Testing for Amps

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Old 10-18-06, 09:05 PM
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Testing for Amps

I'm trying to figure out how to use my multimeter to test for how many amps I've got going through some of the 15 and 20 amp circuits in my main panel. I want to make sure that I'm not exceeding the 80% of each of these circuits.

I've got a GE 2524 Digital Multimeter and I'm just not sure what settings to put it on.

Thanks!

JT
 
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Old 10-18-06, 09:18 PM
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You need to check the meter. You probably will need a clipon
CT which is a seperate piece from the meter. Thats the only way you can use the meter to read amps.
Check here to see how it works. http://www.kilowattclassroom.com/Archive/AN0006.pdf
 
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Old 10-18-06, 09:25 PM
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Question

Most likley, you have the wrong equipment to accurately meassure the draw on these ckts.
You should have a clamp on type of tester, rated for 200 Amps +
Most meters are only good for 10 amps max! If you use this on this type of ckt. you could be seriousley injured.


Don't attempt this with out the propper equipment.

Now to brass tax. Why is this a worry? Are ckts tripping?
Is this an older home? Elabirate on your issues and we may have an answer that can save you some trouble.


I forgot to ask, what type of ckts are these? Do you intend on utilizing every possable point with every appliance you have? Are you going to check with normal load or potential load? 80% is somewhat subjective. If your dwelling unit is running fine now, and your curious, thats fine. Just check under the typical use.
 

Last edited by lectriclee; 10-18-06 at 10:20 PM.
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Old 10-19-06, 04:53 AM
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I agree. It is almost foolish to try this since how do you know what is on or not on at any given time? You cannot do it with everything on since this is not a real world scenario.
The only way to accurately guage this is with a datalogger which will chart the usage over time, or do a load calculation of the whole house.
The load calc will do nothing for individual branch circuits though, just the service.
 
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Old 10-19-06, 06:39 AM
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Thanks for the tips! I'm actually getting ready to hang my Christmas lights this year and have a few dedicated circuits that I was wanting to check. I saw a buddy of mine do this a few years ago. Yes, he had a clamp. I couldn't remember how he did it. I'll see about getting a clamp or maybe I'll just count strings of lights and see how they add up. That's a lot of lights though (20,000+).

Any more tips or comments would be welcomed.

Thanks again,

JT
 
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Old 10-19-06, 06:51 AM
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Be careful with Christmas lights. While most strings are feed through and allow you to connect a second string at the end of the first, and a third at the end of the second, they do limit you. Many allow no more than three to be string "end to end".

Stringing together too many creates a fire hazard because the current through the first string feed through is the sum of the current nedded for each additional string; and while the strings themselves may not need much current, when you add a few of them together it does add up.
 
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Old 10-19-06, 10:08 AM
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Interesting about the xmas lights being the sum etc. in the first string. Never thought of it that way.

I recently checked on the prices of those clamp-on amp checkers to do the same thing (check amperage flow on an outdoor outlet) after finding out the volt meter I had wasn't gonna cut it. I backed away for now due it's expense. Maybe next month.

Good luck.
 
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Old 10-19-06, 10:25 AM
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I'll save you the trouble- just clamped a cheap 100-light string. 0.3A! Surprised me, I'd always figured they were closer to 1A. It comes with a 3A fuse and a warning to never daisy-chain more than 5 strings; 5 strings would be about 1.7A worth. You could probably put 8 or 9 together before blowing fuses, but I wouldn't recommend it; these strings get hot enough as it is- Not worth risking a fire.

(This is a 1000A ammeter so there is a pretty big margin of error for a reading this small; I used a 10x multiplier plug splitter to allow a measurement, but this string could still be anywhere from 0.2-0.4A)

FYI, our 2x 500W halogen light drew 7.7A and a 20" box fan drew 2A on high and 1A on low. This is fun!
 
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Old 10-19-06, 10:39 AM
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Know of any cheap deals on a basic home model ammeter and where to get it (THD, Lowes, etc)? > 30amps would do me.
 
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Old 10-19-06, 11:16 AM
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Check Harbor Freight.
 
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Old 10-19-06, 11:40 AM
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Home Depot and Lowes both had a bunch of inexpensive ($50) clamp meters IIRC. Most are around $100-200, though. You could order one off amazon.com or ebay if you looked around. Try to get one with an AC line splitter (plug adapter) if you can, otherwise you'll have to buy one separately.

Doityourself.com sells one for $75, but I don't think it comes with a line splitter:
http://www.doityourself.com/invt/2873412

I have an extech 1000A with an integral infrared thermometer and AC splitter for $150. I got work to pay for it, though I probably could have pushed for the high-end fluke all with the accessories for $1000, but to be honest, this "cheap" model is fine for my needs and easier to use.

Edit: wow, $15! I might have to get one of these to keep at home, lol. (Looks like the leads are sold separately for $1 extra, hehe)
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=42396
 
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Old 10-19-06, 01:34 PM
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I would not waste my hard earned money on Harbor Freight tools. They are cheap crap.

Harbor Freight = You Get What You Pay For
 
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Old 10-19-06, 05:10 PM
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Hey, cheap for the once/twice a year project guy might be worth it. Now for the professional volt-meister, definitaly not a good idea when you're earning your lively-hood from it.
 
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Old 10-19-06, 05:28 PM
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Unreliable and inaccurate is not cheap at any price.

I don't imply anyone needs to go out and spend $300, but at least drop $40-$100 for an acceptable unit, even if it is for occassional use.

I know from experience, 99% of what H-F sells is junk. That is a big problem with this country, far too many folks consider price as the main consideration.
Same think goes for walmart. I flat out refuse to set foot in that #%@# store. I don't care how cheap they sell toilet paper for.
 
