How many clamps do I need

by Fluidetom on Mon, 26/09/2011 - 15:30

Hi,

I know that I have 3 phases at home.

How many clamps do I need and how do I have to connect them?
I have one big cable between the counter and the main fuse box; is it OK to put one clamp on that tick cable? Or do I need 3 clamps to be connected inside the fuse box where the cable is split in 3 phases (in which case I'd need 3 x 50amp clamps?)

Thanks

icarus75 | Mon, 26/09/2011 - 18:47

Hi Thomas,

You always need one clamp per phase. The clamps should be installed per conductor, i.e. per phase, and not around the cable grouping all phases + neutral. Since current always flows in a circuit, the net current when grouping the entire cable will equal zero. What we have to measure is the individual current per phase (with neutral being the current's return path).

Cheers,
Bart.

Fluidetom | Wed, 28/09/2011 - 11:40

Thanks for the prompt answer.

I've three phases for my cooker so I'll need 3 x 50amp clamps.

I'm just wondering how practically I can install these clamps on the cables.
As explained above, I have one big grey cable going from the electricity counter to the main fuse box. The cable is stripped inside the fuse box to feed the different circuits; but the three main cables are hidden behind the fuses themselves. Are the Flukso clamps big? Are we suppose to strip the main cable outside the fuse box (not ideal).

Ideally, I'd like to attach the Flusko clamps inside the fuse box and put the cover on top; so only the clamps' cables would exit to connect to the flusko itself.

How do you see this kind of installation ?

icarus75 | Wed, 28/09/2011 - 21:36

Hi Thomas,

The dimensions of the 50A clamp are detailed at [1]. You should install these clamps inside the fuse box. Stripping the main cable outside of the fuse box for attaching the clamps is not advised. A typical Fluksometer installation is shown at [2].

[1]: https://www.flukso.net/content/size-current-clamp
[2]: http://www.jokamajo.org/content/flukso-sensor-node-installation

Cheers,
Bart.

Fluidetom | Fri, 30/09/2011 - 13:23

Hi Bart,

Just to make things clear before I order my Flusko + 3 clamps.
Woudl you mind having a look at these pictures?

http://img12.imageshack.us/img12/1731/30sep1121228pm.jpg
http://imageshack.us/photo/my-images/710/img20110929214621.jpg/

It's a photo of my 1st fuse box. The counter is on the left and the main cable coming from the counter is visible on the bottom left. The orange dashes represents the plastic box.

When seeing this setup, could you confirm that:

- the clamps will fit
- i do need 3 clamps

Thanks

icarus75 | Fri, 30/09/2011 - 15:03

Hi Tom,

Your electrical installation doesn't have a neutral wire. This is sort of a special case in three-phase supplies and, as far as I know, was only used in Belgium and The Netherlands. It's not 3x400V + N but 3x230V without N. Your circuits will thus be driven by e.g. L1-L2, not L1-N.

The blue wire should be used as N in single phase circuits. So if you don't have any three-phase loads in your house, you can measure this setup by attaching only two clamps: one to the brown wire and the other to the black wire.

As for fitting the clamps, you can spread them out, e.g. one clamp below on the brown wire and one clamp above the differential on the black wire.

Cheers,
Bart.

Fluidetom | Sat, 01/10/2011 - 00:02

Hi,

I do appreciate your follow-up on this case!

I do use three phases in my house for the induction cooker.
On the picture above, you can see in the bottom right another grey cable with the three phases going to another fuse box in my kitchen to feed amongst other things, the induction cooker with the 3 phases.

So, 3 clamps or 2 ? ;-)

Have a nice weekend

Tom

icarus75 | Sat, 01/10/2011 - 08:56

Having a mix of 3-phase and single-phase loads in a 3x230V without N means that you'll have to compromise on accuracy. You can still hook up two clamps, one on the black and one on the brown phase. Configure the Fluksometer as 3-phase with a 230V voltage. This will cause a measurement error for your 3-phase induction cooker. Instead of 3*amps*133V = 400*amps (W) the Fluksometer will register 2*amps*230V = 460*amps (W) for the induction plates, or a 15% deviation.

I guess that's the best you can do with this setup. If you're a bit adventurous, you could re-wire the induction plates as a single-phase load. But then you'd have to make sure your conductors have a sufficient cross-section (6 mm2) to allow for this.

