Installing a CT sensor


I want to install a CT sensor but I'm not sure exactly where to clip it on. I *think* it goes around the fat wire coming out of these boxes, is that correct? (We're flat 3, so it's obviously the one labelled "3".)

Here are some other images for context:


glyn.hudson's picture

Re: Installing a CT sensor

Yup, I'm pretty sure that's it. Without knowing the setup it's impossible to be 100%. The usual place to clip on the sensor is where on one of the 'tails' coming out of the meter. The meter for flat 1 on the RHS of the bottom photo is a good example. However looking at the 2nd photo it looks like access to the meter 'tails' for flat 3 are not accessible. It doesn't matter where in the circuit the CT is clipped as long as it's just clipped round a live or neutral (not both). 

Take care while clipping on the CT. You will have to massage with wires to get the CT clipped on, take care not to bee too rough or touch any metal bits as the wire goes into the fuse, We recommend plugging the CT into the emonTx before clipping it onto the cable. This 'loads' the secondary winding in the CT and stops a high open-circuit voltage from occurring. This wont get to a harmful voltage but it can cause disconcerting vibrating in the CT. 

Have you got the RFM12Pi working to receive the data? It's a good idea to get it all working on the bench before installing, Once it's been clipped on have a look at the power reading then switch a kettle on. You should see it jump up by about 2900W. 

Good luck, 

jonleighton's picture

Re: Installing a CT sensor

Thanks Glyn, got it up and running! There wasn't enough room to get it around the wire coming out of the box labelled "3", but I managed to get it around the wire coming out of the black box to the RHS. I think one wire is live and the other neutral. This seems to work - the kettle test certainly made a difference.

Robert Wall's picture

Re: Installing a CT sensor

Yes, those are the neutrals - see the blue colour code of the insulation underneath the grey sheath. The c.t. should be OK there.

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