# Nema motor contactars and overload relays



## Coolelectroguy (Nov 13, 2012)

Does anyone know how to size overload relays on nema staters or the. Meaning of w49 heater elements or j41 or w41? For example? Like what's the diffrence. Between them? Whats between nema and iec ? besides the fact that's nemas seem to be a longer lasting contacter ?


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## HARRY304E (Sep 15, 2010)

Coolelectroguy said:


> Does anyone know how to size overload relays on nema staters or the. Meaning of w49 heater elements or j41 or w41? For example? Like what's the diffrence. Between them? Whats between nema and iec ? besides the fact that's nemas seem to be a longer lasting contacter ?


Look here.http://www.southlandelectrical.com/AllenBradlyHeaterTables.asp?url=IND*Allen Bradley Overload Relay Heater Tables For Bulletin 709 & 509*

The Allen Bradley heater tables below are two of the most common used for sizing standard overload relay protection for Type N and type W heater elements. The old style type N heater elements are used with Bulletin 709 motor starters and Overload Relay Blocks. While the Type W heater elements are used with current Bulletin 509 motor starters and Overload Relay Blocks. 
The tables provide heater elements for Class 20 operation and are recommended for General Applications. The "Full Load Amps" listed in the tables are to be used for heater element selection. The rating of the relay in amperes a 40° C is 115% of the "Full Load Amps" listed for the Heater Number. 
*Note: * To select heater elements for non standard applications including those where the motor starter and the motor being controlled are not at the same ambient temperature, give us a call and talk to one of our knowledgeable sales staff who can help you with making the correct heater selection.


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## Coolelectroguy (Nov 13, 2012)

Thanx bro now I know why the overload kept tripping everything I would start up I need a bigger heater element w61 instead of w49


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## HARRY304E (Sep 15, 2010)

Coolelectroguy said:


> Thanx bro now I know why the overload kept tripping everything I would start up I need a bigger heater element w61 instead of w49


Welcome to ET...:thumbup:


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## Wirenuting (Sep 12, 2010)

Coolelectroguy said:


> Thanx bro now I know why the overload kept tripping everything I would start up I need a bigger heater element w61 instead of w49


What's the name plate on your motor?


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## D-Bo (Apr 15, 2012)

Many times the overloads are sized just right but upsizing is the best fix the maintenance man can come up with


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## JRaef (Mar 23, 2009)

D-Bo said:


> Many times the overloads are sized just right but upsizing is the best fix the maintenance man can come up with


 
.... by passing the problem on to the next guy that has to replace the motor later when it smokes and/or pull the new motor leads after they catch fire.

Motor Overload Heaters are NOT something to trifle with. They are the primary protection for the motor windings AND THE MOTOR LEADS. The CBs or fuses in a motor starter circuit are allowed to be over sized to allow for current spikes that happen when starting motors, but ONLY because the wires are being protected by the Overload Heater Elements against long-time over current. Playing around with over sizing them is *quite literally playing with fire*.

The procedure is, READ the motor nameplate, SELECT the heater element that matches it. IGNORE the demands to "tweak it up" unless YOU want to take responsibility for the damage that occurs. Believe me, when it happens, everyone who told you to over size the heaters will forget that the conversation ever took place and YOU will be left twisting in the wind...


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## D-Bo (Apr 15, 2012)

JRaef said:


> .... by passing the problem on to the next guy that has to replace the motor later when it smokes and/or pull the new motor leads after they catch fire.
> 
> Motor Overload Heaters are NOT something to trifle with. They are the primary protection for the motor windings AND THE MOTOR LEADS. The CBs or fuses in a motor starter circuit are allowed to be over sized to allow for current spikes that happen when starting motors, but ONLY because the wires are being protected by the Overload Heater Elements against long-time over current. Playing around with over sizing them is *quite literally playing with fire*.
> 
> The procedure is, READ the motor nameplate, SELECT the heater element that matches it. IGNORE the demands to "tweak it up" unless YOU want to take responsibility for the damage that occurs. Believe me, when it happens, everyone who told you to over size the heaters will forget that the conversation ever took place and YOU will be left twisting in the wind...


big reason why i am not a fan of the chincy "turn a dial and crank it up" style overloads. bimetallic heaters at least require a little bit of physical deterrent from tampering

edit: although i know it still does happen though. someone here posted a hilarious picture of a heater replaced with the mounting strap of a FS box. classic


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## Coolelectroguy (Nov 13, 2012)

Yea that's exactly what I didn't wanna do and the motor was old same as the machine no name plate to be found anywhere until I was able to measure the inrush current at 22 vac with in ten 15 seconds it's will trip. Just wanted to see where ican get answer from 3rd week in maintenance 21 years old food processing in other worn green as grass


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## D-Bo (Apr 15, 2012)

Coolelectroguy said:


> Yea that's exactly what I didn't wanna do and the motor was old same as the machine no name plate to be found anywhere until I was able to measure the inrush current at 22 vac with in ten 15 seconds it's will trip. Just wanted to see where ican get answer from 3rd week in maintenance 21 years old food processing in other worn green as grass


you need to know what this motor is designed to run at full load. inrush current and overloads are not related. the motor was selected to run a specific load and if its tripping overloads now after so long i wouldn't jump to any electrical conclusion until you look at the big picture i.e. mechanical load etc etc


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## John (Jan 22, 2007)

Go ahead and put the W 61 in to get the motor running, then take an amperage reading, do the calculations and then install the proper OL heaters.

