New starter - No hardware purchased from the shop yet

Good afternoon,

I’m a software developer with very theoric (non-practical) electricity knowledge, want to install and get started with OEM for the most basic use case which is energy monitoring, I’m happy with monitoring only my main import. My short-term end goal is to have it running, run the software including EmonCMS, play around, learn etc… Am I right to get the EmonPi2 Single Phase with one or two CT sensors? (Haven’t bought it yet) Here’s my smart meter set up, where would you add a single CT clamp? I have contacted an electrician to ask about other stuff in the next few days, I may consult with them about this too but I’d like to know what to ask them as it’s not guaranteed they know what I’m trying to do etc.

Thanks :four_leaf_clover:

Welcome, Rosana, to the OEM forum.

What you have there is a standard UK single-phase domestic installation. For the present, your only choice is an emonPi2, with a single phase emonVs and a single current transformer.

You can put the current transformer either on the red cable on top of the main supplier’s fuse (labelled “60 A 415 V a.c”) where the hand-written “4” is, or on the loop of grey cable coming from the brown terminal of the meter. It won’t make any practical difference. The arrow on the c.t. should point along the cable in the direction of the consumer unit in each case.
N.B. The cables are safe to handle, provided you can’t see any bare copper - which if the wireman did his job properly, there won’t be. But it’s wise to check first, one member here posted a picture somewhere on this forum of a completely unsatisfactory job by the regional electricity company (or their contractor).

When it comes to monitoring individual circuits with the second or more c.t, you can’t put a c.t. on a flat twin cable - it won’t read anything (I’ll explain why if you wish), so the c.t’s will have to go inside the consumer unit. Unless you know what you’re doing by then, it is probably something you need to ask the electrician about.

Before you buy your c.t, try to get the smart meter to tell you the maximum current (in amps) that you take with as many appliances as possible switched on all at the same time. My thinking is, you may only need a 50 A one, which will give you better accuracy with low loads, rather than the 100 A.

Don’t be misled by your main fuse being 60 A, it won’t “blow” at exactly 60 A. it will carry much more than 60 A for a long time before it ruptures. Get the numbers first, then decide.

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All understood, very clear. Thank you very much.

you can’t put a c.t. on a flat twin cable

I imagine this is because both neutral and hot wire are contained within the same line and the CT clamp will measure an average of zero current. Something within the consumer unit is converting single separated neutral/hot lines into paired lines so if I were to install CT clamps for individual circuits with the help of my electrician, it should be done before they’re paired.

This was very helpful. Exciting.

This is it exactly.

I don’t quite understand what you mean there. There are actually 3 conductors inside the flat cable, a line conductor insulated with brown pvc, an uninsulated earth conductor in the centre, and a neutral conductor insulated with blue pvc. The outer grey pvc is the cable sheath to mechanically protect the other conductors - it is much tougher. Contrary to what many people believe, it is not primarily insulation.
As soon as the cable has entered your consumer unit, it will have the sheath removed. The brown line conductor will go to the output terminal of the circuit breaker, the blue neutral conductor will go to the neutral busbar, and the earth conductor will be sleeved green/yellow and this will go to the earth busbar. If you have residual current (‘earth leakage’) detection on one or more individual circuits, the neutral for that circuit will go to the RCD or RCBO instead of the neutral busbar.
It the circuit is a ring final subcircuit (aka ‘ring main’, serving power sockets), the two ends of the ring will go to the same terminal at all three places.
Your electrician will put the c.t’s on the brown line conductor in each case. If you want to have multiple circuits measured together by one c.t, that’s fine so long as all the individual wires go through the c.t. in the same direction.

Note if you have very old wiring, the wire colours are red–line and black–neutral.

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Hi, I’ve just received it and got it working. The gray (4) wire is too thick for the 50A CT clamp so I placed it on the red one.
I did the test turning oven, dishwasher, air frier, washing machine and hair drier ON and the max current we got was ~30A, lower than 50A and much lower than 100A, so went for the 50A CT.

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