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.
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.
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...
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?
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.
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.
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.
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.
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-----
WHAT?? What kind of motor is that? Normal 220v 1 ph motors have 2 wire connections: 1 "in" & 1 "out". The current HAS to be the same in both wires, unless there is a (fault) path to ground on one of them.
Is your motor different? E.g., does it also have a neutral (not ground) connection? In that case it COULD have an additional 110v winding that draws on one leg, but not the other.
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.
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.
Just reread your post. The unbalanced currents are not right if you don't have a neutral going to the pump. Time to get a megger and measure your leakage.
There are two setups for single phase well pumps, the start cap is mounted right on the pump itself or there is a starting box located above ground with three wires going down the well to the pump. All newer installations also include a ground wire which is the newer NEC.
If you always had the current imbalance I would suspect one of your splices is bad or there is a defect in the wiring. IF the problem were in the pump itself, it probably would have blown up by now. Underwater motors dont have the smoke indicator built into them. :)
The ratings on your breaker should be no more than 80 % of the running current draw of the motor load.
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
Karl , from your description, your pump is at the bottom of a deep well, yes?
As previos poster indicated the amp pull shouldn't be creeping up the way you describe. Does the draw lower in the spring or cooler months?
Amps creeping up from my limited experience are problems in the power run or in the hole.
The power side of the problem has been addressed by other posters, now the other end.
Has the quality of the water changed? Color, odor, sediment?
Here in Fl. when the shallow wells start to run dry the color starts to change, sometime the odor changes. Pumps start to eject allot of sediment due to underground changes. As sinkholes form, debris filter into the water table and can foul well points with fine particles that clog the inlet slits. This begins to lower suction volume which puts more workload on your pump. This shows up as higher amps.
If all other electrical issues have been eliminated, time to call in the pros to check the motor then the hole.
At least you have the satisfaction of being right .
Fan kits are available from Hoffman, and probably Rittal, Hammond, Wiegmann, etc.
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.