Inaccurate Voltage and Watt readings

[crazydane]

I have a system consisting of 3 GEMs and a 1240. I'm finding much greater variances in both Voltage and Power compared to what they should be.

Here's an overall schematic of my layout with my primary Split-200 CTs and PTs:



Per the diagram, GEMs 1 and 2 show the correct incoming voltage, which is typically 123 Volts. The 1240 located 60' away is showing a drop of 2 volts, which should only be 0.2 volts given a 2,000 watt load across 60' of 3 Ga copper wire.

The large discrepancy, however, is GEM 3 which is located 200' away from GEMs 1 and 2. 500 MCM Aluminum cable is used here, and with no load on the shop end (and with no solar generation), GEM 3 is reporting 111 volts where is should be 123 volts.

These are the transformers connected to GEM 3 in the shop building:



They are plugged in as follows right below the shop sub-panel:



Power readings are also off. Right now the CT's at the main disconnect switch is reporting 2486W and 3100W on CH1 and CH2 respectively. The true draw is about half of that. The 2 channels with these CTs are configured as follows:




GEM3 in the shop building also has a pair of Split-200 CTs for measuring solar production. It is currently showing power readings of 1150W across each CT where is should be 1375W as measured by another device. I believe this discrepancy is due to the voltage reading being low on GEM3. These 2 channels are configured as follows:




Thanks!

[crazydane]

I power cycled GEM3 to take the pics of the transformers, and now the voltage readings are all in the ballpark:

[crazydane]

So on the issue with the power readings being off, here's Total Consumption compared to what my main Split-200 CT's are showing:



So CH1 + CH2 = 5,671 watts average.

Total Consumption average is 11,343 watts, which is exactly twice what is should be.

[ben]

Remove the Main setting on your Main CH1 and Main CH2, leave it on the NET channels. It's double-counting due to that setting being set on both your NET Channels and 1/2.

What COM F/W is GEM#3 running? If it's a blue board, can you grab a picture of the mono jack?

We've been adding epoxy to the jack on blue boards due to issues with the jack lifting.

[crazydane]

Unchecking Main on CT 1 and 2 fixed the Total Consumption issue. Thanks!

My board looks black from what I can tell, but it does appear to have some epoxy by the mono jack:



It is on COM 5.13 and ENG 1.49.

Also, the 2 GEMs at my main panels are using these PT's:



Perhaps that is why the voltage readings are slightly different?

[ben]

Can you make the jack connection a bit looser? Looks like it's being pulled pretty tightly. Don't want to put too much strain on the jack.

Voltage will be slightly different at different outlets but not significantly different like it was (110s vs 120s).

[crazydane]

I'm also curious about the readings of my Main CTs vs. my Solar CTs.

Here are my current readings for both:





I choose not to "hide" any of the CT's after selecting the "NET" option.

My Solar CT's are showing the exact same values for the non-NET vs the NET channels for each channel. But my main CTs are slightly off. Not sure why they aren't reading the exact same values.

I created a group for my Main CTs and another one for my Solar CTs. When I plot them, I get this:



The first dip (left arrow) makes sense to me as power is being pushed back into the grid. But the solar peak represented by the right arrow does not. It is almost as if the green curve goes positive again instead of dropping below 0 watts.

[ben]

Are the solar CTs on the main breaker or directly on the breaker from the inverter? They should go negative when generating.

In your diagram, are you actually using Split-400s on GEM1? Split-200s won't work on a 400A panel unless it's split into 4 200A feeds.

[crazydane]

All my solar inverters are connected to a dedicated 200A solar panel. This feeds into a 400A meter base at the shop building. The 3/0 wires from the 200A solar sub-panel are where the Split-200 CTs are on.

Here are the 2 split-200 CTs in the main disconnect:



Here's a another look at the main service entrance showing the main componets:



Feed from shop is how the solar power gets back to the grid.

The transfer switch on the left feeds the 200A panels on the other side of that wall.

I never pull more than 200A, so I'm not sure why I would need to upgrade to split-400s?

[ben]

All my solar inverters are connected to a dedicated 200A solar panel. This feeds into a 400A meter base at the shop building. The 3/0 wires from the 200A solar sub-panel are where the Split-200 CTs are on.

Here are the 2 split-200 CTs in the main disconnect:

Here's a another look at the main service entrance showing the main componets:

Feed from shop is how the solar power gets back to the grid.

The transfer switch on the left feeds the 200A panels on the other side of that wall.

I never pull more than 200A, so I'm not sure why I would need to upgrade to split-400s?

If you're staying under 200A per leg you're fine. The Split-200s actually should be good up-to around 300A.