HEM - power metering query

[AutoFrank 370]

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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Does anybody know which parameter I should be using

 

thanks 

frank

 

 

 

 

 

 

 

 

 

 

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Edited December 2, 2016 by AutoFrank

[morpheus75 75]

hi

did you manage to figure out which sensors are what?

i have just bought this but the 2 sensor version.

i managed to work out that the 1st and 2nd set seem to be for clamp 1

3rd set is clamp 2 and 4th set is clamp 3

but my voltage is always showing as 140v? instead of the expected 240v?

[Sankotronic 1,946]

I have HEM with 1 clamp and it works perfectly. After monitoring group 1 and 2 for some time I selected group 2 since it is showing same readings as i have on my UPS. When installing HEM it is very important to connect supply wires correctly, brown to live (L) and blue to neutral (N) for 1 clamp version or 3 clamp version while 2 clamp version supply wires must be connected between phases (live) as it is show on the installation leaflet. Also clamps have markings on them K -> L and it is very important that they are installed properly with L facing circuit breaker for EU version that is.

 

So, @morpheus75,

 

You have 2 clamp EU version so check that you connected two supply cables properly, blue wires to live phase 2, first clamp brown to live phase 1 and second clamp to live phase 3. Then you also must install clamps on the same phase from which it has supply, first clamp on phase 1 and second clamp on phase 3.

 

BTW 2 clamp version can only be used on 3 phase supply system.

 

 

[AutoFrank 370]

Hi @morpheus75

I have a single clamp version and haven't been able to figure out if it is 1 or 2 as they both seem correct at given times

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I'll need to take extra readings to try and determine..

 

_f

[morpheus75 75]

i bought the 2 clamp version.

1 to monitor my house usage and 2nd clamp to monitor my solar.

there are 2 power leads. i have powered both from my house.

so i should power the 2nd clamp from the solar supply?

will give that a try tonight.

cheers guys

[Sankotronic 1,946]

45 minutes ago, morpheus75 said:

i bought the 2 clamp version.

1 to monitor my house usage and 2nd clamp to monitor my solar.

there are 2 power leads. i have powered both from my house.

so i should power the 2nd clamp from the solar supply?

will give that a try tonight.

cheers guys

 

According to the Aeotec instructions 2 clamp meter in EU can be used on 3 phase 3 wire systems only so I don't think that you can get it to work properly on 1 phase system with two different power sources. You should buy two 1 clamp HEM and then connect them to each system separately, one for main power to the house and one for your solar system. But of course, I could be wrong. What makes me think that I'm right is Aeotec instructions and that you have wrong measurement of the voltage.

 

This is usually because voltage is different between phases and between phases and neutral for ∛ and your 2 clamp meter supply is supposed to be connected between phases which is ∛ times 240V is around 400V. Your meter is showing 140V which is exactly for ∛ less than 240V !!! 

 

Anyway please be careful with electricity and take necessary preparations before putting hands in the electrical box. Also make sure that HEM supplies blue wires are not connected inside HEM to same terminal because if they are, then connecting them to two different power supplies will make possibly unwanted bridge that can do damage to your equipment!

 

 

[morpheus75 75]

@Sankotronic

cheers for info and i think you are right. i did re-read instructions again and the numbers do add up.

thanks for warning re electricity but i forgot to mention that im qualified electrician aswell.

 

i thought i could get away with using 1 meter and 2 clamps but looks like gonna have to get 2 separate units........

 

cheers

[AutoFrank 370]

14 hours ago, morpheus75 said:

@Sankotronic

cheers for info and i think you are right. i did re-read instructions again and the numbers do add up.

thanks for warning re electricity but i forgot to mention that im qualified electrician aswell.

 

i thought i could get away with using 1 meter and 2 clamps but looks like gonna have to get 2 separate units........

 

cheers

 

@morpheus75, Thanks., I'm going to use the same approach so I ordered a second HEM for my panels.

@Jamie mccrostie

 

Question for the electricians among you..

 

This is the way my panels are setup. The electrician said the electricity from the panels is harmonised with the rest of the house

I have one HEM in place at the moment and was thinking about putting the second on the AC supply from the panels (two red dots)

will this work to give me how much the house if taking and what my panels are generating ?

 

 

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[Jamie mccrostie 82]

35 minutes ago, AutoFrank said:

 

@morpheus75, Thanks., I'm going to use the same approach so I ordered a second HEM for my panels.

@Jamie mccrostie

 

Question for the electricians among you..

 

This is the way my panels are setup. The electrician said the electricity from the panels is harmonised with the rest of the house

I have one HEM in place at the moment and was thinking about putting the second on the AC supply from the panels (two red dots)

will this work to give me how much the house if taking and what my panels are generating ?

 

 

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Hem 2 yes.

Hem 1 yes but will it cope when your generating more power than your using and its being pumped back into supply grid, I think you can set it up so it doesn't operate if it senses current flow is in reverse, but Im guessing that.

 

 

 

 

 

 

 

[AutoFrank 370]

8 minutes ago, Jamie mccrostie said:

Hem 1 yes but will it cope when your generating more power than your using and its being pumped back into supply grid, I think you can set it up so it doesn't operate if it senses current flow is in reverse, but Im guessing that

 

Thanks @Jamie mccrostie

Ill have to see how it goes

 

I suppose I could get a third HEM and install it in reverse.

 

Actually now taht you mention it i'm seeing some full readings on the HEM I have installed (between channel 1 and 2) , I wonder if this is related to the reverse flow situation....

