Repairing a franklin well control box and the main overload completely burned out rather than tripping (manual reset button), it's melted on the inside. Start capacitor reads zero as well, run capacitors are ok. Is this caused from the motor side (seized motor or short in the well wiring) or from the power side (ex-lightning strike)? It's on a 40A dedicated breaker so I'd think if it was from the motor side it would have tripped the breaker (overload contact rating is 100A 250V)? Then again the house has a "zap cap" surge protector on the power meter, although I know those dont work great.
What causes manual thermal overloads to burn out rather than trip?
- Thread starter msd
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Overload buttons get hot. This can loosen the wire connection, which causes additional heat. Probably not enough amps to trip the overload, but enough heat to melt the plastic around the overload.
Start capacitors are only engaged on pump start. So, a bad start cap or relay is a sign the pump is cycling on and off too much. Using a Cycle Stop Valve would solve the cycling problem, as well as reduce the running amps of the motor which would be less heat for the overloads to deal with.
Start capacitors are only engaged on pump start. So, a bad start cap or relay is a sign the pump is cycling on and off too much. Using a Cycle Stop Valve would solve the cycling problem, as well as reduce the running amps of the motor which would be less heat for the overloads to deal with.
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Fitter30
Well-Known Member
If the start cap doesn't have a ohm reading, overload is melted wouldn't want trust the potential relay. Panel that takes a hit would want to change it out not fix it. Overload could have welded contacts or from the hit might have changed the thermal disk. The potential relay uses voltage from the start winding to switch the relay to only the main winding, starts using both windings.
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2stupid2fixit
Active Member
In many cases I have seen loose, cracked or poor connections generate a ton of heat closest to where the component failure happens. I am sure you have done this simple thing but just to put it out there, are all your connections 100%? If you have a bad connection on any leg of this system it can and does cause exactly the symptom you describe. Think of what damage a "loose neutral" can do in any 120v environment. It's not so different in your setup. I have seen control boxes wired perfectly but ONE of the AC lines was only wilted lettuce tight. Everything worked 100% but that one loose connection that was not torqued down made a lot of heat that caused other things to burn up. Give it the eyeball once over. Chances are your connections are solid but I hate hearing stories of one loose connector screw ruining expensive stuff.
Fitter30
Well-Known Member
Thermal overloads/motor starters all work by heat bi metal heats up and either by direct or indirect heat trips. Ambient temps especially when protection is outside other than a big swing in temperature there can be sun load. Electronic protection can include amperage, voltage either high, low ,both and can be adjustable how fast they trip as fast as .5 second.
Thanks for the replies.
All the connections in the box were good, checked every one. The relay seemed to work but there was dark char (no melting) on the inside of the casing.
Checked the insulation to ground with a megohmeter at 500/1000V and read 100k, AIM manual says it should be a minimum of 500k so I assume there is a short somewhere.
The start winding was 1.6 ohm and run winding 0.9 ohm- and thats measured at the surface, so values at the motor likely 0.2 ohms less accounting for wire resistance (10awg). AIM says the run winding should be 0.81 and start winding should be 1.8 ohm
So it seems that there is a short in the motor in the start winding? Perhaps that ran too much current and burned out the thermal overload, start capacitor, and charred the inside of the relay?
All the connections in the box were good, checked every one. The relay seemed to work but there was dark char (no melting) on the inside of the casing.
Checked the insulation to ground with a megohmeter at 500/1000V and read 100k, AIM manual says it should be a minimum of 500k so I assume there is a short somewhere.
The start winding was 1.6 ohm and run winding 0.9 ohm- and thats measured at the surface, so values at the motor likely 0.2 ohms less accounting for wire resistance (10awg). AIM says the run winding should be 0.81 and start winding should be 1.8 ohm
So it seems that there is a short in the motor in the start winding? Perhaps that ran too much current and burned out the thermal overload, start capacitor, and charred the inside of the relay?
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Start winding, just like the start cap, start relay, even the pressure switch are all only engaged on START UP. Yes, cycling is a very or the most common problem, which then shortens the life of the motor as well as EVERYTHING else. But it has nothing to do with "running". Pumps are made to run 24/7/365. When running, all those components are out of the circuit.
Fitter30
Well-Known Member
Most don't have a megger especially 1k volts. Pump is still in the well? I'd run it you don't have a baseline. It's not like 50meg ohms or less. I've never meg a well pump. AC compressors and base mounted pumps and fan and blower motors. How does the pressure switch contacts look? 40 amp breaker protects only the wire unless the motor is stuck, shorted or grounded.Thanks for the replies.
All the connections in the box were good, checked every one. The relay seemed to work but there was dark char (no melting) on the inside of the casing.
Checked the insulation to ground with a megohmeter at 500/1000V and read 100k, AIM manual says it should be a minimum of 500k so I assume there is a short somewhere.
The start winding was 1.6 ohm and run winding 0.9 ohm- and thats measured at the surface, so values at the motor likely 0.2 ohms less accounting for wire resistance (10awg). AIM says the run winding should be 0.81 and start winding should be 1.8 ohm
So it seems that there is a short in the motor in the start winding? Perhaps that ran too much current and burned out the thermal overload, start capacitor, and charred the inside of the relay?
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