not2bme
Member
- Joined
- Oct 16, 2017
- Messages
- 517
Just a warning for all folks on the SDM630 that I bought and found to be inaccurate and confirmed by the manufacturer that it is by design.
I bought a Eastron SDM630 CT version two months back through their aliexpress store. It's the version that uses the 0.333V CT and has dual CT input. I chose 0.333V because it usually has better accuracy than the 1/5V at the lower end. I was going to use this to measure the usage at the main power from the grid as well as the circuit going to the inverter. I used the CT version as it didn't require me to disconnect the power from the mains (which would have been almost impossible to do without asking the utility to pull the meter out so I can safely rewire it). So I chose the CT method which just clamps on to the wire. Combine that with the ease of just polling the device for the import and export kWh via modbus makes it quite easy.
What I found out was that something not reported by the manufacturer, but the accuracy of this unit fails to report any actual watthour below 1% of the rated CT transformer used. So if I was to properly use the 200A CT to match my service amp, any amps under 2A would not be reported. 2A at 120V would be roughly 240W.
And for both legs it would be a total of 580W that would go unreported. This is normal according to the manufacturer.
But I also have a Schneider unit that happily reports this watthour. In fact it happily records as low as 0.04A or around 5W. This is with a CT that is rated at 100A.
Funnily, the SDM630 does reports down to as low as 0.04A as well, but since it is under the 1% threshold, it refuses to record the wattage. So it's a design by nature even though it's capable and seems to record the amperage as well as the Schneider. Unfortunately I was going to use this SDM630 to make sure I don't feed back into the grid, but without knowing which direction the amp is going (since the amperage only reports in positive) and the watts record in the negative when feeding back into the grid.
I am mitigating this error in the SDM630 by using a 50A CT, which means at 0.5A@120V is roughly about 60W. But this also puts my maximum capture at 6000W per leg, which shouldn't happen that often in my case.
But in short, I'd avoid this meter if you expect to use it as a submeter as it would under report.
Here's the excerpt from the manufacturer that they are claiming it's as advertised and I have to request a custom.
Here's where my Schneider reports at 0.08A and 0.2A on a 100A CT. That's pretty low on the scale. The SDM630 would display the amperage but not report wattage under 1A.
(Slight difference between the meter and the kill-a-watt due to probably inaccuracies at low amps and the power usage by the kill-a-watt itself that the Schneider is capturing as well)
I bought a Eastron SDM630 CT version two months back through their aliexpress store. It's the version that uses the 0.333V CT and has dual CT input. I chose 0.333V because it usually has better accuracy than the 1/5V at the lower end. I was going to use this to measure the usage at the main power from the grid as well as the circuit going to the inverter. I used the CT version as it didn't require me to disconnect the power from the mains (which would have been almost impossible to do without asking the utility to pull the meter out so I can safely rewire it). So I chose the CT method which just clamps on to the wire. Combine that with the ease of just polling the device for the import and export kWh via modbus makes it quite easy.
What I found out was that something not reported by the manufacturer, but the accuracy of this unit fails to report any actual watthour below 1% of the rated CT transformer used. So if I was to properly use the 200A CT to match my service amp, any amps under 2A would not be reported. 2A at 120V would be roughly 240W.
And for both legs it would be a total of 580W that would go unreported. This is normal according to the manufacturer.
But I also have a Schneider unit that happily reports this watthour. In fact it happily records as low as 0.04A or around 5W. This is with a CT that is rated at 100A.
Funnily, the SDM630 does reports down to as low as 0.04A as well, but since it is under the 1% threshold, it refuses to record the wattage. So it's a design by nature even though it's capable and seems to record the amperage as well as the Schneider. Unfortunately I was going to use this SDM630 to make sure I don't feed back into the grid, but without knowing which direction the amp is going (since the amperage only reports in positive) and the watts record in the negative when feeding back into the grid.
I am mitigating this error in the SDM630 by using a 50A CT, which means at 0.5A@120V is roughly about 60W. But this also puts my maximum capture at 6000W per leg, which shouldn't happen that often in my case.
But in short, I'd avoid this meter if you expect to use it as a submeter as it would under report.
Here's the excerpt from the manufacturer that they are claiming it's as advertised and I have to request a custom.
Here's where my Schneider reports at 0.08A and 0.2A on a 100A CT. That's pretty low on the scale. The SDM630 would display the amperage but not report wattage under 1A.
(Slight difference between the meter and the kill-a-watt due to probably inaccuracies at low amps and the power usage by the kill-a-watt itself that the Schneider is capturing as well)
