Thread: Reading Amperage with a AMP Meter

Hello,

I bought an amp meter and couldn't find a solid answer on how to determine the number on amps a house has with using my amp meter. I understand I can tell by the main breaker and wire size but couldn't tell how to use my amerage meter to find out. Do I add the two hot wires amperage together to find out or do I just use the reading from one of the hot wires? Thanks in advance.

Originally Posted by Derek Worchel

Hello,

I bought an amp meter and couldn't find a solid answer on how to determine the number on amps a house has with using my amp meter. I understand I can tell by the main breaker and wire size but couldn't tell how to use my amerage meter to find out. Do I add the two hot wires amperage together to find out or do I just use the reading from one of the hot wires? Thanks in advance.

Not sure why you are trying to read the amperes in the service, but, because you are, place the clamp-on ammeter on one hot leg and read it, then place the clamp-on ammeter on the other hot leg and read it, then place the clamp-on ammeter on the neutral and read it - the difference between the two hot legs should be what you read on the neutral.

Finally, and this is where the clamp-on ammeter comes in handy - place the clamp-on ammeter on the grounding electrode conductor (the conductor which goes to the ground rods, underground water pipe, ufer ground, etc.) ... you should not have any ammeter reading there (well, sort of 'should not have any' reading there). The neutral goes back to the transformer, but so does the grounding electrode conductor by way of the ground rods, etc., and the ground (earth) itself - that creates two parallel paths, and, with the neutral conductor have much less resistance than the earth has back to the transformer, almost all the "normal" neutral current will be on the neutral conductor with only a small fraction going through the greater resistance of earth ... but ... if your clamp-on ammeter is actually reading current enough to look at, there is a good possibility that something is faulted to ground (ground-fault).

If you find that, use your clamp-on ammeter and go back and read the amperage on the grounds *before* the neutral is bonded to ground - if there is a ground fault then you will have four numbers to add up which should 'add up' ...

Let's say you have a perfectly balanced electrical system and no ground faults - the amperage on the two hots should be the same.

Let's say you have a perfectly balanced electrical system but also have a ground-fault - the amperage on the two hots should be different, and that difference should be on the grounding conductors. (Ground-faults are not good things to have.)

Let's say you have a normal and typical electrical system which is not balanced and no ground-faults - the amperage on the two hots will be different, and the amperage on the neutral should equal the difference between the two hots.

Let's now say that you have a normal and typical electrical system which is not balance - but - there is a ground-fault too ... now the two hots will have different readings, the neutral will have a reading, and the grounds will have a reading ... and depending on where the ground-fault is, the difference between the two hot reading should equal the neutral and the ground-fault reading.

But I was oversimplifying it ...

Thank you for the detailed explanation. If I understand correctly, in a perfectly balanced system, assuming no ground fault, I add up the two hots and the neutral to get my total amperage for the house. Would that be correct?

Originally Posted by Derek Worchel

If I understand correctly, in a perfectly balanced system, assuming no ground fault, I add up the two hots and the neutral to get my total amperage for the house. Would that be correct?

No.

The two hots do not get added together, they get compared together and the lower one subtracted from the higher one - that difference should, under ideal conditions, be what you read on the neutral.

The current is flowing in one hot, through the house, and out the other hot (under perfectly balanced conditions). The neutral just makes up for the unbalance between the two hots.

Ok I understand the concept. Am I able to use the amperage meter to determine the total amperage for house by clamping it on certain wires in the panel? I am trying to see if I can use my amperage meter to determine the amps of the house instead of looking at the main disconnect or the wire size inside the panel. Thanks in advance.

Originally Posted by Derek Worchel

Ok I understand the concept. Am I able to use the amperage meter to determine the total amperage for house by clamping it on certain wires in the panel?

The total amperage *at that moment in time*, but I would not in anyway try to relate that the determining "the amps of the house" and it in now way relates to the service size.

I am trying to see if I can use my amperage meter to determine the amps of the house instead of looking at the main disconnect or the wire size inside the panel. Thanks in advance.

The answer to that is "No. you cannot use your ammeter to determine the amps of the house instead of looking at the main disconnect or the wire size."

Great that is excellent to know. Thank you.

Using the meter you are going to get a snapshot of the usage that may have little to do with the available ampacity of the service. Look at the breaker handle ratings and wire or cable sizes to see the size of the service.

For example using the meter with almost nothing on the meter will show very few amps compared to the available. Suppose the water heater cycles and a few lights are on. The meter will show less than 40 amps. This is not the service size. The usage in a house is very transient in nature.

Also before you start invasive testing you should have training and PPE.

Jerry, I think Jim snagged what Derek is looking for, which is the total(maximum) available amount of Amperage Service coming to the house. What the transformer is supplying.

