Would almost certainly need to spend a small fortune to find something with greater accuracy

NO worries. To quote a co-worker, the only stupid question is the one that doesn’t get asked. :grin:

When used on a single phase system, you simply ignore any of the “measurements” that apply
to a 3-p system. e.g. you’d ignore any L-L reading and use the L-N reading. It really is as simple
as that. :wink:

I use a combination of Wattcore and Magnelab CTs. In the US, the wires we use to feed our circuit breaker panels are significantly larger than those used in the UK, (and I’d guess elsewhere, as well) which is the driving reason behind my choice of CT.

So my first question is what is the diameter of the wires your CTs are attached to?

Second, do you want split core, or solid core CTs?

Hm, ok. So you say the device will just work fine with a CT unconnected and I can safely ignore inter-phase metrics. Naturally I can do any calculations necessary on the other end of the Modbus wire.

It’s an European 230V system. We used to have 3 phases somewhat evenly distributed in the house but it’s not needed any more so we simplified the system to a single phase with the solar inverter also connected to it. Amperage is max. 32A so the wires are relatively thin (IIRC the main wire is 6 mm2 / AWG 9 or so). Split or solid is indifferent for me, but split are obviously easier to apply/remove.

OK, that gives you a wide choice.

What’s your “max budget” for two CTs?

Hmm, I’d like for the system to have at least 0.5% accuracy on all metrics including energy, which doesn’t seem unrealistic. I’ve seen split-core CTs around $20-30 each with 0.2% accuracy on paper. Can’t recall the brand, sorry. I’d expect to pay for them around that amount.

Wattcore has split core CTs that are in your price range, but I don’t know if they have a distributor
in Europe.

The Magnelab SCT series is about 50 USD each, but they do have a European distributor.

(Shipping from the US would increase the cost more than just a little)

That’s about all I can offer, as I’m in the US, so I don’t have any more info on European
avaiablility other than what I mentioned above. Sorry I can’t be of more help.

No, it’s a great help already, thank you. I can order from the US or from Ebay used, I don’t care really. I expect to shell out for shipping, naturally. I’m looking for a system price comparable to the price of an EmonPi with a similar setup (that’s around Ł200, preferably less). I think it’s doable, it would have greater accuracy without all the hassles of manual calibration - I would need to do some additional work but that’s fine. I guess I’ll start hunting for suitable CTs and then think about the next step involving a WattsOn.

Sounds good.

I have three of them, and they’ve worked without a single problem for well over three years.
If you need any help / have any questions, fire away!

In that case, another choice is the Wattcore WC-1 series.
Split core, available in several ratings and as a voltage output type.
They usually go for ~25 USD on Flea-Bay.


That listing is for a mA type, so is just an example.

Thanks, I was eyeing the WC-1 series. The listed accuracy is 0.5%, so it might not meet the system accuracy of 0.5%, but that might be a bit far-fetched after all.

Here’s a revenue grade Magnelab CT:

Thanks, I had a glance on these when you linked Manutech above. They list 0.5% for this too. Do you think there’s a difference accuracy wise between the one on Ebay for less than half of the list price of this (for WC1 phase error is not specified, though)? These are not those Chinese companies that sell the stars from the sky after all.

Given that the best accuracy claim I can recall seeing for an OEM device was 1%
if nothing else, you’d be doing at least that good.

CT accuracy is like building a hot-rod. (fast car)

When he took his engine to the speed-shop to get it souped-up,
the customer was asked by the shop owner
speed costs money, young man. How fast do you want to go?

Better accuracy = more $$$. Sometimes a lot more. e.g.