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HEM - power metering query


AutoFrank
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Hi,

I have a Home Energy monitor (HEM2) and have the clamp in the main live into my meter box to try and understand what the house is drawing power wise.

I seem to be getting two power readings that are different with both changing over time but none seem fully accurate. One power reading seems accurate some times and the other power reading seems more accurate at other times if I look at what is running in the house at the time.

 

I have only one clamp but the inclusion created 12 devices in in total

1471 (device id = 1471)

1471.0 & 1471.0.1, 1471.0.2 (device ID 1472, 1473, 1474)

1471.1 & 1471.1.1, 1471.1.2 (device ID 1475, 1476, 1477)

1471.2 & 1471.2.1, 1471.2.2 (device ID 1478, 1479, 1480)

1471.3 & 1471.3.1, 1471.3.2 (device ID 1481, 1482, 1483)

 

I can get power readings on 1472 & 1475

 

 

1472 - api details (power = 895.79w)

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1475 - api details (power = 2.44 kw)

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The energy readings from both are the same

 

 

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/monthly_2016_12/HEM.PNG.047bc402ddb8466bdc8544922ce1ed7e.PNG" alt="HEM.PNG" />

 

Does anybody know which parameter I should be using

 

thanks 

frank

 

 

 

 

 

 

 

 

 

 

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Edited by AutoFrank
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Hi @AutoFrank,

 

According to parameter 2 settings you need to turn both clamps in same direction and then for the one that is measuring power consumed set it to 2, and the other one that is measuring generated power sent to the grid set to parameter 3.

 

Of course to get totals of consumed and generated power you will have to do math by yourself using scene or VD.

 

I don't have PV panels to test it, but you can try and see if that is correct suggestion.

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  • 44 minutes ago, Sankotronic said:

    Hi @AutoFrank,

     

    According to parameter 2 settings you need to turn both clamps in same direction and then for the one that is measuring power consumed set it to 2, and the other one that is measuring generated power sent to the grid set to parameter 3.

     

    Of course to get totals of consumed and generated power you will have to do math by yourself using scene or VD.

     

    I don't have PV panels to test it, but you can try and see if that is correct suggestion.

     

    Thanks @Sankotronic

    that makes sense  - :-(

    I'll change the second clamp in the morning, that maths is basic enough so should be good there.

    Just need to wait for a sunny day then :-)

     

    I also read in homeseer forum that the power value did not read in the Homeseer controller but they saw that the volts and amp were accurate and they calculated the power from those values...

     

    I'll make the changes and report back ..

     

    _f

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  • Quick one for the electricians/electrical guru's among you....

    @petergebruers, @Sankotronic, @morpheus75, @Jamie mccrostie

     

    If I have a HEM current clamp on the main 230v line into the house, will this read what the house is using or what it is drawing from the grid

    I also have a HEM current clamp on my pv panels...

    I was wondering if the house consumption was the sum of the two or just what is being read from the main feed into the house (on the grid side of the main trip in the utility panel)

     

    I did a very quick non scientific experiment. I switched off /isolated the PV feed so it was no longer contributing electricity to the house and would have expected the HEM clamp in the main line in would have increased to compensate but it appeared to stay the same....

    Edited by AutoFrank
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    35 minutes ago, AutoFrank said:

    If I have a HEM current clamp on the main 230v line into the house, will this read what the house is using or what it is drawing from the grid

    Drawing from the grid

     

    37 minutes ago, AutoFrank said:

    was wondering if the house consumption was the sum of the two or just what is being read from the main feed into the house (on the grid side of the main trip in the utility panel)

    Sum of the three... solar in  + mains in - mains out

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  • 8 minutes ago, Jamie mccrostie said:

    Drawing from the grid

     

    Sum of the three... solar in  + mains in - mains out

     

     

    Thanks @Jamie mccrostie

    I'll run some numbers once I have corrected the direction of the 'out' clamp

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  • HI

     

    I reversed the clamp, set one hem to negative only  and now the readings are staring to come through but not making a lot of sense

     

    Please login or register to see this image.

    /monthly_2017_05/PV.PNG.9d2ebb6752230d1082af036b32c7b4a1.PNG" alt="PV.PNG.9d2ebb6752230d1082af036b32c7b4a1.PNG" />

     

    I assume that there shouldn't be power out as well as in ?

