Voltage meter in CU

[Sophon]

Whenever we have a problem with the power, I take out my trusty multimeter and go measure the voltage at one of the power outlets. For convenience it would be good to have a voltage meter in my Schneider CU, and it would be a nice bonus if it also showed the current load. I have three free slots available in the CU, so would something like this from AliExpress work for me?:

 

If this could work, then exactly how would it have to be wired into the CU? I gather that the live or neutral from the RCBO would prbably have to go through the big hole (and thereby through the internal transformer) in the unit, but how do I connect the "measuring signal" to terminal 1 and 2 on the unit?

 

Some units come with an external current transformer, would that be preferable (might be easier to connect due to the flexibility the transformer leads give)?

 

Thanks in advance for any information you can give me.

 

Sophon

 

 

[bankruatsteve]

Check out this recent thread very similar to yours.

 

https://forum.thaivisa.com/topic/1095361-mains-indicator-light/

 

[Thainesss]

I installed exactly the same thing in my breaker box along with some other things, you can see exactly how I wired it in this thread with pics here:

 

 

Ordered from Lazada, this exact one:

 

https://www.lazada.co.th/-i100408617-s100470139.html?urlFlag=true&mp=1

 

Just make sure your CU is a DIN Mount type. Not sure if Shenider is DIN or not. 

[Thainesss]

1 hour ago, Sophon said:

then exactly how would it have to be wired into the CU? I gather that the live or neutral from the RCBO would prbably have to go through the big hole (and thereby through the internal transformer) in the unit, but how do I connect the "measuring signal" to terminal 1 and 2 on the unit?

 

Picture from that other thread. Youre pretty close. I ran the Neutral through the transformer hole, and picked an RCBO and piggy backed off of that for the L & N supply. 

 

[sometimewoodworker]

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[sometimewoodworker]

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[Thainesss]

3 minutes ago, sometimewoodworker said:

That neutral isn't going through a transformer hole, it is going through the centre of a Rogowski coil. There is usually no transformer needed in that kind of meter.

 

Everything I read on it, even the literature packet for it, calls it a transformer, so I was just using that terminology. 

 

Its chinese, so whatever the cheapest option is, im sure thats whats in there. 

[Thainesss]

4 minutes ago, sometimewoodworker said:

that some of the Rogowski coils are hinged it may be easier to add into your CU.

 

This is a good point. 

[sometimewoodworker]

14 minutes ago, Thainesss said:

 

Everything I read on it, even the literature packet for it, calls it a transformer, so I was just using that terminology. 

 

Its chinese, so whatever the cheapest option is, im sure thats whats in there. 

It certainly could be a transformer. Some are like this

 

if you get the kind of meter that has this fitting you can find it much easier to add to your system

 

or this

[Thainesss]

5 minutes ago, sometimewoodworker said:

if you get the kind of meter that has this fitting you can find it much easier to add to your system

 

I saw a picture of the internals somewhere and it was a wound copper coil that doesnt hinge. 

 

But good point regardless. 

[sometimewoodworker]

5 minutes ago, Thainesss said:

 

I saw a picture of the internals somewhere and it was a wound copper coil that doesnt hinge. 

 

But good point regardless. 

And another version 

[Fruit Trader]

Types of current transformer used to monitor electrical distribution.

 

Conventional

 

 

Split core

 

 

Rogowski coil
 

[Crossy]

99.8% of electrical engineers would call that a current-transformer.

 

[Sophon]

40 minutes ago, Thainesss said:

 

Picture from that other thread. Youre pretty close. I ran the Neutral through the transformer hole, and picked an RCBO and piggy backed off of that for the L & N supply. 

 

Obviously, I would prefer not to have to disconnect the incoming live wire if I can avoid it. So is this correct:

• I turn of the power by flipping the RCBO to off
• I disconnect the neutral at the RCBO, run the wire it through the new unit (or the external coil) and reconnect at the RCBO
• I piggyback a wire to live from a random breaker and connect to terminal 1 on the unit
• I connect terminal 2 with the neutral bar
• I turn the power back on

I will check my CU and see whether a unit with external coil is more practical.

 

I am not actually sure if my Schneider Square D CU is DIN mount (I just always assumed so). This is an old picture of the CU before I was connected to the supply:

 

So is it DIN mount?

 

Thanks to everyone for their input.

 

Sophon

[sometimewoodworker]

5 minutes ago, Sophon said:

Obviously, I would prefer not to have to disconnect the incoming live wire if I can avoid it. So is this correct:

• I turn of the power by flipping the RCBO to off
• I disconnect the neutral at the RCBO, run the wire it through the new unit (or the external coil) and reconnect at the RCBO
• I piggyback a wire to live from a random breaker and connect to terminal 1 on the unit
• I connect terminal 2 with the neutral bar
• I turn the power back on

I will check my CU and see whether a unit with external coil is more practical.

 

I am not actually sure if my Schneider Square D CU is DIN mount (I just always assumed so). This is an old picture of the CU before I was connected to the supply:

 

So is it DIN mount?

 

Thanks to everyone for their input.

 

Sophon

No it isn't, the more correct term is DIN rail mount

 

this is one, the DIN rail here is off white

[Sophon]

So, are there similar units that will fit my CU?

