Breaker Keeps Tripping on my Lake Pump - Gunked up Pump??

[JonBee]

At my off grid cabin I have a submersible pump (Red Lion RL12G05-2W1V , 1/2 HP, 115V, 2-wire submersible) in the lake that feeds a pressure tank for water in the cabin. The pump is on a dedicated 15A breaker in my panel. Everytime the pump is called on it successfully fills the tank almost to end of cycle but then the breaker trips right before reaching final PSI (60). Happens every time. I have done much trouble shooting but can't solve it. Any suggestions to figure this out would be much appreciated.

When I disconnect the wires that run from the pressure switch out to the pump in the lake, the breaker does not trip. So I have isolated the issue to those wires or the pump.

The pump has sat in the lake for two years now so I'm wondering if the pump is gunked up with lake silt so labouring and causing excessive current draw that trips the breaker.

I will pull the pump when the lake warms up a bit but just wondering if anyone else had this kind of problem?

Thanks!!!

System:
- Red Lion RL12G05-2W1V
- 1/2 HP, 115V, 2-wire submersible
- Installed summer 2024
- Lake water system feeding pressure tank
- Pump left in lake for two years
- Franklin Electric disconnect/control box under cabin

Symptoms:
- Pump starts and pumps water normally
- Breaker hums while pump runs
- Pressure rises from ~50 PSI to ~58 PSI
- After ~20 seconds breaker trips before cutout pressure
- Voltage drops from 119.6V idle to ~111V under load

What I checked:
- Swapped breaker with known good breaker → same problem
- Pressure switch has proper voltage
- No obvious burned terminals
- Pump does move water before trip
- Lake had heavy algae/slime last summer
- Pump has never been pulled or cleaned since install

Wiring details:
- Pump label clearly says 2-wire 115V
- Lake cable has black/yellow/red/green conductors
In Franklin box:
- black → L1
- yellow → L2
- green → ground
- red unused/capped
Franklin box appears to be acting mainly as disconnect/junction, not true 3-wire control box

Questions:
Most likely cause?
overloaded/dirty pump?
failing motor?
bad underwater splice/cable?
voltage drop?
pressure switch issue?
Would algae/slime buildup on intake or impeller cause this exact symptom: runs ~20 sec then trips?
Is it common to leave lake pumps submerged year-round for multiple seasons?

 

[Reach4]

A 1/2 HP 115 V pump would usually have a 30 amp breaker, although the maximum amps would be about 12 amps.

You could measure the amps. If amps are under 15, consider a new breaker.

 

[Sponsor]

 

[wwhitney]

A 1/2 HP 115 V pump would usually have a 30 amp breaker, although the maximum amps would be about 12 amps.

You could measure the amps. If amps are under 15, consider a new breaker. If your wire size is 15AWG, then another 15 amp breaker would be the recommendation.

I'm familiar with motors in general, not pumps specifically. How does a submersible pump handle overload protection? Is there a self-resetting integral thermal protector in the pump itself? Or something in the control box?

If the branch circuit breaker does not have to provide overload protection, because it is provided elsewhere, then a 1/2 HP 115V pump has an NEC Table 430.248 FLC of 9.8A. Which means that the conductors to it need to be sized for at least 125% * 9.8 = 12A, so #14 copper suffices. [May need upsizing for long runs due to voltage drop.] And the NEC would permit that #14 copper to be protected at 9.8 * 250% = 24.5A, round up to the next standard size breaker, or 25A.

So a 30A breaker is too large, unless (a) you resort to NEC 430.52(C)(1) Exception 2 which says in effect "if the motor trips on startup on a 25A breaker (and presumably you've ruled out mechanical issues), then you can go up to 400% * 9.8A = 39A (no round up), so you can use a 30A or 35A breaker." Or (b) you upsize the conductors to #10 Cu, which can always be protected at 30A.

Cheers, Wayne

 

[SuperGreg]

Pump motors generally have thermal overload protection built in. The breaker is sized to accommodate inrush current and is primarily short circuit/ground fault protection. wwhitney is correct, generally 15A breaker is used for 240v 1/2 hp motors and 25A for 120v. Maybe someone got mixed up. I'm surprised it's tripping at the end of the cycle and not on startup though. A clamp on amp meter would be really helpful to watch the current draw during the cycle. Typically the current draw goes down as the flow goes down.

That voltage drop is fairly large, where are you measuring that from exactly?

 

[wwhitney]

Pump motors generally have thermal overload protection built in. . . . I'm surprised it's tripping at the end of the cycle and not on startup though.

So shouldn't the built in thermal protection on a 9.8 FLA (or less, the NEC table values are conservatively high) motor kick in before the thermal element on a 15A circuit breaker does?

Agree that unless it's tripping on startup, breaker size is not the problem.

