Page 1 of 2
CT 200 Accuracy and Calibration
Posted: Mon Jun 15, 2015 1:16 pm
by virtualfreak1
I've noticed my GEM is reporting a different total Energy value than what my utility records. It looks like its been doing it for as long as I have historic records. It's not consistent but the utility seems to average be about 10kWh more than my GEM reads.
I have 400A service to my house (2 service panels) I am monitoring 4 feeds (2 per panel) each one on a separate GEM Channel. I use SEG to combine all 4 channels into a calculated total Energy stream.
Here are some samples of the differences
Date GEM/SEG UTILITY
5/17/14 33.6 42
6/17/14 89.9 99
7/17/14 53.5 61
What is the best way to calibrate my CT-200s?
Re: CT 200 Accuracy and Calibration
Posted: Mon Jun 15, 2015 2:07 pm
by ben
What are your PT settings?
Check your voltage readings to see if they're reading obviously low at all.
Re: CT 200 Accuracy and Calibration
Posted: Mon Jun 15, 2015 8:19 pm
by virtualfreak1
ben wrote:What are your PT settings?
Check your voltage readings to see if they're reading obviously low at all.
According to the GreenEye Monitor Setup v2.8 the CT channels are set to split 200
The voltage according to the greeneye monitor is around 103v. It seems low.
Re: CT 200 Accuracy and Calibration
Posted: Mon Jun 15, 2015 9:00 pm
by Teken
In the GEM's setup page what are the values for the PT? What value is being used for the CT?
Ideals are peaceful - History is violent
Re: CT 200 Accuracy and Calibration
Posted: Mon Jun 15, 2015 9:30 pm
by virtualfreak1
Teken wrote:In the GEM's setup page what are the values for the PT? What value is being used for the CT?
I attached a screenshot of the PT values (187 / 3)
The CT is using the Split 200 preset - Type 231 Range 2
Ideals are peaceful - History is violent
Re: CT 200 Accuracy and Calibration
Posted: Mon Jun 15, 2015 9:57 pm
by Teken
Can you provide the values shown in the GEM's internal web setup page.
Ideals are peaceful - History is violent
Re: CT 200 Accuracy and Calibration
Posted: Tue Jun 16, 2015 4:27 am
by virtualfreak1
Teken wrote:Can you provide the values shown in the GEM's internal web setup page.
Ideals are peaceful - History is violent
Here is a screenshot from the GEM Internal website
Re: CT 200 Accuracy and Calibration
Posted: Tue Jun 16, 2015 8:20 am
by Teken
Both values look good if you have a true RMS multi meter please measure the line voltage where the PT is plugged into and report back.
Re: CT 200 Accuracy and Calibration
Posted: Tue Jun 16, 2015 9:31 am
by ben
Teken wrote:Both values look good if you have a true RMS multi meter please measure the line voltage where the PT is plugged into and report back.
You can also try isolating a circuit down to a lightbulb and see if the GEM displays the correct watts. If it's low, adjust the PT Type until the watt value of the lightbulb matches its rating.
Re: CT 200 Accuracy and Calibration
Posted: Tue Jun 16, 2015 6:01 pm
by Teken
I just noticed your values from the GEM's setup page is different from the other tool you used. One references 193 / 3 in the GEM's setup page.
Is channel 1 really been set to 193 /3 for the 200 amp CT? As the web page still shows the base values of 144/ 2 I expect?
As the other tool shows a value of 231 / 2 for the 200 amp CT?
Moving forward please only use the GEM's internal web setup page. The tool you showed earlier has been deprecated long ago.