Hi all. A simple electrical question (I hope).

I have a clamp on amp meter and I'm interested in seeing how much
current
is used at various loads by the feeder line running to my remote
garage.

The feeder is has 2 hots and 1 neutral going to a sub panel that
divides it
into several 110 circuits.

I know that the current on the neutral will be the difference between
the current on
the two hots (less any stray current lost to the grounding rod), but
I'm interested in
knowing the 'total' amps of the 220 circuit.

I'm thinking I could measure the current on one hot, then on the other
hot, and add
the two values together. What I would like to do is install a
permanent meter but
now I'm thinking that I need two, one for each hot. If I try to
measure the current
by passing both hots through the 'clamp', since they are 180 degrees
out of phase,
won't they cancel each other out (and I would end up with the
difference of the
two like on the netural)?

So my long winded question is this - how can I use a single 'clamp-on'
style meter
to measure current on a 220vac circuit?

Thanks.

kpg wrote:
Hi all. A simple electrical question (I hope).

I have a clamp on amp meter and I'm interested in seeing how much
current
is used at various loads by the feeder line running to my remote
garage.

The feeder is has 2 hots and 1 neutral going to a sub panel that
divides it
into several 110 circuits.

I know that the current on the neutral will be the difference between
the current on
the two hots (less any stray current lost to the grounding rod), but
I'm interested in
knowing the 'total' amps of the 220 circuit.

I'm thinking I could measure the current on one hot, then on the other
hot, and add
the two values together. What I would like to do is install a
permanent meter but
now I'm thinking that I need two, one for each hot. If I try to
measure the current
by passing both hots through the 'clamp', since they are 180 degrees
out of phase,
won't they cancel each other out (and I would end up with the
difference of the
two like on the netural)?

So my long winded question is this - how can I use a single 'clamp-on'
style meter
to measure current on a 220vac circuit?

Thanks.

Run one through in the opposite direction.

--
The e-mail address in our reply-to line is reversed in an attempt to
minimize spam. Our true address is of the form .

CJT wrote:

kpg wrote:

Hi all. A simple electrical question (I hope).

I have a clamp on amp meter and I'm interested in seeing how much
current
is used at various loads by the feeder line running to my remote
garage.

The feeder is has 2 hots and 1 neutral going to a sub panel that
divides it
into several 110 circuits.

I know that the current on the neutral will be the difference between
the current on
the two hots (less any stray current lost to the grounding rod), but
I'm interested in
knowing the 'total' amps of the 220 circuit.

I'm thinking I could measure the current on one hot, then on the other
hot, and add
the two values together. What I would like to do is install a
permanent meter but
now I'm thinking that I need two, one for each hot. If I try to
measure the current
by passing both hots through the 'clamp', since they are 180 degrees
out of phase,
won't they cancel each other out (and I would end up with the
difference of the
two like on the netural)?

So my long winded question is this - how can I use a single 'clamp-on'
style meter
to measure current on a 220vac circuit?

Thanks.

Run one through in the opposite direction.

Oh, and divide by two.

--
The e-mail address in our reply-to line is reversed in an attempt to
minimize spam. Our true address is of the form .

"kpg" wrote in message
oups.com...
Hi all. A simple electrical question (I hope).

I have a clamp on amp meter and I'm interested in seeing how much
current
is used at various loads by the feeder line running to my remote
garage.

The feeder is has 2 hots and 1 neutral going to a sub panel that
divides it
into several 110 circuits.

I know that the current on the neutral will be the difference between
the current on
the two hots (less any stray current lost to the grounding rod), but
I'm interested in
knowing the 'total' amps of the 220 circuit.

I'm thinking I could measure the current on one hot, then on the other
hot, and add
the two values together. What I would like to do is install a
permanent meter but
now I'm thinking that I need two, one for each hot. If I try to
measure the current
by passing both hots through the 'clamp', since they are 180 degrees
out of phase,
won't they cancel each other out (and I would end up with the
difference of the
two like on the netural)?

So my long winded question is this - how can I use a single 'clamp-on'
style meter
to measure current on a 220vac circuit?

