Second emonTX not showing correct CT readings - wrong type of cable

Zarch · 1 February 2022 16:49

I’ve had my emonpi for years and my first emonTX for about 18 months.

I got this second (pre-configured id 16) emonTX (and AC adaptor) from the store about 2 months ago and it has been happily reading and sending back a number of temperatures from a breakout board.

But i’ve come to plug in two CT clamps today and I can’t get anything to show. (clamps also from store)

Occasional odd numbers like 1 and 9.
But when I put 3kW of load through them (kettle or immersion), nothing registers.

I see the voltage 236.3, 236.9 etc happily changing.

I see no difference in settings for both my TX in emonhub.conf

I haven’t touched these, this has always been in the emonpi

[[15]]
    nodename = emontx3cm15
    [[[rx]]]
        names = MSG, Vrms, P1, P2, P3, P4, E1, E2, E3, E4, T1, T2, T3, pulse
        datacodes = L,h,h,h,h,h,L,L,L,L,h,h,h,L
        scales = 1,0.01,1,1,1,1,1,1,1,1,0.01,0.01,0.01,1
        units = n,V,W,W,W,W,Wh,Wh,Wh,Wh,C,C,C,p
        whitening = 1

[[16]]
    nodename = emontx3cm16
    [[[rx]]]
        names = MSG, Vrms, P1, P2, P3, P4, E1, E2, E3, E4, T1, T2, T3, pulse
        datacodes = L,h,h,h,h,h,L,L,L,L,h,h,h,L
        scales = 1,0.01,1,1,1,1,1,1,1,1,0.01,0.01,0.01,1
        units = n,V,W,W,W,W,Wh,Wh,Wh,Wh,C,C,C,p
        whitening = 1

And I see info in the emonhub logs being sent to the Pi.

2022-02-01 15:17:12,571 DEBUG    RFM2Pi     5418 NEW FRAME : OK 16 18 85 85 85 116 8 92 85 84 85 85 85 85 85 84 85 85 85 85 85 85 85 85 85 85 85 85 85 85 85 227 86 222 83 101 32 87 85 85 85 (-72)
2022-02-01 15:17:12,578 DEBUG    RFM2Pi     5418 Timestamp : 1643728632.57
2022-02-01 15:17:12,579 DEBUG    RFM2Pi     5418 From Node : 16
2022-02-01 15:17:12,580 DEBUG    RFM2Pi     5418    Values : [71, 238.41, 9, 1, 0, 0, 1, 0, 0, 0, 9.5, 16.75, 300, 2]
2022-02-01 15:17:12,581 DEBUG    RFM2Pi     5418      RSSI : -72
2022-02-01 15:17:12,582 DEBUG    RFM2Pi     5418 Sent to channel(start)' : ToEmonCMS
2022-02-01 15:17:12,583 DEBUG    RFM2Pi     5418 Sent to channel(end)' : ToEmonCMS
2022-02-01 15:17:12,615 DEBUG    MQTT       Publishing: emon/emontx3cm16/MSG 71
2022-02-01 15:17:12,618 DEBUG    MQTT       Publishing: emon/emontx3cm16/Vrms 238.41
2022-02-01 15:17:12,620 DEBUG    MQTT       Publishing: emon/emontx3cm16/P1 9
2022-02-01 15:17:12,622 DEBUG    MQTT       Publishing: emon/emontx3cm16/P2 1
2022-02-01 15:17:12,624 DEBUG    MQTT       Publishing: emon/emontx3cm16/P3 0
2022-02-01 15:17:12,626 DEBUG    MQTT       Publishing: emon/emontx3cm16/P4 0
2022-02-01 15:17:12,628 DEBUG    MQTT       Publishing: emon/emontx3cm16/E1 1
2022-02-01 15:17:12,631 DEBUG    MQTT       Publishing: emon/emontx3cm16/E2 0
2022-02-01 15:17:12,633 DEBUG    MQTT       Publishing: emon/emontx3cm16/E3 0
2022-02-01 15:17:12,635 DEBUG    MQTT       Publishing: emon/emontx3cm16/E4 0
2022-02-01 15:17:12,637 DEBUG    MQTT       Publishing: emon/emontx3cm16/T1 9.5
2022-02-01 15:17:12,640 DEBUG    MQTT       Publishing: emon/emontx3cm16/T2 16.75
2022-02-01 15:17:12,642 DEBUG    MQTT       Publishing: emon/emontx3cm16/T3 300
2022-02-01 15:17:12,644 DEBUG    MQTT       Publishing: emon/emontx3cm16/pulse 2
2022-02-01 15:17:12,646 DEBUG    MQTT       Publishing: emon/emontx3cm16/rssi -72
2022-02-01 15:17:12,648 INFO     MQTT       Publishing: emonhub/rx/16/values 71,238.41,9,1,0,0,1,0,0,0,9.5,16.75,300,2,-72

