8-Sensor Energy Monitor
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121210-2101 EST

The information provided by AADL with any of the energy monitors is relatively meager, and there is no suggested chart for recording measurements. There is no discussion on what you should measure, how measurements should be made, and the significance of any measurements. The relationship of power, energy, voltage, current, volt-amperes, and power factor are not mentioned. To help in some of these areas you can look at portions of my book "Electrical Energy Measurement, Conservation, & Methods to Reduce Your Electric Bill", AADL call number 696 Ro.

The 8-Outlet Wireless Energy Meter is a great disappointment. It is distributed by P3INTERNATIONAL, has the Kill-A-Watt trademark, and consists of two parts. One part of the system is remote sensors that are radio frequency linked to the second part, a display unit. The part numbers are P4220 (each sensor) and P4225 (display).

I expected the sensor to be a single outlet P4460 Kill-A-Watt EZ with the display and buttons removed, and the addition of the RF link. It is not close to comparable. It is substantially downgraded from the 4460. Resolution (smallest readable unit) is worse, and the response time is very long. The P4460 EZ is very good and useful at its price of about $30

The wireless system display emphasizes $ cost and carbon, and de-emphasizes the basic measurements. The wireless display is hard to read. The P4460 EZ has a much better display than the wireless P4225 display. The only advantage the wireless system has is that the sensor can be put behind whatever equipment is being monitored without the need for extension cords to bring the display to a readable position. Mapping multiple sensors to one readout has little value as configured. Because of the long time delay between reading updates you loose any quick sense of whether the system is working or not.

My philosophy is that all energy measurements and thinking should be done in kWh (kilowatt-hours) to avoid confusion and provide a stable consistent reference. To use $ or carbon is only going to lead to confusion. When you really need to know a $ or carbon value, then do the conversion at the current rates.

Illustration on my use of energy:
2006 was 14073 kWh @ $ 0.116 /kWh,
2011 was 14346 kWh @ $ 0.141/kWh,
2012 esti 11521 kWh @ $ 0.162 /kWh.
Comparing total cost of energy between these years is not useful in determining energy usage because the rate in $/kWh is not constant. To judge my energy change efforts I need to look at kWh, not $.

In 2012 the average cost has increased considerably, and I have reduced consumption.
For the 2012 year my consumption will be down almost 20% compared to 2011, but cost is up about 15% from 2011, and about 40% since 2006.

I believe you will find this wireless system non-intuitive, awkward, frustrating, and slow in use. Furthermore tech support at P3 seems to be lacking in knowledge on their own system.

With the wireless system from AADL the response time for a measurement with only one sensor active was about 2.75 minutes. I would have expected 1 to 2 seconds, which is the response time for the 4460 EZ. This wireless system response is so slow I can not practically test for minimum voltage or resolutions, and other factors.

In the auto scan mode, to scan 8 sensors, the total scan time is about 12 seconds. Scanning thru all 8 sensors, vs, just locking the display on one sensor, seems to make no difference in the data update rate. It is still about 2.75 minutes. Also note that in the auto scan mode all sensor addresses are scanned whether a sensor is present or not.

Just after address association the time to the first read may be about 30 seconds. Considerably better than the normal response time, but it is a one-shot.

"Reception Status", a small disk at the display top right, effectively tells you when a new sensor value will be displayed. When the disk transitions from solid black to white the data is updated to the present value from the selected sensor. This disk rotation is 2.75 seconds. Correction 2-2-2013 should read 2.75 minutes, not seconds.

From what is easy to perceive, the wireless system voltage measurement resolution is no better than 1 V compared to 0.1 V for the EZ unit. I can't, meaning won't because of the time delay, determine the minimum working voltage for the sensor, and it is not in the specification. The wireless upper spec is 125 V. The EZ spec is 85 to 125 V. Actual residential voltages may exceed 125 V some of the time in some areas today. In the early Edison days 110 V was nominal, today it is 120 V. The Kill-A-Watt upper specification limit is a stress limit, whereas, if provided, a low limit would be a functional limit. One EZ unit I have works (reads) from about 50 V to 145 V. This would be a functional range, but since the upper specification limit is 125 V the 145 V I applied to the EZ is probably an excessive stress level. Older P4400s tended to fail to operate at much higher low end voltages. I had one 4400 that was unusable because it quit at 107 V. More normally the 4400s were about 100 V.