If you created a loop so that you simultaneously measured one hot backwards
and one forwards it ought to work.
(actually I don't know, but it seems like it should)

Why do you want to do this anyhow? The information is pretty useless.

Why do you want to do this anyhow? The information is pretty useless.- Hide quoted text -

Well, I can't argue with you there. For one, I like gadgets. For
another, I have
a 5hp compressor, some computer equipment, a full time window unit,
and
a part time window unit, a bunch of fluorescent lights, occasionally a
hand drill
or table saw.

It all runs on a 30 amp branch circuit and at times the breaker gets
quite
warm to the touch. I thought it would be nice to be able to monitor
the load on the system, i.e., the amps flowing through the feeder
line.

And did I mention I like gadgets?

I'll do some experiments with the one backwards divide by two
method.

On Aug 13, 11:02 pm, kpg wrote:
Why do you want to do this anyhow? The information is pretty useless.- Hide quoted text -

Well, I can't argue with you there. For one, I like gadgets. For
another, I have
a 5hp compressor, some computer equipment, a full time window unit,
and
a part time window unit, a bunch of fluorescent lights, occasionally a
hand drill
or table saw.

It all runs on a 30 amp branch circuit and at times the breaker gets
quite
warm to the touch. I thought it would be nice to be able to monitor
the load on the system, i.e., the amps flowing through the feeder
line.

And did I mention I like gadgets?

I'll do some experiments with the one backwards divide by two
method.

Each item should have a nameplate. The nameplate will give you a rough
estimate of how much everything is using.

Everything you have listed could be single phase, which means that
each item will cause the reading to go up in only one phase of the
circuit. If you do have 240V stuff it will cause both phases to go up
at the same time.

Measure each leg with nothing on and then turn each item on and read
again.

Unless you are planing to upgrading , try not to use the compressor
and the AC unit at the same time.

The breaker is constantly monitoring the use.

Everything you have listed could be single phase, which means that
each item will cause the reading to go up in only one phase of the
circuit. If you do have 240V stuff it will cause both phases to go up
at the same time.

Yes, all of the equipment is single phase, some on one leg, some on
the
other. This is the source of my dilemma. So what I really am asking
is this: I know its meaningful to measure the current on one leg or
the other, but is it meaningful to measure the current on both at the
same time?

Say I was drawing 8 amps on one leg, and 9 on the other. Am I
using 17 amps? That seems right, but does it have any meaning?

The 30 amp breaker is 30 amps per leg - So who cares if they both
add up to, say, 40?

I'm starting to think measuring each leg independently is the
most correct solution.

You need a watt meter to gauge the total used wattage. The 30 amp breaker
getting warm and not tripping may mean a loose connection. Turn of the 30
amp breaker, remove from the panel. Check to be sure the pinch plate isn't
turning color [getting to hot] and the matching breaker connections are good
as well. Check the lugs on the breaker as well.

You might fare better by calling an experience electrician to check it out.

Zyp

"kpg" wrote in message
oups.com...
Everything you have listed could be single phase, which means that
each item will cause the reading to go up in only one phase of the
circuit. If you do have 240V stuff it will cause both phases to go up
at the same time.

Yes, all of the equipment is single phase, some on one leg, some on
the
other. This is the source of my dilemma. So what I really am asking
is this: I know its meaningful to measure the current on one leg or
the other, but is it meaningful to measure the current on both at the
same time?

Say I was drawing 8 amps on one leg, and 9 on the other. Am I
using 17 amps? That seems right, but does it have any meaning?

The 30 amp breaker is 30 amps per leg - So who cares if they both
add up to, say, 40?

I'm starting to think measuring each leg independently is the
most correct solution.

kpg wrote:
Everything you have listed could be single phase, which means that
each item will cause the reading to go up in only one phase of the
circuit. If you do have 240V stuff it will cause both phases to go up
at the same time.


Yes, all of the equipment is single phase, some on one leg, some on
the
other. This is the source of my dilemma. So what I really am asking
is this: I know its meaningful to measure the current on one leg or
the other, but is it meaningful to measure the current on both at the
same time?

