Items of Inspection

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.

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. 
• 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.

Grounding

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: (1) Be permanent and continuous; (2) Have the capacity to safely conduct any fault current that is likely to be imposed on it; and (3) 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.

How Much Amperage Is Enough?

The NEC outlines ways to calculate the service load requirements. The following information is an outline of one of the options, and an understandable way to determine the load requirements from a building inspector’s perspective.

Article 220 of the NEC provides the necessary information for calculating loads. This is a summary using assumptions in an effort to understand the general requirements of developing load calculations.

Loads

Small appliance circuits should be calculated at 75% of the circuit rating. A 20-amp branch circuit would be computed at 1500 volt-amps or 15 amps. A 15-amp branch circuit would be computed at 1125 volt-amps or 11.25 amps.

eneral lighting and general use receptacles are calculated at 3 volt-amps per square foot (SF) of living space.

Appliances that are fastened in place, permanently connected or located on a specific circuit, ranges, wall-mounted ovens, counter-mounted cooking units, clothes dryers and water heaters should be counted as the actual nameplate rating. Motors should also be counted at the nameplate rating.

Summary:

On-Site Method Watts = Amps X Volts

Example

Watts divided by Voltage = Amps, or a 100 watts (ie., a light bulb) divided by 120 volts (typical circuit voltage) = 0.8 amps. (amount of draw)

You should also understand that 60-amp or higher single-phase services allow you to access 120 and 240-volt circuits. A 100 amp single-phase service will allow you to access 100 amps at 240 volts, or 200 amps at 120 volts, or a combination of 120 and 240-volt circuits. The latter is commonly found in most residences.

Simply add the wattage or amperage required by the existing or probable appliances.

Assume a house with 2000 SF of living space, a fossil fuel heating system, central air, electric range/oven, electric dryer and an electric water heater.

120-volt appliances and equipment:

• Refrigerator – depends on size and model – approx. 4 amps
• >Microwave – depends on size and model – approx. 10 amps
• Hair dryer – 1500 watts – 12.5 amps
• Curling iron – 1200 watts – 10 amps
• Toaster – 1000 watts – 8.3 amps
• Lighting – approx. 1200 watts – 10 amps
• Portable heater – 1500 watts – 12.5 amps
• Washing machine – approx. 1000 watts – 8.3 amps
• Furnace blower – approx. 400 watts – 3.3 amps
• Miscellaneous items – stereo, exhaust fans, blender, disposal, iron, additional TVs, etc.– 1500 to 4000 watts – 25 amps

Total of the 120-volt circuits = 130.15 amps

240 volt appliances and equipment:

• AC – 36,000 BTU – approx. 19 amps
• Range/oven – approx. 10,000 watts – approx. 41.66 amps
• Dryer – 4800 watts – 20 amps
• Water heater – 4500 watts – 18.75 amps

Total of the 240-volt circuits = 99.41 amps

These items represent many of the appliances normally contained in a home. There will be other items such as: well pumps, freezers, saunas, welders, generators and multiple systems, etc. Such items can be added, as long as you know the voltage and wattage.

The 130.15 amps will be distributed across both of the 120-volt poles. This means that the 130.15 has to be divided by 2, suggesting that 65.07 will be taken from each side. We know that the distribution will not be even, however, it will be reasonably close.

If we add the approximate 65 amps from the 120-volt circuits to the approximate 99 amps from the 240-volt circuits, we get 164 amps at 240 volts. This suggests that the maximum current that could be drawn in this sample house, assuming every electric device was on simultaneously, is 164 amps. We know that it is nearly impossible to have a situation where every electric component in the house will be on at the same time. This situation will provide a design cushion. An arbitrary figure would be in the 20% range. 164 amps x 80% = 131 amps.

The example above, according to the Summary method, requires 131 amps to service this house. You will typically find a 200-amp service in this situation, however, 150 amps would be adequate. 100 amps would not be acceptable.