I'd go for the easy option. It's a known 15% deviation and happens only when using the induction cooker, so maybe 15-20min per day.

HTH,
Bart.

tuxdelux | Wed, 05/10/2011 - 12:52

Hi Bart,
I have the same 3-phase 3x230V without N (Ternat / Belgium). According to me, all phases are used in my home.
Is it correct to configure my Flukso like this:
number of phases : 1 (so I can look at each phase individualy)
voltage 133V for sensor #1,#2 and #3

Regards,

Bart.

icarus75 | Wed, 05/10/2011 - 15:25

The problem with the 3x230V without N is that any wire can be used as phase or neutral. If only two phases are used, with the third one acting as neutral, then the solution described above will work, with some compromise in accuracy when a 3-phase load is active. Putting a clamp on each phase and configuring the voltage as 133V will only yield correct results with a true three-phase load.

Fluidetom | Thu, 06/10/2011 - 00:02

Hi Bart (icarus),

OK so with 2 clamps (one on brown, one on black) I'll be able to accurately measure the electrical consumption of my household; except when the induction cooker is working, the Flukso will then measure a +/- 15% load increase to the real consumption.

Is that correct?

Thanks

Tom

icarus75 | Thu, 06/10/2011 - 08:04

Provided the blue conductor is solely used as neutral in your single-phase circuits, yes.

Fluidetom | Thu, 06/10/2011 - 10:55

Good morning,

This is a house from 1966 we bought 6 years ago.

We did some renovation, but for most of the electricity, I do not know how it has been setup.

Is there a (not too difficult) way for me to confirm the blue wire is only used for single-phase?

(Note that I have a voltmeter if it can be of any help)
(Note also that I only have basic knowledge of electricity)

Thanks

Tom

tuxdelux | Thu, 06/10/2011 - 19:38

Hi Bart (Icarus75),

I just came up with the following.
In my case (3x230V between the phases R, S and T, no Neutral) there is 230V between every pair of phases : between R and S, between S and T and between R and T. The clamps are on R,S and T. Every pair can and is used in the house, unbalanced. This means that for the current measured by the clamps on the feeding lines R, S and T :
I(R)is the sum of I(R-S) and I(R-T)
I(S)is the sum of I(R-S) and I(S-T)
I(T)is the sum of I(R-T) and I(S-T)
==> I(R)+I(S)+I(T)=2(I(R-S))+2(I(R-T))+2(I(S-T)
==> The sum of the current measured in the clamps should be divided by 2 to reflect the total current of all my consumers in the house as every consumed amp is measured twice.
If I configure the voltage as 230/2, that should do the trick(I think ;) )
Am I correct?

Regards,

Bart.

icarus75 | Fri, 07/10/2011 - 03:36

Hi Bart (tuxdelux),

First of all, let's assume pure resistive loads in these calculations. Secondly, I'll use a slightly less verbose notation with I(R) = Ir and I(R-S) = Irs, etc.

The key point is that the Irs, Irt and Ist currents cannot be summed in a scalar way, as these currents flow in different phases, with a 120° phase angle between each pair of currents and using complex calculus:
Ir = |Irt| + |Irs|*e^(j*2*pi/3)
Is = |Irs|*e^(j*2*pi/3) + |Its|*e^(j*4*pi/3)
It = |Its|*e^(j*4*pi/3) + |Irt|

|Ir|^2 = |Irt|^2 + |Irs|^2 - 2*|Irt|*|Irs|*cos(2*pi/3)
|Is|^2 = |Irs|^2 + |Its|^2 - 2*|Irs|*|Its|*cos(2*pi/3)
|It|^2 = |Its|^2 + |Irt|^2 - 2*|Its|*|Irt|*cos(2*pi/3)

What we're actually looking for is this:
P = V*(|Irt| + |Irs| + |Its|) with V = 230V

I don't see how we can derive |Irt|, |Irs| and |Its| from the currents we're actually measuring, namely |Ir|, |Is| and |It| without having |Ir-Is|, |Ir-It| and |Is-It| at out disposition. This however requires that we have information about the phase difference between Ir, Is and It, which we do not have.

Cheers,
Bart.

rabarberski | Wed, 28/11/2012 - 14:08

Reading this whole thread, I am still unsure how to setup and configure a Flukso in the scenario C of the following "3x230V without N" scenarios:

Scenario A:
===========
With 1 phase wired consistently across all circuits as 'virtual N' (by convention, but not necessary, the blue wire). No 3-phase equipment in use.

