Emonpi Energy reading way out

Hardware emonPi
1

Hi

Been having two issues with my new Emonpi regarding inaccurate energy usage.

  1. CT2 PV side is reading 50W when sun is down and no solar is being produced, tried adjusting scale and 0 is only way to get it to 0 but then when solar is generated it still shows 0.

  2. Been monitoring energy usage last couple weeks and looked very high from manual calculating by counting all my devices that is switched on to compare and seem to be where i actually use approximately 300W emonpi will report 400-450W so i got hold of a high quality Fluke clamp meter to get more accurate figures and this is what i got. Voltage stay stable at 245V when I have immersion hot water on so used this as a base and this seems accurate compered with emonpi vrms reading.

Fluke Emonpi
1.10A 244V 268W 347W
0.34A 245V 83W 243W
0.10A 245V 24W 64W
0.24A 245V 58W 110W
13.2A 243V 3200W 3370W

So after reading up about calibrating using scale under emonhub I used immersion heater again and calibrated emonpi with about a change from 1 to about 0.8 under emonhub and all this worked great and got the correct figures but then i would switch hot water off the lower average consumption will be completely out.

Any advice would be greatly appreciated.

2

Do you have an AC/AC adapter?

3

HI

Yes and I also found a post after my post with similar issue and resolved it by shutdown and making sure AC/AC is connected before power on, but this has not worked for me. I have also just now got CT clamps off solar and mains and just connected to lead with kettle attached and still get 50w even with kettle off.
I also swapped CT1 with CT2 and same issue where CT2 now shows constant 50w.

4

I got lost with the swapping.

Do you think the lead is faulty? If so please contact the shop.

[edit]

Ah, the CT must be around either the live or neutral - not both (as I expect it is with the kettle unless you have a stripped cable).

5

No, I just swapped them to confirm they are not faulty/eliminate scenarios. Just finished testing and after removing both CTs they both say 50W with no current and now connected everything back as it should be and im still getting about a extra 100-150W more than im actually using.

Side question when I adjust scale do i need to adjust powe1pluspower2 aswell?

6

It sounds like he swapped CT1 and CT2 but the problem didn’t move with the CT.

7

Yes that is correct, thanks

8

I stripped the cable so just around one of them.

9

Trying to make sense of this lot, I got lost too. Can you do a few tests please?

Label the c.t’s 1 & 2. These labels stay with the c.t., I don’t mean the emonPi input.

  1. Plug the c.t’s into their respective inputs and away from any mains cables, and report the emonPi’s readings.

Now earth the emonPi’s case - the only reliable method is to trap a wire under one of the screws fixing the ends on.

  1. With c.t. 1 plugged into Input 1 but a long way from any cable, what does the emonPi indicate for channel 1?

  2. With c.t. 2 plugged into Input 1 but a long way from any cable, what does the emonPi indicate for channel 1?

  3. With c.t. 1 plugged into Input 2 but a long way from any cable, what does the emonPi indicate for channel 2?

  4. With c.t. 2 plugged into Input 2 but a long way from any cable, what does the emonPi indicate for channel 2?

  5. With c.t. 1 plugged into Input 1 and on your kettle lead with the kettle on, what does the emonPi indicate for channel 1?

  6. With c.t. 2 plugged into Input 1 and on your kettle lead with the kettle on, what does the emonPi indicate for channel 1?

  7. With c.t. 1 plugged into Input 2 and on your kettle lead with the kettle on, what does the emonPi indicate for channel 2?

  8. With c.t. 2 plugged into Input 2 and on your kettle lead with the kettle on, what does the emonPi indicate for channel 1?

  9. What does your Fluke read for the kettle current and the (average) mains voltage?

Remember that, except for the immersion heater and the kettle, your house loads are probably reactive to varying degrees, so the VA from reading voltage & current using the Fluke will not agree with the real power reading from your emonPi (when you have the a.c. adapter connected and working). Nor will it agree with the emonPi without the a.c. adapter, because that then guesses apparent power (VA) based on a nominal 230 V mains.

Yes you do - the addition is done in the “emon” front end, a long time before the numbers hit emonHub.

10

Ill perform test after work and update.
Thanks

11

So to update I have done as requested and had same issue as expected so see figures below.

SOLUTION: Put earth to resolve constant 50W usage, this also seems to make real time figure more accurate so will monitor over the next week.

CT 1 IN CT1 IDLE 1-10W
Fluke MM  Emonpi             Emonpi 
11.58A    245V   2837W       244V    2915W    KETTLE
0.10      250V   25W         246V    34W      SOLDERING IRON
8.40A     245V   2058W       242V    2101W    HAIRDRYER 2030
1.59A     246V   391W        243V    409W     HAIRDRYER LOWEST 400W AFTER EARTH

CT 2 IN CT 1 IDLE 50W
Fluke MM  Emonpi             Emonpi 
11.43A    242V   2759W       239V    2912W    KETTLE
0.10      247V   24.7W       244V    79W      SOLDERING IRON
8.33A     243V   2015W       240V    2143W    HAIRDRYER
1.59A     246V   391W        243V    460W     HAIRDRYER LOWEST 400W AFTER EARTH

CT 1 IN CT2 IDLE 1-4W
Fluke MM  Emonpi             Emonpi 
11.50A    244V   2806W       241V    2862W    KETTLE
0.10      248V   24.7W       244V    33W      SOLDERING IRON
8.41A     245V   2050W       242V    2106W    HAIRDRYER
1.59A     246V   391W        243V    413W     HAIRDRYER LOWEST 400W AFTER EARTH

CT 2 IN CT 2 IDLE 50W

Fluke MM  Emonpi             Emonpi 
11.42A    242V   2763W       240V     2936W   KETTLE
0.10      248V   24.8W       245V     80W     SOLDERING IRON
8.38A     244V   2044W       241V     2175W   HAIRDRYER
1.59A     246V   391W        243V     458W    HAIRDRYER LOWEST 400W AFTER EARTH

Thanks for help and will update with final finding in a week or so.

Formatted text. BT - Moderator

12

Not seem that advice before (though I am sure you will have given it) - excellent :slight_smile:

13

I think you’re saying that, with the case earthed, CT1 reads a sensible ‘noise’ value whichever input it’s in, whereas CT2 reads a very high (unusually so) noise. That points to something wrong with the c.t. or its cable.

CT1 appears to be reading, maybe not as close as I’d hope, but certainly within the tolerance of the c.t. itself, at high powers, so although there’s a difference between the inputs, it’s not all that great. So I think the emonPi itself is basically OK.