Question about ECOL09 CTs

Hi all,

I will be ordering Ecol09 solid core CTs, but I am unsure about the exact specs; this is for 20A circuits, 220V / 50Hz.
I found this spec sheet:

… which seems to imply that I have a choice for outputs. Should I go for a
ECOL09-20 with a 50mA output if that actually exists?

If not, would you recommend ECOL09-20/20mA or ECOL09-50/50mA as far as precision is concerned?


The 20A/20mA or the 50A/50mA produce exactly the same output in the 0-20A range. They are both what is commonly called “1000 turns”. I recommend (and sell) the ECOL09-L59D which is 50A/50mA.

I know there is a lot of discussion about precision in other places, but I would respectfully offer that whatever problems that advice is intended to solve do not exist with IoTaWatt. That is to say I don’t believe it is fundamentally a problem with precision of the CT or value of the burden resistor. I believe it has more to do with other fundamental issues with the devices associated with that commentary.

You don’t have to overthink this. 50A CTs will give you excellent results with IoTaWatt.

Sounds great, thanks! You wouldn’t ship 10 of them to France would you :slight_smile:
If not I’ll try alibaba, that seems to be the only option here.


BTW, I am looking at those CTs because space is at a premium in my panel, and because it gets really hard to make sure that a split core CT is snugly closed once it is buried in a forest of cables.