3-wire meter help

[davmax]

Re: 3-wire meter help

If there is no neutral the voltage coil is not operating, no connected circuit that I can see from your diagram. Attached Jpg. Should read " There is NO voltage connect for the top coil"

[pentium]

Re: 3-wire meter help

Can I carry this on tomorrow?
I am dead tired and it's making me have trouble reading your diagrams.

[starfury1]

Re: 3-wire meter help

Again this is of no direct help
(as in, put this wire there etc, which I know is really what your after)

Well Seems there are more ways to skin a cat depending on how you may actually be hooked up and what type of meter.
(see 3 wire connections here)

http://themeterguy.com/

A run down on the meter and a single Active hookup
(as in probably the way you had it wired)

here

3 wire setups Here

(note how the coils are represented for the A B N)

basically deals in the modern type and I could find no reference to the old ones.
for ref here is the 2 wire single phase Here


I don't understand exactly what the schematic representation is of in the circle..I would be guessing so no comment from me on that or the mention of form 1 2 etc, except its maybe the meter construction?

Like I said no electrician here


Thanks Davmax for your input.

I sent this before Id finished it but anyway

[davmax]

Re: 3-wire meter help

Pentium. I hope you have had enough sleep now. I would agree that some elctrical guy who actual has connection experience is your ideal source, but there seems to be no offers.

What puzzles me about your meter.
1. To change from 240V to 120V either the voltage coil must be tapped with three wires (this does not appear to be the case) or the current coils have to be re-arranged (the only apparent option). Current coils either in series or parallel as per my diagrams.
2. If the voltage coil remains at 120V for a 240V supply then error can arise if one phase goes missing.
3. Where is the neutral connection?

I am sure that you can make it work with what has been offered. One caution is that the phasing of the current coil with the voltage coil. Try with voltage coil and one current coil and see if there is a difference when the current coil connections are reversed. If there is a better response one way use that connection as a starting point.

[davmax]

Re: 3-wire meter help

See attached document

Starfury1 sent me a PM with a 240V split system picture. The split system rather than phases is well understood. However the PM made it clear that the neutral in an external connection and that the wattmeter voltage coil may always requires 240VAC. ie the meter always has 2 splits connected. This means that when connecting 120VAC devices they will be attached to a current coil on one of two splits. Each 120V device load is returned to neutral externally. (same config as for 240 but the load is split with the centre to neutral)
This method ensures that if one split voltage is missing there will be no meter error there will be simple zero meter operation, because the volts coil will have no current flow.

If this is correct (it makes a lot of sense) then each current coil is rated for the heavier 120VAC load currents.

Thanks for the input Starfury1

[pentium]

Re: 3-wire meter help

I agree with you there.
First, I'm going to finish off the rest of my wiring before trying again. What I had setup was temporary and I need to make it permanant.

[starfury1]

Re: 3-wire meter help

posting this mainly for those wondering how the American 3 wire single phase system works
here is a couple of links....not to do with meter hook up but it does explain a bit on the American system towards the bottom.

Single-phase power systems

the discussion thread I found it in Here

it does get into the bit were things become a bit grey with phase relationship or rather the confusion that stems from it.

another tibit here

my suspicion Davmax is the first one you draw above (2nd diagram post) is it
but have nothing concrete technically to confirm or write it off as being totally wrong.
you raised some questions I got to work through
In short I dont know....at this point
So I gotta think on it

[davmax]

Re: 3-wire meter help

Thanks Starfury1. Your links confirm my second set of diagrams, last posted.I think we have it there.

It is now for Pentium to get connected and see how it goes.

[starfury1]

Re: 3-wire meter help

No worries Davmax

well that from what little I could find and make some kind of sense of, its probably it.

Pentium is dealing with a meter style and hookup no longer sold
(or standard not being used)
by the looks of it so unfortunately no accurate hook up information can I find.
sorry But your on your own there
You need to identify whats what with your meter and hook it up the right way
(Again I know what you really wanted was "the put this wire there" answer)

I think if the meter is S2 or Form 2 (whatever standard its called)
type he can use it, since Pentium said it was used in a 220V hookup.
(seems some meters are dual purpose, although there are some situations if used in 110V only monitoring it can be inaccurate.
somewhere, possibly in the links above I read it)

The meter from one comment I found says it all,
its an electric motor by any other name LOL.


