How to identify wires

Users who are viewing this thread

James23912

Member
Messages
110
Reaction score
7
Points
18
Location
Vermont
I have an electrician coning out later today to connect the new underground 4/0 4 wire underground wire to the main panel in the house, coming from the meter post 100' away, while getting things ready I have been wondering , the 4 wire that is underground has one smaller wire with a stripe, obviously the ground, but the other 3 are all the same, same size and all black with no differentiating marks that I can tell.so I was assuming we would set up the inside panel while the power at the meter box in still not connected, then connect it last, but I am wondering how we will tell which wires are the hot ones, as they run underground, I am assuming we will have to connect one or two of them at the post outside first and then go into the house to test which is live? Sounds kind of dangerous so I want to ask here before the guy comes out, he is licensed but young and works at a hospital so I want to be sure about this beforehand, he says there is a way to check which is which beforehand but I did not understand what he meant. thanks
 

Sylvan

Still learning
Messages
2,756
Reaction score
689
Points
113
Location
New York
When I was not sure which lines were hot I would use a light bulb connected to a pigtail and place the black wire on the line and the white on the panel or ground. If I wanted to test fro 220 V I used both wires on the hot and the bulb with bur real bright. This way you do not need a meter


8311_3a09f31750aca9e31620ba13d96060d191dc4e7b_original.jpg
 

Stuff

Well-Known Member
Messages
1,221
Reaction score
130
Points
63
Location
Pennsylvania
There are a few ways to do it but safer to do it without power. Install all 4 wires at the service post with power shut off. The neutral will be connected to the ground there. Then use the multi-meter's resistance scale (ohmmeter). Test each big wire to the small ground at other end. The wire that measures zero ohms is neutral and the other two are hots.
 

James23912

Member
Messages
110
Reaction score
7
Points
18
Location
Vermont
There are a few ways to do it but safer to do it without power. Install all 4 wires at the service post with power shut off. The neutral will be connected to the ground there. Then use the multi-meter's resistance scale (ohmmeter). Test each big wire to the small ground at other end. The wire that measures zero ohms is neutral and the other two are hots.


Hi thanks, I figured something like that, but I still don't get how to tell when there is no power, does that men we will turn on the power and then check or does this work with no power? I was thinking maybe we would put a small load on e one end and then check the other, I am nervous about running the power into the house with the wires not connected to anything
 

Reach4

Well-Known Member
Messages
38,798
Reaction score
4,413
Points
113
Location
IL
Hi thanks, I figured something like that, but I still don't get how to tell when there is no power, does that men we will turn on the power and then check or does this work with no power? I was thinking maybe we would put a small load on e one end and then check the other, I am nervous about running the power into the house with the wires not connected to anything
James, do you have a multimeter? If so, take ohms (resistance) readings across things like coins, your fingers, a book, etc to get a feel for that. Don't try measuring powered circuits at this point. A multimeter has its own power for resistance readings, and the power is not harmful. Do not attempt to measure powered circuits with a meter in resistance mode.

When your electrician comes, he can take readings very quickly. If he sounded like he wanted you to figure this out in advance, he would rethink that if he knew your experience level with a multimeter.
 

Stuff

Well-Known Member
Messages
1,221
Reaction score
130
Points
63
Location
Pennsylvania
Simple safety rule: Do not turn power on until everything is hooked up. Identifying and installing wiring is done without power.

A cowboy electrician does things hot to save time. Your situation doesn't warrant that.
 

James23912

Member
Messages
110
Reaction score
7
Points
18
Location
Vermont
Okay
James, do you have a multimeter? If so, take ohms (resistance) readings across things like coins, your fingers, a book, etc to get a feel for that. Don't try measuring powered circuits at this point. A multimeter has its own power for resistance readings, and the power is not harmful. Do not attempt to measure powered circuits with a meter in resistance mode.

When your electrician comes, he can take readings very quickly. If he sounded like he wanted you to figure this out in advance, he would rethink that if he knew your experience level with a multimeter.