     

    i'm reasonably sure the HEM gen 5 are reading okay but not so sure about the previous generation one I have

    I'll need to run a few experiments 

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    4 minutes ago, AutoFrank said:

    HI

     

    I reversed the clamp, set one hem to negative only  and now the readings are staring to come through but not making a lot of sense

     

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    I assume that there shouldn't be power out as well as in ?

     

    i'm reasonably sure the HEM gen 5 are reading okay but not so sure about the previous generation one I have

    I'll need to run a few experiments 

     Looks wrong

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  • a little experimentation later reveals that the following seems to work for parameter 2

     

    setting 2 - reports positive value

    setting 3 - does not report negative value (reverse flow)

     

    For reverse flow detection and concurs with another user on the homeseer site

    setting 1 - power is zero but volts and amps are accurate and the product will give an accurate reading for power 

     

     

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  • the numbers are starting to look a little better I think...

    I wonder is the grid power in what the house is actually using and not what its drawing from the grid 

    Both 

    Grid power in and house power are around the same cable 1/2 inch apart

    PV on the PV cable after the invertor where it connects to the rest of the house...

     

    any thoughts anybody....

     

    Please login or register to see this image.

    /monthly_2017_05/PV.PNG.d4c8a20050d53d5398ec043b9e412bcf.PNG" />

    Edited by AutoFrank
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    14 minutes ago, AutoFrank said:

    the numbers start to add up but not what I expected 

     

    Any  ideas anyone ?

     

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    Id would have thought  it would show either HPO or GI but not both at once in positive

    So both of those clamps are next to each other on your mains in?

    I guess it migh go backwards and forwards as loads like fridges etc click on and off 

    Does it have a interval time it reports over ?

     

     

    Edited by Jamie mccrostie
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  • 3 hours ago, Jamie mccrostie said:

    Id would have thought  it would show either HPO or GI but not both at once in positive

    So both of those clamps are next to each other on your mains in?

    I guess it migh go backwards and forwards as loads like fridges etc click on and off 

    Does it have a interval time it reports over ?

     

     

     

    that's an interesting thought @Jamie mccrostie re the back and forth

    The readings are realtime

     

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  • More puzzling now....

     

    I checked the HEM with a clamp outside the utility box and found that parameter 2 set to 2 (negative readings)  was giving the desired results with a little jig

    My jig was a 20w halogen bulb connected to a plug with the live cable exposed (with outer sheath intact :-) )  I connected it the 'wrong way round to mimic a current flowing 'backwards' and confirmed that watts was zero but volts x amps = load (22 w) 

     

    I then use the clamp in the utility box and the readings are all over the place

    I had two clamps with the leads running parallel and though one was interfering with the others so I re-routed

    No difference...

     

    I wonder if having the two ferrite heads of the clamps so close together are causing an issue with reading from a type of ringing effect...

    Looks like i;ll have to remove one and see if it makes any difference....

     

    Update:

    removing one clamp didn't have any impact...

    If I remove the clamp and place it around my jig - all reads correctly

    If I place the clamp on the in-feed to the house I get all wrong readings.

     

    I've even turned off the PV panels and this makes no difference...

     

    not sure where to go from here...

     

     

    @morpheus75, @jompa68

    Do either of you have a similar issue.... ?

     

     

        

    Edited by AutoFrank
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    I have packed my HEM up and put on eBay. I'm just waiting for the single phase HEM to arrive. Until then I will continue to monitor what u are doing. 

    Thanks

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  • 48 minutes ago, morpheus75 said:

    I have packed my HEM up and put on eBay. I'm just waiting for the single phase HEM to arrive. Until then I will continue to monitor what u are doing. 

    Thanks

     

    Thanks @morpheus75

    I'll keep plugging away (pun intended :-) )

     

    _f 

     

    EDIT

    The only difference I can see is the size of the cables I am clamping around..

     

     

    EDIT 

    All clamps reinstalled and some pics

     

    PV Setup (gen 5 HEM)

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    Main Utility Panel

    2 clamps on same cable (into main isolator trip)

    One Gen 2 and one Gen 5

     

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    Now time to play around with the settings and parmeters

     

     

     

     

     

    Edited by AutoFrank
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