double-tapped circuit?   
Double-tapping, also known as “double-lugging,” is a condition where there is more than one wire conductor terminated in a service panel fuse or circuit breaker. Double-tapping is permissible only if the terminals are identified for that use. Most breakers and fuse connections are designed to hold and handle just a single incoming circuit, although there are some manufacturers, such as Square-D™, that market breakers designed to allow two wires to be securely attached. Any time repairs are performed on or within the electrical system and its components, a licensed electrician should be contacted to make these repairs.

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Service Entrance Cable Should be Secured:

  • Within 12 inches of the masthead
  • At intervals not to exceed 30 inches

Service Drops required Building Clearances:

  • 18 feet over public roadways
  • 15 feet over alleys
  • 12 feet over private driveways
  • 10 feet over finish grade and sidewalks
  • 10 feet over platforms, decks, and porches
  • 8 feet over roofs with less than a 4 in 12 pitch
  • 8 feet over flat roofs
  • 3 feet over roofs with more than a 4 in 12 pitch
  • 3 feet horizontally from fire escapes, porches and decks
  • 3 feet from windows
  • 18 inches over roofs where there is a 4 foot or less overhang

Clearances in Closets for Light Fixtures

  • 18 inches between fixtures and where combustibles may be stored
  • 6 inches between flush mounted fixtures and where combustibles may be stored

Recessed Lighting (typically inspected from the attic):

  • One half inch spacing of recessed portion of the fixture from combustible materials
  • 3 inch spacing of thermal insulation between recessed light fixtures and combustible materials with nothing above the fixture (Non-thermally protected)

Special appliances (such as laundry equipment):

  • 6 feet maximum distance from outlet to appliance

Supply Cords for Air Conditioners:

  • 10 feet maximum for 120 volt wire
  • 6 feet maximum for 208/240 volt wire
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There are many specific deficiencies that may be encountered during the inspection of an electrical system. The following are some of the more common concerns:

  • Open or uncovered junction boxes. All junction boxes must be properly covered.
  • Exposed wires outside the junction boxes. All terminations of electrical wiring must be made inside an approved and covered junction box.
  • Improperly spliced wire. All splicings or connections must be made inside a junction box or panel box. Exception: knob and tube wire that has been soldered and taped. Splices, which are in the panel, are only allowed to extend a wire.
  • Improperly wired outlets. Use your receptacle analyzer to check the outlets at the user end. Note any defects, such as reversed polarity, open ground, etc.
  • Improperly hung or unsecured electrical wires. Wire must be secured to studs or passed through drilled holes in studs/beams/joists.
  • Lack of GFCI control devices. Current lectrical building code  does require all exterior, bathroom, kitchen (within 6' of sink), garage, and one basement circuit to be protected by Ground Fault Circuit Interrupters. Check with the authorities in your area for local requirements.
  • Improperly stapled wiring. All staples should be an improved type, insulated, and must not dig into or otherwise damage the insulation of the wiring.
  • Extension cord wiring. Extension cord wiring is considered temporary, and should never be used as permanent wiring.
  • Wiring that rests on heat pipes, heat ducts, or other pipes is prohibited.
  • Wiring passing through or over sharp metal objects, fireproofing or heat ducts, must be properly secured/protected to prevent damage.
  • Frayed, brittle or fragile wiring insulation or other deterioration that could create a hazard should be replaced.

Knob and Tube Style Wiring
Evaluate the older 2-slot outlets. Note that these outlets do not provide a third ground slot. Upgrading to 3-slot outlets should be considered, if proper grounds can be installed without a disproportionate amount of work. Knob and tube wiring was the most widely used type in frame buildings until the 1920s and had virtually disappeared by the early 1930s when BX wiring systems replaced it. The dangers of knob and tube wiring lay in a combination of issues of both exposed and concealed systems. Early in the 1900's, the NEC began to recognize the inherent problems with concealment of this type of wiring. They began to require placement of the wires in dry areas only and a separation distance of 5 inches between the wires. Extreme caution should be used when encountering this type of wiring due to its age and very possible damaged or deteriorated insulation.

  • Wiring smaller than #6 in size should pass through holes in joists when running perpendicular to them.
  • Wires running across the ends of joists need to be fastened to running boards.
  • Wiring running across the joists must be installed so that the wire is not at the exposed end of the joist.
  • Staples and hangers should be no more than 4½' apart, and no less than 12" from any enclosure or junction box.

Overcrowded Junction Boxes
This can be established by determining the number of conductors entering and leaving the junction boxes. Junction boxes are sized in accordance with NEC 370-16. The determination is beyond the scope of a visual home inspection. However, a prudent consultant would note the presence of a large number of circuits in any system. It is not recommended that the covers to the junction boxes are removed for this analysis, however, it is the best way to evaluate older wiring.

A Lack of Sufficient Outlets
This is typical in older homes and it may not be a problem or a situation that can be enforced.

Evaluate conditions in closet areas. Check to insure that there is 18 inches of clearance between incandescent lighting fixtures, and 6 inches of clearance between florescent fixtures, and combustible materials. Note any bare or exposed light bulbs that may exist in a closet area.

Most of the items listed above may create serious safety concerns. Others, such as, the lack of a ledger or label, anti corrosive gel or the presence of a low voltage transformer in the panel, may not pose the same urgency.

