Current leakage on residential service

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iwire said:
Bill I have some nice clamp meters and I will not trust the accuracy at those low levels.

As far as Brian, he makes a living running an electrical testing company and I bet he has at least 20 years of experience doing so.

Do what you want but you have a couple of guys with at least 40 years experience between them telling you that your method may be flawed.
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Bob:

I'm a newbie and lurked for sometime before posting my question here, mainly because I couldn't find the answer anywhere else so far. I have no problem being wrong and my equipment far exceeds my knowledge!

What I don't understand why somebody would own a AEMC 565 and not trust it's readings below 1A. Gosh, it even has a ma scale! Of course, some people don't complain about products, they just live with it.

I was asked above, what's my electrical problem? Isn't there anything like a "perdictive or preventative maintainence" program in the electrical contracting business? You just wait for a problem to happen?
 
Bill,
What type of appliance are you measuring this "leakage" current on? Where is the other path for the current? When clamping around all 3 conductors of the power cord, the reading will always be zero unless there is another current path.
Don
 
don_resqcapt19 said:
Bill,
What type of appliance are you measuring this "leakage" current on? Where is the other path for the current? When clamping around all 3 conductors of the power cord, the reading will always be zero unless there is another current path.
Don
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Don:

Gas dryer, dehumidifier, room air filter and microwave. A drill press and a small lathe. Most all set on plastic wheels or rubber/plastic feet except the lathe who's metal cabinet is anchored to a cement basement floor.

Okay, they "should" read zero but as was mentioned above, >3ma would be a problem. This is close to the max of 5ma which I've seen mentioned for medical equipment.
 
I have also used similar meters for more than 20 years and agree I would not trust the low end current readings. This is not what I would consider a "high quality" meter. Many such meters are also susceptible to "noise currents".
I have encountered many situations where such a meter will indicate a current that is inaccurate when in an "electrically noisy environment".
Many times I have gotten a questionable reading. When this occures I usually re-measure using a quality meter inserted in-circuit (series connection amp reading). This has many times proven that the lower quality clamp on can be unreliable in many situations.
Keep in mind that many times such a meter is reading higher frequencies also, not just the 60 hz component.
 
ELA said:
I have also used similar meters for more than 20 years and agree I would not trust the low end current readings. This is not what I would consider a "high quality" meter. Many such meters are also susceptible to "noise currents".
I have encountered many situations where such a meter will indicate a current that is inaccurate when in an "electrically noisy environment".
Many times I have gotten a questionable reading. When this occures I usually re-measure using a quality meter inserted in-circuit (series connection amp reading). This has many times proven that the lower quality clamp on can be unreliable in many situations.
Keep in mind that many times such a meter is reading higher frequencies also, not just the 60 hz component.
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That's why this meter and others on the market have a filter option, to filter the higher frequency out.

How about some values that you've run into, the values you read when in series, what meter(s) are inaccurate and which are accurate?
 
Your profile states that you are a contractor. You have 7/8 current clamp meter that you don't trust below 1A! Reading a branch circuit, my AEMC 565, F25 and MeterMan CT238 probe all show around .4A.
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First off in there is seldom an issue where current below 1.0 amp is an issue, I bight the AEMC for those times and found it to be unreliable. You asked a question I stated my response based upon MY experience, but then I have only been doing this a couple of months.

Use your multimeter to measure in this range.

Additionally in typical distribution systems of any size (ANY SIZE is open for discussion) it is not unusual to have between .5 and 2 amps ground current, depending on loads, age of equipment and distribution system, length of feeders and branch circuits, ECT.

If you truly think you have a leakage current issue with particular equipment utilize a megger to test the conductors/appliance.

On the THD issue if you have minimal current lets say 1 amp and this current is from any type of electronic load high percentages of current THD in the 80%-100 are not unusual but then 80% of 1 amp is .8 amps. On a 3 phase 4 wire wye distribution system with all electronics loads, percentages of neutral THD current will be high also. depends on the loads and type of distribution system.
 
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Bill,
Okay, they "should" read zero but as was mentioned above
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If there is no other path there is no current flow and any meter reading that says there is is in error. In you examples, the only item that I would expect to have another current path is the gas dryer. Readings above zero on the other items may becaused by something as simple as the conductors not being exactly centered in the amp clamp.
Don
 
don_resqcapt19 said:
Bill,

If there is no other path there is no current flow and any meter reading that says there is is in error. In you examples, the only item that I would expect to have another current path is the gas dryer. Readings above zero on the other items may becaused by something as simple as the conductors not being exactly centered in the amp clamp.
Don
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Don:

If your using a meter with a 10 micoAmp resolution and reading 20-30 microAmps that isn't much error, is it?

As far as not being in the center of the jaw. One of the three AEMC clamps states that it uses a double Hall effect sensor, so centering doesn't matter but I don't remember which one for sure but I think that it's the F25! Keeping a clamp centered and perpindicular to the conductor is almost impossible at times as you should know.

I wondered why you mention the gas dryer but I forgot about the gas line itself. Good call!
 
brian john said:
First off in there is seldom an issue where current below 1.0 amp is an issue, I bight the AEMC for those times and found it to be unreliable. You asked a question I stated my response based upon MY experience, but then I have only been doing this a couple of months.

Use your multimeter to measure in this range.

Additionally in typical distribution systems of any size (ANY SIZE is open for discussion) it is not unusual to have between .5 and 2 amps ground current, depending on loads, age of equipment and distribution system, length of feeders and branch circuits, ECT.

