triping circuit breaker

Drought here in cemtral MN...
I'm running the irrigation well 24 hours a day. Its a 15 horse one phase unit and draws 60 amps on one leg and 55 on the other. During start, when
water pressure is still low the numbers can be as high as 75 and 80. Pumps move more water at lower pressure and this takes more power.
Last drought, I had trouble tripping an 80 amp breaker so I changed it out to a 100 amp.
Now, the 100 amp is tripping. its VERY hot, so I removed the circuit box metal cover and I'm trying it that way.
Do circuit breakers just wear out? Other possibilities? I keep watching that amp meter, its always the same and nowhere near the limit on the breaker.
<BTW, a well pump always draws a bit harder on one leg - normal>
Karl
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Karl Townsend wrote:

Try cleaning the connections on the breaker and where it plugs into the panel. Also clean the contacts in the box itself. If they are not clean they will heat up under load and trip the breaker from the heat.
John
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Good suggestion. I'll do it.
Karl
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On Sat, 07 Jul 2007 16:57:24 GMT, "Karl Townsend"

Put a fan in the breaker box to move the air.
--
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They do, but only if they've been tripped a lot. If you've got a pump that's supposed to be drawing 80A, and it's popping a 100A circuit breaker, yes you've got a problem. Don't know why it isn't turning up on the ammeter...
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They sure do wear out. During the summer, with a lot of fans running that draw a lot, we take the covers off of breaker boxes and direct a fan into them. That helps a lot! Do you have heavy enough wire to the pump?
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This is exactly how I'm getting by today. But can I just see a 5 year old going up to the open panel and grabbing a couple wires. Do you think his momma might sue???
Karl
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Child labor laws? Kid's job---Conductor!
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LMAO
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If it's a Zinsco type breaker, that would explain the heat and tripping.....Paul
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Same comments as everyone else: it shouldn't be getting that hot! Check the lugs, check the clips where it plugs into the panel, replace the breaker (they do wear out if you trip them!) In the meantime, put a fan on it.
If you have one of the non contact thermometers, look for the hot spot. http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber983 http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber984 http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber778
Given the critical nature of the problem, I'd consider rewiring the entire panel (assuming you have the wire length). New box, new breaker, snip 1" off the existing wire, use the antioxident on any aluminum wire. Make sure the breaker is industrial duty. It would probably be worth a call to Graybar in Minneapolis on Monday. I'm partial to Square D QO systems but I haven't pushed one as hard as you are doing.
One other thought: is the pump running in a start/stop mode? I found on one of my pumps that I could raise the cutout pressure 5 psi and get the system to run 2 lines at full pressure with no cutout. I get max flow, max total water, and no start/stops.
Karl Townsend wrote:

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On Sat, 07 Jul 2007 16:23:59 GMT, "Karl Townsend"

In my experience breakers that get tripped regularly weaken over time. They usually have an electromagnetic mechanism that trips them with extremely high current levels (think short circuit) and some sort of thermal mechanism that trips with extended moderate overloads. The later extended method is probably acting up.
The breaker contacts themselves can get pitted and cause excessive resistance/heat too. This was common with breakers being used as switches, especially with heavy loads. Do you switch this breaker regularly with a heavy load on it? Most breakers were never intended to be used as a switch.
Heat build up around the breaker itself can cause it to trip with heavy loads. Is the hot sun bearing down on it directly? If so can you make some shade for it and maybe even add a small cooling fan for this hot weather? Are there other breakers co-located beside it in the panel with heavy loads that are adding to this breakers heat?
Some breakers are better than others. Who made yours? We always had the best luck with Square D products and not their Homeline stuff...
Bruce may have some ideas/suggestions for better manufacturers nowadays. I've been out of the trade for some time now.
--
Leon Fisk
Grand Rapids MI/Zone 5b
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Have you checked the voltage with a good meter while the pump is running? Your utility may be providing lower than advertised voltage or faulty connections may be lowering the available voltage.
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You'd better find the ground fault in that circuit before someone gets electrocuted.

Unless you *know* that the circuit conductors are rated for at least 100A, that was a very poor idea.

If you're tripping a 100A breaker, something's very wrong.

Yes, they do. But replacing a tripping breaker with one of a higher rating in an effort to stop the trips is pretty much the same principle as replacing a blown fuse with one of a higher rating to avoid blowing fuses -- that is, dangerous and foolish. Breakers and fuses are there to protect the wiring from hazardous overcurrents. If you repeatedly trip a breaker, or blow a fuse, then it's time to start looking for the fault in the circuit, or in the load connected to the circuit, that's causing the overcurrent.

