# Motor OL relay tripping too low.



## Wirenuting (Sep 12, 2010)

Adjustable & Bimetallic? 
Are you talking about the class ~ 10-20-30~ settings?


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## Jarp Habib (May 18, 2014)

No, not the timing class settings. 

Specifically, this unit: https://www.imc-direct.com/product_p/c306gn3.htm

Trim screw dial adjusts amp rating depending on the installed heaters. The ones we have installed adjust between 18.7 and 30.7


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## JRaef (Mar 23, 2009)

If everything is working right, a single phasing situation will cause an OL relay to trip early, but if the currents were all balanced, that eliminated that possibility. I'm in the bad heater element camp on this one. Sometimes if they trip a lot, bi-metal strips will develop a "thermal memory" to where they don't go all way back to normal.


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## Wirenuting (Sep 12, 2010)

If you have the proper O/L’s installed and they are tripping early, replace the elements or go electronic. 
I don’t know about Eaton, but the SquareD electronic O/L retro kit works well but is a Pain to install.


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## CMP (Oct 30, 2019)

Jarp Habib said:


> I have an Eaton/CH starter with adjustable thermal overload relay & bimetallic heaters. Setpoint on the OL is 22.7 amps but it's tripping the OL at about 14. Motor megohms fine, and *each phase amps within ~0.2A of the same phase of the redundant alternate motor*.



What does that mean? Forget the redundant motor. How well are the voltages and currents of each phase, of the motor under test, balanced?


IEC style overload relays respond to unequal currents on each phase, is yours perfectly balanced? Are the line voltages balanced? Unequal line voltages result in unequal currents.


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## gpop (May 14, 2018)

If you are measure imbalance a quick and dirty way is to put all 3 phases in the same amp clamp.

if the overloads tripped on me once they would have been replaced as its a quick way to count that problem out. (i can always put them back if thats not the problem) On some you can power down the unit and knuckle touch the overloads to tell which one is hot. The ones i have seen do this normally have arcing,dirt between the overloads and the tabs they attach to.


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## micromind (Aug 11, 2007)

I've had trouble with bi-metal O/Ls doing this too. 

They seem to get weak over time even if not tripped and once they start tripping, they get weak faster. 

I've also had them fail to trip when they were supposed to, especially when the motor is single-phased.


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## paulengr (Oct 8, 2017)

micromind said:


> I've had trouble with bi-metal O/Ls doing this too.
> 
> They seem to get weak over time even if not tripped and once they start tripping, they get weak faster.
> 
> I've also had them fail to trip when they were supposed to, especially when the motor is single-phased.




Me too.

Eutectics do this when the operator hammers the motor over and over and vaporizes the solder out. Bimetallic are the same plus they drift over time as they seem to lose spring tension.

Only seen two eutectics fail to trip though. Had a goofy Square D that had one piece off to the side that was adjustable instead of 3 normal heaters where the mechanism jammed. Hard to explain and only seen one. And an Allen Bradley that was so full of dust that the eutectic worked but the mechanism itself was jammed shut. Once vacuumed out it was fine. That’s why I prefer them over bimetallics. And microprocessor over those. Haven’t seen enough RC failures to judge yet.


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## Roger123 (Sep 23, 2007)

micromind said:


> I've had trouble with bi-metal O/Ls doing this too.
> 
> They seem to get weak over time even if not tripped and once they start tripping, they get weak faster.
> 
> I've also had them fail to trip when they were supposed to, especially when the motor is single-phased.


Just had a single phasing event a couple of days ago, caused by an auto accident on the poco side. Out of 12 motors running at a water treatment plant found all the Allen Bradley over load tripped except two. Both the contactors where the overloads didn't trip were burned up.


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## JRaef (Mar 23, 2009)

Unfortunately eutectic alloy OL relays are going to be eliminated soon due to the RoHS* rules. It's time to embrace Solid State OL relays now.



