# Electronic Over Load



## BBQ (Nov 16, 2010)

You mean they passed the same load wire through the CT twice?

If so the CT would see twice the ampaerage.

So if the motor draws 1 amp the CT will read it as 2 amps which may explain why the OL seems oversized.

I suspect someone did not have a small enough OL unit so they cheated. I see no reason why this would not work fine.


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## Wireman191 (Aug 28, 2011)

Thats what I was wondering, So If I loop a wire I will read twice the current? Just does not sound right to me for some reason.


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## Wireman191 (Aug 28, 2011)

We are talking a 1/2 horse motor on an 11 amp OL.... So they obviously didn't know what they were doing.


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## Wirenuting (Sep 12, 2010)

Wireman191 said:


> We are talking a 1/2 horse motor on an 11 amp OL.... So they obviously didn't know what they were doing.


Some people remember how they weren't accurate at the low range. Just like an analog Amprobe, they thought more was better.
But I see this all the time. But it's due to the wrong size o/l being installed from the beginning. 2-3 wraps and it works.

The old analog amprobes came with a 10x multiplier.


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## Forsythe (Feb 6, 2012)

You can typically loop wiring thru SSOLR up to three times. Remember that any noise on the line or unbalance also get multiplied which on certain solid state devices can cause it to nuisance trip.


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## sstlouis03 (Jun 23, 2011)

Wireman191 said:


> We are talking a 1/2 horse motor on an 11 amp OL.... So they obviously didn't know what they were doing.


Knowing that they needed to loop it shows they obviously *knew* what they were doing, could have been all they had at they time and never changed it back out, either way I've seen this several times and done it myself on after hour call outs when it was all I had.


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## crazymurph (Aug 19, 2009)

That's a normal practice with smaller motors. My only beef with the electronic overloads is some machine operator or maintenance guy turning up the dial to a level that could harm the motor.


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## 90Deg.bend (Dec 19, 2011)

I told you crazy it wasn't me it must have been that guy on night shift! sheesh:whistling2:


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## micromind (Aug 11, 2007)

crazymurph said:


> That's a normal practice with smaller motors. My only beef with the electronic overloads is some machine operator or maintenance guy turning up the dial to a level that could harm the motor.


This is the main reason I don't like electronic O/Ls. I can't think of how many motors I've been accused of burning up only to find that the amp dial had been turned up.

Same with IEC O/Ls. 

BTW, when installing % load meters, there's usually no choice but to loop the secondary through the CT a few times.


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## Wirenuting (Sep 12, 2010)

crazymurph said:


> That's a normal practice with smaller motors. My only beef with the electronic overloads is some machine operator or maintenance guy turning up the dial to a level that could harm the motor.


I like when they adjust them for "auto" reset. 
I'm glad them kind of folks are smarter then me. LoL


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## Wireman191 (Aug 28, 2011)

sstlouis03 said:


> Knowing that they needed to loop it shows they obviously *knew* what they were doing, could have been all they had at they time and never changed it back out, either way I've seen this several times and done it myself on after hour call outs when it was all I had.


 A 1/2 motor runs at a little under an amp. 1+1= 2, So the one loop they had would not protect the motor set on 11 amps.


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## MDShunk (Jan 7, 2007)

Was it a phase conductor or the ground wire? I've seen starter buckets with ground fault protection that pass the ground through a CT.


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## McClary’s Electrical (Feb 21, 2009)

That's one of my favorite tricks to see if the person beside me is on their toes. Wrap the wire in my amp clamp twice and show them the meter. See how long it takes for them to say WTF?


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## Wirenuting (Sep 12, 2010)

MDShunk said:


> Was it a phase conductor or the ground wire? I've seen starter buckets with ground fault protection that pass the ground through a CT.


Single buckets?
I've seen it for a whole MCC, but never just a bucket. 
Is it just the single bucket loads ground wire that had it? I can understand that if it latched a PLC input.


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## MDShunk (Jan 7, 2007)

Wirenuting said:


> Single buckets?
> I've seen it for a whole MCC, but never just a bucket.
> Is it just the single bucket loads ground wire that had it? I can understand that if it latched a PLC input.


Yeah, single bucket. They have a relay inside, and normally a switch on the bucket door to turn the GFP on or off. That relay inside is actually part of the switch. No matter who's brand MCC it is, that GFP switch/relay thingy will almost always be GE. 

Here's a picture of one in an A-B bucket door:









and here's a (dark) picture of the CT inside:









Never really thought to take a picture of the rather specialized relay that hangs off the back of that door switch. I see these so often in food and pharma work that I just figured everyone else had too.


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## Wirenuting (Sep 12, 2010)

MDShunk said:


> Yeah, single bucket. They have a relay inside, and normally a switch on the bucket door to turn the GFP on or off. That relay inside is actually part of the switch. No matter who's brand MCC it is, that GFP switch/relay thingy will almost always be GE.
> 
> Here's a picture of one in an A-B bucket door:
> 
> ...


Thanks,
I've not seen it were all 3 phases and the ground go thru it. 
I'll have to go find an MCC at work that has one.


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## MDShunk (Jan 7, 2007)

I actually took that pic because that's an error on the installer's part. Only the phase conductors should go through this particular CT. It's looking for a zero sum. Put the ground in there too, and if you have a ground fault, the sum will always be zero.


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## Wirenuting (Sep 12, 2010)

MDShunk said:


> I actually took that pic because that's an error on the installer's part. Only the phase conductors should go through this particular CT. It's looking for a zero sum. Put the ground in there too, and if you have a ground fault, the sum will always be zero.


Thats an answer I can understand better.:thumbup:
Thought it looked funny.


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## electric mike (Jun 15, 2009)

Siemens actually has instructions for looping through the ct's on some models of their electronic overloads, for the exact reasons stated above. Page 5 of this document for example:
http://www.industry.usa.siemens.com...ESP200_Class_48_3PH_IS_3ZX1012-0UB80-1AA1.pdf


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