Say I was drawing 8 amps on one leg, and 9 on the other. Am I
using 17 amps? That seems right, but does it have any meaning?

The 30 amp breaker is 30 amps per leg - So who cares if they both
add up to, say, 40?

I'm starting to think measuring each leg independently is the
most correct solution.



Nobody cares if they add up to 40 amps in your hypothetical example...
simplifying a little bit here, but if you have 29 amps on one leg and 11
amps on another, the current on the neutral will actually be 18 amps (it
won't actually in real life, but close enough) if you have 20 and 20, it
will be zero.

nate

--
replace "roosters" with "cox" to reply.
http://members.cox.net/njnagel

"kpg" wrote in message
oups.com...
Everything you have listed could be single phase, which means that
each item will cause the reading to go up in only one phase of the
circuit. If you do have 240V stuff it will cause both phases to go up
at the same time.

Yes, all of the equipment is single phase, some on one leg, some on
the
other. This is the source of my dilemma. So what I really am asking
is this: I know its meaningful to measure the current on one leg or
the other,


That's how it is done.


but is it meaningful to measure the current on both at the
same time?


You probably won't get a reading.



Say I was drawing 8 amps on one leg, and 9 on the other. Am I
using 17 amps?

Yes.


That seems right, but does it have any meaning?


It means you are drawing 17 amps and the load is almost perfectly balanced.
You can also measure amps on the neutral. I usually check the grounding
electrode conductor also. Once in a while I find current on it and then I
explain to the customer that there may be a problem somewhere.


The 30 amp breaker is 30 amps per leg - So who cares if they both
add up to, say, 40?


If I was concerned about the load, I would care.



I'm starting to think measuring each leg independently is the
most correct solution.

You are correct.

kpg wrote:
Hi all. A simple electrical question (I hope).

I have a clamp on amp meter and I'm interested in seeing how much
current
is used at various loads by the feeder line running to my remote
garage.

The feeder is has 2 hots and 1 neutral going to a sub panel that
divides it
into several 110 circuits.

I know that the current on the neutral will be the difference between
the current on
the two hots (less any stray current lost to the grounding rod),

Actually, no it won't. If you had a pure 240 load the current on the
neutral would be *zero.* Since you have 120VAC branch circuits, some
will have more load than others, and some will be connected to one phase
and some will be connected to the opposite phase. So you will have
*some* current on the neutral, but it should be significantly less than
the current on either of the "hot" wires.

I realize that sounds very, very strange, but google for "Edison
circuit" for an explanation - a feeder to a remote subpanel is
essentially a really big Edison circuit.

but
I'm interested in
knowing the 'total' amps of the 220 circuit.


It's probably slightly unbalanced. Measure one leg, then the other.

I'm thinking I could measure the current on one hot, then on the other
hot, and add
the two values together. What I would like to do is install a
permanent meter but
now I'm thinking that I need two, one for each hot. If I try to
measure the current
by passing both hots through the 'clamp', since they are 180 degrees
out of phase,
won't they cancel each other out (and I would end up with the
difference of the
two like on the netural)?

So my long winded question is this - how can I use a single 'clamp-on'
style meter
to measure current on a 220vac circuit?

Thanks.


Current is current. You measure it directly.

nate

--
replace "roosters" with "cox" to reply.
http://members.cox.net/njnagel

On Mon, 13 Aug 2007 22:59:25 -0400, Nate Nagel
wrote:

kpg wrote:
Hi all. A simple electrical question (I hope).

I have a clamp on amp meter and I'm interested in seeing how much
current
is used at various loads by the feeder line running to my remote
garage.

The feeder is has 2 hots and 1 neutral going to a sub panel that
divides it
into several 110 circuits.

I know that the current on the neutral will be the difference between
the current on
the two hots (less any stray current lost to the grounding rod),

Actually, no it won't. If you had a pure 240 load the current on the
neutral would be *zero.* Since you have 120VAC branch circuits, some
will have more load than others, and some will be connected to one phase
and some will be connected to the opposite phase. So you will have
*some* current on the neutral, but it should be significantly less than
the current on either of the "hot" wires.

Isn't this what he said?

