Contactors in Series, Solved but wanna see how other minds would look at it.

[garbo]

Pushing in contacts not 100% full proof. Sometimes contactors & starters movement gets sluggish and even with full power ( coil voltage ) will not pull in all contacts. We had over a hundred Danfoss VFD'S that were exercised every month during ATS testing. Had to replace at least 8 GE junk M2 contactors every year that while receiving 118 to 121 volts to coil would not fully seal contacts. So prefer to perform testing with power on. Usually quicker. When a three phase motor is single phasing from lost of one phase and power travels thru a contactor & a starter will remove motor leads from last set of contacts then take voltage readings. I'm old school and prefer to use a Ideal Voltron tester because it places more load on the circuit. With a digital meter especially in a damp location and while only having one lead on a 480 volt source and other test lead in the air often will get 50 to 90 volt reading. Started out using a Simpson model 260 analog meter and old reliable Square D "Wiggee " tester. Found the Wiggees to work great troubleshooting lost of power on circuits.

 

[Errorsfordays]

What do you folks think of the "mindset" of non-voltage testing, like securing power and using an ohm meter to test contacts by manually pushing the starter in? It is "mindsets" that I'm really interested in here.

I think non-voltage testing is great for series circuits, but for any complex parallel circuits or test points spanning great distances, its slow or difficult to check. Personally, I wouldn't feel comfortable manually activating an energized contactor to test it(unless its low voltage), being that the circuit is faulty. I would have made a makeshift switch and wired it into where the level switch goes. But I agree with a previous poster, humming and no rotation, disconnect motor(out of the contactor at the local panel if the motor is hard to get to), activate circuit, test voltage everywhere.

 

[kwired]

What do you folks think of the "mindset" of non-voltage testing, like securing power and using an ohm meter to test contacts by manually pushing the starter in? It is "mindsets" that I'm really interested in here.

Manually pushing it in may not do the same thing as some mechanical failure does when relying on the solenoid to pull it in.

 

[kwired]

Personally, having never come across a "jammed" pump in the wild I would be inclined to focus on the control side of things.

I cannot imagine what would possess someone to come up with such a screwy setup in the first place though.

I've had city worker tell me about having jammed sewer lift station pump before, when they took it apart a mop head was jammed in it.

On the farms fertilizer pumps or even manure pumps that have been sitting a while since last use seem to be jammed quite a bit when you want to use them again.

 

[kwired]

That is, the remote contactor would not close completely electrically. The local contactor did not close electrically because the missing phase went to the coil. Closing the local contactor manually closed all three contacts, but there were only 2 phases.

?

If missing phase goes to the coil then the coil shouldn't draw current and won't pull the solenoid in at all on it's own.

 

[TwoBlocked]

?

If missing phase goes to the coil then the coil shouldn't draw current and won't pull the solenoid in at all on it's own.

That's right, the local contactor (the one downstream from the remote contactor which was only closing on two legs) was only getting voltage [Edit: being provided with voltage] on one terminal of the coil. That is why I needed to push it in manually. The local contactor coil was also providing backfeed voltage to the missing leg, which I did not do well in recognizing... I wanted sooooo badly to get my meter on both terminals of that coil, but decided not to risk it.

 

[TwoBlocked]

I think non-voltage testing is great for series circuits, but for any complex parallel circuits or test points spanning great distances, its slow or difficult to check. Personally, I wouldn't feel comfortable manually activating an energized contactor to test it(unless its low voltage), being that the circuit is faulty. I would have made a makeshift switch and wired it into where the level switch goes. But I agree with a previous poster, humming and no rotation, disconnect motor(out of the contactor at the local panel if the motor is hard to get to), activate circuit, test voltage everywhere.

Thanks for the reply. There's a time and place for everything.

I keep looking back at my "mindset" during different steps in troubleshooting to see how I might guide my thoughts better in the future. This is at a higher level than the actual troubleshooting techniques. That is, the mindset determines what techniques to use. There's a time and place for everything.

AND the environment can drastically affect the mindset... I was not at my best. The place is a sitshole.

Anyhoo, there was something I noticed at the very beginning, that I could not decide on and our fine folks here have not mentioned. There were two symptoms - The local contactor did not pull in electrically AND when pushed in manually the motor hummed without turning the pump. Were these two symptoms a result of the same fault, or different faults? I was unable to see during initial troubleshooting how they were related. My mindset wasn't at that level.

 

[TwoBlocked]

So here is a question for all you fine folks: When there are multiple symptoms, how likely is it that the same fault causes them all?

 

[garbo]

I've had city worker tell me about having jammed sewer lift station pump before, when they took it apart a mop head was jammed in it.

On the farms fertilizer pumps or even manure pumps that have been sitting a while since last use seem to be jammed quite a bit when you want to use them again.

You were lucky to never coming across a jammed pump. I spent 50 years in large plants and came across probably hundreds of jammed pumps from water, sewage, fat & grease, chocolate , oil, coolant , vacuum pump motors etc. First thing I did was if pump was on say a love joy coupling with a rubber spider would try to turn pump shaft then motor shaft to see if they were free. On pumps that bolt onto motors would try to turn the cooling fan on TEFC motors. Had our facilities and even outside vendors rebuild pumps that would not turn. I was the only sparky on second shift with 14 maintenance guys. A few lazy ones always insisted it was an e!ectrical problem whenever a pump did not run. Had t tell the boss that little pump turns. Yelp turns very hard while using a 24" pipe wrench on the 1/2 HP motor shaft. Told the boss he had two choices either have the lazy guy fix the pump problem or replace the 1/2 HP with a 25 HP motor that might be able to turn the jammed pump for a very short time. If pump was bolted to a motor would ring out the motor leads and compare readings & megger motor. If they were good then the pump had to be removed from motor for future checking. Nobody is perfect . Several times after replacing bearings on 1/4 to 250 HP motors myself & other sparkies did something wrong and either shaft did not turn or very hard to turn so we had to take end bells off to find our mistake.

