Home Electrical Overview

Electric Meter Solid State Home Inspections

Electricity can heat our homes, our water for showers, provide light in darkness, wash our clothes, and power countless other products to entertain us and make our lives easier. For Home Inspectors though, electricity is often a place where amateur work can present the biggest life safety hazards found in a home inspection. This is why identifying electrical service to the home and doing electrical safety inspections is such an important part of every home inspection.

Electrical Service and 'The Grid'

Electricity is generated many different ways but the most common are hydroelectric dams, coal or gas fuels power plants, nuclear reactors, and growing renewable sources like wind and solar farms. While different regions of North America produce electricity based on locally available energy sources, all these power plants are connected across North America on a massive network of distribution cables commonly referred to as 'the grid'.

The grid allows local markets to buy and sell power as it is needed. For example, in British Columbia we produce a very constant level of electricity from cheaper hydroelectric sources. During much of the day, BC sells our surplus power to 'the grid'. However, BC cannot increase our supply enough to meet peak levels of power demand (typically 5-10pm) so we need to buy back power from 'the grid' during our peak periods.

Electricity losses energy as it travels distances down wires but it is an electrical fact that higher voltage levels loose less energy at high voltage levels. This is why Electricity is carried from power plants on the grid to community sub-stations along a series of high-voltage transmission lines. High voltage however is very dangerous for use in homes so community sub-stations reduce high voltage to street voltage levels and then transformers on the street reduce voltage to household levels.

The final leg of delivering electricity from 'the grid' to our homes is connecting the electricity from the street to our homes. This can be done through overhead wires to an electrical mast on the home, or through underground wires. Underground wires are preferred as they improve the appearance of the home, are less susceptible to damage from trees and weather, and are less likely to be contacted by workers. They do however create a risk to workers that may be digging on the property. There are many safety concerns around electrical service wires that home inspectors will investigate to insure your electrical service is safe.

Volts, Amps, Watts, Hz, , Resistance, AC, and DC

Electricity is an amazingly versatile energy type and it needs its own glossary of terms to explain its current state and levels to operators.

  • Watts (W) - Watts are a measurement of electrical power being used each second. Our electrical meter on our home measures the consumption of watts used in our home and defines it as kilowatts hours (kWh) and the electrical utility bills homeowners for each kWh which is the equivalent of 1,000W being consumed continuously for 1 hour. For example, ten 100 watt light bulbs burning for an hour would consume 1kWh of electricity, or, one 1,000 watt microwave would consume 1kWh in 60 minutes at full operation. Wattage is directly related to the voltage and amperage. Watts (W) = Volts (V) x Amps (I)
  • Voltage (Volts, V) - Voltage is the difference in potential energy between two sides of a charge. In our homes, voltage is commonly delivered by the utility with three lines, two 'phased' 120V 'hot' lines, and one neutral return line. Most electrical appliances are designed to use 120V which means one of the two hot lines are used in conjunction with the neutral line to create a 120V differential of power between hot and neutral which is delivered to the appliance. Some very power hungry appliances like ovens and clothes dryers require more electricity. By using the power differential in the two 'phased' hot 120V lines, a difference of 240V can be supplied to the higher demand appliances.
  • Amperage (Amps, I) - Amperage is a measurement of the flow of electrons in the wire. More electrons moving means more available power. Amperage is also defined as the 'load' on a circuit in home electricity. The more amperage a circuit draws, the higher the 'load' on the lines. When the load becomes too high, it can cause the wires to burn insulation and melt which is why breakers and fuses are safety devices meant to stop amperage from exceeding the line capability.
  • Resistance - Electricity only flows in materials that are conductive. Plastics for example do not conduct electricity while most metals do. Gold, copper, and aluminum are excellent conductors of electricity but they are not perfect conductors and they offer 'resistance' to the flow of electricity. Electrical resistance acts like water in a pipe. The smaller and longer the pipe, the harder it is to get water to flow through it. Wires in houses have to be sized correctly to accommodate the designed power level for the length of the run needed. Resistance can be overcome by reducing the amperage being transmitted down the line.
  • Hertz (Hz), AC, and DC - Voltage is the difference of charge between two conductors. Electricity delivered constantly with a positive and negative side is called direct-current (DC) and is found in batteries which have a positive and negative pole where electrons travel from one pole to the other in only one direction. A second method of creating voltage is called alternating-current (AC) which is created by alternating the flow of electrons between the poles rapidly. The frequency the poles alternate at is called the Hertz (Hz) and in North America, the system operates at 60Hz or 60 cycles per second. Thanks to some advanced physics, AC power can be transmitted 4x more efficiently than DC power which is why it is delivered to our homes. Some devices like electronics require DC power to operate and there are transformers which convert the AC power to DC for these appliances often referred to as 'bricks' on the power lines.

Voltage and Amperage in Our Homes

Electricity use in our homes is calculated and used as watts however the loads of all our appliances are calculated into amps. Our homes electrical system needs to be able to safely manage the load of amps across different 'circuits' in the home.

