Electric Meter Selection Wizard!
Wizard Overview
There are a variety of parameters that much be considered when selecting a
electric meter. This wizard will step you through
them one at a time and offer an explanation of the different options. If you don't understand the material as it is
presented, you probably do not know enough about electricity and electrical wiring to safely install a meter. We suggest you
contact a licensed electrical contractor in your area.
Choose an Electrical System
The voltage rating of the electric meter must match the voltage of the electrical system. What is not so obvious is that the meter
must also match both the electrical system and the requirements of the load to be measured. If you have only single phase loads,
you probably need a single phase meter. But if you are measuring power to single phase loads in a building that has three phase power,
you will need a three phase meter if you are are using power from all three
phases.
Another consideration is that each EZMeter measures each phase independently.
This means that you can use a three phase meter
in place of a single phase meter. You just have some unused terminals on
the meter and extra current transformers. If you are temporarily
installing electric meters for short term tests, you only have to buy a three phase meter
and you can measure both three phase and single phase loads.
Voltage Tolerances
Different utility companies use different transformers and provide
electricity at different voltages in around the country. Each EZMeter is
marked with the range of acceptable voltages. Most meters are marked
90-140 VAC. This means that the meter can be used on any electrical system
that provides any voltage between 90 volts and 140 volts between any one of the
hot wires and neutral. Other voltage ranges are 200-250 and 250-300.
Three Phase Configurations
There are three three-phase configurations commonly used within the United
States and Canada: 4 wire wye, 3 wire delta, and 4 wire delta. Using a
meter designed for a different configuration is likely to destroy the
meter.
To determine which system, open a breaker and measure between the neutral and
each of the hot legs. If there is no neutral, you have a 3 wire
delta. If the voltage between each of the hot legs is the same, you have a
4 wire wye. If the voltage to one of the legs is the same as the voltage
between and two of the hot legs, you have a 4 wire delta.
Three wire delta systems work accurately if you have a balanced load.
Most of our meters use the neutral for a reference for measuring the current and
voltage. If there is no neutral, we use one of the hot legs. It
works fine as long as the load is balanced. If controls circuits or lights
are connected to the system and create an unbalance load, the meter will not
give an accurate indication of the power actually used. For this reason,
we suggest you use a 4 wire wye meter if you have a neutral anywhere in your
system.
3 Wire, Single Phase, 120V to Neutral, 240V line to line
This is the most common configuration in most homes and small offices. Even if you
only have 120 volt loads, choose this configuration if you will be using power on
more than one circuit. This is also the meter to use if you will be measuring power
used by 120 volt loads in a building with a 4 wire, three phase delta transformer (common
in apartment buildings in some areas).
2 Wire, Single Phase, 120 Volts to Neutral
Use this meter if the only thing you are measuring is a single circuit unless you are sure
that all the circuits are the same phase (You could touch the wires to each other and not get
a spark). It is commonly used for measuring a single appliance or in marinas where each boat
gets a single 120 volt receptacle to plug into.
2 Wire, Single Phase, 220 Volts to Neutral
This is the common electrical system used everywhere except North America and parts of South America.
2 Wire, Single Phase, 240 Volts to Neutral
This meter is usually used to measure power used by an air conditioner or other large motor. Don't use
it if there is a neutral present and a chance that you will need to connect a 120 volt load to it.
3 Wire, 3 Phase Delta, 208-240 Volts Line to Line
This meter is usually used to measure power used by a large motor, air conditioner or industrial machine.
See the discussion above about Three Phase Configurations. Try to avoid this one unless you know you
have a balanced load.
4 Wire, 3 Phase Wye, 120/208 Volts
This meter should be used whenever you have a three phase wye power system, unless you are sure you will
only be using power from one or two of the phases. Large buildings, office, industrial and residential,
often have three phase power for air conditioning, elevators and other uses. Even if the unit to be metered
will only have 120 volt loads, use this meter because you need to meter the loads on all three phases.
4 Wire, 3 phase Delta, 120/208 Volts
This type of electric service is sometimes called a wild leg or stinger system because one of the
legs is 208-240 volts to neutral while the others are 120 volts to neutral. When this service is installed
in an apartment building, only the two lower voltage legs are fed to the apartments so a regular 3 wire, 120/240
meter can be used here.
4 Wire, 3 phase Wye, 277/480 Volts
This usually found in industrial buildings. Be sure you have a wye and not a delta. Connecting this meter
to a delta service will fry the meter.
4 Wire, 3 phase Delta, 277/480 Volts
If you're working with this kind of power, you should be an experienced electrician and you don't need any
help from us.
3 Wire, 3 Phase Delta, 480 Volts Line to Line
Sorry. We don't make a meter for this configuration. We can make it but our calibrator won't go that high.
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