*Reduction of Hazardous Substances, an international law requiring manufacturers to stop using HazMats like lead and cadmium, which are in the melting alloys.


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## Wirenuting (Sep 12, 2010)

JRaef said:


> Unfortunately eutectic alloy OL relays are going to be eliminated soon due to the RoHS* rules. It's time to embrace Solid State OL relays now.
> 
> 
> 
> *Reduction of Hazardous Substances, an international law requiring manufacturers to stop using HazMats like lead and cadmium, which are in the melting alloys.


What about single phase “Tac” switches? 
Any insight about their demise?


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## JRaef (Mar 23, 2009)

Not sure what a “tac” switch is. Single phase manual motor starter?


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## Wirenuting (Sep 12, 2010)

JRaef said:


> Not sure what a “tac” switch is. Single phase manual motor starter?


Yes, single phase manual motor starters.


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## paulengr (Oct 8, 2017)

IEC has gone to RC overloads on small stuff. On large equipment it’s microprocessor controlled. On the small stuff pretty much any MMS is similar. Almost all of it is being built by either Sprecher and Schuh in Poland or LSIS in Spain. Does not matter if the name on the outside is GE, Siemens, AB, CH, Schneider, etc...all built in the same two plants. The basic relay is about the same price as 3 eutectic overloads.

On larger equipment GE Multilin 269 used to be the way to go but it’s been discontinued and the replacement is crazy overpriced. On the low end with similar functions to GE is the Motortronics RX. On the high end (but still half of a GE 369) is the SEL-710. All of these are microprocessor relays. Switching over is relatively painless except in half height starters.

Finally many of my customers are waste water plants and paper mills. Anything constructed with silver especially and to a lesser degree zinc and copper gets eaten and destroyed by H2S fumes. We used to not have so many problems when solder was lead-tin and everything else was tin plated copper. I will accept the responsibility to be the adult and instruct my crews not to lick the wiring if the dumb European whiny babies will drop trying to enforce RoHS outside of Europe. The market is so small we can just let the Germans and Italians have it.


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## JRaef (Mar 23, 2009)

Wirenuting said:


> Yes, single phase manual motor starters.


 For now, the RoHS rules only apply to anything that ends up, or MIGHT end up in Europe, so since they don't really use those type of MMS devices there, they may not change. The problem however is that for those that use melting alloy heater elements, once the manufacturers stop selling them for other uses, they will likely stop making them at all. It may take a decade or two to be completely gone because of the vast installed base, so many of us may not be in the working world by then. But long before they are completely gone, they will get expensive.


8 states in the US are also following the RoHS model used in Europe, mostly those with the biggest cities or industrial bases; California, New York, New Jersey, Illinois, Indiana, Minnesota, Wisconsin and (for some reason) Rhode Island. But from what I was told, it ONLY applies to "electronics", whereas the RoHS rules for the EU were expanded to all electrical equipment.


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## jcaden (Oct 30, 2016)

How hot is the room and enclosure where the starter is located? Higher temperatures will cause earlier trips.


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## paulengr (Oct 8, 2017)

JRaef said:


> For now, the RoHS rules only apply to anything that ends up, or MIGHT end up in Europe, so since they don't really use those type of MMS devices there, they may not change. The problem however is that for those that use melting alloy heater elements, once the manufacturers stop selling them for other uses, they will likely stop making them at all. It may take a decade or two to be completely gone because of the vast installed base, so many of us may not be in the working world by then. But long before they are completely gone, they will get expensive.
> 
> 
> 8 states in the US are also following the RoHS model used in Europe, mostly those with the biggest cities or industrial bases; California, New York, New Jersey, Illinois, Indiana, Minnesota, Wisconsin and (for some reason) Rhode Island. But from what I was told, it ONLY applies to "electronics", whereas the RoHS rules for the EU were expanded to all electrical equipment.




Good thing you can buy an electronic overload for the cost of the heaters alone and with roughly 3-4 models cover the entire range of sizes where with heaters it was never practical to stock every size.


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