Testing a sealed sewer pump

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Besoeker said:
You can test for winding continuity. But probably not a lot else.
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Thank you. This sealed pump apparently had shorted and melted its neutral in two in the service panel and melted other wires (insulation) close to it. I didn't want to take a chance on having to repair that again if the breaker didn't trip fast enough. I got an ohm reading of 1 to 8 on the 20 M scale but only Overload on a pump right next to it ( from the power prong to neutral prong on the cords). I decided to install a gfi outlet and plug in the pump in question, to hopefully protect the panel. It tripped the gfi immediately. So I told the customer to get a plumber. (When the house was built it didn't require gfi). I still wonder if those ohm readings were telling me it is shorted.
 
Stevenfyeager said:
Thank you. This sealed pump apparently had shorted and melted its neutral in two in the service panel and melted other wires (insulation) close to it. I didn't want to take a chance on having to repair that again if the breaker didn't trip fast enough. I got an ohm reading of 1 to 8 on the 20 M scale but only Overload on a pump right next to it ( from the power prong to neutral prong on the cords). I decided to install a gfi outlet and plug in the pump in question, to hopefully protect the panel. It tripped the gfi immediately. So I told the customer to get a plumber. (When the house was built it didn't require gfi). I still wonder if those ohm readings were telling me it is shorted.
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Was the GFCI receptacle installed correctly? If so, then you can further check the pump. I would check L-L and L-G, and to 3rd phase or neutral if present. If there are no electrical problems there, look for a mechanical problem, like seized bearing(s), jammed impeller, pump overload, either via being undersized for the application, pumping something too thick, or a discharge valve opened too far. Jammed impellers are common in applications where the influent isnt properly screened, or lack a grinder, like a Muffin Monster, on the intake of the pump.

An ohm reading of 1-8? You should be able to get more precise reading that that.

What size is the pump, i.e, what is the voltage, # of phases, horsepower, nameplate data? How long had it been in operation before overheating - five seconds, five days, five years?
 
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Depending on where you read...the pump has a float switch that controls it. Was the switch closed when you read the cord? Did you read the cord that goes directly to the pump? On the 20M scale, that's Megohm. If you read the winding line to neutral you'd read a dead short. If line to ground, you should use a megger, not an ohmmeter. Motor windings (cord hot to neutral) should read just a few ohms, depending on motor size. Ohms to ground should be infinite (OL). Some larger pumps have capacitive start with a centrifugal switch. Best to get a manual describing what you have rather than guessing. Melted wires sounds like a connection problem, not a motor problem. The breaker should trip if the motor has problems. Most of the pump problems I've dealt with are mechanical failures in the motor (bearings) or pump. If the GFCI tripped immediately, you've likely got a ground problem on the "hot" wire in either the wiring or the motor, since the GFCI compares line and neutral (return) current. Any difference means some current is flowing to ground instead of back to neutral.
 
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Stevenfyeager said:
Thank you. This sealed pump apparently had shorted and melted its neutral in two in the service panel and melted other wires (insulation) close to it. I didn't want to take a chance on having to repair that again if the breaker didn't trip fast enough. I got an ohm reading of 1 to 8 on the 20 M scale but only Overload on a pump right next to it ( from the power prong to neutral prong on the cords). I decided to install a gfi outlet and plug in the pump in question, to hopefully protect the panel. It tripped the gfi immediately. So I told the customer to get a plumber. (When the house was built it didn't require gfi). I still wonder if those ohm readings were telling me it is shorted.
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Replacing the pump might be the most economical option.
 
Besoeker said:
Replacing the pump might be the most economical option.
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the customer called a plumber as I suggested. The sealed pit pump float had stuck in "on" position and burned out the motor. The gif tripping immediately meant something was wrong. And it did save my service panel from damage again. Not sure why the breaker didn't trip. Thank you.
 
Stevenfyeager said:
the customer called a plumber as I suggested. The sealed pit pump float had stuck in "on" position and burned out the motor. The gif tripping immediately meant something was wrong. And it did save my service panel from damage again. Not sure why the breaker didn't trip. Thank you.
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The float being stuck would just keep the motor running continuously. If there was no overload, there's no reason the breaker would have tripped. I still think you had wiring problems as well, since you had a melted neutral and the GFI immediately tripped.
 
Ingenieur said:
most pump mfgs will give you a cold coil Z spec
usually in the manual

an example
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Your table appears to be for submersible well pumps, OP has a sewer lift pump. Most will have a float switch, and when water is below float you get an open circuit reading, otherwise they often are split phase or capacitor start and reading will include start and run winding as well as capacitor in start winding circuit if it has one.

If neutral conductor was melted at the panel, my first guess would be poor termination of that conductor caused the melting. Short circuit/overload protection (if anywhere close to proper selection) should otherwise keep it from getting hot enough to do that.
 
just an example
similar for most pumps
residential fractional hp pump
https://www.femyers.com/en/productd...hnical documents/downloads/my881_lr.pdf?la=en

Connect one meter lead to each of the black terminal leads. Meter should read about 1.9 ohms. This is the resistance of the main winding for a 115 volt stator. This reading for a 230 volt stator should be about 7.7 ohms.
Now remove the capacitor and connect one meter lead to each of the brown wire terminals. The meter should read about 12 ohms for a 115 volt stator. For a 230 volt stator this reading should be 21.3 ohms. This is the resistance of the start winding
 
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