Nonsense. The two legs of a 240V circuit are in series with each other and with the load. Basic electrical circuit theory tells us that the current is the same at all points in a series circuit. Thus a 240V load *always* has *exactly* the same current on each leg, unless there's a fault to ground somewhere -- which is probably why you're tripping that breaker.
This imbalance may appear to be "normal" for *your* pump, because you've always had a slight leakage to ground somewhere, and you assumed that's the way they all work. But that's not so. It sounds to me like what started out as a slight leakage to ground has suddenly gotten a whole lot worse. You need to find out where the ground fault is and repair it.
--
Regards,
Doug Miller (alphageek at milmac dot com)
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On Sat, 07 Jul 2007 18:13:39 GMT, snipped-for-privacy@milmac.com (Doug Miller) wrote:

Not necessarily, for a motor branch circuit.

You're jumping to conclusions here. If this is a cap start, cap run motor in a submersible pump, then there are three conductors leading to the motor, supplying a main and an auxiliary winding. The current in the three conductors should sum to zero, but Karl may be mentioning only the current in the two highest.
--
Ned Simmons

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I KNEW this would bother people and make them go off my query. A one phase pump has a third wire that is connected by run caps to one of the input legs, makes it draw a bit more current. I thought I'd keep the discussion simple and just talk about the circuit breaker.
The breaker has held all day with the covers off. I'm on interruptible power. When I'm shut down at 4:00 PM, I'll pull the breaker out and clean everything.
I'll buy a new cutler hammer breaker on Monday. I'll place the new one so no other breakers are near. Is it OK to add AL cooling fins to a circuit breaker? This is a 200 amp main panel. Is there a code legal cooling fan I could add to this panel - I know I'd need to cut intake and exhaust holes and screen them to be mouse proof.
Karl
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This still bothers me! Where are you measuring the amp draw? Right at the breaker? At the breaker the draw should be equal on both legs, period. Now if you are measuring after the split in the line to the motor capacitors, no problem. The amp draw on the run leg, plus the amps on the start leg should equal the amps"common" hot leg. If you are getting an imbalance at the breaker, you got problems, leak to ground somewhere!
Back to you original problem, like others have said, make sure the terminals are clean where the breaker snaps in. Wire connections clean and tight, and the wire is the proper size. Don't forget to increase the wire size for a long run! Running amps less than 80% of the breaker size. Greg
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On Sat, 07 Jul 2007 19:56:52 GMT, "Karl Townsend"

At least you have the satisfaction of being right <g>.

Fan kits are available from Hoffman, and probably Rittal, Hammond, Wiegmann, etc. http://www.hoffmanonline.com/stream_document.aspx?rRID 647&pRID267
A muffin fan simply circulating the air *inside* the enclosure will lower the ambient significantly by increasing the heat transfer thru box. I've avoided venting NEMA12 control enclosures in dusty environments with this dodge. Whether this violates some provision of the NEC for a distribution panel, I can't say.
--
Ned Simmons

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NO, By doing so you would only be attacking the symptom of a problem, nothte problem.

Essentially no. By doing so you effectively change the trip rating of the breakers (all of them), if it changes to the point where the trip rating exceeds the ampacity of the conductors, it is a code violation. Instead you need to attack the SOURCE of the heat, and remove that.

jk
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Do you know whether the breaker is tripping upon startup or when running steady state? I suspect that the actual max current upon startup is even higher than the 75/80 in the first few milliseconds. As one poster suggested, are you sure you have big enough wire? How far is it from box to pump? Maybe wire size is okay for a shorter run, but need bigger for your situation. Check voltage drop on the leads and across the connection points to see if there is some hot spot someplace that points to a high resistance connection. Check for any resistance at all between motor leads and case for leakage. Since you say you have unequal current on each "leg" need to know why there is a difference. Need to measure current between each hot wire and neutral There MUST be some flow there or there could not be this difference. Is this motor too small for the application? If the design is right, is there possible some obstruction/ valving change that is causing a water restriction problem? What was the last thing you changed before this problem occurred? Go back to that time and rethink that situation in light of the breaker tripping. We hate to believe that "we is the enemy", but-----
Pete Stanaitis ----------------------
Karl Townsend wrote:

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