CT's ok on Neutral Wires?

[johnstonf]

I've been searching for this, and my electrician is coming soon... so I'm going to fire this q off...

Is there any reason, if it makes joining a couple of circuits onto one channel/CT easier, that I can't put the CT onto the 'Neutral' (vs. the Line) of 115v circuits?

Also, for 220v circuits, with a neutral, such as my stove, (and my stove doesn't have a 115v receptacle to plug appliances into), is it fairly close to just use ONE CT on it? (I imag

Also, is it ok to put 4 of 115v circuits (4x15/2 wires) into one CT-80?
(and again, using neutrals?)

Thanks!

Fred

[Teken]

Hello Fred,

Is there any reason, if it makes joining a couple of circuits onto one channel/CT easier, that I can't put the CT onto the 'Neutral' (vs. the Line) of 115v circuits?

The CT should always be placed on the line as this is where the load will be drawn from. The neutral wire is the return path and doesn't always reflect the consumed load.

Also, for 220v circuits, with a neutral, such as my stove, (and my stove doesn't have a 115v receptacle to plug appliances into), is it fairly close to just use ONE CT on it?

For a stove with a neutral to obtain the most accuracy both line feeds need to be monitored. Otherwise you will only be measuring half the stoves energy consumption. Meaning you could literally turn on one side of the top element and the GEM won't see it because you don't have a CT monitoring that line.

Also, is it ok to put 4 of 115v circuits (4x15/2 wires) into one CT-80?
(and again, using neutrals?)

No . . . The first reason is you can't guarantee all of the 120 volt lines will be on the same phase. Assuming you had luck on your side and all four lines were indeed on the same electrical leg of the service panel. It would be a tight squeeze to get all four wires inside that donut and that's assuming copper wire.

What is the reason behind that ?

[johnstonf]

Great bunch of info... thanks Teken!
I had forgotten the phasing issue...
That being said, is there any LEGAL issue to NOT put CT's on a couple of Neutrals?
(if i got lucky and they were on the same phase? (and they were handy close to each other)

And as for the stove, i guess it maybe doesn't always use 240v?...
(would some elements drop to 115v for lower heat??)
(I just thought the clock/timer/logic would be the only thing to use 115v, very minimal)

On the Neutral being less accurate because it's return...
I'm not quite understanding where power would be LOST...
Unless some was LEAKING to ground... (bad)
How else would current ever be any different from line and neutral?

On the "why"... the reason is I'm a little short on CT's, so I'm going to need to double
or triple up on a couple of channels. I'm not even overly anal (at this point) about
being accurate to the penny, just a close idea.

Fred

Hello Fred,

Is there any reason, if it makes joining a couple of circuits onto one channel/CT easier, that I can't put the CT onto the 'Neutral' (vs. the Line) of 115v circuits?

The CT should always be placed on the line as this is where the load will be drawn from. The neutral wire is the return path and doesn't always reflect the consumed load.

Also, for 220v circuits, with a neutral, such as my stove, (and my stove doesn't have a 115v receptacle to plug appliances into), is it fairly close to just use ONE CT on it?

For a stove with a neutral to obtain the most accuracy both line feeds need to be monitored. Otherwise you will only be measuring half the stoves energy consumption. Meaning you could literally turn on one side of the top element and the GEM won't see it because you don't have a CT monitoring that line.

Also, is it ok to put 4 of 115v circuits (4x15/2 wires) into one CT-80?
(and again, using neutrals?)

No . . . The first reason is you can't guarantee all of the 120 volt lines will be on the same phase. Assuming you had luck on your side and all four lines were indeed on the same electrical leg of the service panel. It would be a tight squeeze to get all four wires inside that donut and that's assuming copper wire.

What is the reason behind that ?

[Teken]

Hello Fred,

Nothing is stopping you from using the neutrals to monitor the energy consumption. But I can tell you depending upon the load type you will indeed see a difference. With respect to the stove - yes in a standard range top the top elements are all 120.

Depending upon which one you turn on will result in the energy consumed on that electrical leg of the single phase split circuit. When you turn on the oven the same thing also happens as there is a top burner and a lower burner. Both use one side of the electrical leg of the 120/240 VAC system.

You may be wondering (assuming) you didn't consider this part is that the GEM can double the value in software. But this assumes a balanced 240 load with out a neutral and if you did this it would throw your energy consumption's and readings off too.

Because if you turned on one top element the system would think its 240 and also double the consumption and thus offer you incorrect energy consumption. So don't use the voltage doubling feature in this case.

If you ran short on CT's I would humbly suggest you order them because this really is a one shot deal. Meaning you will probably only do this once and you might as well do it right the first go round.

Given the CT's costs so very little its worth the time and effort to do so.

[ben]

In terms of combining wires into one CT. It is possible if the wire fits. For alternating phases, you must put the secondary wire in the opposing direction.

I asked Paul about the neutral, he says you can monitor from the neutral as long as it's not a 240V load.

[johnstonf]

Maybe a dumb question, but if the Neutral is the return path for BOTH lines in a 240v circuit with a Neutral, why can't you put a CT on the neutral, and it be the sum of both lines?

In terms of combining wires into one CT. It is possible if the wire fits. For alternating phases, you must put the secondary wire in the opposing direction.

I asked Paul about the neutral, he says you can monitor from the neutral as long as it's not a 240V load.

[Teken]

You can try it and find out why later.

[johnstonf]

Am I not allowed to ask why?
Knowledge is not a bad thing, is it?

You can try it and find out why later.

[Teken]

Am I not allowed to ask why?
Knowledge is not a bad thing, is it?

You can try it and find out why later.

LOL . . .

Fred,

Personal first hand knowledge when you undertake this endeavor will show you. When the electrician is on site both of you can discuss the pros / cons of doing the above. Keeping in mind simple resistive loads normally show a small variance. Whereas reactive / inductive loads will show more variance when monitored.

As I noted up above my humble suggestion is that you invest the extra money for more CT's for the system which is ultimately a long term investment.

[ben]

Maybe a dumb question, but if the Neutral is the return path for BOTH lines in a 240v circuit with a Neutral, why can't you put a CT on the neutral, and it be the sum of both lines?

In terms of combining wires into one CT. It is possible if the wire fits. For alternating phases, you must put the secondary wire in the opposing direction.

I asked Paul about the neutral, he says you can monitor from the neutral as long as it's not a 240V load.

From my understanding (I'm not an electrician, just attempting to re-phrase what Paul has told me).

The 240V side of things will cancel on the neutral as they're on opposing phases. You'll only get the amperage from the 120V side of things.

So if you hook a CT onto the neutral of a new dryer circuit for example, it'll only pick up the amperage used from the display, chime, etc.