# Overloads



## cdnelectrician (Mar 14, 2008)

I was talking to an engineer from a company that sells cutler hammer starters and other equipment the other day and we got into the subject of overload settings. I have always set my overloads to 125 % of the FLA on the motor nameplate (taking into account the service factor of course).

He insists that the newer IEC overloads take that into account and that you must set the OL for whatever the FLA of the motor it is protecting without adding 125 %. 

I'm not so sure I buy it!:001_huh:


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## Grimlock (Aug 4, 2009)

Better ask Cutler Hammer tech support. 1-800-326-9513. Let us know what they say.


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## sparky105 (Sep 29, 2009)

cdnelectrician said:


> I was talking to an engineer from a company that sells cutler hammer starters and other equipment the other day and we got into the subject of overload settings. I have always set my overloads to 125 % of the FLA on the motor nameplate (taking into account the service factor of course).
> 
> He insists that the newer IEC overloads take that into account and that you must set the OL for whatever the FLA of the motor it is protecting without adding 125 %.
> 
> I'm not so sure I buy it!:001_huh:


go to 28_306 -(1) that's our code book
2002 edition I haven't splurged on the new 09 it's like $150.


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## Bob Badger (Apr 19, 2009)

In my opinion we are never supposed to add 25% to the FLA for overload selection.


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## sparky105 (Sep 29, 2009)

our code reads 

"(1)Overload devices responsive to motor current, if of the fixed type shall be selected or rated or, if of the adjustible type, shall be set to trip at not more than the following

a) 125% of the full load current rating of a motor having a marked service factor of 1.15 or greater: or

b) 115% of the full load current rating of qa motor which does not have a marked service factor or where the marked service factor is less than 1.15

(2) where a motor overload device is so connected that it does not carry the total current designated on the motor nameplate, such as for wye-delta starting , the percentage of the motor nameplate current applying to the selection or setting of the motor starter shown in the motor starter manufacturer's overload selection table."


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## Bob Badger (Apr 19, 2009)

So you can (and I bet we can too) add 15 or 25% but do not have to as opposed to the conductors which must be sized 25% higher.


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## fraydo (Mar 30, 2009)

sparky105 said:


> our code reads
> 
> "(1)Overload devices responsive to motor current, if of the fixed type shall be selected or rated or, if of the adjustible type, shall be set to trip at *not more than* the following
> 
> ...





Bob Badger said:


> So you can (and I bet we can too) add 15 or 25% but do not have to as opposed to the conductors which must be sized 25% higher.


I agree with Bob. IMO the phrase _not more than_ sets the maximum limit at which to set the OL's but precludes it from mandating the 15% or 25%.


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## sparky105 (Sep 29, 2009)

fraydo said:


> I agree with Bob. IMO the phrase _not more than_ sets the maximum limit at which to set the OL's *but precludes it from mandating the 15% or 25%.*


I think that that is the magic statement and I have never interpreted the code like that thank you for the enlightenment.


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## fraydo (Mar 30, 2009)

I've been enlightened here by many , glad I could reciprocate!


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## cdnelectrician (Mar 14, 2008)

sparky105 said:


> our code reads
> 
> "(1)Overload devices responsive to motor current, if of the fixed type shall be selected or rated or, if of the adjustible type, shall be set to trip at not more than the following
> 
> ...


Yep! Very familiar with that rule, and I have always been taught to go by it. That was my argument with him. And when I used to do a lot of motor controls at my last company (MCC retrofits etc.) The inspector always checked for the FLA of the motor and that the O/L was set to 125% of the nameplate FLA. So, do I really want to argue with an inspector?:blink:


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## captkirk (Nov 21, 2007)

Nice to see that we still get an occasional helpfull thread.....​


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## Ray Cyr (Nov 21, 2007)

cdnelectrician said:


> Yep! Very familiar with that rule, and I have always been taught to go by it. That was my argument with him. And when I used to do a lot of motor controls at my last company (MCC retrofits etc.) The inspector always checked for the FLA of the motor and that the O/L was set to 125% of the nameplate FLA. So, do I really want to argue with an inspector?:blink:


I'm hoping that the inspector was checking to make sure that the O/Ls were _not_ set _above_ 125% and not checking to make sure they were set _at_ 125%. Why would he care if they were set lower? That would just give better protection for the motor.