Setup: you only need 2 clamps, clamped around the 2 phases in use.
Configuration Flukso: single phase, voltage=230V for each sensor
Accuracy: 0% deviation

Scenario B:
===========
Same as A, but with some 3-phase equipment connected (typically an electric cooker or oven)

Setup: same as in scenario A, i.e. 2 clamps
Configuration Flukso: 3-phase, voltage=230V for each sensor
Accuracy: 15% deviation, or lower if the 3-phase equipment is used not so often.

Scenario C:
===========
All phases used and no consistent 'virtual N' wire/phase, potentially with a dedicated 3-phase equipment like a cooker?

Setup: ?
Configuration Flukso: ?
Accuracy: ?

I would assume scenario C is the most common. But I am not sure about the required setup (2 or 3 clamps?), Flukso configuration and accuracy. Might also make sense to split scenario C up in an additional scenario D depending on whether a 3-phase equipment is present or not.

jrbenito | Fri, 30/11/2012 - 02:03

Hi,

I read all the thread and ended up with a question about my setup.

Here in Brazil, residential installations varies a little.

-Old installations are 1Phase + 1N (this is grounded at the street transformer and, hopefully, at house entry fuse box). This is 110V installation (almost all gone nowadays)

-Newer installations are 4-wire, 3Phase + 1N. A small/medium residence normally receives 3 wires (2Phase+1N) while bigger residences normally receive all 4 wires. Wire N is always grounded at street transformer and at home entry fuse box. A Phase-to-N connection is 127V while Phase-to-Phase is 220V.

So, here is really common to have both 127V (Phase to N) connections for things like TVs, refrigerator, lamps. However things like water heating or air conditioning are mostly 220V (Phase to Phase).

My home is 3 wire connected. All the illumination goes goes through 127V as well as most of my appliances. I have things mixed in the kitchen, microwave, toast and exhaustion are 220V and refrigerator, oven*, coffee machine, etc are all 127V. Ar conditioners are 220V while computers are powered by 127V (even do they are bi-volt). In summary I have both 127V (1P+1N) and 220V (1P+1P) running at same time.My Fluksometer have two clamps, each one connected to each Phase I have, none connected to the Neutral.

The question is: Is that correct? I will experience accuracy issues due to 220V and 127V being together?

Thanks,
Benito

mbusscher | Fri, 30/11/2012 - 11:02

Damn, I ordered a Flukso with three current clamps (it's about to be delivered) and now I discover this thread... of course I also have a 3 x 230V supply with the circuits distributed over all three phases and one true three phase load (cooker).
If I manage to rewire my distribution box such that I can measure the actual phase current for the three phases separately, would that be a solution to provide a correct result?

Thanks,
Marc

user4344 | Tue, 16/04/2013 - 14:30

Hi!
Is this the correct place to post a question?
I live in Italy and I gather I have a monophase. Basically, for residential use, I think I need the main unit FLM02A and just one clamp FLS01-50.

Is this correct?

Thanks!

icarus75 | Wed, 17/04/2013 - 08:13

Correct. You need one clamp per phase.

BFlament | Sun, 02/02/2014 - 18:52

So do I, I have got a 3 x 230 V without neutral. The distribution of the loads over the three phases is unequal. Would it be possible to build a real wattmeter with 2 analog voltage measurements in the Flukso ?

Thanks

Fluc | Sun, 02/02/2014 - 19:10

Please read the comments of ICARUS75 above in this topic.

BFlament | Sun, 02/02/2014 - 20:33

I've already read. But I would like to get a real wattmeter for the 3 phases.
Should I understand that I have to buy a real wattmeter and transmit the power signal in pulse to the Flukso to get it in order ?

Thanks

rabarberski | Mon, 03/02/2014 - 09:49

As this thread seems to be revived, does anybody have any idea how the smappee energy monitor seems to be able to measure also 3 x 230 V without neutral? At least that's what they claim in their FAQ (http://www.smappee.com/be_en/support):

Can I use smappee if my home has three-phase electricity?
Yes. Smappee can be used on both 3x220V or 3x380V+N power installations. In this case, you will need to attach three current clamps to the cables. Your smappee will be specially configured for this during the ordering process in the e-shop.

As far as I can see they also only use 3 current clamps, just like the Flukso.