 

[kwired]

You were lucky to never coming across a jammed pump. I spent 50 years in large plants and came across probably hundreds of jammed pumps from water, sewage, fat & grease, chocolate , oil, coolant , vacuum pump motors etc. First thing I did was if pump was on say a love joy coupling with a rubber spider would try to turn pump shaft then motor shaft to see if they were free. On pumps that bolt onto motors would try to turn the cooling fan on TEFC motors. Had our facilities and even outside vendors rebuild pumps that would not turn. I was the only sparky on second shift with 14 maintenance guys. A few lazy ones always insisted it was an e!ectrical problem whenever a pump did not run. Had t tell the boss that little pump turns. Yelp turns very hard while using a 24" pipe wrench on the 1/2 HP motor shaft. Told the boss he had two choices either have the lazy guy fix the pump problem or replace the 1/2 HP with a 25 HP motor that might be able to turn the jammed pump for a very short time. If pump was bolted to a motor would ring out the motor leads and compare readings & megger motor. If they were good then the pump had to be removed from motor for future checking. Nobody is perfect . Several times after replacing bearings on 1/4 to 250 HP motors myself & other sparkies did something wrong and either shaft did not turn or very hard to turn so we had to take end bells off to find our mistake.

They built a new county jail a few years ago where I live. I did not go to the so called open house they had before they started to use it but had someone tell me the jail cell toilets design performance says they should be able to flush a bed sheet. Which very well might be true. I doubt the city sewer system can necessarily handle said sheet once it is in the system though. Something like lift station pump would be prime place for it to cause problems if it hadn't done so further up the line.

 

[TwoBlocked]

... the jail cell toilets design performance says they should be able to flush a bed sheet....

If you knot it up right, it won't go down. Um, uh, so I've been told.

 

[garbo]

They built a new county jail a few years ago where I live. I did not go to the so called open house they had before they started to use it but had someone tell me the jail cell toilets design performance says they should be able to flush a bed sheet. Which very well might be true. I doubt the city sewer system can necessarily handle said sheet once it is in the system though. Something like lift station pump would be prime place for it to cause problems if it hadn't done so further up the line.

Sounds worst then the research center of the hospital that I worked at. They had research animals in lowest basement level a good 70' below the ground. Rather the collect the bedding from cages they would wash them down the drain causing pumps to jam up and clogging the waste pipe where they had to hire a contractor with a huge vacuum truck and another truck to collect waste. Kept telling them that not only the waste pipe but pumps were undersized. After they replaced the waste pipe with a larger diameter and went from 7.5HP to 15 HP chopper pumps ( pump would cut up waste into small pieces ) no more clogged waste pipe. Loved when they told me that original plans called for larger pipe & pumps but they " Valued engineered it " smaller to safe money. At a large slaughter house that I worked out they were made to collect blood ( kills oxygen in water ) and undigested food & manure from going down into city drain pipe. They installed stainless steel vibrating screens and filled at least fifty 55 gallon drums of that smelly matter. They had heavy duty trash pumps in the basement that would chew up soda cans and handle maybe 1" pieces of bones.

 

[Jraef]

Humming motor should have been first clue for single phasing.

Bingo. As I was reading the description, I got to "bad contact in the starter" before they even finished describing the steps. If there are no fuses and no bad connections, that's all that's left.

 

[mtnelect]

How about the motor bearing are shot ?

 

[mtnelect]

They built a new county jail a few years ago where I live. I did not go to the so called open house they had before they started to use it but had someone tell me the jail cell toilets design performance says they should be able to flush a bed sheet. Which very well might be true. I doubt the city sewer system can necessarily handle said sheet once it is in the system though. Something like lift station pump would be prime place for it to cause problems if it hadn't done so further up the line.

I was in law enforcement for a while, when I graduated from the academy you where required to spend time at Main Central Jail. The inmates had a term called "Curtesy Flush".

 

[TwoBlocked]

How about the motor bearing are shot ?

Yep! Or broken rotor bars. Just because it hums, doesn't mean it's single phasing.

 

[ptonsparky]

Yep! Or broken rotor bars. Just because it hums, doesn't mean it's single phasing.

So the first thing I should think about is broken rotor bars and tear down looking for them?
Bearings would show with amp meters but would also have confirmed the lost phase.

 

[TwoBlocked]

So the first thing I should think about is broken rotor bars and tear down looking for them?
Bearings would show with amp meters but would also have confirmed the lost phase.

Sure, take what I post to the point of ad absurdum.

 

[Ken_S]

I've always started troubleshooting problems like this with an amp meter.

 

[TwoBlocked]

I've always started troubleshooting problems like this with an amp meter.

Thanks! This is the kind of reply I was looking for - a different mindset. Part of the problem I have in trouble shooting at these nasty facilities is being sure my meter probes are making good contact due to corrosion. With a clamp on, you don't worry about that. And also, measuring voltage and/or resistance doesn't mean you have a functioning circuit; having current does.