 

Sophon

[Thainesss]

4 minutes ago, Sophon said:

I am not actually sure if my Schneider Square D CU is DIN mount

 

No its not DIN mount so you cant actually mount that in your panel, so youre better off IMO going with the ones listed above with a hinging coil. 

[bankruatsteve]

If you hook up to RCBO it doesn't matter whether L or N in the coil but if you hook up to mains you want to use the Live as it will show any faults to earth.

[Thainesss]

4 minutes ago, Sophon said:

So, are there similar units that will fit my CU?

 

You might have to try and find a Schneider brand one because I think the way the breakers snap in is kind of proprietary. Forces you to use their products. 

 

I would leave you CU like it is and keep the extra spaces for expansion/added circuits later. 

 

Maybe buy a small separate box for and a different style of meter and mount it near that existing CU. 

[sometimewoodworker]

At the moment mine is just sitting on one of my CU's I will get round to putting it in a box sometime.

[Thainesss]

2 minutes ago, sometimewoodworker said:

At the moment mine is just sitting on one of my CU's I will get round to putting it in a box sometime.

 

If I could do it over again I would buy one like that. Looks cooler LOL

[Sophon]

1 minute ago, sometimewoodworker said:

At the moment mine is just sitting on one of my CU's I will get round to putting it in a box sometime.

My box is embedded in the wall, so the unit would fall off if I tried to balance it on top of the CU. And I really don't want a separate box, so unless I can find something that fit in my existing box, I will abandon the idea.

 

Sophon

[CGW]

30 minutes ago, Crossy said:

99.8% of electrical engineers would call that a current-transformer.

 

& the mericans wouldn't have a clue? 

[bankruatsteve]

4 minutes ago, Sophon said:

My box is embedded in the wall, so the unit would fall off if I tried to balance it on top of the CU. And I really don't want a separate box, so unless I can find something that fit in my existing box, I will abandon the idea.

 

Sophon

You don't really want to use a slot for that anyway although I doubt you would find one for Square-D.  I used "Velcro tape" to attach mine.

[sometimewoodworker]

16 minutes ago, Sophon said:

My box is embedded in the wall, so the unit would fall off if I tried to balance it on top of the CU. And I really don't want a separate box, so unless I can find something that fit in my existing box, I will abandon the idea.

 

Sophon

It will happily fit into a standard surface mount power/switch boxes, you just have to modify the cover plate.

 

Probable cost under 50 Baht and a couple of minutes with a Stanley knife.

 

This one has something wrong with the current sense side and I haven't bothered to find out what the problem is, so I got the fancy blue backlight one.

[Sophon]

I just opened by CU, and I am almost positive that the DIN rail unit will fit in my box. No, since my box doesn't have a DIN rail it won't clip on like it normally would, but I am sure I can find a way to fix it to the box even without the rail. Since we are only talking about 400-500 Baht, it's worth a try.

 

Thanks again to everyone.

 

Sophon

[bankruatsteve]

40 minutes ago, Sophon said:

I just opened by CU, and I am almost positive that the DIN rail unit will fit in my box. No, since my box doesn't have a DIN rail it won't clip on like it normally would, but I am sure I can find a way to fix it to the box even without the rail. Since we are only talking about 400-500 Baht, it's worth a try.

 

Thanks again to everyone.

 

Sophon

It will not "fit" in your box.  But, if you think you can jam it in, go for it.  Just don't try to hook up to the live rail.

[sometimewoodworker]

1 hour ago, Sophon said:

I just opened by CU, and I am almost positive that the DIN rail unit will fit in my box. No, since my box doesn't have a DIN rail it won't clip on like it normally would, but I am sure I can find a way to fix it to the box even without the rail. Since we are only talking about 400-500 Baht, it's worth a try.

 

Thanks again to everyone.

 

Sophon

The unit you have shown has to have either the incoming line or neutral going through it so you options for placement are extremely limited. 

 

I certainly would not want to try fitting it in the box you show. It would need a degree of bodging that would make me very uncomfortable, I don't think that it could be done safely.

 

Conversly the unit I have would most likely be able to be fitted to the cover plate with minor moderation, cutting a hole for mounting it, and looks as if there would be adequate clearance for it. 

[Wirejerker]

99.8% of electrical engineers would call that a current-transformer.
 

Sweet. I finally found a group I’m in the high percentile, where do I sign up


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[Sophon]

35 minutes ago, sometimewoodworker said:

The unit you have shown has to have either the incoming line or neutral going through it so you options for placement are extremely limited. 

 

I certainly would not want to try fitting it in the box you show. It would need a degree of bodging that would make me very uncomfortable, I don't think that it could be done safely.

 

Conversly the unit I have would most likely be able to be fitted to the cover plate with minor moderation, cutting a hole for mounting it, and looks as if there would be adequate clearance for it. 

 

1 hour ago, bankruatsteve said:

It will not "fit" in your box.  But, if you think you can jam it in, go for it.  Just don't try to hook up to the live rail.

No need to "jam" anything, there is plenty of space to fit the unit in the three empty spots on the right. I will reroute the neutral wire so that it goes around the breakers to the right on it's way to the earth bar. The unit can be double taped to the last breaker on the right, and will also be supported by the very stiff 16 sq.mm. neutral wire going through it. If that is not enough, it can also be fixed to the right side of the C.U. by adding a suitably sized plastic box or piece of styrofoam. There would be no safety issues at all.

 

Sophon