submerged pump prob

[jetlag]

I have customer with 3 hp water pump submerged in lake to run yard sprinklers. The pump runs a few seconds and trips the overload reset switch in the control box. We removed the pump and cleaned it out to be sure it was not jammed with trash but it was free. It has a 45 mfd run capacitor and a 208-250 mfd start capacitor . Is there any way to check these capacitors? I tried to ohm the motor out but am not sure how many ohms it should have. It is suppose to pull max 17 amp but is pulling over 30 a for about 20 seconds before the the overload trips. I want to eliminate everything before buying new pump. It is in the $ 900 range.

 

[ptonsparky]

If it is a Franknlin pump motor you can find all the information you need at their web site.

You can do a quick check of caps with your vom or continuity tester. Run caps will be bulged and open if they have failed. Starts usually have visual signs of leaking if failed.

An amp meter, a low voltage xfmr & vom along with (2650*I)/E = MFD will give you capacitance within 10%. Measure applied voltage and current.

Remove the bleed resistors, if any, before testing.

I=2.3
E= 21.7
MFD=280.8

 

[hillbilly1]

Sounds like the start capacitor has failed, an easy but not foolproof way to check it is to take it out of the circuit, using an analog meter set on ohms, connect across the two terminals. The needle should deflect almost full scale then slowly return as the capacitor charges. If it shows a constant open or short immediately, then it has failed. Usually the manufacture will put a diagram on the inside cover giving the resistance readings for the motor windings. Could also be a defective start relay, but most of the time it is the start capacitor that fails.

 

[Jraef]

Frst question should be is this a new installation or one that has been working and now stopped?

If it was existing and ran fine until recently, it does sound as though your start cap and/or speed switch (or voltage relay as the case may be) has failed.

If it is new, what is the voltage, cable, distance etc. etc.?

 

[hockeyoligist2]

We removed the pump and cleaned it out to be sure it was not jammed with trash but it was free. QUOTE]

Did you check the surface the pump is sitting on? Sometimes there will be something below the pump stopping the flow, like a piece of plastic or a turtle shell.

 

[jetlag]

thanks

thanks

If it is a Franknlin pump motor you can find all the information you need at their web site.

You can do a quick check of caps with your vom or continuity tester. Run caps will be bulged and open if they have failed. Starts usually have visual signs of leaking if failed.

An amp meter, a low voltage xfmr & vom along with (2650*I)/E = MFD will give you capacitance within 10%. Measure applied voltage and current.

Remove the bleed resistors, if any, before testing.

I=2.3
E= 21.7
MFD=280.8

Thanks you guys are very helpful. The run cap is not bulged and both caps show 3 or 4 mega ohms resistence. Is that considered open ? I do see some material that looks like ear wax around top of start cap.

 

[jetlag]

thanks hillbilly

thanks hillbilly

Sounds like the start capacitor has failed, an easy but not foolproof way to check it is to take it out of the circuit, using an analog meter set on ohms, connect across the two terminals. The needle should deflect almost full scale then slowly return as the capacitor charges. If it shows a constant open or short immediately, then it has failed. Usually the manufacture will put a diagram on the inside cover giving the resistance readings for the motor windings. Could also be a defective start relay, but most of the time it is the start capacitor that fails.

I remember I have checked caps this way before but i think i was set on voltage and watch it fall. I didnt have analog with me that day. Is there a good way to check start relay?

 

[KentAT]

like a piece of plastic or a turtle shell.

I do see some material that looks like ear wax around top of start cap.

...do turtles have ears?

 

[jetlag]

Thanks Jraef

Thanks Jraef

Frst question should be is this a new installation or one that has been working and now stopped?

If it was existing and ran fine until recently, it does sound as though your start cap and/or speed switch (or voltage relay as the case may be) has failed.

If it is new, what is the voltage, cable, distance etc. etc.?

It is existing and been working long time. The owner said another electrician installed a start cap and it ran a week or two. I dont have much experience with voltage relay, I am used to speed switch to disconnect the start cap. How does that voltage relay work to disc the start cap after the motor starts. Im thinking it might be sticking and the motor running on the start cap which would explan the new cap failing

 

[jetlag]

thanks hockey

thanks hockey

We removed the pump and cleaned it out to be sure it was not jammed with trash but it was free. QUOTE]

Did you check the surface the pump is sitting on? Sometimes there will be something below the pump stopping the flow, like a piece of plastic or a turtle shell.

