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Inspecting Commercial Buildings and Their Power Supply

Electrical Power

In electrical engineering, single-phase electric power refers to the distribution of alternating current electric power using a system in which all the voltages of the supply vary in unison. Single-phase distribution is used when loads are mostly lighting and heating, with few large electric motors. A single-phase supply connected to an alternating current electric motor does not produce a revolving magnetic field; single-phase motors need additional circuits for starting, and such motors are uncommon above 10 or 20 kW in rating.
In contrast, in a three-phase system, the currents in each conductor reach their peak instantaneous values sequentially, not simultaneously; in each cycle of the power frequency, first one, then the second, then the third current reaches its maximum value. The waveforms of the three supply conductors are offset from one another in time (delayed in phase) by one-third of their period.

Defining the Terms

Amps vs. Volts:
Think of electricity as water flowing through a pipe. The amperage is analogous to the amount of water flowing through the pipe. Amperage is also called current. Larger diameter wires can handle more current, just as larger pipes can handle more flow.

Voltage is analogous to pressure, the force which moves the water through the pipe. A small pump (low voltage) would produce less pressure than a big pump (high voltage).

In most buildings the voltage will either be 208 volt (low voltage) or 600 volt (high voltage). The critical question is how much voltage and amperage the system is rated at, or in other words, how much equipment can I use in the building?

208 Volt vs. 600 Volt:
Most modern buildings are equipped with 600 volt services. Equipment such as air conditioning units (over 5 tons), larger exhaust fans, electric heaters, and some lighting will utilize 600 volts. However, standard outlets and most lighting operate at 208 volts.

In North America, individual residences and small commercial buildings with services up to about 100 kV·A (417 amperes at 240 volts) will usually have three-wire single-phase distribution, often with only one customer per distribution transformer. In exceptional cases larger single-phase three-wire services can be provided, usually only in remote areas where poly-phase distribution is not available. In rural areas farmers who wish to use three-phase motors may install a phase converter if only a single-phase supply is available. Larger consumers such as large buildings, shopping centers, factories, office blocks, and multiple-unit apartment blocks will have three-phase service. In densely populated areas of cities, network power distribution is used with many customers and many supply transformers connected to provide hundreds or thousands of kV·A, a load concentrated over a few hundred square meters.

Buildings equipped with 600 volt services will always have a transformer to reduce the 600 volts to 208 volts for the main building panels. These transformers are generally located near the main electrical service entrance.

When comparing the amount of power available for different voltages, a 200 amp, 600 volt service has nearly three times the power of a 200 amp, 208 volt service.

This is of less importance. All 208 volt and 600 volt services are three phase. This means there are three power wires coming into the building.

Single phase services may be found in older, smaller buildings and are found exclusively in houses.

In some older buildings you can find a single phase and a three phase service. This is usually identifiable, on the outside, by two separate services leading to the building.

Determining Amperage of Service

When you are inspecting the electrical room, the two items of information you are looking for; the are amperage and voltage. The presence of a transformer in the electrical room is usually indicative that it is 600 volts. They do make transformers that can used to step up a 208 volt service to 600 volts, for a specific piece of equipment.

What you should typically see is a small conduit (high voltage, low current) going into the transformer and a larger conduit (low voltage, high current) coming out and leading to a breaker panel or a splitter panel.

The ratings on the switches and splitter panel are not to be relied on; they only tell you the maximum amount of current or voltage the equipment can handle. Do not rely on the rating of the hydro meter(s), for the same reason.

The best way to verify the amperage is to open the door of the main power switch and read the rating of the main fuses. This is sometimes impossible to do without turning the power off, but is always dangerous, unless you know what you are doing. Even with the power off, half the box is live. You can end your real estate career, right there in somebody’s electrical room.

Reading the gauge (size) of the main power wires (in the meter cabinet or main splitter panel) can also help to determine the amperage of the service. The gauge number is typically printed on the wire sheathing. Common wire gauge sizes, for copper conductors and the allowable amperages are as follows:

Wire Gauge Allowable Amperage
3 100 amps
000 200 amps
350MCM 300 amps
500MCM 400 amps

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Preparing for your Home Inspection

Originally posted 2009-01-02 12:01:00. Republished by Blog Post Promoter


This first section will deal with home owners who are still living in their homes and will be having a home inspection to have condition removed from Real Estate Offer.


