Modified wiring, your thoughts?

[paulmars]

Id like to move the red wire for the kwh meter shown from before to after the coil. Your thoughts?

 

[Diver300]

It won't make any difference in practice.

The voltage before and after the coil will be almost exactly the same. There will be a tiny difference, as there has to be a very small difference as some energy is transferred to from the wire by the current transformer, but that difference will be so small that it would be hard to mesure.

 

[For The Popcorn]

If the meter is powered from the output side of the coil, the meter reading will include the small amount of current needed to power the meter.

But there's no need to de-solder the connection if that's your goal. Just pull the blacked tape connection through the coil. It will accomplish exactly the same thing.

 

[Diver300]

If the meter is powered from the output side of the coil, the meter reading will include the small amount of current needed to power the meter.

But there's no need to de-solder the connection if that's your goal. Just pull the blacked tape connection through the coil. It will accomplish exactly the same thing.

I'm sorry, but that's wrong. It is the total current going through the magnetic core that is measured, not just the current in the largest wire.

You could disconnect the red wire, loop it around and though the magnetic core so from left to right, and reconnect it. The the current taken to run the meter will also be measured.

 

[Nigel Goodwin]

Makes sod all difference - it's a 100A circuit, it's not even going to be able to measure the few mA the circuit takes.

 

[For The Popcorn]

Perhaps you are right, because the current flow in the meter lead would be going in the opposite direction.

With the connection point as shown, the current through the supply wire to the load will be measured.

If you push the connection through the coil, the supply wire with be carrying supply current + meter current. But current through the meter wire will be flowing in the opposite direction, so you'd only read the current to the load.

Sorry, my mistake.

 

[Nigel Goodwin]

Perhaps you are right, because the current flow in the meter lead would be going in the opposite direction.

It makes no difference, the meter current will be so low that it won't be detectable on a 100A scale. If the meter takes 1A that's only 1% of the scale, and it will take a LOT less than that, I would imagine less than 10mA? - so less than 0.01% of FSD.

 

[For The Popcorn]

Thank you Nigel Goodwin. In this case you're right, the difference will to too small to matter.

I made an erroneous statement and wanted to show my reasoning in correcting it for those cases where it might matter. Aren't we all here to learn?

 

[paulmars]

The meter is capable of reading a max of 100a. That will not be the typical load. Even if the current used by meter is considered by some to be too small to mater, that is still what will hypothetically occur. Which is why i asked this. I want to be sure that there is nothing here that i missed when i suggested this modified wiring. It would be a lot easier to wire it my modified method, but it would be a real hassle to have to change it back.

 

[paulmars]

I have looked at the wiring diagram of 20 similar units and they all wire it as shown, none wired it my modified method.

 

[For The Popcorn]

The only difference is that as the picture is now, the cutting needed to run the meter is not measured by the meter. If you connect the meter on the other side of the coil, the current it uses will be added to meter reading.

The meter doesn't care. It will work either way. The current used by the meter is tiny compared to the current used by the motor. Will it matter if the reading is off by less than a percent?

 

[Nigel Goodwin]

The only difference is that as the picture is now, the cutting needed to run the meter is not measured by the meter. If you connect the meter on the other side of the coil, the current it uses will be added to meter reading.

Except, as I've already said, the difference is so small that it won't be added to the reading, as it will be considerably under the minimum resolution of the meter.

Assuming the A2D in the meter is ten bit, then the minimum resolution for a 100A FSD meter is 97mA - if it's 16 bit (which is highly unlikely) then the minimum resolution is 1.5mA.

I would imagine the meter consumes more than 1.5mA, but considerably less than 97mA?.

 

[For The Popcorn]

Except, as I've already said, the difference is so small that it won't be added to the reading, as it will be considerably under the minimum resolution of the meter.

I made an erroneous statement and wanted to show my reasoning in correcting it for those cases where it might matter. Aren't we all here to learn?

Nigel Goodwin, you're made your point three times now. As did Diver300, and indeed, I did as well. I am not arguing with you about it.

I try not to make bombastic statements but rather to provide some knowledge. It seems the original poster gives not a rat's ass about the theory, but perhaps other people reading this thread will appreciate it.

 

[JimB]

Makes sod all difference - it's a 100A circuit, it's not even going to be able to measure the few mA the circuit takes.

Well, that all depends on who is looking at the figures...

To an engineering type - OK no problem
but
To an accountant bean counter type, if the numbers don't add up exactly, the world will come to an end!

JimB

 

[Nigel Goodwin]

Well, that all depends on who is looking at the figures...

To an engineering type - OK no problem
but
To an accountant bean counter type, if the numbers don't add up exactly, the world will come to an end!

JimB

Except the numbers will add up - as the difference is below the measurable resolution.

 

[paulmars]

0.001 resolution.

Received meter today. Will hook it up soon.

 

[Nigel Goodwin]

0.001 resolution.

Incredibly optimistic

 

[paulmars]

Looks ok?

 

[For The Popcorn]

Is the 3 terminal block the connection to the kiln? Should be fine. You can extend the leads to the meter to put it in a convenient location.

 

[paulmars]

Yes and i want the meter above the kiln plug. So wiring looks good? I tested the meter on 120vac and hooked it up as shown hot and neutral & it worked fine. I never wondered why it's labeled neutral. So,now it's hooked up to the 240 hots. No neutral. I know that is fine, but still it concerns me why they labeled it like that.

P