Kill-A-Watt wireless resolution is no better than 1 W, 1 VA, and 0.01 A, and may not be this good. The response time is too slow to run tests. The 4460 EZ resolves 0.1 W up to 100 W, then switches to 1 W. Similarly for volt-amperes. The EZ current resolution is 0.01 A.

The various Kill-A-Watt models are usable in a nominal 120 V circuit with plug-in loads up to 15 amperes. This means you can test entertainment centers, refrigerators and freezers, toasters, flat irons, small kitchen appliances, vacuum sweepers, electric mowers and other tools, etc.

You can not measure most air conditioners, installed electric water heaters, furnace blowers, wall ovens, range tops, and dryers. Also built-in lights can not be measured with any Kill-A-Watt unit. Some of these are your largest power users, but may not be your greatest energy user. We seldom use our wall oven, thus not a lot of energy is used, but power is high when on. Energy is the integral of power over time.

You can measure the motor on a gas clothes dryer, and a washing machine.

Unlikely you can measure a microwave because the RF radiation will probably jam the Kill-A-Watt communication channel.

None of the Kill-A-Watts provide data output to a computer. Data output is available with a TED System (The Energy Detective). But the TED System is not feasible for the AADL to provide on loan. Some data collected using a TED System are provided at the following page on my web site http://beta-a2.com/energy.html . This provides you an idea of how my power use varies. Most homes will drop off more at night than mine. Homes with no one, but the dog, home during the day may show a daytime dip.

If P3International had taken their P4460 EZ, removed the display and keys, added a good RF link, combined these with a communication unit that interfaced with a personal computer, and good software, then a desirable system could have been provided. I have to classify the present wireless Kill-A-Watt system as unacceptable. For individual measurement of plug-in 120 V loads I suggest using the Kill-A-Watt EZ P4460 with two #14 wire extension cords. One cord should have a straight plug and the other a right angle plug. The straight plug is used to plug into the wall and make removal easy.

The Kill-A-Watt instruction manual is too small, hard to read, and provides no information on different loads and how to interpret the data. The provided specifications are on page 23.

In the AADL Kill-A-Watt wireless system each sensor has a number, 1 - 8, on the front to identify the sensor address. This seems to be absolute in contrast to the description under flashing L in the manual, p 15. So AADL units may be different than over the counter systems. To associate (teach) a sensor with the display you must first have that sensor unplugged from the wall, get the display into the flashing L mode (press - key for about 3 seconds to enter flashing L mode), then early on within a limited time (flashing L disappears after about 20 seconds) plug the sensor into a hot (meaning on) wall outlet. When association has taken place the sensor address is displayed. About 10 seconds to associate. I do not know what happens to sensor association on loss of AC power. A test below seems to indicate the association is retained.

The sensors are not supposed to lose or change accumulated data (cumulative time and kWh) with loss or large fluctuations in AC voltage. This is true of the Kill-A-Watt EZ also. But with an EZ unit I have experienced scrambled data sometimes. It does appear that loss of power for a short time does not cause a loss of association of a sensor with the readout. But I did not see any indication on the display that power was lost, and the presently displayed values at power loss remained at their last value. Should have been a change of the display in some fashion to indicate the power loss.

For evaluation of a refrigerator or freezer a monitoring test needs to run for several days to a week. You do not want a small power interruption to cause your cumulative data to change. This problem exists in the standard Kill-A-Watt P4400.

When you checkout the 8-Outlet Wireless Energy Meter verify that everything is in the package that is on the list of items for that package.

121211-0931 EST

An additional point.

Short time loss of power to a sensor does not cause a loss of address registration information with the display. This I determined and mentioned above.

Last night I depowered the only active sensor. This morning, about 8 or 9 hours later, I found the sensor was not recognized by the display. Thus, the registration process had to be repeated. This meant removing power from the sensor, put the display in the flashing L mode, and reapplying power to the sensor.

I don't know and won't find out how long power can be removed from the sensor before it has to be re-registered.
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