Then be a nice guy and write down somewhere/someplace what you just found out for the guy that will some day follow in your foot steps.:thumbsup:


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## micromind (Aug 11, 2007)

D-Bo said:


> big reason why i am not a fan of the chincy "turn a dial and crank it up" style overloads. bimetallic heaters at least require a little bit of physical deterrent from tampering


Same here; I can't think of how many times I've installed one of the cheap IEC starters, set the O/L properly then had a callback that the motor is burnt up. 

Invariably, the O/L has been turned up, usually all the way up. But no one knows how this happened.....

And I get blamed for wrecking the motor. 

It's come to the point that I'll pretty much refuse to install any type of easily adjustable O/L, even the new-fangled NEMA ones.


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## Wirenuting (Sep 12, 2010)

JRaef said:


> .... by passing the problem on to the next guy that has to replace the motor later when it smokes and/or pull the new motor leads after they catch fire.
> 
> Motor Overload Heaters are NOT something to trifle with. They are the primary protection for the motor windings AND THE MOTOR LEADS. The CBs or fuses in a motor starter circuit are allowed to be over sized to allow for current spikes that happen when starting motors, but ONLY because the wires are being protected by the Overload Heater Elements against long-time over current. Playing around with over sizing them is quite literally playing with fire.
> 
> The procedure is, READ the motor nameplate, SELECT the heater element that matches it. IGNORE the demands to "tweak it up" unless YOU want to take responsibility for the damage that occurs. Believe me, when it happens, everyone who told you to over size the heaters will forget that the conversation ever took place and YOU will be left twisting in the wind...


We know there are several "classes" of O/L relays. But based on what the OP posted, I don't think he's to sure of what he's looking at. 
A reading of 22volts & trips in 15 sec?


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## D-Bo (Apr 15, 2012)

Wirenuting said:


> We know there are several "classes" of O/L relays. But based on what the OP posted, I don't think he's to sure of what he's looking at.
> A reading of 22volts & trips in 15 sec?


that threw me off too. theres really not much we can offer without the whole scoop


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## sparky 1965 (Nov 14, 2012)

Coolelectroguy said:


> Does anyone know how to size overload relays on nema staters or the. Meaning of w49 heater elements or j41 or w41? For example? Like what's the diffrence. Between them? Whats between nema and iec ? besides the fact that's nemas seem to be a longer lasting contacter ?


 W is the style (Allan Bradley) 49 is the overload rating in amps the Values are found in the AB catalog or inside the motor starter cover Nema is good IEC is garbage.


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## Coolelectroguy (Nov 13, 2012)

D-Bo said:


> that threw me off too. theres really not much we can offer without the whole scoop


I believe to be reading inrush but never ever able to see a steady current befor it tripped mechanicly the motor was just blowing wind so I wouldn't really understand why it would trip until I walked In today saying the overload where bad when I had just changed them
Yesterday so they went in with an IEC for conveince lol 
Sounds like I need a better understanding of stuff also a better knowledgeable co worker. I am set to believe that those 22 volts where to trip my fuses of it passed what it was set from 25. Other then three that I believe that the motor might be only pulling like 6 7 amps but still don't understand how it would trip an overload set for 19 amps. Or I
Im I not understanding the ratin of nema overloads ??


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## micromind (Aug 11, 2007)

To properly select O/L heaters, you need to know the FLA of the motor, the service factor (SF), the NEMA size of the starter, and the manufacturers table or amps vs. heater. If you don't have all of these, you cannot properly select the heaters. 

In some cases, there is a difference in ambient temperature at the motor and starter. If it's more than about 20ºF different, you'll need to size the heaters accordingly. 

I don't know of any manufacturer who uses actual amps for the heaters. It'd be nearly impossible to do so since any given heater will trip at a different amperage in a different size starter. 

Allen Bradley offers 3 types of heaters based on the trip class. Other brands very likely have the same types, but I usually use AB. 

1) The J type. this is a class 10 heater, meaning it will trip in 10 seconds at 6 times its current rating. These are useful for spindle motors, submersible pump motors and in my opinion, most IEC frame motors since they simply cannot handle the abuse that a NEMA frame one can. 

2) The W type. This is a class 20 heater; 20 seconds at 6 times its rating. This is by far the most common type. Any normal installation will use this heater. 

3) The WL type. This is a class 30 heater. This one will trip at 30 seconds at 6 times its rated current. These are commonly used with NEMA design D motors. Usually this design is used to power machines with huge flywheels that take forever to come up to speed. Care needs to be taken if they're used on a standard design A, B or C motor. 30 seconds at 6 X FLA is pushing even the best motor a bit. 

Selecting heaters is the only place the code allows (actually requires) the use of nameplate amps; all other calculations must be based on the tables given in article 430. 

It's not difficult to pick the right heater, but as noted, the consequences of the wrong one can be pretty serious.


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## Coolelectroguy (Nov 13, 2012)

micromind said:


> To properly select O/L heaters, you need to know the FLA of the motor, the service factor (SF), the NEMA size of the starter, and the manufacturers table or amps vs. heater. If you don't have all of these, you cannot properly select the heaters.
> 
> In some cases, there is a difference in ambient temperature at the motor and starter. If it's more than about 20ºF different, you'll need to size the heaters accordingly.
> 
> ...


Thank u bro very imformative answer something I was lookin for.


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## erics37 (May 7, 2009)

I'm doing a job at one of the fish plants here in town, they've got a few old Furnas starters that aren't being used, they want to repurpose them for some new equipment. I have a 5th term apprentice I've been towing around on this job, I traded him spots for a little bit and ran some conduit while I made him go crunch the numbers on the motor calculations for the stuff we're wiring up. Conductor size, short-circuit & ground fault protection size, overload size/setting, etc. He needed some real-world experience. :thumbup:


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