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Clamp on amp meter that records highs for the day

Mickey_D

Stainless
Joined
Apr 18, 2006
Location
Austin, TX
I am in the process for building a new facility and working on planning the electrical build out. I presently have 400 amps of high leg (delta) and 200 amps of 240 single phase. We have a fairly typical transformer on the pole, gutter and 3 disconnects on the back of the building and 1 single phase panel and 2 3 phase panels. Other than one lightning strike that took out a breaker we have not had any electrical issues in ten years.

I just back the first quote and is looks like he is way over engineering everything. He took the max load ratings from every thing in the shop, added them up and then added about 40% to it, which is overkill on the buildout and my wallet. I am looking for a clamp on amp meter that will record the daily highs and average to get a better idea on what is going on. Any good ideas?
 
Fluke 87 meter with any AC clamp on that is rated high enough in amps. Will record min max and average for 36 hours.
 
This looks interesting, and very cheap: 120/480V Electric KWh Meter Din rail Up to 7500 Amps CTs. 2x200 Amps. CTs Incld. | eBay

I don't think it datalogs, but you can set up a cheap video camera on it and record the readings with that, then review after purposely turning on as much equipment as you'd like. You can add a third pickup for true 3ph readings, but you'd have to get a price for the third unit or higher amp pickups (can't be much).

I might get one of these for myself...
 
Your utility may provide this too.

They can do power analysis for you.

They provide the clamp meters for a period and determine needs.

Did that for past house where pole pot was bad.

Sent from my SAMSUNG-SM-G930A using Tapatalk
 
I might be able to dig-up the old style recorder, Uses a chart that moves over a meter, speed is adjustable. Meter has no arm, a disk with a point mounted and a cam that raises it to make a dot on the chart. I also have current transformer some place, a simple Donut insulated and designed for the purpose of amp measurement, no connection to the line so no voltage rating but wire must pass thru the donut hole.
 
Bear in mind that you want maximum demand, not just the absolute maximum. You don't care about the peak caused by starting a large motor unless it lasts for 10 minutes.

Old-school analogue maximum demand meters had a thermal element (like a CB trip) moving a pointer, plus a second pointer that recorded the highest value reached. They also sometimes had a third pointer to show the instantaneous current.

They're not readily available now, but you'll probably find them second hand easily along with a suitable CT. No voltage connections required.
 
I might be able to dig-up the old style recorder, Uses a chart that moves over a meter, speed is adjustable. Meter has no arm, a disk with a point mounted and a cam that raises it to make a dot on the chart. I also have current transformer some place, a simple Donut insulated and designed for the purpose of amp measurement, no connection to the line so no voltage rating but wire must pass thru the donut hole.

The "donut" is called a current transformer. A clamp on is the same thing split in half. A split core current transformer is almost automatically not as accurate. CTs, as they are commonly referred to, are available in almost any rating, but you cannot just stick the wire through it and hook a meter to the leads. They need to have a load resistor or an ammeter to absorb the current produced. An unloaded CT can produce some spectacular voltages. If you use one, get advice from an instrument man. The average plant electrician is no help there.

Bill
 
I would venture a guess is that you could take max load ratings and multiply by 50% and probably would never hit that. Unless his method is mandated by local building codes which I doubt since you are in Texas, I think I would find another electrician. As mentioned in post #8 if you have something with a large inrush current the number you get off peak is misleading. I had a 15hp CNC lathe that would cut metal using about 25 amps, but it had a direct drive hydraulic pump that ran everything. On start up it pulled over 300 amps for a couple seconds.
 
The "donut" is called a current transformer. A clamp on is the same thing split in half. A split core current transformer is almost automatically not as accurate. CTs, as they are commonly referred to, are available in almost any rating, but you cannot just stick the wire through it and hook a meter to the leads. They need to have a load resistor or an ammeter to absorb the current produced. An unloaded CT can produce some spectacular voltages. If you use one, get advice from an instrument man. The average plant electrician is no help there.

Bill

Split cores aren't that bad. Automation Direct has them in 1% accuracy, same as their solid cores and more than good enough for these purposes. They cost ~3x as much, so the question is whether not having to disconnect the conductors is worth it to you.

All you have to do is make sure there is always a short circuit on the output while the primary has current flowing, whether it be just a wire link or a low-impedance load like a current meter. Not that rocket science, most just haven't dealt with them.
 
Split cores aren't that bad. Automation Direct has them in 1% accuracy, same as their solid cores and more than good enough for these purposes. They cost ~3x as much, so the question is whether not having to disconnect the conductors is worth it to you.

All you have to do is make sure there is always a short circuit on the output while the primary has current flowing, whether it be just a wire link or a low-impedance load like a current meter. Not that rocket science, most just haven't dealt with them.

Quite so. The concept is simple once you get your mental ducks lined up, The problem is that most of these guys have grown up regarding transformers as boxes that 'lectric goes in one side and comes out the other. They have never heard of magnetic flux, excitation losses, saturation, etc. I had a project hang for over a year. They wanted a set of split core CTs for an arc melting furnace that ran 12,000 amps per leg. The current was carried on multiple buss bars that would be a major job to disassemble. They wanted replacement CTs that could be installed quickly and not hold up production. I replied that I could make the transformer but needed the voltage across the CT winding so I could calculate the core size. Their reply was, in effect, that it didn't matter. Then a new supervisor came on the scene, one of the hotshots from out of town. He also could not understand CT loading. At one point he said that he tried to keep the load a low as possible, exactly the wrong approach. Then, in big corporation trading, the man formally the supervisor of maintenance of a huge industrial complex wound up in charge of the foundry, I guess a sort of conciliation prize since the original complex no longer existed. This was a very smart dude, used to solving problems. He suggested that he call me the next time they were running and I could bring my meter and make any readings I wanted. Hallelujah, just what I had been asking for all that time. I made the readings and the transformers.

Bill
 








 
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