Intermittent Breaker Tripping

T

the blur

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I'm dealing with a 2 pole 20a pool pump breaker that trips 3-4 a week. Changed the breaker, and it still trips 3-4 times a week.
I'm thinking there's a bad winding in the pump. Ground leakage... nope. Pump runs fine for 8 hours.

But, Just for giggles, I moved the plug to another 250v-20a outlet off the same panel. . Now the pump is no longer tripping the breaker, not in over a month.

There is still no ground current. No current in the bonding wire. and I haven't had a phone call in a month.

I have seen this wierdness before, with no explanation. These are regular breakers, not GFI.

any ideas ?
 
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Running current is fine. These new VS pool pumps are all invertor driven, soft start. Using a clamp on for 5 minutes is not finding a problem that happens on occasion. No one is leaving their meter on site .. out side.. for a week, to catch a rare event. Especially with the panel open in the rain.
 
Based on the evidence, not a bad breaker nor a bad pump. The common point after the breaker swap is the buss stabs, so my guess is a problem there.

Damaged buss stabs can cause a poor connection to the breaker. This causes heating. Breakers work by current heating up a sensing element and tripping when the temperature gets too high, external heat can make them trip at lower current.
 
the blur said:
Running current is fine. These new VS pool pumps are all invertor driven, soft start. Using a clamp on for 5 minutes is not finding a problem that happens on occasion. No one is leaving their meter on site .. out side.. for a week, to catch a rare event. Especially with the panel open in the rain.
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Get a meter that can read AC millivolts. Take a voltage drop reading from the line side of buss to load side of breaker. Same phase. Repeat with the other phase. Compare the results. They should be very close to the same and not more than 100 mV +-. The biggest flag will be the difference. If one is 124 and the other 284 you found the connection problem. (random numbers). Use a temporary resistive load if need be.

A typical amp meter is useless for these checks.

eta: 400mV is excessive even if on all phases
 
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The panel is only 4-5 years old. But i will sand down the buss stabs if I get another call. It's definitely not the breaker, and definitely not the pump. The only other bad connection point to develop heat close to the breaker would be the wire connections, but I would have noticed melted insulation. I did tighten all the breaker screws in the entire panel.
 
the blur said:
The panel is only 4-5 years old. But i will sand down the buss stabs if I get another call. It's definitely not the breaker, and definitely not the pump. The only other bad connection point to develop heat close to the breaker would be the wire connections, but I would have noticed melted insulation. I did tighten all the breaker screws in the entire panel.
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It's a pool pump. Is the panel exposed to chlorine?

Is sanding the buss stabs an appropriate repair method?
 
winnie said:
It's a pool pump. Is the panel exposed to chlorine?

Is sanding the buss stabs an appropriate repair method?
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Sanding may be bad term- polishing lol.

Either way I bet not—— old jman I use to work with would cut taps of the breakers off to now allow the rejection clips——- I truly think 90% of jman are morons. I toe the line half the time lol
 
winnie said:
It's a pool pump. Is the panel exposed to chlorine?
Is sanding the buss stabs an appropriate repair method?
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Chlorine, no. the panel is 40' from the pool. Does pool water splash around when servicing the pumps. Absolutely 100%.

Sanding down light oxidation buildup on an outdoor panel. I say it should be considered a yearly maintenance item. Condensation happens in any outdoor panel.
 
It should just oxidize around the parts the breakers not in contact with the part we care about should be a nice tight bond and not oxide- I don’t see it a problem

I’d be more worried about a loose connections from breaker to buss than oxidation
 
You should never sand the bussing of a panel, especially if its aluminum. Aluminum is coated with tin to protect it. Sanding will remove the coating. It will also make the stab slightly thinner.

If the buss bars show any sign of deterioration they should be replaced.
 
Any splices between the breaker and the pump? You mentioned a receptacle? Did you check the receptacle or over heating or bad connections?

What HP or FLA on the pump and what is the wire size?

Is the pumps voltage 230V or 208?
 
Elect117 said:
Any splices between the breaker and the pump? You mentioned a receptacle? Did you check the receptacle or over heating or bad connections?

What HP or FLA on the pump and what is the wire size?

Is the pumps voltage 230V or 208?
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This house is pushing 250v... or close. Probably 245v if I remember. It's a standard 3hp VS pool pump.. 12ga 250v/20a receptacle.
 
I’m in the bus stab/breaker connection camp. The VS pumps have a built in VFD, so it is creating harmonics, which can cause additional heating that would not be accountable to normal current draw. I’ve seen that show up big time in any sort of compromised connection, I think because the harmonic current is at higher frequencies, so travels mostly on the outer surfaces of the conductors where poor connections show up more readily as resistance and heat. I’ve seen it melt terminals even though breakers or fuses don’t clear. So your heat may not be that bad yet, but because it’s happening right there at the breaker, it is getting transferred right into the thermal trip sensor.
 
Fall-of-Potential test the breaker. As for sanding a bus stab... Scotch Brite should be as far as you go.
 
I'm going with Jraef. Because once I moved the pump 2 spaces down in the panel, all the problems went away. In fact I know it's been problem free for over 2 weeks now. Nothing else changed. It's the same pump, same running current; just a different space in the panel.

and I have seen weirdness problems before resolved just by moving breakers around. Especially recently with all the fancy electronics. QO panels are especially sensitive.

Now I'm leaning more towards bolt-on panels, which I have never had a problem with. and I have many many pictures of buss stabs melted.
 
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