Derek, is the bottom line of your question the maximum size service panel you can install????

You could be looking at having an energy meter system installed. It records and displays the usage with a couple of clamp meters permanently installed on the service conductors.

Derek, I think others have explained this well, but another way to look at this is the service size is similar to the size of the main water supply pipe. What you are measuring is what is flowing at that time. You could have a 2-inch main but with one faucet running you would not measure much flow.

Generally the only thing I use my ammeter for is to measure the amperage of the auxiliary heat on heat pumps. It gives me an indication of whether all (or enough) stages are working.

Originally Posted by Derek Worchel

Hello,

I bought an amp meter and couldn't find a solid answer on how to determine the number on amps a house has with using my amp meter. I understand I can tell by the main breaker and wire size but couldn't tell how to use my amerage meter to find out. Do I add the two hot wires amperage together to find out or do I just use the reading from one of the hot wires? Thanks in advance.

You will get a momentary reading of the current (measured in amps) running on that particular conductor. If you read the two live conductors, you still can not attempt to add them to gain any beneficial information as on a 240 volt circuit the load on each side will be the same for that appliance. On a 120 volt circuit the load will be shared between one of the hot conductors and the neutral.

So.. yes you can measure what the load happens to be at that time, might be zero, might be ten amps or might be fifty amps!! Regardless, all meaningless for what you are likely doing.

This in no way relates to the capacity or sizing of load-center. The measurement examples I gave above could be on a sixty, one hundred or four hundred amp panel. Furthermore unless you are trained, placing a clamp on amp meter around live conductors of that size is not recommended.

Originally Posted by Robin Wells

Furthermore unless you are trained, placing a clamp on amp meter around live conductors of that size is not recommended.

I totally agree, and would further add: Unless you are trained, placing a clamp on amp meter around live conductors, regardless of size, can cause problems ranging from smoke to death.

Originally Posted by Robin Wells

Furthermore unless you are trained, placing a clamp on amp meter around live conductors of that size is not recommended.

Originally Posted by Dave Ruth

I totally agree, and would further add: Unless you are trained, placing a clamp on amp meter around live conductors, regardless of size, can cause problems ranging from smoke to death.

I'm trying to follow you two and your thinking - putting a clamp on ammeter around conductors and not touching them creates almost no hazard, and occasionally bumping a conductor should not create any more hazard than any conductor occasionally being moved/disturbed by removing the panel cover.

Granted, ones hands are, to some extent, "in the panel", but so is ones hands with doing other things.

Just trying to follow your thinking and reasoning ... I may be missing the obvious?

Originally Posted by Derek Worchel

Hello,

I bought an amp meter and couldn't find a solid answer on how to determine the number on amps a house has with using my amp meter. I understand I can tell by the main breaker and wire size but couldn't tell how to use my amerage meter to find out. Do I add the two hot wires amperage together to find out or do I just use the reading from one of the hot wires? Thanks in advance.

This is all a joke, right?? please?

Isn't this type of testing outside the scope of a general home inspection?

Originally Posted by bob smit

This is all a joke, right?? please?

I don't think it is a joke. I thin it is anther case of someone hanging a Home Inspector sign without proper training. But in defense of this guy at least he di ask.

Originally Posted by Jerry Peck

I'm trying to follow you two and your thinking - putting a clamp on ammeter around conductors and not touching them creates almost no hazard, and occasionally bumping a conductor should not create any more hazard than any conductor occasionally being moved/disturbed by removing the panel cover.

Granted, ones hands are, to some extent, "in the panel", but so is ones hands with doing other things.

Just trying to follow your thinking and reasoning ... I may be missing the obvious?

Quite often larger conductors may be lying against or fairly close to the back of the load center and require putting your hand, or something else in to get the clamp around conductor. These are usually the first conductors placed into the load center and many other conductors would typically be in front or over top of them. Typically the lugs where they connect are closer to the back of panel than those of connections for breakers. Depending upon routing of conductors there may be some area on top where conductors run fairly straight and clamp can be placed around without much effort or risk, however you are dealing with higher ampacity than on normal branch circuits and the benefit of performing this task is rather inconclusive for the purposed of a home inspection.

If somebody knows what they are doing, it can be performed safely, however why take risk if not necessary and especially if the results are meaningless.

If you are testing a branch circuit it is somewhat safer, smaller conductor, more flexible, further from back of panel and you could even turn the breaker off when placing clamp if you felt it to be safer.

I have seen personally in my career many times the consequences of live conductors touched something unintentionally, and I know too many individuals who have hand hands or limbs injured (one who now has two artificial arms) because of accidental contact.

Originally Posted by William Heuberger

I don't think it is a joke. I thin(k) it is anther case of someone hanging a Home Inspector sign without proper training. But in defense of this guy at least he di ask.

