We’ve recently had a few reports of “faulty” ENVIs, whereby people are reporting power readings from their solar panels on the ENVI after dark.
One of our customers thought initially that it could be power being generated by moonlight!
In actual fact, it appears that the inverter is drawing power after dark, typically 70-90W, but occasionally spiking to over 200W.
The reaction from the solar inverter manufacturers has been that the ENVI must be faulty, or it could be that the inverter is causing interference to the transmission. Naturally, we have been very worried about this, and have been working our socks of to work out what is going on. This included using a variety of different wireless electricity meters on the same circuit – they all agreed to within a couple of Watts, ruling out the interference suggestion.
Eventually, the answers have become clear. A Fluke Multimeter was reading 0.31 Amps being drawn after dark. A service engineer also reported a power draw of 300mA. 0.31A x 240V = 74.4 Watts.
This has been established in two cases so far, and in no cases have we received any evidence to show that the Current Cost ENVI is reading incorrectly. We’re not going to name the manufacturers involved here for liability reasons, and will continue to keep you posted with any new information we receive.
Showing posts with label Google PowerMeter Australia. Show all posts
Showing posts with label Google PowerMeter Australia. Show all posts
Sunday, September 12, 2010
Tuesday, August 31, 2010
New Google PowerMeter Feature for the Current Cost ENVI in Australia and New Zealand
Google have added some new features to the Google PowerMeter interface!
The first is a "mouseover" ability that shows you exactly how much power was being drawn at a particular point in time.
[caption id="attachment_75" align="alignnone" width="300" caption="Google PowerMeter Australia connected to a Current Cost ENVI, demonstrating the latest mouseover feature to be added"]
[/caption]
Very useful - it's a feature that has been lacking and we're very pleased to see it arrive.
More information available here: http://www.smartnow.com.au/current_cost_google_powermeter_australia.html
The first is a "mouseover" ability that shows you exactly how much power was being drawn at a particular point in time.
[caption id="attachment_75" align="alignnone" width="300" caption="Google PowerMeter Australia connected to a Current Cost ENVI, demonstrating the latest mouseover feature to be added"]
[/caption]Very useful - it's a feature that has been lacking and we're very pleased to see it arrive.
More information available here: http://www.smartnow.com.au/current_cost_google_powermeter_australia.html
Wednesday, August 11, 2010
Accuracy of Wireless Home Electricity Monitors
We often get enquiries about the accuracy of wireless home electricity monitors, so here is a summary of our findings.
Almost all real-time displays available in Australia and New Zealand currently get their data from fitting a CT (Current Transformer) clamp to a cable.
The current flowing through the cable generates a magnetic field. The magnetic field subsequently generates a current in the CT Clamp, which is measured and the data is sent to the display via the transmitter.
As a result, because a CT Clamp cannot take into account such things as Power Factor and varying voltage, it can never be 100% accurate. From experiments with the Current Cost ENVI we ave found it to be 1 – 2% accurate up to 1000W, and 3-8% from 1kW – 10kW (with the accuracy decreasing as the power increases).
The Current Cost ENVI default voltage is 240V, so in areas where the voltage is noticeably different, the accuracy will decrease. However, the ENVI-R (due to be available in October / November) comes with a new transmitter that allows multiple voltages to be set (200V, 210V, 220V, 230V, 240V, 250V, 260V).
With regards to Power Factor, some people make a big fuss about this. However, most household appliances have a Power Factor of close to 1 (the assumed PF in the Current Cost ENVI and most other wireless electricity monitors). It is only in commercial environments where there are large electric motors in operation does this become a real issue.
As an example, the Graham Restaurant in Port Melbourne has an ENVI connected up. Since they’ve connected it, their power consumption has reduced from approx 440kWh per day to 260kWh per day – their monthly bill is usually within 3% of the kWh reading that the ENVI has determined. 260kWh a day is a LOT of power – the average house should be using less than 10kWh per day. http://smartnowenvironmental.blogspot.com/2010/05/turn-off-your-coffee-machines.html
However, all the points above are largely irrelevant in my opinion. If you’re after accurate measurement of power used, you’ve got to spend $thousands for an expensive bit of kit to be installed to do this. The Current Cost ENVI http://www.smartnow.com.au/current_cost_envi_store.php costs $139.95 in Australia, and is compatible with Google PowerMeter Australia and New Zealand http://www.google.com/powermeter/about/about.html. This will tell you clearly that your electric heater is drawing 200 times as much power as your energy efficient light globe, and hence turning lights off in your house is not going to have anywhere near as much impact on your bill as turning off your electric heater / excluding drafts / insulating your house.
It’s all about behvioural change – these electricity monitors provide the information people need to be able to make educated decisions about their power consumption and importantly at this time of rising prices, be able to do something about them in an informed and pragmatic fashion.
Almost all real-time displays available in Australia and New Zealand currently get their data from fitting a CT (Current Transformer) clamp to a cable.
The current flowing through the cable generates a magnetic field. The magnetic field subsequently generates a current in the CT Clamp, which is measured and the data is sent to the display via the transmitter.
As a result, because a CT Clamp cannot take into account such things as Power Factor and varying voltage, it can never be 100% accurate. From experiments with the Current Cost ENVI we ave found it to be 1 – 2% accurate up to 1000W, and 3-8% from 1kW – 10kW (with the accuracy decreasing as the power increases).
The Current Cost ENVI default voltage is 240V, so in areas where the voltage is noticeably different, the accuracy will decrease. However, the ENVI-R (due to be available in October / November) comes with a new transmitter that allows multiple voltages to be set (200V, 210V, 220V, 230V, 240V, 250V, 260V).
With regards to Power Factor, some people make a big fuss about this. However, most household appliances have a Power Factor of close to 1 (the assumed PF in the Current Cost ENVI and most other wireless electricity monitors). It is only in commercial environments where there are large electric motors in operation does this become a real issue.
As an example, the Graham Restaurant in Port Melbourne has an ENVI connected up. Since they’ve connected it, their power consumption has reduced from approx 440kWh per day to 260kWh per day – their monthly bill is usually within 3% of the kWh reading that the ENVI has determined. 260kWh a day is a LOT of power – the average house should be using less than 10kWh per day. http://smartnowenvironmental.blogspot.com/2010/05/turn-off-your-coffee-machines.html
However, all the points above are largely irrelevant in my opinion. If you’re after accurate measurement of power used, you’ve got to spend $thousands for an expensive bit of kit to be installed to do this. The Current Cost ENVI http://www.smartnow.com.au/current_cost_envi_store.php costs $139.95 in Australia, and is compatible with Google PowerMeter Australia and New Zealand http://www.google.com/powermeter/about/about.html. This will tell you clearly that your electric heater is drawing 200 times as much power as your energy efficient light globe, and hence turning lights off in your house is not going to have anywhere near as much impact on your bill as turning off your electric heater / excluding drafts / insulating your house.
It’s all about behvioural change – these electricity monitors provide the information people need to be able to make educated decisions about their power consumption and importantly at this time of rising prices, be able to do something about them in an informed and pragmatic fashion.
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