Ensure your annual maintenance items have been done, which are not limited but can include the following:

  1. Check all eaves troughs to ensure not blocked, splash pads are installed correctly, downspout supports are intact, no low areas in area of discharge, gutters are well supported and not sagging.
  2. Basement window wells are debris free, drains are filled with clean stone or covered with screen, screens are intact and correctly installed.
  3. Exterior siding is secured. Re-secure any loose pieces of siding, this can sometimes be as simple as snapping back into place or sliding siding into neutral position to cover gaps from expansion or contraction.
  4. Re-caulk any exposed holes on doors, windows, exterior   electrical fixture, flashing and any area where water entry may be a concern.
  5. Re-level any patio stones that have heaved from frost.
  6. Replace any rotted boards on wood decks and porches. Ensure all hand rails are secure with all guards being secured.
  7. Check your attic to see if any problems have occurred from last inspection or if any work was done, that insulation was properly replaced.
  8. Test your GFCI outlets and ensure they trip and reset. These will be located on exterior outlets and all bathrooms in newer homes. Newer homes will have arc fault protected devices in bedroom and kitchen, which should also be tested.
  9. Open and close all your doors and windows to ensure proper latching and operation. Check for door stops and any holes created by door knobs hitting drywall. Repair and Replace as required. Most problems can be fixed with minor adjustments.
  10. Check all your lighting fixtures to ensure proper operation.
  11. Check your sump pump to ensure it has a proper fitting cover and will operate when tested.
  12. Check your furnace filter and replace if dirty or ripped.
  13. Check all your visible wiring in basements to ensure cables are not touching any hot air ducts.   There is no issue with wires touching cold air returns.
  14. Make sure your electrical panel and attic hatch will be both accessible by home inspector.   Most professional inspectors will definitely inspect both.
  15. You might want to have mason or siding installer repair any visible cracks, missing, chipped, damaged or loose brick or siding. This cost will be taken into account by any prospective buyer and having done prior to selling only improves your homes look and value.


This section will list some of the more common issues usually found.


Water and Moisture Problems


Most new home purchasers in the Barrie area place water and moisture damage high on their list of items they want identified. It would only make sense to look for any visible concerns and have them repaired prior to listing your home. Covering sump holes and removing any source of water and moisture will usually also eliminate the unpleasant odour associated with moisture problems.


Remove any old stains that might be present from past leaks or renovation projects. Installing new drywall and painting is preferable to leaving water marked material or rotted drywall material exposed to view.


Inspect your bathrooms and look for any mildew or water staining. Check caulking around bathtubs, showers, sinks and floor joints. If your bathroom window is in your shower area, inspect for rotted wood and missing caulking. Replace and repaint as necessary.


Garage Inspection


Two items that pop up during inspections is the fume barrier and door closure in the garage.  Newer homes are required to have fume barrier between shared walls separating living area and garage. Most homes have drywall which is required to be taped but not painted. Check your walls and ceiling as patch any holes or gaps that have occurred. The other item that is required when newer homes are built is the automatic door closure on the interior door.   This is required at construction but can be removed by home owners at their own discretion. This item will be noted at time of inspection.


Attic Inspection


The attic will be checked for adequate insulation and proper ventilation. Many home owners will enter their attic to install pot lights or ceiling fans etc and fail to replace insulation when finished. Even some in-experienced home inspectors will tramp around the attic and compress or move insulation without replacing.


Soffit baffles should be installed in any attic where the insulation can block soffit ventilation area between sheathing and installed insulation. This can lead to ice dams and premature shingle replacement.




Check furnace filter and replace if dirty. Look at flame on gas furnace and if there is a lot of visible orange and yellow flame during operation have serviced by qualified technician. Look for signs of leaking water in furnace cabinet or excessive rust on exterior or interior of cabinet.   If you have a humidifier installed on duct work, check to ensure it is working and the filter is in good condition.   If humidifier is not in working condition I would recommend replacing or removing.


Electrical Panel


Check your panel for neatness. No visible open holes in panel, wires neatly stapled and circuits clearly identified. If you are un-sure about any of these items I would recommend having a certified electrician inspect and make any necessary repairs.




Have any inspection and building permits that were taken out for renovations. If any work, maintenance, service or upgrades were performed on any of your homes systems; it is a good idea to have these items available for prospective buyers. This will allay any fears that your home had work performed by un-qualified personnel.


Real Estate Agent


Your listing real estate agent can be one of your best resources for identifying items that will cause concern and affect the sale value of your home. Take the time to thoroughly inspect every part of your home with your agent and repair all questionable items prior to listing.


In-Complete List of Items


This list is not a complete list of items that can or should be checked. The average home can have countless more items that could and should be repaired prior to listing your home, this is just a brief overview that lists some items found during an average home inspection.   My Pre-delivery inspections of new homes would probably average out at thirty items per inspection, with most items being found in most homes but some items unique to that one particular home.


Caveat Emptor – Buyer Beware    Experience and training can not be accomplished over-night, always verify who your hiring.



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