A little knowledge can cause someone to extrapolate that there is an easy answer. When in fact once they understand all that is involved they realize that it is not all that simple. Buy an Amp Meter and you can tell amps. Seems/sounds so simple in theory. Being able to turn it on does not mean the person knows what it is really for and how to effectively use it much less being able to interpret the results.

I seriously do not think any direct inspector training would have taught someone about the use of an Amp Meter, Most people teaching in the HI field really don't have a clue how to use one. Why, because they hold to the creed of visual inspection and concept of only a generalist. Like Chris Sticher asked "Isn't this type of testing outside the scope of a general home inspection?" Which is what so many are taught. I personally believe that an HI should be able to use and interpret an Amp Meter, even though they may never use one on an inspection.

Originally Posted by Jerry Peck

I'm trying to follow you two and your thinking - putting a clamp on ammeter around conductors and not touching them creates almost no hazard, and occasionally bumping a conductor should not create any more hazard than any conductor occasionally being moved/disturbed by removing the panel cover.

Granted, ones hands are, to some extent, "in the panel", but so is ones hands with doing other things.

Just trying to follow your thinking and reasoning ... I may be missing the obvious?

Well I see what you mean, my first thought upon reading the original post was that someone with little enough experience to ask original question was not likely to be qualified enough to be sticking hands in live panel box. Not talking about smart vs. dumb, talking about experience. As I am not a HI, but an electrician, my thinking may be skewed and I may be way off-base, hope I don't sound condescending. By the way I have been very impressed with the knowledge and wisdom found at this forum.

Originally Posted by Garry Sorrells

Jerry, I think Jim snagged what Derek is looking for, which is the total(maximum) available amount of Amperage Service coming to the house. What the transformer is supplying.

Derek, is the bottom line of your question the maximum size service panel you can install????

The transformer does not supply any amps. What the transformer supplies is measured in volts. Your usage is measured in watts. Using watts creates amps (watts divided by volts equals amps created -not amps supplied.)

Highlighting by me:::::

Originally Posted by Derek Worchel

Ok I understand the concept. Am I able to use the amperage meter to determine the total amperage for house by clamping it on certain wires in the panel? I am trying to see if I can use my amperage meter to determine the amps of the house instead of looking at the main disconnect or the wire size inside the panel. Thanks in advance.

Originally Posted by Garry Sorrells

Jerry, I think Jim snagged what Derek is looking for, which is the total(maximum) available amount of Amperage Service coming to the house. What the transformer is supplying.

Derek, is the bottom line of your question the maximum size service panel you can install????

Originally Posted by Leigh Goodman

The transformer does not supply any amps. What the transformer supplies is measured in volts. Your usage is measured in watts. Using watts creates amps (watts divided by volts equals amps created -not amps supplied.)

Leigh, sorry if you misunderstood. I was trying to figure a way to qualify what I thought the real question Derek was asking, in simplest way possible. I think Derek was looking for available amps coming to the service panel. I think that Derek is looking at what the transformer is supplying is what shows up at the house and therefore determines maximum amperage for panel. I know Derek didn't understand what goes on with line voltage, I just wanted to qualify what his approach (thinking) was and what he thought he could do. Not what reality is.

Originally Posted by Leigh Goodman

The transformer does not supply any amps. What the transformer supplies is measured in volts. Your usage is measured in watts. Using watts creates amps (watts divided by volts equals amps created -not amps supplied.)

Leigh; Garry was very kind with his reply. Your post was the worst explanation with the most mis-information I think I have ever read on this forum. How about a re-write?

I am always ready to learn. Which part of my words needs editing?

Originally Posted by Leigh Goodman

I am always ready to learn. Which part of my words needs editing?

The xfmr supplies amps according to the load demand at a fixed voltage. Usage is measured in watts which is the the product of current times voltage.

Lets not get into a huff. Most will respect inspectapedia definition/explanation or maybe not.

I didn't want to get into explaining the dynamics of amperage involved in house power or its service. Only wanted to understand what the actual question was by determining what the desired outcome of the test was to prove from Derek.

Maybe to head off an argument between members you can argue what a non forum source says.
But then you got-to love math: Volts= Amps x Watts it is all in what you know

What is Electricity? Electrical definitions: definition of amps, definition of volts, definition of watts
Amperage or Amps provided by an electrical service is the flow rate of "electrical current" that is available. Mathematically, Amps = Watts / Volts. (Amps = Watts divided by Volts)

Speaking practically, the voltage level provided by an electrical service, combined with the ampacity rating of the service panel determine how much electrical demand, or in another sense how many electrical devices can be run at one time in the building. Sketch courtesy of Carson Dunlop Associates.

