Pool Pump??

[jahilliard]

I have a high end customer that called today about the fact that his pool pump has been replaced 5 times in seven years. He asked his "handy man" to determine the problem but he said it was too difficult for him so he called me. Well other than the obvious, if there is anything obvious, there could be a million places to start. I haven't actually been to the residence but he says he has sufficient surge protection and nothing else has been effected like the pump. Since there have been multiple pumps it would seem the problem lies somewhere else, but where? How would I go about determining the problem if everything is currently running fine, surge protections in place, and nothing seems too obvious. is it possible the pump may be overworked based on what it's being asked to do?? Any ideas about what to look for would be greatly appreciated...this guy will want to hear or see some kind of answer I'm sure. Thanks for ANY feedback!!

 

[sawdust454]

I would start with all connections, check for voltage drop and see if the pump motor is exposed to the weather.

 

[jahilliard]

the voltage drop would occur while under load right? So if i were to kick on the motor and check for voltage drop at start up or while running?? And what level of voltage drop would prob be significant enough to cause the motor to burn up. It obviously takes a while for that to happen so the drop may be very little??

 

[Volta]

... is it possible the pump may be overworked based on what it's being asked to do??...

Could be. If the run is long, and or a large diameter it may be moving too much water.

Sometimes the simple number of accessories can add too much resistance to the flow. Things like heaters, chlorinators, filters, etc. and the elbows used to connect them can be a drag on the system.

I've taken current readings on pump motors receiving a reasonable voltage and found them drawing way too much current. Shunt the flow around some accessories and it goes back to a normal range.

Less likely could be a blockage in the lines somewhere. Check the voltage with and without the load, of course, and the current under max. load, but if that is okay you might have to try to think like a plumber.

 

[notoriousdln]

could be as simple as an undersized pump working too hard

 

[Ken9876]

How did they fail?

 

[aaatraker]

Did you figure it out?

Did you figure it out?

What was the cause?

 

[kwired]

Sometimes the simple number of accessories can add too much resistance to the flow. Things like heaters, chlorinators, filters, etc. and the elbows used to connect them can be a drag on the system.

Centrifugal pumps draw more current when there is not a restriction in the flow of the pumped media. More flow = more work to move the media = more power required by the motor.

I have solved pump motor overloading problems by restricting the flow of pumped media.

As far as why motors are failing first check is voltage and current. If these are alright then make sure motor gets enough ventilation for cooling. Check voltage and current while other loads are running also.

Are the old motors available to investigate? They could give you clues as to what has happened.

Is there proper overload protection?
Are bearings failing?
Are pool chemicals causing failure of some component eventually leading to winding failure?
How frequently does motor start and how long of cool down period between starts?

 

[CFL]

Centrifugal pumps draw more current when there is not a restriction in the flow of the pumped media. More flow = more work to move the media = more power required by the motor.

I have solved pump motor overloading problems by restricting the flow of pumped media.

Are you saying that a pump running with no load would draw more current than one that is dead-headed? Can you elaborate so your statement makes a little more since?

 

[mcclary's electrical]

Are you saying that a pump running with no load would draw more current than one that is dead-headed? Can you elaborate so your statement makes a little more since?

he said NOT a restriction. A dead headed pump is a restriction


Voltas example of valving things off to relieve the pump seem inaccurate or there was someting else going on

 

[CFL]

he said NOT a restriction. A dead headed pump is a restriction


Voltas example of valving things off to relieve the pump seem inaccurate or there was someting else going on

I know what he said. According to that, the dead headed pump would draw less current than a pump with no load.

 

[CFL]

To me, Voltas solution makes more since.

 

[infinity]

The current of the pump will increase with the amount of work it is doing. More work equals moving more liquid. Restrict the flow and the pump is doing less work and the current will be lower. Pump impellers may also be subject to cavitation which is air bubbles forming around the impeller. The impeller would be spinning in air and liquid. This would allow the pump motor speed to increase therefore the load on the motor would be reduced as would the current. Same principle applies to restricting the air flow on a fan.

 

[KWH]

Pump Failure

Pump Failure

Is the failed pump motor being rebuilt or just replaced, you need to get your hands on the old pump/ determine maybe the problem is system is being clogged resulting in damaged motor

 

[Volta]

Centrifugal pumps draw more current when there is not a restriction in the flow of the pumped media. More flow = more work to move the media = more power required by the motor...

I agree. My example was about bypassing equipment to remove resistance from the path. Same volume of water with less length, bends, and equipment to push it through.

 

[dmagyar]

differential pressure

differential pressure

If you can do a differential pressure reading, you can determine the TDH that the pump is operating under. Looking at different HP pump motor curves then you can determine if the motor is sized correctly, which it may not have been. Like the earlier posts, if the amount of extra accessories are creating too much load then you'll have poor pump performance, and the motor will suffer the consequences. The differential pressure can be checked with any options in the circuit to assess those also. Make sure to mention to the owner that if you embark on determining the cause of the motor failures that you expect to be compensated at some agreeable rate because you don't want to be doing this just for the experience. Here are two links to reference for pump curves and trouble shooting. Good Luck.

http://www.cheresources.com/centrifugalpumps5.shtml
http://www.cheresources.com/centrifugalpumps5.shtml.

 

[kwired]

Are you saying that a pump running with no load would draw more current than one that is dead-headed? Can you elaborate so your statement makes a little more since?

I wouldn't say a pump with no liquid in the impeller would necessarily draw more than a dead headed pump - it is circulating the liquid that is in the pump housing - but it will be near the same draw.

Centrifigal pumps and fans are loaded by the volume of media they are moving not the pressure. You can close valves or dampers and they draw less current because they are moving less media.

volts x amps = power (disregarding efficiency and power factor)

power = amount of work done in a specific amount of time.

if volts stays the same and amount of work being done decreases amps must also decrease. (again disregarding efficiency and power factor)

I agree. My example was about bypassing equipment to remove resistance from the path. Same volume of water with less length, bends, and equipment to push it through.

If you do that you create less resistance to water flow and thus increase the amount of water the pump can move. This should result in the pump drawing more current.

 

[aaatraker]

History/Troubleshooting

History/Troubleshooting

You need to get a lot of troubleshooting history, to solve this one.
Who changed out the first bad pump AND was it replaced with the correct one?
What was the reason given Why the first pump failed?
Has the pump failed only during hot weather only ( pump cooling? )
Any tripping of breakers,motor resets?
Any changes to the wiring or the plumbing of the pump system? ( new filter or strainer added or the old ones relocated ) Don't know what handyman might have done to keep system.
Is it the pump that is failing or the motor?
Does the owner have paper work and manuals for the pool system, check all the control boxes for paper work, get the manufacture name off pump and call tech line for correct install info and compare it to what you see, also can see if manufacture has website to download manuals.
Then do a complete troubleshooting walk through.
From breaker panel to motor connection box, it could have been installed wrong from the start. Check for voltage drop across all breaker, disconnect switch, and controller connections, check connections in pump motor connection box.

Put clamp amp meter and a volt meter on system when pump is running.
You will need to know as much about the system as the guy who installed it to troubleshoot it.

Kurt