Hello we have an open loop geothermal with Grundfos ¾HP well pump and 2 ClimateMaster TZ heat pumps. We are having an issue this morning. The well pump was stopped. When we restarted it by switching off and on, it started but was consuming 29amps. It usually consumes 9amps when it works. So it is working for 30 sec, we get up to 20psi in the tank and than it stops again. It will restart by itself after few minutes, than stop again... It seems there is a thermal protection in the pumps that trips because it's not the breaker... Later on, if we turn it on, it consumes only 5amps but no water is coming out. We are not sure with these symptoms what it means... Broken motor or a pipe that disconnected and the pump is just cycling water around? Any clues would be welcome before we tear it out of the well form its 80ft deep. Cheers!
How old is the pump? Sounds like thermal overload or one of the scenarios you have described. Either way it needs to come out for inspection and a verified diagnosis. Eric
Motor is being overloaded by the pump causing high running current that then trips the thermal element. Thermal element cools and the motor restarts only to repeat again because it is still mechanically overloaded. Possibly caused by pump impeller drag on the wear ring or failed bearing. Motor running with 5 amps and no water flow indicates whatever was causing the overload no longer exists, possibly due to a broken pump shaft or pump impeller has disintegrated or broken free from the shaft.
The pump is only 4 years old! We are investigating but it seems we might have loss one of the two 120ac phase... I just hope it did not ruined the motor if this is the case...
Is this a standard 240V AC motor or a variable speed motor? If a standard 240V AC motor, that is a single phase motor with two hot leads. If you lost one of the hot leads there is no return path for the other hot leg and you would have no current flow. This would not explain the high running current that was seen. But the repeated overload condition may have damaged the motor controller or the motor windings. On a three phase induction motor, if you loose one of the three phases, the other two phases will pull much higher than normal current.
Ok it is a 4 wire pump not variable speed... The controller box was faulty. One of the 4 wire was affected by corosion and a capacitor was blown. So it seems the pump is safe! Case closed!
Funny enough, we are running tests with CSV (cylcing stop valve) because we fear over cycling the pump. So there is an amp meter with a torrus I bought on ebay in China for a few $ with a display constantly connected and this way we can follow the consumption in real time and calculate what is best to operate the pump... So we were quite informed about normal numbers hehe.
Ok. If you were measuring 29 Amps on either of the two hot leads, you must have lost the third connection to the start winding. The motor was likely not starting at all or not coming up to rated speed/HP and drawing starting current for an extended time period until the thermal overload device shut it down. Sorry I didn't think about that as a possible cause. Hopefully the thermal overload device was conservatively sized and no harm was done to the motor windings.
Yeah we hope the motor is not damaged... Now the numbers are back to normal, and we could inspect the pump physically because the guy that came thought of the control box only when he had the pump in his hands and saw the four wires... The pump looked fine, no loose between motor and impellers... After 4 years of ultra heavy winter usage, we were interested to see the pump itself. We could only get 10psi so I suppose the motor was not running high speed. Though I do not know how it works except a motor has to get its speed to counter balance the current...