Cheers, Wayne

 

[Reach4]

The breaker is sized to accommodate inrush current and is primarily short circuit/ground fault protection. wwhitney is correct, generally 15A breaker is used for 240v 1/2 hp motors and 25A for 120v.

Would you suggest changing the breaker to 25 amps if the wire is 14AWG?

 

[wwhitney]

Would you suggest changing the breaker to 25 amps if the wire is 14AWG?

It's allowed, but doesn't address the OP's problem. If the OP fixes their problem and then the 15A breaker holds, not much upside to changing the breaker size.

Cheers, Wayne

 

[Reach4]

It's allowed, but doesn't address the OP's problem. If the OP fixes their problem and then the 15A breaker holds, not much upside to changing the breaker size.

Cheers, Wayne

Measuring the current is definitely a good idea. A new 15 amp breaker may well not blow. But working around a problem with a 1/2 HP motor pulling 16 amps by putting in a 20 or 25 amp breaker is a workaround that I would not feel so bad doing.

 

[wwhitney]

But working around a problem with a 1/2 HP motor pulling 16 amps

The NEC FLA for 1/2 HP 115V is 9.8A, and my understanding is that is a conservatively high number. So if it's actually pulling 16A (speculative), that's a problem right there.

Cheers, Wayne

 

[RetiredInGueydan]

Would you suggest changing the breaker to 25 amps if the wire is 14AWG?

An electric motor has different requirements than does an electric resistance heater. I suspect that the wire sized for 240 volts is now undersized for 120 volts due to it's length.

 

[Fitter30]

Amp meter can be purchased for $30 HF or Amazon.
100' of 14 ga wire 111 vac 12 amps is 105 vac
Here is a voltage calculator
www.inchcalculator.com/voltage-drop-

 

[JonBee]

Thanks for all of the input. Good points on the breaker size. It looks like my 15A breaker was undersized for my set up.

The previous owner installed the current 2 wire pump just before I bought the cabin in July 2024. It looks like he removed an old 240V pump (there are 3 wires running to the pump but the red wire is now capped in the Franklin Box) and replaced it with the 120V pump - drawing twice the current. He left the 15A breaker in the panel which was sufficient for the old 240V pump.

I was looking at the Franklin AIM Manual and it says for my motor spec I can go up to 160' with 12 gauge wire and use up to a 30A breaker.

I just measured all distances and checked wire gauge again. It goes like this...

Pump to shore = 30'
Shore to Franklin Box = 105'
Franklin Box to Pressure Switch = 5'
Franklin Box to Electrical on/off switch = 4'
Electrical on/off switch to Breaker in Panel = 17'

So total measured wire run is 161' The first 135' from pump to Franklin Box is either 10ga or 8ga. The remaining 26' from Franklin Box to Breaker in panel is 12ga.

So I went ahead and swapped in the 20A breaker based on the info in the Franklin tables and my wire run looks to be able to support it. I now see no breaker trips (so far after a few test cycles). The pump kicks in at 38 PSI and kicks off at 58 PSI after about 28 seconds. Nothing feels warm - breaker, pressure switch, wires. So I'll monitor it now and hopefully was just an undersized breaker.

Can't have anymore trips because my wife and kids arrive tomorrow. Thanks again for all the help.

My pump is first line in this Franklin Table --> 30A Breaker

 

[JonBee]

Pump motors generally have thermal overload protection built in. The breaker is sized to accommodate inrush current and is primarily short circuit/ground fault protection. wwhitney is correct, generally 15A breaker is used for 240v 1/2 hp motors and 25A for 120v. Maybe someone got mixed up. I'm surprised it's tripping at the end of the cycle and not on startup though. A clamp on amp meter would be really helpful to watch the current draw during the cycle. Typically the current draw goes down as the flow goes down.

That voltage drop is fairly large, where are you measuring that from exactly?

I was measuring across the load terminals in the pressure switch while the pump was on.

 

[JonBee]

Measuring the current is definitely a good idea. A new 15 amp breaker may well not blow. But working around a problem with a 1/2 HP motor pulling 16 amps by putting in a 20 or 25 amp breaker is a workaround that I would not feel so bad doing.

I changed the 15A breaker early on. Made no difference.

 

[Valveman]

My Franklin book shows you need a 30 amp breaker for 1/2HP on 115v. But also check the amps. Amps increasing as the pressure increases is a sign of a worn thrust bearing and the gunk from the bearing building up in the motor. Those short 28 second cycles let the motor shut off too soon and the heat stays trapped in the motor.

 

[GReynolds929]

Based on the chart you posted you need a 30 amp breaker for 115v 2 wire pump. 28 seconds is way too short of a cycle. As stated above.

 

[wwhitney]

The previous owner installed the current 2 wire pump just before I bought the cabin in July 2024. It looks like he removed an old 240V pump (there are 3 wires running to the pump but the red wire is now capped in the Franklin Box) and replaced it with the 120V pump - drawing twice the current. He left the 15A breaker in the panel which was sufficient for the old 240V pump.