Here, as I said... this is the Provence of "licensed Electricians"
so All disclaimers apply here legal and otherwise
You do at your own risk and we assume
what you are doing is legal in your state and meets your states regulations...
Any injuries deaths property damaged etc is your responsibility
we accept no responsibility for your actions

Cheers

[pentium]

Re: 3-wire meter help

I completed a better and more clearly marked diagram of the meter. I wull try to scan it in tomorrow I hope.
I'm going to also wait until my new 20A breaker is installed. Part of the problem that I am trying to go 3-wire through a single 120V line ( )
Call me stupid.

[starfury1]

Re: 3-wire meter help

That put a whole different slant on it, the assumption was 240V with 2 Actives
As per the above 1 phase 3 wire

[starfury1]

Re: 3-wire meter help

If you are branching a single 120V ac line and then trying to get the meter to monitor both branches I don't think it was designed for that...you would have to put it before the the split as per 120V hook up
(as I was thinking was the case before)
It might be doable but not really sure

"Do not" used the above hook 3 wire 240V, it won't work!

rethink time

[davmax]

Re: 3-wire meter help

The problem is that the meter is designed for 240VAC on voltage coil.
Could try 120V on coil and use one current coil. Theoretically you would get half the wattage reading because voltage coil field is half.

[pentium]

Re: 3-wire meter help

..........
Those two posts just sent our understanding back to square one.

Just let me do what I need to do here and let's start over again.

[starfury1]

Re: 3-wire meter help

pentium did have the meter set up for 120 VAC operation and the meter can from what I understand do both.

The key is with the way you arrange the two current coils (I think)...I sort of remember reading something on that in relation to the maths ....that the two have to be setup in a particular setup for 120Vac so the meter reads accurately

I dont think he can do what he wants to do with it,
it wasn't designed to work that way
He may get it to work but it wouldn't be accurate.

I also remember reading something on under some conditions use of 120 VAC setup, can result in inaccurate measurement.
(what they were I can't recall)

He would have to put it in circuit before he branches the circuit and from what I gather the way he is planing to have the second circuit will not allow him to put the meter before the branch set up is done.

If you can pentium post a diagram (from the meter information that you got)
of exactly what the meter is suppose to be setup as for 120Vac KWH operation, if you can relate that back to the physical meter as well thats even better

You have to remember these were designed to monitor a houses "total consumption" the individual (branch) circuits would came after the meter

The "240 volt 3 wire hook up" will not help you in this instance if you are paralleling (branching) a single Active / Neutral 120 VAC (Earth) setup
It just wont work
(0 volts across voltage coil, since its the same Active)

BTW so we a clear on this, you are not building a "single phase 3 wire 240V"
setup
You are paralleling 2 120V VAC circuits
(to a common point, that common point must be suitably rated as per your rules and regs)
(since you mentioned 120VAC only)

yep your right back to square 1,

but I dont think you will be able to do want you want

Hope you Dont take this the wrong way pentium but I really think its a job for a licensed spark as to do want you want sounds like you got to go back to the board and have a meter put there.

[pentium]

Re: 3-wire meter help

If you can pentium post a diagram (from the meter information that you got)

Will do.

The "240 volt 3 wire hook up" will not help you in this instance if you are paralleling (branching) a single Active / Neutral 120 VAC (Earth) setup It just wont work
(0 volts across voltage coil, since its the same Active)

Yeah, I biffed up there. The diagram will clear that up.

BTW so we a clear on this, you are not building a "single phase 3 wire 240V" setup
You are paralleling 2 120V VAC circuits
(to a common point, that common point must be suitably rated as per your rules and regs)
(since you mentioned 120VAC only)

No.
Both circuits must not get wired together in any way.
One is rated 15 amps and is for the smaller systems, the second one is 20 amps and supplies power to my two deskside systems. wiring them together would be a really bad thing.
I am just exploiting the 3-wire configuration to meter two individual circuits and not one circuit.

Shoot. Gotta go. Bell.

[pentium]

Re: 3-wire meter help

Okay, I was cut off befor I could finish that last sentence so I'll say it again.