 

I wonder how other people have solved this ?

[morpheus75 75]

@AutoFrank

 

HEM 2 should be connected between the inverter and the main utility box. the power from panels to inverter is DC and not AC and is of the 500v magnitude.

HEM 1 hopefully will have a setting for reverse detection.

(i am a solar electrician aswell)

[Jamie mccrostie 82]

Just now, AutoFrank said:

 

Thanks @Jamie mccrostie

Ill have to see how it goes

 

I suppose I could get a third HEM and install it in reverse.

 

Actually now taht you mention it i'm seeing some full readings on the HEM I have installed (between channel 1 and 2) , I wonder if this is related to the reverse flow situation....

 

I wonder how other people have solved this ?

Just googled it and there is parameter to stop recording if reverse flow detected so as long as you can use that as a trigger you can compare with code 

[AutoFrank 370]

3 minutes ago, morpheus75 said:

HEM 2 should be connected between the inverter and the main utility box

 

Thanks @morpheus75

In the drawing its in the AC side, I assume it doesn't matter if it is on one side of the trip v the other side as long as it's on the AC side ?

4 minutes ago, Jamie mccrostie said:

ust googled it and there is parameter to stop recording if reverse flow detected so as long as you can use that as a trigger you can compare with code 

 

@Jamie mccrostie

So it sounds like I'll need a third one to get the info I want ?

[Jamie mccrostie 82]

5 minutes ago, morpheus75 said:

@AutoFrank

 

HEM 2 should be connected between the inverter and the main utility box. the power from panels to inverter is DC and not AC and is of the 500v magnitude.

HEM 1 hopefully will have a setting for reverse detection.

(i am a solar electrician aswell)

I think Franks drawing shows it in the right spot

 

1 minute ago, AutoFrank said:

 

Thanks @morpheus75

In the drawing its in the AC side, I assume it doesn't matter if it is on one side of the trip v the other side as long as it's on the AC side ?

 

[morpheus75 75]

@AutoFrank

from your diagram it shows that the PV is connected to the fuse inside your main board so you need to clamp to this supply to measure the power for the solar alone

 

Basically connect the clamp between INVERTER and HOUSE MAINS

Edited May 23, 2017 by morpheus75
update

[Jamie mccrostie 82]

1 minute ago, morpheus75 said:

@AutoFrank

from your diagram it shows that the PV is connected to the fuse inside your main board so you need to clamp to this supply to measure the power for the solar alone

Yes but the inverter is feeding a sub board first which may or my not have other out going circuits as well so thats where he needs his clamp for the solar measurement.

[AutoFrank 370]

39 minutes ago, morpheus75 said:

@AutoFrank

from your diagram it shows that the PV is connected to the fuse inside your main board so you need to clamp to this supply to measure the power for the solar alone

 

Basically connect the clamp between INVERTER and HOUSE MAINS

 

@morpheus75

@Jamie mccrostie

Perfect .. hopefully I'll have it in a few days and can try that

.. but it does look like I'll need a third one to get the data I need

 

It actually will still be cheaper as a Smart meter from our electricity supplier is €350 (HEM's are €80) and it looks more like a dumb meter than a smart meter as I don't think the home owner can query it at all.

 

Thanks a lot guys ....

 

Edited May 23, 2017 by AutoFrank

[AutoFrank 370]

@Jamie mccrostie

@morpheus75

 

I may have found a parameter for reverse flow that may solve the reverse flow part

 

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from 

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[Jamie mccrostie 82]

14 minutes ago, AutoFrank said:

@Jamie mccrostie

@morpheus75

 

I may have found a parameter for reverse flow that may solve the reverse flow part

 

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from 

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Frank, maybe you do need three with the extra one reversed at mains switch in. It would only measures when solar generated power is feeding back into grid otherwise you cant see the house usage in this state.

Then you could compare values between generated and (Mains supply in or Mains supply out) to find house usage.

[AutoFrank 370]

53 minutes ago, Jamie mccrostie said:

Frank, maybe you do need three with the extra one reversed at mains switch in. It would only measures when solar generated power is feeding back into grid otherwise you cant see the house usage in this state.

Then you could compare values between generated and (Mains supply in or Mains supply out) to find house usage.

 

 

I think you're correct @Jamie mccrostie , now that I've read it again, The parameter looks like it may just report as positive a negative vale if the clamp is reversed and not positive for 'inflow' and negative for 'outflow'. I think I'll start another post in case somebody has done this before

 

[AutoFrank 370]

Hi @Jamie mccrostie, @morpheus75, @jompa68, @Sankotronic, @petergebruers

 

I've all three HEM installed in my effort to measure what my PV panels are generating and whether the house is drawing extra from the grid or sending excess back to the grid. 

 

One HEM on the PV Panel that is matching the readings on the cloud app I have

 

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I have two HEM installed clamps (2 separate HEM devices) in the incoming cable into the house and am looking at the configuraton part now

The two clamps are installed  with the direction on the clamp opposite to each other.

The idea here is to measure power when the house draws from the grid and and when the house (PV panels is sending excess power to the grid)

 

This is the reference in the data sheet to parameter 2

 

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It looks like I should configure my HEM measuring outbound current as negative only (value = 3) and the HEM measuring inbound power as positive only (value = 2)

I am now wondering if I should have installed both clamps in the same direction instead of opposite to each other

 

Lastly if I was at the parameter is it as simple as this ....

 

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Thanks

_f