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Old 10-19-06, 08:57 PM
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So for a slick "Do-It-Yourselver" who really only needs like a unit that measures say, 0-100 amps somewhat accurately without giving up xmas, what would be a good piece and where would I find it?
 
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Old 10-25-06, 09:55 PM
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I got a Craftsman Clamp meter from Sears the other day. It measures up to 400 amps and seems to do what I need it to do. $50 bucks and I'm measuring all kinds of things. Woo Hoo!!!

I start putting up my lights next week.

Thanks for all the help!

-JT
 
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Old 10-26-06, 01:24 AM
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jtpro1: I just searched Sears' web site for a $50 ammeter, but the least expensive one I saw was $100. Could you provide more info about yours?

Other DIYers: If you have an ammeter, can you give an example of what you have used it for that was valuable to you. I'm thinking about buying one, but am not real sure what I'll use it for if I do. I'm thinking it might help figure out which bulb is bad in a string of Xmas lights when one whole group of lights goes out. But, I can't think of anything else right off the top of my head. I currently use a multimeter (VOM) for troubleshooting all my electrical problems, which is very helpful.
 
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Old 10-26-06, 06:28 AM
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Many clamp-ons also measure voltage so except for continuity you can do most checking with just the clamp-on. Working an apartment building with old breakers and reconditioned window ACs I found it very usefully when a breaker tripped to determine if it was the breaker or AC. Previous maintenance man had just replaced the breaker and assumed it was the AC if it kept tripping. (The owner had a whole box of previously used breakers she expected me to reuse until one worked or if none worked replace the AC. I put a quick stop to that.)
 
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Old 10-26-06, 07:20 AM
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Hi, I'm Manny. You may remember me from classic threads such as "my neighbors are stealing my electricity".

I recently bought a great clamp ammeter from ebay, $39. It's a 200 amp model, even though the auction title stated 400a. Works great and very easy to use. Has 2a, 20a, and 200a settings.

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=270039369656
 
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Old 10-26-06, 07:48 AM
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Hey Manny of "my neighbors are stealing my electricity", I just went and bought the same item/same source looking for a basic tool to measure amperage thru a circuit. I relied on your referral. I hope it works as good as you say it does. I was one hour from purchasing another unit off Ebay for $71 + shipping.
 
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Old 10-26-06, 10:04 AM
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Originally Posted by Boater59
Hey Manny of "my neighbors are stealing my electricity", I just went and bought the same item/same source looking for a basic tool to measure amperage thru a circuit. I relied on your referral. I hope it works as good as you say it does. I was one hour from purchasing another unit off Ebay for $71 + shipping.
It seems to be well made and it's easy to use. The size is just about right for checking my panel and I'm using it in the 20a mode where accuracy goes to hundredths of an amp. There were only a few circuits which were difficult to get the jaws around, I did have to gently bend a few wires
out of the way. I've been taking regular readings thru the day/night and so far no monkey business, I think the one cable I discovered sneaking in from next door might have been the only "tapped" circuit in my panel. For me the price of the meter was well worth the peace of mind.
 
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Old 10-26-06, 10:24 AM
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Most of the amp clamps measure AC current only, If you have a little extra money you may look for one that will measure both AC and DC current.
DC amp clamp my help you check your charging system on your car.

On refrigerators I use an AC amp clamp to tell me when the defrost heater is on, without disassembling the freezer.
If your good you can tell if the igniter is weak on some gas appliances.

Just some links on using your VOM's
http://mechatronics.mech.northwestern.edu/design_ref/tools/multimeter.html


http://www.boatsafe.com/nauticalknowhow/electricity2.htm
 
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Old 10-26-06, 10:27 AM
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I looked on the Sears website and didn't see the same meters that I saw in the store. In the store they had 4 or 5 different clamp meters ranging from $39.00 up to about $200.00. I'm out of town on business right now, but I'd be happy to look up the model number when I get home if needed.

For checking bulbs and shorts on my mini-christmas lights I use the Lightkeeper Pro http://lightkeeperpro.com/ I got it at Lowes for about $20.00. WELL WORTH THE MONEY!!!! Check out the video on the website.

-JT
 
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Old 10-26-06, 10:46 AM
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jtpro1: Thanks for the tip re the Lightkeeper Pro. I have devised a way to find defective bulbs using a voltmeter that's pretty good, but this sure sounds easier, and quicker. I'm planning on getting me one of these.

Don't worry about getting me the Sear model for the ammeter. I have a Sears nearby that I visit pretty often. I'll take and look and see what they have.
 
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Old 10-26-06, 11:30 AM
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bigfred: I have devised a way to find defective bulbs using a voltmeter that's pretty good.
Do tell. This could save hundreds of manhours each holiday season when stringing up the lights. So do you do, and how? You should actually start aother post Titled "Xmas lightbulb troubleshooting with volt-meter".
 
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Old 10-26-06, 09:41 PM
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Boater59: Okay, I'll add a new thread called "Testing Xmas Lights". By the way, after checking my notes from last year I realized I used an AC neon light tester, not a VOM.
 
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Old 10-26-06, 10:20 PM
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Heck, as much time as I spend each season troubleshooting those darn things, any method would be good for me.
 
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Old 05-31-09, 09:21 PM
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Originally Posted by jtpro1 View Post
or maybe I'll just count strings of lights and see how they add up. That's a lot of lights though (20,000+).
Sounds like about how many Id have to put up to replace the 'glow' I had in the front yard from a big pine tree with 100 large bulbs (700w total). 100 LED lights sure dont cut the mustard..

Did you ever determine how many separate feeds that gonna need for your 20000+ bulbs ?
 
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