Motor overload issues

[ashhardy]

I have an issue with a three phase submersible pump. The pump is controlled via a 55v control panel. The panel consists of the mains isolator, the 240 - 55v transformer for the control circuit, relay, contactor and overload. The pump works off three floats, one start one stop and one high level alarm. All floats work as supposed to and the control circuit seems to be working correctly, as in when the start float triggers the relay engages as does the contactor. The pump will run for a minute the the overload triggers and disengages the contactor. My first suspicion was that the pump that was slightly seized due to the visual condition, the pump has been replaced with a new three phase Lowara dirty water pump. This did not resolve the issue and the overload behaved the same with the new pump installed. I replaced the overload and contactor with a direct replacement and the overload still behaves the same.

I am looking for advice on my next point of call to investigate as i have no experience with industrial pumps or pump wiring.

Thank you in advance for any help.

Pictures and more info can be added if required.

 

[Darkwood]

Check motor rotation is correct, this may seem a stupid thing as its pumping the right way but some pumps will pumps one direction regardless of phase sequence although very inefficient in one direction which can see O/L conditions.

Looking at the shape of the pumping vanes sometimes is also misleading as it can work the opposite way to which common sense would denote.

Finally as with all these kind of questions.. if your not experienced in motor controls and set-ups then why have you taken on this work?

You may have already cost the client unwanted outlay on parts that are functioning perfectly.

What does your clamp meter say the pump is pulling, are the phases balanced etc etc .

 

[Marvo]

What does your clamp meter say the pump is pulling, are the phases balanced etc etc .

As DW says, check the running current and compare it with the manufacturers figures and check rotation. Just for an encore you might as well check the insulation readings. Also check all 3 phases are reaching the pump. Finally check the head pressure and make sure there's no blockage on the suction side either.

 

[Knobhead]

It could prove a little difficult to check the supply at the motor, it’s a sealed submersible.

As for the rotation it usual to check the starting reaction.

As has been said check the current for O/L and balance, voltage for balance also do IR and CR checks to the motor and cable. You will only be able the do IR to earth, do not try to open the motor.
When checking the voltage, do so on the O/P this should show up any problems with the contactor and O/L’s

You don’t say what make the starter is so a photograph would help.

Also as has been said, why take on work you are not competent to do?

 

[ashhardy]

Firstly gentlemen. Thank you all for your quick and helpful response. Apologies for my initial rather nondescript post. As for my competency it was more a question of confidence and needing some moral support. As although I have installed pumps and pump panels I have NO experience of fault finding on them. If I could figure how to attach a photo you will see the initial installation was not executed to most peoples standards and more resembled a spiders web than any panel I have ever seen or installed, thus making fault finding slightly more difficult than the task already was.

As you all suggested and I should have really outlined in my first post. All the obvious points were covered re new pump spinning right way, no blockages in the pipework, etc. All readings were conclusive enough to suggest that the pump was fit for purpose and the overload and settings were correct for the installation.

As for peoples kind concerns for my clients financial outgoings, the contactor and overload was sourced out of our stores and the pump was a spare we have for such emergency's. As after a VI on the pump itself, replacing the pump turned out to be right avenue to venture down as the pump was slightly seized (not enough to not run) and as a result had been pulling too much current for some time and scorched the overload, which turned out to be incorrectly rated for the pump anyway.

The outcome was as follows: The old pump had been in place almost longer than I have been alive, at sometime the contactor and overload had been replaced and was not providing the correct level of protection for the pump. The build up of rust and other foreign objects on the pump had led the pump to pull too much current and take out the overload.

During the process of which I was replacing the old pump with a new one and replacing the contactor and overload to provide the right level of protection a temporary pump was put in place to clear the reservoir and prevent further flooding of the building.

Upon the commissioning of the new pump (despite being fully submerged) the overload kept blowing. This transpired to be the lack of water above the new pump. After speaking to Lowara I learnt that the pump requires a minimum volume of water to run effectively (everyday's a school day). So although the new pump was fully submerged in water there is a required amount of water to enable the pump to work within the parameters. Consequently the float levels were corrected and once the reservoir had filled we ran the pump all day without issue and re checked all readings and calibrated the overload accordingly.

If any of you have made it to the bottom of this vast expanse of text dribble I thank you for your commitment and for those who were asking why I took this job on ill will enlighten you a little about myself as I'm sure I will be needing peoples assistance again at some point in time.

I am a fully time served apprentice trained electrician (AM2, 2361, 2362, NVQ3) After leaving college I gained my 2391. I am fully up to date with my 17th edition and currently working towards my Bridge course.

I work for the Chapter of York as head electrician. The Chapter of York own York Minster Cathedral (in York) along with almost 50 residence property's, three schools, large offices, library's and period buildings within the precinct.

I am predominantly a domestic and commercial electrician although with some light industrial experience. Everything electrical in the Chapter falls under my remit, therefore when this pump failed despite not having any experience with fault finding on motor circuits I have to fix it. I believe in adopting a can do attitude for everything and I like to push myself into areas of uncertainty as to learn and broaden my knowledge on my subject.

Thank you all again for your help. I hope to return the help one day and aid someone in these things that are sent to test us.

Regards. Ash

 

[electron1]

Thank you for the update

 

[Marvo]

Thanks for letting us know the outcome.

.......Upon the commissioning of the new pump (despite being fully submerged) the overload kept blowing. This transpired to be the lack of water above the new pump. After speaking to Lowara I learnt that the pump requires a minimum volume of water to run effectively (everyday's a school day). So although the new pump was fully submerged in water there is a required amount of water to enable the pump to work within the parameters.

I'm not sure I understand. Pumps often have a minimum head pressure requirement and a required NPSH, the first is to prevent impeller lift in multistage centrifugal pumps and the latter is to prevent cavitation of the fluid being pumped. Is this what you're referring to?

Can you also give us the make and model number of the pump please just for reference?

 

[ashhardy]

Yeah sure, it will be week after next as I'm off on holiday tomorrow.

 

[silva.foxx]

55v control circuit? Surely 110v. Irrelevant to your fault but pricked my eyes.

Check your connections between the panel and pump, looking for degraded wires, loose or corroded conductors in ferrules/crimps/terminations/plugs/isolators. Check at glanding for signs of overflexing or chafing leading to internal cable damage.

Is the supply to the panel solid? Loosing a phase intermittently?

Any observations of contactor or relay chatter?

Is the cable out to the pump sized correctly?

Anything else supplied off the pump supply?

What FLC rating is your motor and overload?

Is your contactor a contactor... some contactors and relays look very similar! (Moeller)

Good luck.

 

[plugsandsparks]

Its working now was a lack of head issue

 

[silva.foxx]

... I learnt that the pump requires a minimum volume of water to run effectively (everyday's a school day). So although the new pump was fully submerged in water there is a required amount of water to enable the pump to work within the parameters. Consequently the float levels were corrected and once the reservoir had filled we ran the pump all day without issue and re checked all readings and calibrated the overload accordingly...

Regards. Ash

Obviously a lesson here... and float levels to be re-corrected, if plugsandsparks is reporting the job conclusion.