It is all clear ,we moved it over to the edge of the dock for testing. it is not near the bottom

 

[mxslick]

Thanks you guys are very helpful. The run cap is not bulged and both caps show 3 or 4 mega ohms resistence. Is that considered open ? I do see some material that looks like ear wax around top of start cap.

The start cap is bad...it should as stated in a previous post start off with low resistance and gradually climb..

Replace the start relay AND the cap (make sure you're using the right value for that cap, it's possible that it was replaced with the wrong one) and you'll be back up and running.


Oh, and a blocked intake on most pump designs results in LOWER current, not higher. Unless the impeller is jammed.

 

[mdshunk]

Probably ought to get yourself a capacitance checker. They're sold at HVAC supply houses, and they're not at all expensive. Hook up a cap, and read out right on the screen the micro farads. The potential relay can be a bit harder to source, since they're not very interchangable. They drop out at a very specific, calibrated value.

 

[jetlag]

Thanks Mdshunk

Thanks Mdshunk

Probably ought to get yourself a capacitance checker. They're sold at HVAC supply houses, and they're not at all expensive. Hook up a cap, and read out right on the screen the micro farads. The potential relay can be a bit harder to source, since they're not very interchangable. They drop out at a very specific, calibrated value.

I wont be back on job till monday but i have the caps with me. Another posts said if the cap shows open with continuity tester it is bad. I dont think that is true because I checked and both caps show open and 4 meg ohms on digital meter. Guess what I took the start cap off a 1 hp compresser that i know is good and it also shows open with bulb tester and 5 meg ohm. I tried the start cap in question on the compresser and it runs fine even though it is more mfd. I also tried another test by placing each cap in series with a 60 watt light bulb . They all did the same, the two i am checking and the one i know is good. The bulb burns fine and there is approx 5 v across the good cap and the one im checking. Turning off the bulb breakes the circuit and the caps fall very gradually from the 5 v on the v meter. The run cap does the same but has 26v and falls gradually fromm 26v dc when the bulb is turned off. Does that mean the caps are good. I know the start cap will start 1 hp comp.

 

[hillbilly1]

An easy test for the start relay is to put an amp clamp on the start wire ( start capacitor must be good and the pump is building pressure, if it is not the motor is not turning or locked up) the current should drop to zero rather quickly after the pump starts. If current draw continues the relay is stuck or the motor is not turning. The relay uses current not voltage to release, the coil is in series with the run winding. The high startup current closes the contacts energizing the start winding, then when the run current drops to a predetermined level it drops out, not having enough current to keep the contacts closed.

 

[jetlag]

thanks hillbilly

thanks hillbilly

An easy test for the start relay is to put an amp clamp on the start wire ( start capacitor must be good and the pump is building pressure, if it is not the motor is not turning or locked up) the current should drop to zero rather quickly after the pump starts. If current draw continues the relay is stuck or the motor is not turning. The relay uses current not voltage to release, the coil is in series with the run winding. The high startup current closes the contacts energizing the start winding, then when the run current drops to a predetermined level it drops out, not having enough current to keep the contacts closed.

Thats a big help I should be able to find the prob now. I didnt know for sure what cut the start cap off. I thought it might be a time delay or a metal strip that heated and broke the contact. I wont be at at my computer for few days so thanks to every one that replied.

 

[jetlag]

found prob

found prob

Thats a big help I should be able to find the prob now. I didnt know for sure what cut the start cap off. I thought it might be a time delay or a metal strip that heated and broke the contact. I wont be at at my computer for few days so thanks to every one that replied.

Took the caps by supply place and had them ckecked, just as i thought they were both good. Got to job and found info inside control cover to check start relay. It was good also. I found info to ohm the motor out and it checked also. The underground feeder to pump is 10/3 uf w/g . I had already checked each wire for open by joining all together one end and ohm out other end. Decided to try one more thing and took wire back a part each end and ohm them again. Guess what some how the red wire that carries the current from caps is shorted to bare ground wire. I took bare ground off both end and pump runs fine. Wont try to find short will just bury new wire.

 

[bsh]

I have a water well for my home and had to replace the pump last year after 22 years of service. The problem was a failed motor bearing which caused high run current.