# Good troubleshoot today!



## erics37 (May 7, 2009)

Got a call from the fish plant today. One of their ice machines was down and they decided it was electrical.

The machine is basically a big cylinder with a rotating apparatus inside. The interior of the cylinder walls has refrigerant passing through it, making the inside surface really cold. The rotating thing spins around and squirts water on the inside wall, which then freezes into a thin sheet. Then the other end of the rotating thing comes by with a blade and scrapes it off, where it falls down into a giant ice bin below. It's a giant snow cone machine.

Anyway the motor operating the rotating part was out. They couldn't tell me what happened because they don't speak English very well, so I shut off the circuit and disconnected the T-leads from the starter. Switched the controls on, and the starter actuated just fine. Megged the motor leads while it was still disconnected, megged out just fine. Motor actually looked reasonably new anyway. Wired it back up to the starter, got my PPE, and started up the machine. Amp readings were more or less normal; B phase was a bit on the high side. Let it run for a few minutes, nothing happened.

Then I got out the multimeter and did a millivolt drop test across each pole of the starter. A phase and C phase were both losing about 500 mV from line side through to the T-leads. I've seen 500 mV or thereabouts plenty of times on those sort of things. When I tested B phase my meter read OL, so I switched it to regular volts (not mV) and found a voltage drop of 9 volts 

Ordered a new set of contacts for the starter. I've never seen a voltage drop that high across a contact. I thought it would have tripped the thermal much more quickly but when I looked closer, someone had oversized the O/Ls by like 300% so apparently it took a while for them to trip. Ordered a set of properly sized heaters as well. I'm hoping the starter isn't totally cooked inside there when I open it up.

Anyway I learned that test on this site so thanks y'all :thumbsup:


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## JRaef (Mar 23, 2009)

Nice catch. :thumbsup:


erics37 said:


> ... I thought it would have tripped the thermal much more quickly but when I looked closer, someone had oversized the O/Ls by like 300% so apparently it took a while for them to trip. Ordered a set of properly sized heaters as well. I'm hoping the starter isn't totally cooked inside there when I open it up.
> 
> Anyway I learned that test on this site so thanks y'all :thumbsup:


Most likely it WAS tripping, so bubba just upped the size of the heater elements a few times until the problem went away...
At 300% FLA for who knows how long, you may very well find that the innards of that contactor are cooked and crystallized now.


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## 8V71 (Dec 23, 2011)

Good job Eric, but you didn't mention anything about the new QC girl. Was she off today?


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## ponyboy (Nov 18, 2012)

Nice job. I'd kill for an interesting troubleshoot job. I used to get stuff like that all the time now it's just pipe pull terminate. Time to move on maybe. Anyways, good find


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## Cow (Jan 16, 2008)

When you get into the bigger starters that need contacts, an entire pump panel is the same price as just the contacts. Just ask Platt how much Nema Size 4 contacts are compared to an entire size 4 pump panel. $1700 either way On top of that, we already told them their pump panel pricing sucks too!

So, we got poking around online after one customer kept burning up starters because of a bad hydraulic pump overworking a motor. Come to find out there are aftermarket companies that make contacts that "meet or exceed OEM quality." I can get those $1700 contacts for less than $400. I'm going to try aftermarket next time I have a big starter smoke a set of contacts.


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## greenman (Apr 20, 2012)

ponyboy said:


> Nice job. I'd kill for an interesting troubleshoot job. I used to get stuff like that all the time now it's just pipe pull terminate. Time to move on maybe. Anyways, good find


It gets old fast, you can have my job,anytime


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## ponyboy (Nov 18, 2012)

greenman said:


> It gets old fast, you can have my job,anytime


Grass is always greener.


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## erics37 (May 7, 2009)

8V71 said:


> Good job Eric, but you didn't mention anything about the new QC girl. Was she off today?


She was at the shrimp plant. I was at a different plant.

But I did go over there to eat lunch in my van in the parking lot. She walked by and waved, which in my mind means she's ready for me to **** her in the ass right there in the middle of the street.

Realistically though she was probably just saying hi.


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## erics37 (May 7, 2009)

JRaef said:


> Nice catch. :thumbsup:
> 
> Most likely it WAS tripping, so bubba just upped the size of the heater elements a few times until the problem went away...
> At 300% FLA for who knows how long, you may very well find that the innards of that contactor are cooked and crystallized now.


We'll see :laughing:



Cow said:


> When you get into the bigger starters that need contacts, an entire pump panel is the same price as just the contacts. Just ask Platt how much Nema Size 4 contacts are compared to an entire size 4 pump panel. $1700 either way On top of that, we already told them their pump panel pricing sucks too!
> 
> So, we got poking around online after one customer kept burning up starters because of a bad hydraulic pump overworking a motor. Come to find out there are aftermarket companies that make contacts that "meet or exceed OEM quality." I can get those $1700 contacts for less than $400. I'm going to try aftermarket next time I have a big starter smoke a set of contacts.


Yeah replacement contacts are crazy :blink: Had to change a set of them out in a big Cutler Hammer starter last year. I had them priced out and almost ordered them for like $1500 but then I found a little plastic baggie sitting on a random shelf in their maintenance shop with a brand new set of the exact contact kit I needed :laughing:


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## JRaef (Mar 23, 2009)

Years ago I worked for Furnas Electric. They had a huge marketing program telling people to NOT buy aftermarket contact kits, especially those made by Hoyt. Then one day about 10 years later when I worked for Siemens, who bought Furnas, I was at the factory in Juarez, Mexico where the Furnas starters were being made and saw a huge shipment of contact sets come in for production. They came from Hoyt...