If you truly think you have a leakage current issue with particular equipment utilize a megger to test the conductors/appliance.

On the THD issue if you have minimal current lets say 1 amp and this current is from any type of electronic load high percentages of current THD in the 80%-100 are not unusual but then 80% of 1 amp is .8 amps. On a 3 phase 4 wire wye distribution system with all electronics loads, percentages of neutral THD current will be high also. depends on the loads and type of distribution system.
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Brian:

Yes, my searching in this forum prior to posting found only mentions of current leakage but not much discussion. Unless I haven't used my clamps in the right/wrong situation they read about the same. The F25 manual states not for use around a phase and grounded conductor, yet if the amperage is high enough, it reads exactly what the 565 does.

If you been only at it for a few months, you've beat me and have more variety too!

BTW: The high THD was coming from a fairly new RCA Flat Screen TV and not the antenna amp.
 
Does your meter read voltage also? If so, does it read zero-volts when not connected to anything? None of the digital meters that I have ever used have read zero in this situation. For this reason I would not trust them for small amperage or voltage readings, regadless of what the specs say.
 
haskindm said:
Does your meter read voltage also? If so, does it read zero-volts when not connected to anything? None of the digital meters that I have ever used have read zero in this situation. For this reason I would not trust them for small amperage or voltage readings, regadless of what the specs say.
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I mentioned that above too! A RMS DMM while in AC volts function won't read zero, it's a fact of life. Fluke claims that this doesn't affect the accuracy. I'm not sure how this affects RMS current though. I remember somebody in another forum asking about this that was using a Fluke 337.

I do know that the AEMC F05 when switched to AC current stays at zero but it's a AC/DC current model whereas the F25 and 565 read only AC current. The 565 doesn't read zero in the ma range, not sure about the amp range. Not sure about the F25. I'll check'em all the voltage scale later.
 
Why don't you try something you know doesn't leak to test the meter calibration. Go to Radio Shack and buy a small AC "wall wart" adapter, or a small generic transformer. Buy some resistors of various sizes and wire different ones across the output so you can get a known current (I = E/R).

See if your meter accurately measures the current in one wire of the secondary and gives you 0 with both secondary wires. See how stable the reading is too.
 
haskindm said:
Does your meter read voltage also? If so, does it read zero-volts when not connected to anything? None of the digital meters that I have ever used have read zero in this situation. For this reason I would not trust them for small amperage or voltage readings, regadless of what the specs say.
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Yes, the 565 reads zero in AC volts range but it's only in tenths, I mean like 120.1V. As far as center the conductor in the jaw on the 565, it only makes a difference in the ma range but not in the higher amps range.
 
suemarkp said:
Why don't you try something you know doesn't leak to test the meter calibration. Go to Radio Shack and buy a small AC "wall wart" adapter, or a small generic transformer. Buy some resistors of various sizes and wire different ones across the output so you can get a known current (I = E/R).

See if your meter accurately measures the current in one wire of the secondary and gives you 0 with both secondary wires. See how stable the reading is too.
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I emailed AEMC about this and they said only in a perfect world will you see balanced phases and read zero, what I'm seeing is leakage.
 
Bill,
I emailed AEMC about this and they said only in a perfect world will you see balanced phases and read zero, what I'm seeing is leakage.
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If you are still talking about the clamp on around all 3 conductors of a cord to an isolated appliance, there is no measurable leakage as there is no path for current other than the conductors in the cord. If the meter does not read zero in that case, it is meter error, not leakage.
Don
 
don_resqcapt19 said:
Bill,

If you are still talking about the clamp on around all 3 conductors of a cord to an isolated appliance, there is no measurable leakage as there is no path for current other than the conductors in the cord. If the meter does not read zero in that case, it is meter error, not leakage.
Don
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Don:

The meter will not go to zero but it will read .01ma. If what I'm reading at times is error, the error would be in the range of ten times the resolution of .01ma. The AEMC application engineer doesn't seem to agree with the answers provided here.

My drill press which rests on thick rubber pads I'm sure is isolated from ground. I'll post readings over all thee wire, phase and grounding wire with/without a load later.
 
Bill,
The meter will not go to zero but it will read .01ma. If what I'm reading at times is error, the error would be in the range of ten times the resolution of .01ma. The AEMC application engineer doesn't seem to agree with the answers provided here.
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Current needs a path to flow on. Ask the engineer where that path is. Also I have little faith in the information provided by a manufacturer(remember he has a job to do...to defend his equipment). Give me a megger reading between the metal case or frame of the equipment being tested to something that is bonded to the electrical system. If there is no path this reading will max out the megger. If there is no path there is no leakage current and the clamp on is in error. Even if there is leakage within the equipment, if you are clamping all 3 conductors and there are no other paths, the net current around all 3 will be zero.
Note the rubber pads may be more conductive than you think, so you will have to use a megger to be sure there is not a path.
Don
 
I own $100,000.00 of test equipment and I often call application engineers when issues arise with this equipment. One thing to remember this equipment was tested in lab conditions in a pristine enviorment. Field use may and does effect the operation. I have been told this by numerous manufactures.
 
Bill,
It sure mentions small amounts of current flow over and through insulation even with high resistance readings.
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No matter what the resistance is, the current will follow ohms law. It would not be unusual to get a megger reading of over 100 meg for an appliance. A 100 meg would result in a leakage current of 1.2 micro amps. Your meter has a resolution of 10 times that with a plus or minus 5 count accuracy. I guess the only way to continue is if we know the resistance of all of the possible leakage paths.
Don
 
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