Solid Conductor Aluminum Wiring
Small, solid conductor aluminum wiring, such as 10 gauge, rated 20 amps and 12 gauge rated 15 amps, was used from 1965 to 1974. In 1975, the NEC prohibited the use of solid conductor aluminum wiring.

The main concern with small gauge, solid conductor aluminum wiring is its expansion characteristics when heated. If the wire is in a situation where the amount of current that is being drawn does not heat the wire, there will be no typical aluminum wire related concerns (i.e., if an aluminum wire circuit only serves a lamp and a TV, it will not draw enough current to cause expansion problems). A 15-amp circuit that is serving a lamp and a TV will have a maximum load of only about 3 or 4 amps. This is not nearly enough to cause aluminum wire concerns due to heat.

To determine how much current a circuit is drawing, divide the wattage rating of the lighting and or appliances on the circuit and divide by the voltage. Watts = Amps X Volts so a 100 watt light bulb divided by 120 volts equals .8 amps.

When almost anything is heated, expansion will occur. Materials of different densities will expand at different rates. When an aluminum wire is attached to a steel alloy contact with a similar steel screw, and the contact, screw and wire is heated by the current moving through the circuit, everything expands. During this process, the density of the steel will tend to distort the aluminum wire. When the contact cools, the steel alloy will return to its original size, while the aluminum, which was distorted, will not.

When aluminum is exposed to air, a film of aluminum oxide forms on the metal's surface. The oxide formation causes the wire to loosen under the mounting screws. When the screws are worked loose, the oxidation of the aluminum wire under the screws heat and create a fire hazard.

When there is enough distortion, the aluminum wire will become loose at the contact. It may not appear loose, because it may not come off, as you would expect from a loose wire. The loose aluminum wire may function with micro arcing, which will cause more heat at the contact and make the problem worse. The additional heat causes stress on the wire, and may cause a slight fracture in the run of the wire about 1/8 inch from the contact. This fracture causes additional micro arcing and even more heat. Fractures occur at this point because this is the point of maximum temperature difference or change. When multiple arcing occurs, the potential for excessive heat and possibly a fire may be present.

The apparent solution to the problem would be to remove the aluminum wire from the steel alloy contacts. The original suggestion was to pigtail the aluminum wire with a piece of copper wire and to attach the copper wire onto the steel contact. This would have been acceptable, except for the fact that the aluminum and copper, being dissimilar, corrode due to oxidation when they are in contact with each other.

To help eliminate the problems and concerns, device manufacturers developed switches and outlets designed to receive copper or aluminum. These devices were called co/al devices, however, they were not as effective as the manufacturers had anticipated, and were revised. The revised devices are called co/alr, the "r" meaning revised.

With the co/alr devices, the switch and outlet concerns were addressed, however, there is still a concern with fixtures that are wired directly, such as a chandelier. In most cases, and assuming they are wired correctly and the loads are properly calculated, there should be no problems, because the amount of heat generated by these fixtures is not enough to stress or overload the wire. The concerns are related to situations that are unknown or where the wiring or calculations are incorrect.

AMP Corporation designed a wire crimping tool and system that will provide dependable results with aluminum to copper connections. The crimp is designed to ensure that air does not come between the aluminum and copper. After the connection is crimped, it is covered with a sleeve, which is shrunk around the connection. This process minimizes oxidation at the contact. This is the only system that the Consumer Product Safety Commission (CPSC) has accepted.

  1. The CPSC does not recognize any other system or correction as acceptable. This creates legal concerns for anyone who may recommend a different solution.
  2. AMP Corporation does not sell the crimping tool; they have patents pending and only allow users to lease the equipment. This limits access for residential or small work, because it is difficult to justify leasing costs for one house.
  3. The number of "qualified" electricians that have gone through the AMP training creates further limitations. There are very few electricians in the country that have gone through the training, and most are commercial electricians. Based on this situation, we as home inspectors cannot recommend this as a solution, because most of our clients will not be able to find a qualified electrician in their area.
  4. Our posture is to explain the aluminum wire situation so that our client understands the concerns, and recommend a licensed electrician to determine the best action.

The NEC and most jurisdictions recognize twister wire nuts and co-alr device usage. The CPSC has not required the removal of the other two methods from the marketplace. This would suggest that there is insufficient research to ban the use of these products.

ASHI and NAHI standards, as well as the ERC inspection guide require inspectors to report the presence of solid conductor aluminum wire.

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Common Defects

  • Aluminum single conductor wiring on 120-volt circuits
  • Broken light fixtures or devices
  • Loose or inoperative ceiling fans
  • Double tapped circuits in service or distribution panels
  • Permanently installed extension cords or temporary wiring
  • Frayed, deteriorated or melted insulation
  • Missing or inoperative GFCIs
  • Grounds loose, wire connections/clamps corroded or not properly connected
  • Improper junctions or splices
  • Improper main disconnect
  • Improper exterior wiring
  • Loose outlets and switches
  • Knob and tube wiring (age and condition concerns)
  • Missing cover plates
  • Outlets with open grounds
  • Inadequate overhead service cable clearances
  • Oversized breakers or fuses
  • Inoperative smoke detectors
  • Missing carbon monoxide detectors
  • Reversed polarity at outlets
  • Unsecured or inadequately secured electrical cables and wiring
  • Subpanel grounds and neutrals not separated
  • Missing knock out(s) or unsafe openings in panel/boxes
  • Bath lights on GFCI circuit
  • Mystery switches (operation is not apparent)
  • Zinsco or Federal Pacific Panels in use (Safety hazard)
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