The description of a building's electrical service is probably
the most common mistake we find on listings. To some, this
may not be shocking; particularly if you've been burned before
...
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.
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, a 200 amp, 600
volt service has nearly three times the power of a 200 amp,
208 volt service.
Three Phase vs. Single Phase (3
vs. 1):
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.
Sizing It Up
When you are standing in the electrical room, the two pieces
of information you are looking for are amperage and voltage.
The presence of a transformer in the electrical room is usually
a dead giveaway that it is 600 volts. On a very rare occasion,
the transformer could be 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 |
|