I’ve checked the dip switches and it seems i’m set for UK

So i’m at a bit of a loss what to look at next.
Are there any other configs I need to look at on my emonpi?

Any help would be very much appreciated.

Cheers, Mick

Bill.Thomson · 1 February 2022 16:56

If you connected the CTs while the power was on, cycling the TX’s power should resolve it.
One other thing, ensure the plugs are pushed fully home in the jacks.
(more than one user has been bitten by that one)

Zarch · 1 February 2022 17:07

Thanks Bill

I should have said I’d seen both those issues in other threads I searched, but I’m still getting the issue after power cycling and confirming the jacks are well plugged in. I even tried all of CT1 to CT4 whilst I did that.

Bill.Thomson · 1 February 2022 17:08

+1 for searching!

Robert.Wall · 1 February 2022 17:08

What sort of cable is the c.t. around? If it’s a 3-core, you’ve got zero nett current flowing, so the c.t will read zero.

But your emonTx does appear to be working correctly. (The numbers are not a solid zero - that’s good.)

Zarch · 1 February 2022 17:50

Been searching all afternoon!!

I originally had it to around 3 core coming from the new Eddi Immersion installation.
So to rule that out, I brought the TX into the kitchen and tested it using the Kettle.
Sadly, didn’t seem to make any difference?

Zarch · 1 February 2022 17:56

Doh, the kettle is 3 core too isn’t it?

So I need to ask my electrician to expose the live cable on my Eddi extension.
Is there a preferred method of doing this?

Robert.Wall · 1 February 2022 19:16

But you must have missed this: EmonPi Install Guide — OpenEnergyMonitor 0.0.1 documentation

Is it “permanent” or just for testing?

If just for testing, I’d pull either line or neutral out of the plug, instead use a shortish piece of single-core wire into the plug at one end and join it onto the wire that came out of the plug using one way of a screw connector strip.

If it’s permanent and portable, then you should get a plastic terminal box, cable glands and an extension lead. Cut the extension lead in the middle, put the ends into a 4-way (at least) terminal strip, and put the c.t. in the box again using some single-core cable (or just strip back enough of the extension lead) to go through the c.t.

If it’s permanent and fixed, then it’s the same as portable but you can use grommets instead of glands (no need for strain relief) and fix the box to a solid surface and clip the cables in position so they cannot be disturbed.

Zarch · 10 February 2022 09:10

For completeness. There is nothing wrong with my setup, all working great.

I was able to place the CT clamp inside the Eddi device and i’m monitoring that fine now.

Note to self (and others watching/searching): You can’t monitor 3-core wire… I repeat, you can’t monitor 3-core wire without stripping back to the wires inside.

Robert.Wall · 10 February 2022 11:11

Sorry to point out that this has been repeated innumerable times on this forum (and the old one, now archived), it’s in the FAQ and it’s in more than one place in the installation instructions.

I think that in another forum that I won’t mention, you’d have been told very early on ‘Go and RTFM’.

Zarch · 10 February 2022 11:20

What’s most embarrassing Robert is that in searching the forum I found I had encountered this problem a few years ago in one of my very own posts.

I’m claiming having a senior moment!

Your patience is appreciated.