BTW so we a clear on this, you are not building a "single phase 3 wire 240V" setup
You are paralleling 2 120V VAC circuits
(to a common point, that common point must be suitably rated as per your rules and regs)
(since you mentioned 120VAC only)

No.
Both circuits must not get wired together in any way.
One is rated 15 amps and is for the smaller systems, the second one is 20 amps and supplies power to my two deskside systems. wiring them together would be a really bad thing.
I am just exploiting the 3-wire configuration to meter two individual circuits and not one circuit.
Since split-phase is made from +120v, neutral and -120v all that is needed to do to make two individual 120v circuits is to tie together the neutral wires (reduces stress on the wire) and in the place of the +120v connection you put the hot lead for one circuit and in the place of the -120v connection you put the hot lead for the other circuit.

If my theory is right, one mwter will then tell me how much power TWO individual circuits are consuming.

I will post that sketch soon. I need to get to the scanner.

[pentium]

Re: 3-wire meter help

Here's the sketch I made. I also color-coded the wires.

[starfury1]

Re: 3-wire meter help

Thanks for the diagram, it will help me understand how it was setup

what I meant was at some point they will *tie together....from what you say it seems both circuits are individually being brought out from the box. that being the common point (box wiring).
(*or to the individual Actives + or - in the split phase case)

Sorry pentium I think your out of luck with what you what to as far as using it on both circuits unless you put a sub board in for those two circuits


Just to cover this point here

No.
Both circuits must not get wired together in any way.
One is rated 15 amps and is for the smaller systems, the second one is 20 amps and supplies power to my two deskside systems. wiring them together would be a really bad thing.
I am just exploiting the 3-wire configuration to meter two individual circuits and not one circuit.
Since split-phase is made from +120v, neutral and -120v all that is needed to do to make two individual 120v circuits is to tie together the neutral wires (reduces stress on the wire) and in the place of the +120v connection you put the hot lead for one circuit and in the place of the -120v connection you put the hot lead for the other circuit.

If my theory is right, one meter will then tell me how much power TWO individual circuits are consuming.

The problem is for "single phase 3 wire 240 VAC setup it MUST be BOTH a RED and BLACK ACTIVE
If you use say 2 RED actives...its the same thing so no voltage drop across voltage coil (active to active) of meter. Ditto black Active

Doing what you saying if you use a 120V hook up (which uses the Neutral)
tie the voltage coil across one Active to Neutral and use the 2 coils each in series with the single active line for 15 A, 20 A branches, it may work but would not run correctly.
(apart from the fact its possibly illegal)

As I said the meter is not designed to work (correctly) that way from what I understand

even if it was a single phase 3 wire setup you would need to have a "common feed" to the meter "before" the circuits are branched off into there 15A 20A configuration.

There is no way by the sounds of it that you are bringing them out from the box as a common feed...Thats why I said you would need to have a meter put in the box.

Your only other alternative is 2 meters in 120VAC setup on each branch (leg) circuit which would probably need to go on a sub board panel anyway.
(again I don't know what the legal aspects are to this either)

The meter its self becomes part of the circuit so you just cant go running wires back to it from different places
(anything like that I very much doubt would be legal, apart from inaccuracies that maybe generated)

Given the age and style of the meter I doubt that you would be able to use it legally in a new setup...(I could be wrong)

The setup must be done in accordance with your local wiring code or it would be deemed illegal
If your house Burnes down and illegal wiring was found you would get no payout this is why everything has to meet your local electrical code and be inspected were inspection is required.

it would be simpler if I could draw diagrams but I cant scan anything cause the new box doesn't have a parallel port and the scanner is parallel only.
(got to sort that out)

Maybe this book might help, unfortunately its like $90 US dollars
you might see if your local library has it in their system.

Handbook for Electricity Metering - Tenth Edition

http://www.eei.org/products_and_serv...ok_meterng.htm

It might help.

really wish I could be of more help and give a you a positive out come.

Cheers

[davmax]

Re: 3-wire meter help

Pentium. You say that you are driving to seperate circuits/loads, one from each 120V split. That is how the meter is intended to operate, you are right on. This is the connection I last sent, and yes the power on both circuits will be measured correctly so long as the voltage coil is connected to 240V as per my diagram and yours of the meter. Neutral is external, the return for each split, neutral current is minimised by having each split current close to equal. Looks like your going to be successful.