OK, now I get it, I have used a multimeter before, but mostly for 12 volt vehicles, I did not realize that the ohm setting produces power, (actually I thought it was only used by Buddhists) now it makes sense. even when I used ohms on my riding lawnmower, I assumed it worked bec of the battery.

I guess I will stick to carpentry in the future

thanks for the input, everyone
 

James23912

Member
Messages
110
Reaction score
7
Points
18
Location
Vermont
Hang on, I am still a bit confused, if I were to connect all 4 wires to the meter box outside and there is no power connected, as is what I understand Stuff to be saying , why would the neutral wire have no reading and the 2 hot wires show anything? That is what I don't get, it seems like any piece of wire just laying on the floor would show the same thing, not trying to be difficult, IOW, if there is no power, wouldn't all the wires show the same thing? Unless there is some sort of load coming from one end while I measure it at the other end?

Or would the readings be different depending on what each is connected to in the meter box, even if no power?

to put it more simply, the wire came on a big wooden spool, so if i found each end while still wrapped up on the spool, , could I determine which is which and then color code them in advance?

again, sorry if I am being dense
 

Reach4

Well-Known Member
Messages
38,798
Reaction score
4,413
Points
113
Location
IL
Hang on, I am still a bit confused, if I were to connect all 4 wires to the meter box outside and there is no power connected, as is what I understand Stuff to be saying , why would the neutral wire have no reading and the 2 hot wires show anything? That is what I don't get, it seems like any piece of wire just laying on the floor would show the same thing, not trying to be difficult, IOW, if there is no power, wouldn't all the wires show the same thing?
If I have 4 wires laying on the floor, and I know two of them are connected together at the far end. Can I use an ohmmeter (multimeter on ohms scale) to detect which two are connected together?

Again, play with that meter a bit. No danger, as long as you don't hook it to a powered circuit yet.

It's safer than playing with a table saw that has the power off.
 

Stuff

Well-Known Member
Messages
1,221
Reaction score
130
Points
63
Location
Pennsylvania
When you put a multi-meter on the ohms scale it uses its internal battery. It basically connects the red/+ lead to the + terminal of the battery. Then it measures what it sees on the black/- lead and does a mathematical calculation. If nothing is touching then it will see the full battery voltage between + and - leads which it will display as infinite resistance/ohms. If it sees the same battery voltage on both (wires touching/shorted) it will display zero ohms.

This is also a similar device known as a continuity checker. It has a battery and when the wires touch a light and/or sound goes off.

So yes, if you had a wooden spool and access to both ends you could determine which wire is which with an ohmmeter and color code the wires in advance. This is not done in the field because you usually don't use the whole roll and would cut off an end that you marked.

Google "measuring ohms" and there are some decent explanations out there.
 

Jadnashua

Retired Defense Industry Engineer xxx
Messages
32,770
Reaction score
1,190
Points
113
Location
New England
When measuring voltage, the meter is connected between the two leads and moves (or displays) based on how high the voltage is coming in.

When measuring ohms, the meter is putting a voltage on one lead, and looking to see how much of that voltage is returning on the other lead, and the calculation drives the meter.

When measuring current, you 'break' the circuit, and insert the meter in series with the load. The meter measures how much current goes through it, unless you have an inductive (clamp-on) meter. Then, it measures the magnetic field strength caused by the power going through the coil from the wire.

On many meters, you not only have to change the mode, but also may have to move a lead on the meter to a different position. If it's not autoranging, you also have to change the scale so you don't damage the meter portion. Some can self-protect, and will just display something like OL for overload, but some will literally be damaged. On an analog meter, you can literally bend the needle if it gets jammed up against the stop by being in the wrong scale.

With a 240vac supply, the ground and neutral will be connected together, so the resistance between the two at the other end should be very close to zero (or a short). Measuring from the ground/neutral wires to either 'hot' lead would be an open or infinity. You cannot measure resistance (readout is in ohms) with power on...you'll likely damage your meter.
 

