400V TN-C-S setup

I’m living in Norway and have a 400V TN-C-S setup. So I have L1, L2, L3 and N, 400x3 and 230v.
But I can’t find how I should configure the IotaWAtt power monitor inputs in the manual. Could someone please guide me to the right point in the manual or forum? With my current setup, I get a consumption of 7kWh, but it should be about 3kWh.


Are you saying that you have 400V phase-phase loads? Are the circuits that you list 230V?

Correct, but some of the loads are 400v x 3 as well.

The documentation describes how to setup a three-phase wye configuration here.

I don’t see any set of two or three inputs indicating a delta (three-wire) connected load. If you have one, you can measure it using two CTs. Place one CT on the phase A conductor, specify mains phase C-A and check reverse. Place another CT on phase B and specify mains phase B-C. The total power will be the sum of the two.

Alternatively, you can put a CT on each of the three phases and specify that phase as the mains phase. The total power would be the sum of all three.

Thanks for the fast feedback, in the manual it says that I need to identify phase A. But my voltage reference is between L2 and N, so then L2 is my phase A conductor and should be configured as C-A with a CT on my L2 conductor? And I only need to use 2 channels? So I can remove the CT on my phase C? My consumption is still way too high.

Not exactly. It says that the phase where the VT is connected is phase A. It goes on to explain how to identify phase B and C.

You had asked about measuring a three-wire load, and that can use two CTs as explained, but your mains are a four-wire load and require a CT on each of the three hot wires. Their reference is phase A, B and C as in the basic derived reference setup procedure in the docs. The sum of the three incoming mains should match your meter.

I think I have followed the manual… But something is still wrong, when I connect a 1800w load to phase A it rises with 6500w, the same if I connect it to phase B. And my total consumption is 3066w , but the wattmeter says it’s 12067w.

I see above that you had all of the CTs configured as ECS24200. I haven’t sold those for several years now. Are you sure that’s what you have installed?

1 Like

Thanks, that did it. I could not see the name on my CT in the dropdown list, so I used the one in the manual. But when I changed to AcuCT-H040-50 it all worked out great.

1 Like