Not counting the part about stray current lost through the grounding
rod, which I don't really understand. It's rare, isn't it, for any
current to go back through the ground or a grounding rod?

I realize that sounds very, very strange, but google for "Edison
circuit" for an explanation - a feeder to a remote subpanel is
essentially a really big Edison circuit.

It's rare, isn't it, for any
current to go back through the ground or a grounding rod?

I thought so until I did some research. There are several situations
where
there can be dangerous current in the ground wire at the ground rod.

Obviously, a fault in the neutral will cause current to use the ground
wire as a return path, but also if your neighbor has a fault in his
neutral his current could be returning to the transformer via your
ground
rod.

Moral: before disconnecting the ground wire to service the ground rod
always check for current. Even if the main is off.

Thanks for all the replies.

I don't know if any electrician reading this post
he must be laughing his head of
what is total amps on 220 whatever you are
reading on your amprob dummy
do you have any knowledge in Ohms law.
and neutral at properly design and grounded system
IS carrying current it is not at zero ever unless on your
screwed up system ground is carrying current
which is not suppose to ever.
and if you take 220 then split the phase of the same
source/cable for 110 the neutral will carry double the current
of single hot wire!
Tony
www.cas-environ.com

"kpg" wrote in message
oups.com...
Hi all. A simple electrical question (I hope).

I have a clamp on amp meter and I'm interested in seeing how much
current
is used at various loads by the feeder line running to my remote
garage.

The feeder is has 2 hots and 1 neutral going to a sub panel that
divides it
into several 110 circuits.

I know that the current on the neutral will be the difference between
the current on
the two hots (less any stray current lost to the grounding rod), but
I'm interested in
knowing the 'total' amps of the 220 circuit.

I'm thinking I could measure the current on one hot, then on the other
hot, and add
the two values together. What I would like to do is install a
permanent meter but
now I'm thinking that I need two, one for each hot. If I try to
measure the current
by passing both hots through the 'clamp', since they are 180 degrees
out of phase,
won't they cancel each other out (and I would end up with the
difference of the
two like on the netural)?

So my long winded question is this - how can I use a single 'clamp-on'
style meter
to measure current on a 220vac circuit?

Thanks.

You really should learn some punctuation before you call someone
dummy.


On Aug 14, 8:36 pm, "Tony" wrote:
I don't know if any electrician reading this post
he must be laughing his head of
what is total amps on 220 whatever you are
reading on your amprob dummy
do you have any knowledge in Ohms law.
and neutral at properly design and grounded system
IS carrying current it is not at zero ever unless on your
screwed up system ground is carrying current
which is not suppose to ever.
and if you take 220 then split the phase of the same
source/cable for 110 the neutral will carry double the current
of single hot wire!
Tonywww.cas-environ.com

"kpg" wrote in message

oups.com...



Hi all. A simple electrical question (I hope).

I have a clamp on amp meter and I'm interested in seeing how much
current
is used at various loads by the feeder line running to my remote
garage.

The feeder is has 2 hots and 1 neutral going to a sub panel that
divides it
into several 110 circuits.

I know that the current on the neutral will be the difference between
the current on
the two hots (less any stray current lost to the grounding rod), but
I'm interested in
knowing the 'total' amps of the 220 circuit.

I'm thinking I could measure the current on one hot, then on the other
hot, and add
the two values together. What I would like to do is install a
permanent meter but
now I'm thinking that I need two, one for each hot. If I try to
measure the current
by passing both hots through the 'clamp', since they are 180 degrees
out of phase,
won't they cancel each other out (and I would end up with the
difference of the
two like on the netural)?

So my long winded question is this - how can I use a single 'clamp-on'
style meter
to measure current on a 220vac circuit?

Thanks

"Tony" wrote in news:tUrwi.4051$%55.3250@trnddc04:

I don't know if any electrician reading this post
he must be laughing his head of
what is total amps on 220 whatever you are
reading on your amprob dummy


Well, I'm not an electrician, this is why I asked the
question. Dummy.

do you have any knowledge in Ohms law.