Sylvan

Still learning
Messages
2,756
Reaction score
689
Points
113
Location
New York
I still think my way is the easiest and if it is 220 the Bulb will be very bright as HJ stated but if it is only 110 the bulb will light normally

When I tested a Buzz bar to make sure I had 220 for my welding machine I used the Bulb rather than my old Simson 260
 

hj

Master Plumber
Messages
33,602
Reaction score
1,041
Points
113
Location
Cave Creek, Arizona
Website
www.terrylove.com
I do not know about you , but I would NEVER connect wires based on what SOMEONE ELSE checked and told me the results. I was working on a commercial job once and the pipefitters, not plumbers, went to plug their extension into an outlet painted red. I told them not to since it was a 240 receptacle with a 120 duplex. They said I was crazy, because they had been using it for their Ridgid 300 die for weeks. I got the electrician to prove it and they said, "No wonder we have been getting threads done so quickly". But the job super also "measured" my tape against his ruler when I told him his bench mark was incorrect.
 
Last edited:

WorthFlorida

Clinical Trail on a Cancer Drug Started 1/31/24. ☹
Messages
5,727
Solutions
1
Reaction score
982
Points
113
Location
Orlando, Florida
.......I have an electrician coming out later today ..............

An electrician will easily figure it out, that is his job. When he is done, the neutral wire should have white tape wrapped around it at both ends and may wrap red tape around the L2.
 

Sylvan

Still learning
Messages
2,756
Reaction score
689
Points
113
Location
New York
When I was a stationary engineer one of the larger pumps was making a strange noise and there was no electrician around

I took a pigtail went to the main electrical panel and tested each bar with a light bulb pigtail and found one phase was not working

A bulb will not give amperage BUT it will let you know if the line is hot
 

hj

Master Plumber
Messages
33,602
Reaction score
1,041
Points
113
Location
Cave Creek, Arizona
Website
www.terrylove.com
There was a power failure at the police station when a transformer blew out. It was replaced and a week or so later the twin ejector pumps both stopped pumping water. We pulled the pumps and the nuts holding the impellers had both unscrewed. It turns out they connected the three phase transformer incorrectly and the pump was running backwards. I interchanged two of the leads and the problem was solved for the pump motors. Never found out if anything else had a problem.
 

James23912

Member
Messages
110
Reaction score
7
Points
18
Location
Vermont
Hi all, thanks for the replies, I always unplugged my cords when I had my carpentry business, last summer Ileft them plugged in in the new house and one Sunday morning my neighbor came over, black smoke pouring out the roof, my little table saw , not running, has burnt up , just a pile of burnt plastic and metal and horrible black acrid smoke.

Trust me, Ihave no desire to try anything myself, I just like to know about stuff and my question I guess was as much about the physical aspect as the technical, I couldn’t figure how, with one set of wires in the cellar, and the other end outside 100’ away owing out of the ground , you could tell which wire was which if you were alone. I don’t see why they don’t mark the wires somehow, seems it would be much safer, only the ground has a stripe and the wire is smaller anyway

if anyone reads this, I am also wondering if it would be better to get a whole new outside mater box, mine is from about 1992, and was used with 3 wire rather than the 4, the electrician as well as the person from the power co who came out didn’t say anything about that but they don’t seem all that expensive
 

DIYorBust

Active Member
Messages
745
Reaction score
94
Points
28
Location
Long Island, New York
I don't know if you should replace the meter box, I guess that's up to you. But one thing I'll say is that you should not attempt this project with your level of knowledge. You could very easily hurt yourself or damage something. If your electrician does not know how to do this, you have the wrong electrician.

One thing I would advise if you move forward with the project, is take this opportunity to put a switch between the meter and the main panel. This would enable you to work in the panel later with the power completely off which is much more pleasant than working in a panel with hot lugs.
 
Top
Hey, wait a minute.

This is awkward, but...

It looks like you're using an ad blocker. We get it, but (1) terrylove.com can't live without ads, and (2) ad blockers can cause issues with videos and comments. If you'd like to support the site, please allow ads.

If any particular ad is your REASON for blocking ads, please let us know. We might be able to do something about it. Thanks.
I've Disabled AdBlock    No Thanks