Well pump keeps cutting out

[Dan Charrois]

Hi there. I have a Gould's 1/2 HP 4" submersible well pump with a Franklin 2801054915 1/2 HP pump controller, which is turned on and off manually (for watering lawn and gardens, so no pressure switch or pressure tank - just wired directly to 230V power with a switch). The pump is not in a well, but rather in a creek (well screened from debris) so there's never an issue of the water level running low. It's worked fine for at least 5 or 6 years with no issues at all.

However, it's recently began cutting in and out - it pumps for 2 or 3 minutes then turns off for a minute or two, then starts again.

I figured that maybe there was some debris in the pump itself causing the motor to potentially overheat, so I pulled the pump out and took it apart to clean. But I needn't have bothered - there wasn't any significant amount of sludge inside, and there was no obvious binding to either the pump or motor - everything is rotating freely. It should have no shortage of water for cooling the motor - it's in a box with external screens but they're definitely clean. But after putting the pump back and rechecking the electrical connections, it's still acting up in the same manner... even when I pump water with several sprinkers open (more than usual) so it should have a relatively easy job with very little back pressure.

Down at the pump, I notice that it "stutters" for a few seconds before turning off when it does this. And I've just noticed that the control box in the house "buzzes" quietly just as it starts and then for those few seconds while the pump is stuttering and then turning off for a minute or so.

Could the QD relay in the control box be suspect? Though I know it has a relay, triac, and reed switch inside, I haven't been able to find an internal schematic of the QD relay to check and see if it may be consistent with this type of fault. I'm trying to sort out if perhaps the connection from L1 to Black within the relay may be cutting out intermittently causing the buzzing and ultimately causing the pump to shut down for a minute or so before starting up again.. or if the thermal overload in the motor is turning things off, which in turn is causing the buzzing in the control box.

I'm hoping I can just replace the relay (or control box) to fix the problem rather than the entire pump if people think this symptom isn't necessarily a problem with the pump itself. On the other hand, if the pump has to be replaced, I'd also prefer not to replace the control box as well

Any suggestions?

Thanks! Dan

 

[Dan Charrois]

A followup with a bit more testing that I did... that unfortunately is implying to me that the pump motor may be actually the culprit.

I measured the current on the 4 wires running to the pump (230V). The ground (green) never has current in it, so that's good. The red energizes for about a second, as it should, when the motor starts, and the black and yellow carry the same current - about 6 amps on startup, so that all looks good from the outset. However.... after a few seconds, the current slowly starts to rise, reaching 10-11 amps on the black and yellow after a minute or so (I can think of no good reason for this - it's just pumping water through several sprinklers, and it isn't as though the work should be slowly getting harder. Then, suddenly, current on the black and yellow spikes up to 18A for a few seconds, while the red also energizes at 4A, and then everything shuts down, waiting a minute or two before things start over again. With that kind of current running through the motor, it might make sense why it would overheat and then do a thermal shutdown until things cooled off again. Though I'm at a loss as to what would cause it to draw that kind of current in the first place.

So now I'm having a hard time justifying to myself that the problem might be with the controller - it's seeming to be more likely that the pump motor itself is having problems. Thoughts?

Thanks again! Dan

 

[Sponsor]

 

[Valveman]

Yeah sounds like a motor problem. The pump usually will not start at all if it is a control box problem. Most likely the motor windings are swelling and grabbing the rotor. This is caused by overheat. Usually in a creek like situation a flow inducer or shroud is needed to keep the motor cool. Also running the pump with "more than usual sprinklers on" actually causes higher amps. Back pressure on the pump is a good thing, it makes the motor draw lower amps and run cooler. When trying to get a motor to draw lower amps, the pump needs to be restricted. Wide open flow is the hardest thing for a pump/motor to do.

 

[Dan Charrois]

Thanks for the response. Your theory of the motor windings swelling due to an overheating condition does seem to match the symptoms, particularly because the current seems to slowly ramp out (presumably as friction increases) and then suddenly shoots up really high (presumably as the motor stalls) before cutting out a few seconds later. I forgot to mention, I do have a shroud around the motor in the creek - it's encased in a little box I made with external screens for debris, such that the water has to flow around the motor to get to the pump. Though perhaps it might cool the motor better if it was a bit smaller so the flow rate past the motor would be higher - it's a box around 8 inches across, enclosing a 4" diameter pump.

I hadn't realized that back pressure kept the current down on the motor, though it began exhibiting these symptoms when there was only one sprinkler on, and a fair degree of back pressure, so that's why I tried turning more sprinklers on to see if that helped. In any case, there is always some back pressure, as there is something like 30'-40' of head and around 200' of friction loss in pipe to get the water out of the creek ravine in the first place.

Interestingly, I tried pumping water with the sprinklers completely detached, so it was wide open flow other than the head and friction loss, and the pump survived without cutting out for a couple of hours. Checking the current flow, it was still on the high side (about 6.5 A, and I seem to recall that a 1/2 HP motor should be drawing more in the neighbourhood of 5.5 A). As I restricted the flow, the current draw tended to increase.

This may not be how pump motors are supposed to behave - after all, it does appear as though the motor is failing considering that the lowest current draw I've observed is higher than the full load current is supposed to be.

I think the next step is going to have to be to look for a solid and reliable pump designed more specifically for my situation.

Thanks again!

Dan

 

[Valveman]

Increasing amps as the back pressure increases means the motor thrust bearing is out. The smaller the shroud the better for the motor. A 3.5" pump in a 4" shroud still leaves enough room to pass up to 60 GPM.