I have an Ohm meter. Does that count?

and neutral at properly design and grounded system
IS carrying current it is not at zero ever unless on your
screwed up system ground is carrying current
which is not suppose to ever.
and if you take 220 then split the phase of the same
source/cable for 110 the neutral will carry double the current
of single hot wire!

Um, the neutral will carry the difference between the two hot
wires. The total current must be the same coming and going
- do you have any knowledge in Kirchhoff's Law?

"kpg*" wrote in message
20...
"Tony" wrote in news:tUrwi.4051$%55.3250@trnddc04:

I don't know if any electrician reading this post
he must be laughing his head of
what is total amps on 220 whatever you are
reading on your amprob dummy


Sorry I did not mean it as it sound


Well, I'm not an electrician, this is why I asked the
question. Dummy.

do you have any knowledge in Ohms law.

I have an Ohm meter. Does that count?

NO I have few of them and I do not see myself an engineer
or expert by any standard and please don't go there
because I am anticipating that would be your next step


and neutral at properly design and grounded system
IS carrying current it is not at zero ever unless on your
screwed up system ground is carrying current
which is not suppose to ever.
and if you take 220 then split the phase of the same
source/cable for 110 the neutral will carry double the current
of single hot wire!

Um, the neutral will carry the difference between the two hot
wires. The total current must be the same coming and going
- do you have any knowledge in Kirchhoff's Law?


It is been so long since I stody the basics of Kirechhoffs Law,
That I would not atempt to go there
Tony

Tony wrote:

and neutral at properly design and grounded system
IS carrying current it is not at zero ever unless on your
screwed up system ground is carrying current
which is not suppose to ever.

Not true. The two hots in a 240V circuit are 180 degrees out of phase.
Only the difference between the loads on the two sides flows through
the neutral. Thus, if you have equal 120V loads on each side, the
neutral will have zero current flowing in it.

and if you take 220 then split the phase of the same
source/cable for 110 the neutral will carry double the current
of single hot wire!

If the neutral carried double the current it would have to be oversized
compared to the hots. In reality, it is often *undersized*. The only
way this can make sense is if your statement is false.

This is why split-wire (aka "edison") circuits need to have the two hots
on opposite legs. If they were on the same leg the neutral *would*
carry the sum of the two legs, which could cause overheating.

Chris

"Chris Friesen" wrote in message
...
Tony wrote:

and neutral at properly design and grounded system
IS carrying current it is not at zero ever unless on your
screwed up system ground is carrying current
which is not suppose to ever.

Not true. The two hots in a 240V circuit are 180 degrees out of phase.
Only the difference between the loads on the two sides flows through the
neutral. Thus, if you have equal 120V loads on each side, the neutral will
have zero current flowing in it.

I would like wet one of hand and put it on the ground
ant other to the neutral to see if is carrying current
in close loop circuit and use something small to close
loop like 100 watt bulb that should do it
yes why don't try that and let us know
because what you saying 0 potential 0 current
that should be perfectly safe


and if you take 220 then split the phase of the same
source/cable for 110 the neutral will carry double the current
of single hot wire!

If the neutral carried double the current it would have to be oversized
compared to the hots. In reality, it is often *undersized*. The only way
this can make sense is if your statement is false.

This is why split-wire (aka "edison") circuits need to have the two hots
on opposite legs. If they were on the same leg the neutral *would* carry
the sum of the two legs, which could cause overheating.

Chris

plonk

"Tony" wrote in message
news:xfHwi.7146$xc5.2631@trnddc06...

"Chris Friesen" wrote in message
...
Tony wrote:

and neutral at properly design and grounded system
IS carrying current it is not at zero ever unless on your
screwed up system ground is carrying current
which is not suppose to ever.

Not true. The two hots in a 240V circuit are 180 degrees out of phase.
Only the difference between the loads on the two sides flows through the
neutral. Thus, if you have equal 120V loads on each side, the neutral
will have zero current flowing in it.

I would like wet one of "YOU" hand put it on the ground
ant other to the neutral to see if is carrying current
in close loop circuit and use something small to close
loop like 100 watt bulb that should do it
yes why don't try that and let us know
because what you saying 0 potential 0 current
that should be perfectly safe


and if you take 220 then split the phase of the same
source/cable for 110 the neutral will carry double the current
of single hot wire!