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## Ray Cyr (Nov 21, 2007)

cdnelectrician said:


> I was talking to an engineer from a company that sells cutler hammer starters and other equipment the other day and we got into the subject of overload settings. I have always set my overloads to 125 % of the FLA on the motor nameplate (taking into account the service factor of course).
> 
> He insists that the newer IEC overloads take that into account and that you must set the OL for whatever the FLA of the motor it is protecting without adding 125 %.
> 
> I'm not so sure I buy it!:001_huh:


Just today I was reading the specs on some O/Ls (I don't remember which brand) and in the specs it said that the relay would trip at 125% of the selected setting.


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## TheRick (Apr 13, 2008)

Many of the new solid state overload relays do indeed take the service factor into account, and some (I know GE does) have an adjustable service factor. One dial for the FLA and one for the service factor, you simply set the FLA of the motor, and set the second dial for the service factor of the motor.


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## John Valdes (May 17, 2007)

How would the overload *know* what the service factor is? :whistling2: Not all motors have the same service factor. OLR's cannot automatically adjust for SF. Always set the OLR to the FLA.
Motors should not be run in the service factor. The service factor is there for temporary overload protection of the motor. Ideally, you want your motor to run at or below FLA.
There used to be a notion that the higher the service factor was, the better constructed motor you had. In reality, the motors plated with high service factors had lower FLA's. It was just a marketing ploy by some motor manufacturers. Check the nameplates on a few motors and you will see. 



TheRick said:


> Many of the new solid state overload relays do indeed take the service factor into account, and some (I know GE does) have an adjustable service factor. One dial for the FLA and one for the service factor, you simply set the FLA of the motor, and set the second dial for the service factor of the motor.


I hope this adjustable service factor dial is also connected to an internal trip timer. See above for the details.


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## sparky105 (Sep 29, 2009)

cdnelectrician said:


> Yep! Very familiar with that rule, and I have always been taught to go by it. That was my argument with him. And when I used to do a lot of motor controls at my last company (MCC retrofits etc.) The inspector always checked for the FLA of the motor and that the O/L was set to 125% of the nameplate FLA. So, do I really want to argue with an inspector?:blink:


It's not arguing if you can convince them they are right but that you are also right because the code reads.... I have had some very good debates and sometime it goes my way sometimes theirs


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## cdnelectrician (Mar 14, 2008)

Ray Cyr said:


> I'm hoping that the inspector was checking to make sure that the O/Ls were _not_ set _above_ 125% and not checking to make sure they were set _at_ 125%. Why would he care if they were set lower? That would just give better protection for the motor.


That's a good point! I am not sure!


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## RIVETER (Sep 26, 2009)

cdnelectrician said:


> I was talking to an engineer from a company that sells cutler hammer starters and other equipment the other day and we got into the subject of overload settings. I have always set my overloads to 125 % of the FLA on the motor nameplate (taking into account the service factor of course).
> 
> He insists that the newer IEC overloads take that into account and that you must set the OL for whatever the FLA of the motor it is protecting without adding 125 %.
> 
> I'm not so sure I buy it!:001_huh:


Don't buy it.


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## cdnelectrician (Mar 14, 2008)

RIVETER said:


> Don't buy it.


Yea, I need to read some MFG's literature. When setting O/L's depending on the application I think it's safe to set them at 125%. I would hate to set an overload too low, say on a pump where the load will be changing all the time. The whole reason that this issue came up with this guy was because of a job I had completed awhile back. There were 2 new air handling units being installed in a mechanical room, the company I was working for ordered the starters from the company this engineer worked for.

When I got the starters on site, I noticed the O/L's were too small for the motors I was working on (this includes the 125%) they could have been set for the nameplate value of the motor but no more.

Notified my boss of the issue, and he said go ahead and install the starters and the O/L's will get changed later. Well, I got a call from the engineer who works for the company that sells these starters.

He insisted that the overloads need not be adjusted to 125% of the FLA. So, it was decided that the overloads shipped with the starters would not get changed.

Guess what? I get a call on a friday afternoon that the O/L's are tripping out and that I have to go change them. I don't mind, I am getting OT but for some reason the boss makes it sound like it's my fault.

I will add that I checked both motors with a megger, checked the inrush and running amps with my clamp meter AND had the HVAC tech check the belt tension and fan bearings. Everything was ok. The O/L's were too small. So if said O/L's take into account this 125% why did they keep tripping?


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