Wiring diagram for a kWh meter

[DeepBass9]

When I went off grid, Eskom left their meters behind. I would like to connect one of them to measure the power coming from my generator, but all of the wires were pulled out on the Eskom box so I can't see how to wire it. Does any bright spark know how to do this? 

Here's a pic:

[DeepBass9]

Here's a close up of the bottom with the face plate off. 

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Are the middle two terminals bridged? Looks like it in this photo.If it is, I would expect that to be the common neutral, and the outer ones to be live. Then it is simply a matter of looking which way the disk spins to figure out what is in and what is out.

I found the attached figure on the internet, which bears this out. Live goes through two electromagnets that creates an alternating magnetic field corresponding to the current passing through there, and this in turn induces eddy currents in the disk which makes the magnetic force that makes it spin, so that force is then proportional to the current going through the coils below. The neutral connection is really just there to power the potential coil, that is, to create a magnetic field corresponding to the voltage waveform that interacts with the one created by the current waveform so that it measures real power and not apparent power.

For safety, take a DMM and check that there is no connection between the outer terminals and the two inner ones, and that there is a connection via the outer two (going via the coil obviously).

You can also power it from a transformer, say 12VAC with an automotive lamp, that should also spin the disc, and then you're not dealing with dangerous voltage :-)

[DeepBass9]

So should it be wired in series  (Left to right), teminal 1 connected to live in, 2 to neutral, 4 to live out (to load)

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Just now, DeepBass9 said:

So should it be wired in series  (Left to right), teminal 1 connected to live in, 2 to neutral, 4 to live out (to load)

I would imagine so. But you can check it. If there is no connnection between 1 and 2, no connection between 3 and 4, but there is a connection between 1 and 4 and and 2 and 3, then my theory is correct.

There is a trick I've seen on the internet (this is illegal and mentioned here only for educational purposes!), where you use a transformer to generate a low voltage high-current signal which you then wire in reverse across the current coil (or the live terminals in this case). This works because the transformer isolates the output voltage from the input. This passes a high reverse current through the current coil which spins the meter backwards.

It is not only illegal, it's potentially also dangerous. But such quack devices exist in the wild...

[DeepBass9]

Ok working now like this :   (Left to right), teminal 1 connected to live in, 2 to neutral, 4 to live out (to load).  1 is bridged to 4 and 2 bridged to 3. I'm not sure what use it will be, just curiosity I suppose to see how many diesel kWhs I use over winter.  

I have another two meters if anyone else is interested.

Any ideas on how to clean up the very yellow plastic cover for the meter? I've heard toothpaste takes the yellow off of plastic and perspex?

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1 hour ago, DeepBass9 said:

Any ideas on how to clean up the very yellow plastic cover for the meter? I've heard toothpaste takes the yellow off of plastic and perspex?

I don't know of a way and I have a very strong suspicion it cannot be done. Plastic is a byproduct of oil. So there's a bunch of mineral oily stuff left in there and it's not 100% stable and over time it leaches out and discolours and its not really something sitting on top that you can just remove... it's just how it looks now.

[PaulF007]

On 9/30/2016 at 11:02 AM, DeepBass9 said:

Any ideas on how to clean up the very yellow plastic cover for the meter? I've heard toothpaste takes the yellow off of plastic and perspex?

We usually would use brasso to polish perspex works wonders just use some proper elbow ....

[SOLARWIND]

On 9/30/2016 at 11:02 AM, DeepBass9 said:

Ok working now like this :   (Left to right), teminal 1 connected to live in, 2 to neutral, 4 to live out (to load).  1 is bridged to 4 and 2 bridged to 3. I'm not sure what use it will be, just curiosity I suppose to see how many diesel kWhs I use over winter.  

 

Left to right: No 1 is Live in, no 2 and no 3 is just a convenient terminal connection for the neutral (neutral in and out) and no 4 is the Live out to the load.

In other words, the live is connected in series with the current coil of the meter (between 1 and 4). The little copper bridge link on terminal 1 feeds the one end of the internal voltage coil of the meter. The other end of the the voltage coil terminates on the link between terminal 2 and 3 (Neutral connection).

 

[SOLARWIND]

On 9/30/2016 at 10:35 AM, plonkster said:

 

There is a trick I've seen on the internet (this is illegal and mentioned here only for educational purposes!), where you use a transformer to generate a low voltage high-current signal which you then wire in reverse across the current coil (or the live terminals in this case). This works because the transformer isolates the output voltage from the input. This passes a high reverse current through the current coil which spins the meter backwards.

It is not only illegal, it's potentially also dangerous. But such quack devices exist in the wild...

If you really want to (or have to) run it in reverse, simply use terminal 4 as the live input and terminal 1 as the live output to the load.

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Credit goes to Big Clive for that, here is the video :-)