Help selecting the right CTs for Scandinavian install

I am trying to figure out the right selection (types and amount) of CTs to buy with a European bundle.

This is a photo of the inside my box:

The box is in Denmark and I plan on having the CTs and the Iotawatt installed by a certified electrician.

The photo shows:
Two 230 volt groups for 13A (numbered “1” & “2”).
Three 400 volt groups. The one numbered “3” has a “Max. 13” label on the cover. The one numbered “4” has a “Max. 16” label on the cover. Finally the one numbered “5” has two “Max. 13” labels on the cover. That last mentioned group numbered “5” is by the way going to the garage in where there is a local box.

Finally the buttom left corner is the mains coming in to the HPFI switch.

From what I figure I need 9 CTs for the 400 volt groups (3 for each of them since they are three fased) and 2 for the 230 volt groups (1 for each since they are single fased). And finally I guess I should have three CTs for the three fased mains?

Is this correct and can anyone help me figuring out the right CT versions to buy?

I’d recommend using 100A CTs for the mains, and 50A CTs for everything else.

I think your math is right:

Mains 3/100A
230V breakers 2/50A
400V breakers 9/50A

The IoTaWatt has 14 CT inputs so you would need to use derived three-phase reference as you would lose two for additional VTs. It should work out fine.

Thank you for the fast reply.
With that confirmed I believe the following will be the right purchase?

Base Unit: IoTaWatt Standard Base V5 × 1
USB Power Supply: USB Power Supply (Euro Plug) × 1
AC Reference Transformer: 9V AC Reference Transformer 230V Euro Plug × 1
Mains Current Transformers: Current Transformer 100A x 16mm split-core × 3
Additional 50A Current Transformers: Current Transformer 50A x 10mm split-core × 11

And that the installation should be as illustrated here:

  • Yellow "[]"s are the three 100A split core CTs in Iotawatt input 1,2&3
  • White "[]"s are the eleven 50A split core CTs in Iotawatt input 4-14

Would that be correct?

The only thing I would question is the placement of the mains CTs. The 100A split-core CTs have a 16mm opening, and getting that around two conductors in that tight space may be difficult. The input side is a single cable, so to the extent you can get the CTs in there, that would be an alternative.

A mixed approach is OK, with some CTs on the bottom and others on the top. In particular I’m looking at the #1 incoming main might be hard to put a CT around and the corresponding #2 pair looks easier (provided the 16mm CT can fit around two cables). The other two phases may be easier to do from the bottom.

If the electrician can get at more exposed cable on the bottom, that would eliminate any guesswork.

I will consider those possibilities when I am going to talk to a electrician. Thanks for your responses - just ordered a complete bundle.

In my further planning I ended up figuring out that I don’t have any nearby 230v wall power plugs on the same floor as my breaker box. Therefore I think the right solution would be to have a new 230 group/breaker installed right beside the “2”-breaker in the breaker box to power a a series of 2-3 new wall plugs that should be installed right next to my breaker box.

Would it be possible to run two "fase cable"s (one from the breaker marked “2” and a new 230V breaker powering the AC Reference Transformer and the IoTaWatt USB power supply) through a single 50A CT? Or should I get another CT and a stereo mini jack headphone splitter?

The 50A CT has a 10mm opening, so you can measure the conductors and see if two will fit. I think there is a good chance because what I see coming off #2 looks fairly thin.

Another approach would be to “daisy chain” the inputs to #2 and the new breaker so that all of the current passes through the upstream conductor feeding both.

A 100A CT would certainly be able to handle two conductors.

And finally, yes, a second 50A CT could be combined with a splitter.