Energy Monitor Submetering Options

Basic Electric Metering

A measurement for a quantity of electric energy, at any point in time, is called a "watt". Example, 100W bulb, 1500W hairdryer or electric heater, etc. To simplify the numbers, 1000 watts equals a "kilowatt" or simply kW. This energy measured over time is called a "Kilowatt-Hour" or "kWh". One kWh means the usage of 1 kW for one hour or sixty minutes.

The traditional utility glass meter monitors and records kWh increments on a digit counter or dial counter. The electric energy usage is simply a continuous accumulation of kWh counts.

In addition to recording kWh, most electric energy meters also have a built-in method of determining short-term interval or real time kW. Glass utility meter has a rotating disk, ET-SP has a pulsing LED and direct kW readout on a PC upload capability.

• Utility meter disk - by counting the black mark rotations over a short interval time (60 seconds) a simple formula can easily calculate or represent the average kW energy over the selected time.

• Example - 4 REV, 72 seconds = 1.44 kW or 1,440 watts
• Note: The "7.2" number is the Kh designator or value of the meter itself. In normal residential meter this is 7.2 and the Electro Industries' electronic meter it is also 7.2. In other metering arrangements this can be a combination of the CT ratio and the actual meter Kh. In the case Electro Industries' ET-SP series the CT ratio is not used to determine Kh, for simplicity all units are pre-calibrated with Kh = 7.2.
• ET-SP series - a pulse from the yellow LED is identical to a black mark rotation from the glass meter. Apply the identical formula above, 1 LED pulse is 1 REV.
• ET-SP series - loading Electro Industries' proprietary software (Windows based, ET-SOFT-SP) and a special cable from any PC 9 pin com port, will allow any PC to display the real time kW value and is retrieved with a simple ALT-D keyboard function.

Applications

• Off-peak rate
• Industrial equipment energy monitor
• Apartment sub-metering
• Marine boat dock plug-in
• Mobile home/RV park
• Rental parking stall plug-in
• Electric heat rate
• Dual fuel rate
• Load survey monitoring
• Remote kWh register
• Automatic meter reading input

Electro Industries’ Electronic Sub-Meter

Designed for low cost and simplified installation.

The metered load power wires are simply strung through the “doughnut” device commonly called CT.  This can be one load or several.  Each power source wire is run through the CT.  This becomes the current or “amp” component for the kWh energy calculation.

The meter module is connected to a convenient 120 or 240 voltage source.  The setup parameters determine whether this source should represent itself, 240, 208, or 277/480.  This becomes the voltage component for the energy kWh calculation.

The meter module has precise digital measurement capability and software to correctly monitor and record the electric energy.  In addition to storing the energy kWh values within itself, there are hardware ports and software conversion options for a variety of outputs.

A Palm OS™ or standard PC computer is used to:

• Download various setup parameters and/or offset for field calibration
• Display real-time Amps, Volts and KW. This means the connected computer (Windows) has direct access to real-time energy data

Product Variables

A. Some configuration parameters relate to specific hardware component sizes, CT type, method of stringing CT, reference voltage, etc. These are factory assembly controlled and are represented by specific model number within the ET-SP product family.

B. Using PC software (and special cable) user can easily download other variables.

• Nominal power factor
• Preset internal kWh register
• Single point voltage calibration offset
• Single point current calibration offset

PC Software

PC 9 pin com port (typically COM1 or as setup under the Communications menu) is connected to this unit with Electro Industries' manufactured and furnished special cable. This cable typically has the 9-pin connector on one end, a "barrel" containing circuitry approximately halfway along the cable, a flat cable going to a flat 6-pin connector. If ordering separately, request ET-RS232-WF.

On this unit's circuit board locate the small pin plug (J1) soldered to the board. This is a 6-pin header with the second from the top pin cut off (5 pins sticking up at you).

Observing the special cable flat connector end, you will notice the second hole from one end is plugged. This will be the keying pin when plugging into this unit's circuit board.

It is permissible to plug in with this unit's power on; however, realize there is power on the board and around the transformer it is 240, line voltage.

This unit must be powered up (green light on) to activate or read data from the PC.

Initiate PC using normal Windows process and procedures. This software also has a HELP file. The primary field usage of this software will be the first screen or ALT-D. Repeated samples (or data reads) can be accomplished by pressing the space bar.

For field calibration, use ALT-R.

There are other calibration routines within this software, the user should not go there, unless directed by Electro Industries' factory representative.

Real Time kW Monitor (also Checking Multi-Loads)

The PC first screen (or ALT-D) shows a calculated kW each time the space bar is pressed. This is for observation purposes only, but allows the user to verify kW at any time.

Multi-loads - this kW value can be used to quickly verify proper CT stringing when monitoring multi-loads.

1. Using source circuit breakers, only turn on the first load (the one which provides 240 to this unit) and have the other breakers off.
2. Verify kW value approximately represents this load.
3. Turn on the next circuit breaker, recheck kW displayed and verify it has increased by the value of the load.
4. Turn on next consecutive breakers and verify the kW value continues to increase in approximate correct value.
5. If at any time, when adding loads, the kW value (pressing space bar) decreases, the wires going through the CT for that load are incorrectly strung.

Field or User Calibration

Comment: If the yellow LED is not on solid, this unit has been factory calibrated with certified and traceable volt meter and current meter. This calibration is accomplished at approximately 10% and 90% current end points and at 105 and 130 voltage points. Also the approximate midpoint is rechecked and current and voltage offset are downloaded to bring these midpoints to the exact current and voltage represented by the factory calibrated instruments. Realizing this, the following should be used as an overall verification of the correct operation and accuracy of this unit, but the user must discern the accuracy of his voltage and amp meter before downloading any offsets or before attempting to recalibrate this unit. In simpler terms, clamp-on amp meter is not a very accurate device. However, it can be used to make sure things are within "range".

1. Select a load value or monitoring point which represents the majority of the energy recording. Use handheld current device to read the current to the load(s). If it is multi-loads, all currents must be represented by the field connected device.
2. Attach volt meter to the same point represented by the black and red wire going to this device.
3. Using PC software, observe first screen, and acquire a representative number of samples by repeatedly pressing the space bar. Note the current and voltage values on the screen and compare to the attached handheld instruments.
4. If after careful observation user determines an adjustment should be made, subtract (plus or minus) the values. Note this difference (plus or minus) and proceed to PC screen entry.
5. Enter the plus or minus offset for either current and volts. Permanently record this offset by selecting the Communications menu and WRITE.
6. If desirable (also suggested) go back to ALT-D and repeat steps 3-5 above.

Warning: Suggest entering offset values of less than ±2A. If it appears you need to enter an offset greater than ±1, caution, there may be something wrong with the setup, with the field instruments, calibration technique, etc.

AMR (Meter Reading Devices) Application or Interface

This unit contains an internal pulse initiator with an open collector/emitter isolator interface at each "black mark" point output is a 200 ms pulse. Typically the external KYZ input meter terminal or AMR device is connected to J2-1 and J2-2. Note: J2-1 (or red/blk wire) must be DC positive. The AMR device is setup for 2-wire, KZ, and Kh = 7.2. For convenience order accessory cable ET-KZ-SP with easy plug-in connector and 4-foot wires.