CT 200 Accuracy and Calibration

virtualfreak1 · Post by **virtualfreak1** » Mon Jun 15, 2015 1:16 pm

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?

Post by **ben** » Mon Jun 15, 2015 2:07 pm

What are your PT settings?

Check your voltage readings to see if they're reading obviously low at all.

virtualfreak1 · Post by **virtualfreak1** » Mon Jun 15, 2015 8:19 pm

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.

Post by **Teken** » Mon Jun 15, 2015 9:00 pm

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

virtualfreak1 · Post by **virtualfreak1** » Mon Jun 15, 2015 9:30 pm

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

Post by **Teken** » Mon Jun 15, 2015 9:57 pm

Can you provide the values shown in the GEM's internal web setup page.

Ideals are peaceful - History is violent

virtualfreak1 · Post by **virtualfreak1** » Tue Jun 16, 2015 4:27 am

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

Post by **Teken** » Tue Jun 16, 2015 8:20 am

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.

Post by **ben** » Tue Jun 16, 2015 9:31 am

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.

Post by **Teken** » Tue Jun 16, 2015 6:01 pm

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.

CT 200 Accuracy and Calibration

CT 200 Accuracy and Calibration

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