Error in Kwh consumed - 230 VAC / 60Hz


#1

So I received my IotaWatt A few days back. The grid power here is 220 Vac / 60Hz.

I have noticed that my power consumption reading on IotaWatt is completely out of whack.

On 13-03-2018 13:05

  • electric meter reading 5973.9 KWh
  • iota watt reading: 0.3 Kwh

On 15-03-2018 08:20

  • electric meter reading 5981.8 KWh
  • iota watt reading: 17,7 Kwh

So net usage: as per electric meter: 7.9 KWh / as per IotaWatt: 17.4 KWh. (I have similar readings on emoncms dot org server).

I have check with a fluke meter that the voltage and the power in the status page are correct. (within 1%).
I can’t seem to wrap my head around the issue. since the instantenous power is more or less in the ballpark, how can the accumulated power be so much distorted.

Any help would be much appreciated.

My current setup:



#2

Where are you located? I have not seen a 60Hz 230V system before. The time this came in suggests you are either nocturnal or living in North America. That’s a big clue to what might be wrong here (not that there’s anything wrong with being nocturnal):sleeping:


#3

Haha. true that. I am currently living in one of the handful of countries that use this system - South Korea.

I will collect more data over the next few days to try and figure it out.

Can you point me to certain commands I can use in the browser to get hold of raw numbers? Then I can try and sum them in excel, graph etc.


#4

So there might be something wrong with living in NA? :joy:


#5

Lately? I’ll give you three guesses.

Do you have any alternative energy sources like solar?

Can you post a local graph app screenshot of the power and energy of “total” over a day? Like this:


#6

In the above graph app, you can click “show csv” and get a comma delimited dataset of the points that you can copy and paste into a spreadsheet.


#7

Thanks for the quick response.
I don’t have any alternative energy sources.

here you go.


#8

I tried that. If I select to get the CSV for a whole day, the samples are 120 seconds apart.
I have to reduce graph range to a couple of hours to get sample which are 10-20 seconds apart.

Is there any way to get all the samples for a whole day which are less than 20 seconds apart in one go?


#10

just downloaded all the samples at feed rate resolution (10 seconds) from emoncms dot org server.

When calculating in excel. it gives the same result as accumulator in IotaWatt or Power_to_kwh funtion on emoncms server.

The only thing now could be that the instantaneous power is indeed wrong. Will recheck readings in a couple of hours when I am back home.


#11

Your power factor is quite away from unity. So either you have very unusual loads or your service is two phases of a three phase supply. This would be common in an apartment or other multi-family dwelling. I believe there is a way to get iotawatt to handle this correctly.


#12

I was waiting for the result of this. Perhaps you found the problem by now? In the universe of things it could be, I think that the computation of kWh from watts is pretty low on the list of possibilities, so I let you run that to ground. Like @frogmore I raised as eyebrow at those power factors, but they are not completely unrealistic, so maybe that’s it.

The simplest test I can recommend at this point is to connect an incandescent light and put a CT on one of the wires serving that exclusively. You should get a power reading that pretty much matches the nameplate rating of the bulb. If it’s off by a lot it’s probably a phase problem. If it’s correct, you might start to consider your meter may be real slow, which you may not see as a problem.


#13

Well, for the record, this is not IotaWatt’s problem.
My iotawatt CT was hooked up at the input of the main supply two pole breaker (phase + neutral).
This is (obviously) downstream to the electric meter.

For some reason the current at the input of the supply circuit breaker and input of the electric meter is not the same.
Upon further investigation I found out that this apartment building apparently has some part of power supplied free of cost (mostly for the fixed appliances). then any thing you hook up to the wall, has to be paid by the person living in it, hence the different reading.
wired? you bet.