If the neutral carried double the current it would have to be oversized
compared to the hots. In reality, it is often *undersized*. The only
way this can make sense is if your statement is false.

This is why split-wire (aka "edison") circuits need to have the two hots
on opposite legs. If they were on the same leg the neutral *would* carry
the sum of the two legs, which could cause overheating.

Chris

According to Tony :

"Tony" wrote in message
news:xfHwi.7146$xc5.2631@trnddc06...

"Chris Friesen" wrote in message
...
Tony wrote:

and neutral at properly design and grounded system
IS carrying current it is not at zero ever unless on your
screwed up system ground is carrying current
which is not suppose to ever.

Not true. The two hots in a 240V circuit are 180 degrees out of phase.
Only the difference between the loads on the two sides flows through the
neutral. Thus, if you have equal 120V loads on each side, the neutral
will have zero current flowing in it.

I would like wet one of "YOU" hand put it on the ground
ant other to the neutral to see if is carrying current
in close loop circuit and use something small to close
loop like 100 watt bulb that should do it
yes why don't try that and let us know
because what you saying 0 potential 0 current
that should be perfectly safe

Even after spelling and gramatical corrections, that's linguistically and
technically wrong, not to mention just plain silly.

Even if the neutral was carrying current, you're not going to get a shock
between the neutral and ground because the voltage difference between the
neutral and ground is at most a volt or two[+]. This is true even in a 120V
circuit pulling 15A.

Remember, the neutral and ground are connected together in the panel.
They're never going to be more than a volt or two different. Unless
something goes very wrong.

The neutral in a 3 wire 240V/120V circuit only carries the difference
current between the two hots. If it wasn't and currents added on the
neutral, then 3 wire 240V/120V circuits would be illegal. I assure you,
they're not. In fact, up until a few years ago, they were _mandatory_
in the Canadian electrical code for kitchen counter outlets (and used
to be fairly common practise in the US). This has only changed in Canada
because of new requirements for GFCIs on kitchen counter outlets, and GFCI'ing
split duplex receptacles requires expensive dual GFCI breakers.

If the hots are equal current, the current in the neutral wire is _zero_.
Not only that, but the voltage between neutral and ground will also be _zero_[+].

[+] presuming of course that the neutral and ground are properly connected
to where they're supposed to be - connected together at the main
panel.
--
Chris Lewis,

Age and Treachery will Triumph over Youth and Skill
It's not just anyone who gets a Starship Cruiser class named after them.

On Aug 13, 10:21 pm, kpg wrote:
Hi all. A simple electrical question (I hope).

I have a clamp on amp meter and I'm interested in seeing how much
current
is used at various loads by the feeder line running to my remote
garage.

The feeder is has 2 hots and 1 neutral going to a sub panel that
divides it
into several 110 circuits.

I know that the current on the neutral will be the difference between
the current on
the two hots (less any stray current lost to the grounding rod), but
I'm interested in
knowing the 'total' amps of the 220 circuit.

I'm thinking I could measure the current on one hot, then on the other
hot, and add
the two values together. What I would like to do is install a
permanent meter but
now I'm thinking that I need two, one for each hot. If I try to
measure the current
by passing both hots through the 'clamp', since they are 180 degrees
out of phase,
won't they cancel each other out (and I would end up with the
difference of the
two like on the netural)?

So my long winded question is this - how can I use a single 'clamp-on'
style meter
to measure current on a 220vac circuit?

Thanks.

There is a lot of mis-information in the other posts. The answer to
your question is you can use one meter. You need to pass both hot
leads through the clamp on meter, but one hot lead has to pass through
in the "reverse direction". This may be hard to arrange with heavy
wires.

Now the meter will give an indication of the 110V current. If you
have 10 Amp 110V load on one hot lead the meter will read 10 Amps. If
you have a 10 Amp 220 load, the meter will read 20 because you are
using 10 Amps in both hot leads. If you have a 10 Amp 110 V load on
the other hot lead, the meter will read 10 Amps.

Have fun
Mark