CT Clamps - some Qs.

WIAWSNB

Well, got all my bits, and now just need to join them together; 3 of 5.7kWh Alpha-Ess batteries, Sofar ME300SP AC-coupled inverter, and all the gubbins.

The two CT clamps have short wires, so I need to extend them. I understand Cat cable is good for this. Q1 - for neatness and convenience, can I share the same Cat cable for both clamps, one on each twisted pair?

Q2 - one clamp has a snapped ferrite collar thingy in the lid, but it fits neatly together - will this fracture affect its performance? Should I superglue the parts together?!

Q3 - If the clamp's cable hole is larger than the phase cable so it's super-loose, should I wrap tape around the cable so the clamp sits on it perpendicular, and not at a sloppy angle? Does it make any difference?

Thanks.

Grumpy_chap

If one of the clamps is damaged, why not get the supplier to remedy?

WIAWSNB

https://forums.moneysavingexpert.com/discussion/comment/81992043#Comment_81992043

'cos it's all second hand stuff. They don't cost much either, but just wondered if anyone knew if it was an issue. I should be able to test it soon anyhoo.

QrizB

Q1 - I extended my CT cables with bell wire / speaker cable. If you're using CAT 3/ 5 / 6 / whatever UTP, you'll probably get away with sharing a cable.

Q2 - suck it and see. The important CT with a ME3000SP is the one measuring household import/export; the one measuring solar PV is optional.

Q3 - I left mine loose. No adverse effects noticed yet, after five years or so.

gawthorpe4

Ideally use a twisted pair of the Cat5 for each CT clamp.

If you use solid colour for + and striped for - then it's consistent and you can remember where you are.

The cracked ferrite is probably best to just test it, it will probably be ok.

Regarding the sloppy angle, I wouldn't worry unless you see very innacurate readings, mine and loose and have always seemed to report what I expect.

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QrizB

Vaguely related, I've finally (after all this time) got around to installing the Solarman app and linking my ME3000SP to it. It looks nice and gives some statistics of varying accuracy (as it's relying on CTs).

Here's a screenshot for anyone who's interested (inevitably, a cloud has just gone over and PV output has plummeted):

WIAWSNB

Thanks Gawthorpe. I'll see how it goes, and get another CT if needed.

Wow, QrizB - that is my level of App!

Reed_Richards

Q3. - I'm pretty sure the clamp just needs to surround the cable; the angle is irrelevant.

Heedtheadvice

Q1 The twisted pairs will be fine as long as it is one twisted pair per CT clamp and ok over several metres. Make sure the joins are good and appropriate for the cable types being used solder sleeves, crimps or wagon or chock block. Best in a small enclosure. Plug and socket best avoided unless of a locking types.

Q2 Change it for a new one of the same type. You may get a reading but you cannot know if it is an accurate value and that will not be good. [Edit and potentially unsafe]

Q3 Not an issue provided it totally clamps the wire and no others. Others in the vicinity not a problem neither.

WIAWSNB

A couple more Qs about CT clamps, please…

Would it be the case that if a clamp was fitted t'wrong way around, it could be corrected by reversing the wires at t'other end?

And, my clamps are buzzin' as soon as fitted, with the inverter not yet turned on - the grid one in particular when a load is drawn. I'm assuming this is normal, but it's still annoying - will a dollop of glue on the coil/core tamp it down a tad?

Ta.

QrizB

Would it be the case that if a clamp was fitted t'wrong way around, it could be corrected by reversing the wires at t'other end?

Yes. I think the Sofar ME3000SP also lets you reverse them on software, no physical changes required.

And, my clamps are buzzin' as soon as fitted, with the inverter not yet turned on - the grid one in particular when a load is drawn. I'm assuming this is normal, but it's still annoying

I've never noticed mine buzzing, but then they're hidden away in a cupboard. Sort I can't help here.

How close are you to switching everything on?