FYI that was a mistake on the previous owner's part. Reusing a circuit sized for a 240V pump with an equal power 120V pump will approximately quadruple the effects of voltage drop (P = V^2 / R). So if you ever have to pull the pump, I suggest replacing it with a 240V pump.

Also, if your 15A breaker was tripping after 20 second, that suggests to me that the motor was never properly up to speed and/or the pump is overloaded, e.g. due to voltage drop and/or what Valveman said in post #15 (I don't know anything about pumps). Looking at a random trip curve for a small circuit breaker, tripping in 20 seconds corresponds to a current of 150% to 300% of rating. So at a minimum an average of around 23A over those 20 seconds (during startup it would be more, at the 20 second mark it could be less but still over 15A).

As to voltage drop, your measurements are at the pressure switch, so to determine the voltage at the pump, you need to subtract the voltage drop on the wires between them. Given the distances you mentioned, if your wire to the pump is #10 copper, the impedance between your pressure switch and the pump would be about 0.3 ohms. Meaning that when it is carrying 20A, the voltage would drop an additional 6V. Putting the voltage at the pump during startup down at ~105V. Maybe worse.

Cheers, Wayne

 

[SuperGreg]

I was measuring across the load terminals in the pressure switch while the pump was on.

OK. I'm questioning why the voltage drop is so much, so close to the panel. I'd really suggest putting an amp meter on the circuit, it's entirely possible the pump is pulling upwards of 30A which would trip the 15A breaker but may be low enough that the 20A breaker doesn't trip before the pump cycles off.

 

[Fitter30]

Thanks for all of the input. Good points on the breaker size. It looks like my 15A breaker was undersized for my set up.

The previous owner installed the current 2 wire pump just before I bought the cabin in July 2024. It looks like he removed an old 240V pump (there are 3 wires running to the pump but the red wire is now capped in the Franklin Box) and replaced it with the 120V pump - drawing twice the current. He left the 15A breaker in the panel which was sufficient for the old 240V pump.

I was looking at the Franklin AIM Manual and it says for my motor spec I can go up to 160' with 12 gauge wire and use up to a 30A breaker.

I just measured all distances and checked wire gauge again. It goes like this...

Pump to shore = 30'
Shore to Franklin Box = 105'
Franklin Box to Pressure Switch = 5'
Franklin Box to Electrical on/off switch = 4'
Electrical on/off switch to Breaker in Panel = 17'

So total measured wire run is 161' The first 135' from pump to Franklin Box is either 10ga or 8ga. The remaining 26' from Franklin Box to Breaker in panel is 12ga.

So I went ahead and swapped in the 20A breaker based on the info in the Franklin tables and my wire run looks to be able to support it. I now see no breaker trips (so far after a few test cycles). The pump kicks in at 38 PSI and kicks off at 58 PSI after about 28 seconds. Nothing feels warm - breaker, pressure switch, wires. So I'll monitor it now and hopefully was just an undersized breaker.

Can't have anymore trips because my wife and kids arrive tomorrow. Thanks again for all the help.

My pump is first line in this Franklin Table --> 30A Breaker

secondsView attachment 107587

You won't feel anything warm in 28 seconds of run time. Motor amps will go up as pumping pressure rises. Didn't see a pump curve on line. Still shouldn't get above full load amps except our running 111 vac which low voltage raises the amps

 

[JonBee]

I thought my tipping issue was solved when I swapped out the 15A breaker for a 20A breaker. And it did solve the tripping because I have had no trips since. But another interesting twist came about a couple days ago.

We are off grid and I had a new solar system installed approximately 3 weeks ago including a new inverter which is the Victron MultiPlus-II 48/5000/70 (120V). A couple days ago I noticed the red overload LED flashing on the Victron inverter when the Lake pump is running AND the Microwave (1100W) is running. Happens every time. Only other loads were minimal lights and couple plugs.

This doesn't make sense if you base everything on the rated power of the pump and the microwave. They should not push the inverter into an overload warning.

• Red Lion RL12G05-2W1V.
• 1/2 HP, 115V.
• Nameplate current:
  • 10.0A running
  • 12.0A maximum

Approximate running power:

• Pump ≈ 1150W
• Microwave ≈ 1100W
• Combined ≈ 2250W

Inverter Rating: 4000W continuous output , with significantly higher surge capacity for short durations

So it is seeming to hit overload warning at only 60–65% of rated continuous output. Doesn't seem right.

I'm wondering again as others mentioned, is the pump drawing more current than its nameplate?
Is the pump partially fouled?
How much actual power (W/VA) is the inverter seeing during the warning?

Today I bought a Klein Clamp Meter to measure the current. Will do so on my next trip out on Tuesday. And will finally be able to pull the pump to inspect it. But it has been running fine since the breaker swap.