Volt, formally, is defined as the potential difference across a conductor when a current of one ampere dissipates one watt of power

Along the line of of this discussion - the issue of safety came up - Glad it too. Especially for the folks who are green (so to speak). Years ago an electrician I worked with never wore a wedding ring - he said it was because of an incident that occurred when he was an apprentice and the electrician he was working for reached into a box and his ring made contact on an exposed wire but it was enough to hold him there - lesson learned - Don't where jewelry when in Breaker boxes - also if you un-easy - I suggest getting a pair of electrician gloves - nothing worse than a nervous hand.


and I thought the clamp was to hold the meter in place (LOL)

Originally Posted by Dwight Doane

Along the line of of this discussion - the issue of safety came up - Glad it too. Especially for the folks who are green (so to speak). Years ago an electrician I worked with never wore a wedding ring - he said it was because of an incident that occurred when he was an apprentice and the electrician he was working for reached into a box and his ring made contact on an exposed wire but it was enough to hold him there - lesson learned - Don't where jewelry when in Breaker boxes - also if you un-easy - I suggest getting a pair of electrician gloves - nothing worse than a nervous hand.


and I thought the clamp was to hold the meter in place (LOL)

Agreed. In fact we were not allowed to wear any jewelry when I was working full time with power. Some guys I worked with had their ring tattooed their finger.

Vern,
We all try to provide a shot simplistic answer most of the time. When it comes to electric the short answer leaves out much that some can see as totally missing. Then if you take it to the other extreme you have a novel. I will admit to failure at simplifying things at times in conjunction with exactly how I attempt to put the words together. Cobble that together with a disjointed textual discussion and you can get miscommunications or understandings of what is being said.


What transformers actual do and how they do it (technically speaking) is involved. Why you have different transformers along with their applications gets involved. Then you get into the difference of single and triple phase systems and you are even deeper. It is a grand area of study though at times math and physics intensive. Not to mention what you get to work with once you get the power into a house.

I understood what Leigh was driving at and the perspective.

- - - Updated - - -

Vern,
We all try to provide a shot simplistic answer most of the time. When it comes to electric the short answer leaves out much that some can see as totally missing. Then if you take it to the other extreme you have a novel. I will admit to failure at simplifying things at times in conjunction with exactly how I attempt to put the words together. Cobble that together with a disjointed textual discussion and you can get miscommunications or understandings of what is being said.


What transformers actual do and how they do it (technically speaking) is involved. Why you have different transformers along with their applications gets involved. Then you get into the difference of single and triple phase systems and you are even deeper. It is a grand area of study though at times math and physics intensive. Not to mention what you get to work with once you get the power into a house.

I understood what Leigh was driving at and the perspective.

I believe the original poster was trying to learn something they did not know, as in we all have things we do not know, and the way to learn is:
- go out and do it (sometimes do it once, then be laid horizontally below the dirt - I believe in trying to stay vertical above the dirt)
- ask questions about how to do it
- watch others do it

The original poster has started out on the right foot by asking questions about it.

My first post(s) was/were trying to get the proper terminology used and in the thinking and discussion process as that often times leads to better understanding of what is being discussed.

Some here, however, appear to be more than willing to get their monthly exercises in all at one time by jumping to conclusions so quickly and rapidly that they don't take time to stop and think that "Hey, I was in those shoes once ... there is A LOT that I don't know now, and I now know 100 or a 1000 times more than I did, which means I didn't know much back then ... (and the rest is best left unsaid ) ... "

I think Garry was thinking along the correct lines in that things like using clamp on ammeters and what their 'best uses', 'practical uses', and 'not to be used for' uses is not taught in HI schools, so coming here is a good place to start asking questions.

[QUOTE=Jerry Peck;251715]I believe the original poster was trying to learn something they did not know, as in we all have things we do not know, and the way to learn is:
- go out and do it (sometimes do it once, then be laid horizontally below the dirt - I believe in trying to stay vertical above the dirt)
- ask questions about how to do it
- watch others do it

The original poster has started out on the right foot by asking questions about it.

My first post(s) was/were trying to get the proper terminology used and in the thinking and discussion process as that often times leads to better understanding of what is being discussed.

Some here, however, appear to be more than willing to get their monthly exercises in all at one time by jumping to conclusions so quickly and rapidly that they don't take time to stop and think that "Hey, I was in those shoes once ... there is A LOT that I don't know now, and I now know 100 or a 1000 times more than I did, which means I didn't know much back then ... (and the rest is best left unsaid ) ... "

I think Garry was thinking along the correct lines in that things like using clamp on ammeters and what their 'best uses', 'practical uses', and 'not to be used for' uses is not taught in HI schools, so coming here is a good place to start asking questions.[/QUOTE good points