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## MTW (Aug 28, 2013)

Good find, Eric. :thumbsup: And of course: :nerd:


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## Safari (Jul 9, 2013)

erics37 said:


> Then I got out the multimeter and did a millivolt drop test across each pole of the starter. A phase and C phase were both losing about 500 mV from line side through to the T-leads. I've seen 500 mV or thereabouts plenty of times on those sort of things. When I tested B phase my meter read OL, so I switched it to regular volts (not mV) and found a voltage drop of 9 volts :


well I must admit iam not familiar with this test.so do you use DC milivolts or AC milivots.?
also when getting the milivolts test do you energize the contactor?

the only time I have come close to such a test is getting the milivolts of each segment of a commutator of a DC motor. 



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## just the cowboy (Sep 4, 2013)

nickson said:


> well I must admit iam not familiar with this test.so do you use DC milivolts or AC milivots.?
> also when getting the milivolts test do you energize the contactor?
> 
> the only time I have come close to such a test is getting the milivolts of each segment of a commutator of a DC motor.
> ...


Both sides of the contact should be at the same potential, if they are not making a good connection there will be voltage present. Real good test to see if contacts are good.


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## JRaef (Mar 23, 2009)

nickson said:


> well I must admit iam not familiar with this test.so do you use DC milivolts or AC milivots.?
> also when getting the milivolts test do you energize the contactor?
> 
> the only time I have come close to such a test is getting the milivolts of each segment of a commutator of a DC motor.
> ...


Here is a great description from member Brian John, (post #6 of this thread)

http://www.electriciantalk.com/f2/overloaded-loose-wires-5443/#post58934


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## Ultrafault (Dec 16, 2012)

nickson said:


> well I must admit iam not familiar with this test.so do you use DC milivolts or AC milivots.?
> also when getting the milivolts test do you energize the contactor?
> 
> the only time I have come close to such a test is getting the milivolts of each segment of a commutator of a DC motor.
> ...


It is called a FOP (fall of potential test). Not to be confused with the FLOP test (wherein eric flops out what nature gave him to see if the QC girl likes what she sees).


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## Big John (May 23, 2010)

I know I post this every time this topic comes up, but here's a good article on millivolt drop versus contact resistance.

What was your current, Eric? To show the importance of even very small numbers I like to do the math for the customer to explain how many watts the connection was dissipating. Just ran into a Magnablast breaker that was conducting all the load through the arcing-contacts and I figured that was literally about two kilowatts per phase, or the equivalent of having a 6,000 watt heater inside the circuit breaker.


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## erics37 (May 7, 2009)

Big John said:


> I know I post this every time this topic comes up, but here's a good article on millivolt drop versus contact resistance.
> 
> What was your current, Eric? To show the importance of even very small numbers I like to do the math for the customer to explain how many watts the connection was dissipating. Just ran into a Magnablast breaker that was conducting all the load through the arcing-contacts and I figured that was literally about two kilowatts per phase, or the equivalent of having a 6,000 watt heater inside the circuit breaker.


Small motor running at 480. I think the current on the phase in question was 2.8 amps at full load.

2.8 amps x 9 volts dropped = 25 watts or so. Like sticking a 25 watt light bulb in a tiny enclosed space for months or years.


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## erics37 (May 7, 2009)

nickson said:


> well I must admit iam not familiar with this test.so do you use DC milivolts or AC milivots.?
> also when getting the milivolts test do you energize the contactor?
> 
> the only time I have come close to such a test is getting the milivolts of each segment of a commutator of a DC motor.
> ...


In a perfect world, electrical contacts would have zero resistance. Of course it's not perfect; even brand new contacts have some resistance, and it gets worse the older and more used they get. Series resistors, of course, drop some amount of voltage depending on current flow.

This test is a quick and fairly easy way to determine how much voltage you're losing through a contact. Normally this is in the millivolt range for the small breakers and contactors I usually deal with. Load has to be energized to test (wear PPE of course). In this case I just tested the mV drop from line to load of each pole on the starter. I don't think I've ever seen one over 1000 millivolts, which is why my eyes bugged out when I saw 9 volts dropped through the contact.

The AC mV setting is the one to start use.


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## Safari (Jul 9, 2013)

erics37 said:


> In a perfect world, electrical contacts would have zero resistance. Of course it's not perfect; even brand new contacts have some resistance, and it gets worse the older and more used they get. Series resistors, of course, drop some amount of voltage depending on current flow.
> 
> This test is a quick and fairly easy way to determine how much voltage you're losing through a contact. Normally this is in the millivolt range for the small breakers and contactors I usually deal with. Load has to be energized to test (wear PPE of course). In this case I just tested the mV drop from line to load of each pole on the starter. I don't think I've ever seen one over 1000 millivolts, which is why my eyes bugged out when I saw 9 volts dropped through the contact.
> 
> The AC mV setting is the one to start use.



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## Safari (Jul 9, 2013)

nickson said:


> today while in the plant I decided to test this method out.then i realised my multimeter has 200mv as the higher range so anything above 200mv will not show
> I have posted a pic of the multimeter I use.guess I will have to get. a new meter to be able to get accurate results. I even explained the same method to fellow technicians
> 
> Sent from my HUAWEI Y210-0100 using Tapatalk 2




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