Most 'circuits' in the home use 120v of power with 15 amps of load available. Under full load, the circuit is designed to deliver a maximum 1,800 watts of power (120V x 15amps). This would allow 18 100-watt light bulbs to operate on the same circuit, but if you had two 1,000-watt microwaves, they would attempt to draw 2,000 watts, which is 16.6amps (2,000W divided by 120V), and would overload the circuit. This is why in kitchens, where multiple high wattage devices are used simultaneously, two 15-amp circuits or one 20-amp circuit are often wired to one outlet. (Note, electricians do not design circuits to run at maximum, they often design them to max out at 80% of capacity for a margin of safety)

Larger appliances like ovens, heaters, and clothes dryers consume huge wattages and because of electrical resistances in increasing amperage, it is not reasonable to keep increasing amperage in the line. To increase the available watts to the appliance, the electrician can tap both hot 120V lines from the utility which thanks to the phasing of the system create a 240V differential in power. A typical oven will have a 40-amp breaker on a 240V circuit which allows 9,600-watts of electricity to be safely delivered at the outlet. 

Homes built up to the late 60's were designed with an expected 60-amps need for electricity. As electricity demands increased and more appliances and suites have been added, 100-amps then 125, 150, and now even 200-amps of service need are not uncommon. The maximum amperage the home will draw is often referred to as the 'service' level and the maximum service the home can draw from the utility is protected by the main electrical breakers or fuses which protect the main wiring and distribution panel in the home. It is not uncommon to find home owners have increased the main fuses in an older home to draw more power but this is at risk of burning out the service wiring and causing an electrical fire.

Breakers and Fuses

Breakers and fuses perform the same role in the electrical system which is to protect all the wiring and appliances on the circuit from an overload. When a circuit is overloaded, the resistance in the wire can create so much heat that insulation can melt causing short circuits and electrical fires. Breakers and fuses monitor the current level on the ciruct and are designed to fail when the circuit draws more power than it can safely handle.

Breakers have become more common than fuses as they are re-settable where fuses need to be removed and replaced and they provide electricians a 'switch' to turn off a circuit for service. A common amateur mistake with breakers and fuses is to 'over-fuse' the circuit in an attempt to stop nuisance tripping of the breaker of fuse. For example, if a home occupant blew the fuse every time they run the microwave and coffee maker at the same time, they may be tempted to increase the breaker from a 15-amp to a 20-amp breaker and gain the addition wattage. The risk to this is that the wire was only designed for a15-amp load and particularly with time the insulation and wire can overheat and cause an electrical fire. Home inspectors are looking for this condition.

If you are in a home where the fuse or breaker trips regularly, first, this is a good thing as the line is being protected. Second, you may want to call in an electrician to make the professional changes you need to have more power available where you need it.

Distribution Panel

Power into our homes is broken up into a number of segments. First, the utility lines go from the street to our electrical meter (typically located outside). Then main lines go from the meter to our main service box where the primary breakers or fuses for the home are, then the power goes from the main service box to a distribution box to be sent out to each circuit in the home. On more modern systems, the main service box is integrated into the main distribution panel.

The distribution panel has slots for all the breakers/fuses that protect each circuit. A home inspector will open this panel during a home inspection to identify the types of wire used in the home, to verify the correct sizes of breakers/fuses, and looking for any amateur signs of installation that may need repair. The distribution panel can tell a home inspector a lot about the integrity of the electrical system in the home and is a common location to find deficiencies.

Electricity from the distribution panel should be delivered directly to outlets, switches, and lights.

Condo Electrical

Electricity in condo's has a similar end result at the outlet but the path to delivering electricity is often different. First, many commercial buildings (like condo's) will recieve what is called 3-phase power which brings in three 120V lines rather than two. This third 120V line greatly increases the potential difference in power as now there are multiple potential difference combinations available to electricians. There is no change to the 120V delivery of power (the difference of any one 120V line and the neutral) but because of the way the phases work in the 120V lines, there is only a maximum voltage of 208V available rather than 240V in two-phase residential system. Appliance makers are aware of this however and if you look at the data plates for 240V appliances, they nearly always will say 208/240V indicating they accept both voltage levels.

Condo electrical distribution also varies slightly. Power from the utility is often delivered to a main building electrical room which often has its own transformers for the building. This electricity is broken into useable energy for each suite and energy for building systems like elevators. The suite electricity is delivered to electrical 'closets' which contain the electric meters for each suite along with the main suite electrical turn offs. Then finally the electricity is delivered to each suites individual distribution panel which contains over-current protection for the suite.

Final Thoughts

Providing electricity in our homes is about harnessing a massive power to safe user levels. Electricity is a place where amateurs should not attempt to make changes as lives and homes can be put at risk. Home Inspectors are trained to look for signs of amateur or unsafe work in home electrical systems and they will always suggest repairs be done by a qualified electrician. If you are buying a new home, always call in a home inspector so you know your home will be safe and solid.

By James Bell - Owner/Operator of Solid State Inspections Inc.