60's-vintage motor overload heaters

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Original on the left, purchased replacement on the right.

Questioning whether these are equivalent for an old General Electric motor  
starter overload (CR106).

Seems like slightly different approaches to get a bimetalic bend effect when  
a specified current flows through each of these. One requires a resistance  
wire to heat the metal, whereas the newer one incorporates the resistance in  
the metal? Is that what?s happening?

Does the element do the physical ?tripping? of the OL, or do these do  
nothing more than generate heat which heats up the separate mechanism that  
opens N.C. contacts?

Thanks.


Re: 60's-vintage motor overload heaters
In article < snipped-for-privacy@news.eternal-
september.org>, snipped-for-privacy@home.cow says...
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All they do is generate heat.  The part that is heated is in the block  
those things go in. That is where the actuall tripping goes on.  It  
trips a small switch and if you look at the block they go in you will  
see the screw terminals for the actual switch.  If you could turn them  
so they are outside the block, nothing would actually be heated and the  
switch would never trip.

  If you look at the bottom of them, near the screw holes you will see a  
set of letters and numbers.  That tells the rating of the heater (a  
chart will show the current range the overloads will trip at).  

I think you will find that you have 2 that are of greatly different  
current ranges.  The one with the wire is a much smaller current rating  
than the large flat one.


Re: 60's-vintage motor overload heaters
On 1 Jun 2016, Ralph Mowery wrote:

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You are correct! (c;

With the wire: 5.46A; without: 19.8A.

So they are compatible (will work in the same OL)?

Thanks.


Re: 60's-vintage motor overload heaters
In article < snipped-for-privacy@news.eternal-
september.org>, snipped-for-privacy@home.cow says...
Quoted text here. Click to load it

The main overload block is made to take a wide range of the heaters.  It  
has been a while ( I retired about 4 years ago)  but I think there were  
atleast 2 to 5 sizes of the GE overload blocks.  The heaters from one  
size will not fit the other sizes.  Each block will hold a lot of  
different size heaters.  

The way they are most often uses is that you have the motor starter
(relay) mounted vertically and the heater block is attached just under  
it.  The heater goes from the bottom contacts of the starter through the  
heater and then out to the motor (load).  You install the heater to  
match the current of the load.  

The heater heats up something in that block that trips a switch in the  
block.  That switch is in series with the motor starter coil and the  
stop/start switches and only carries the small current that activates  
the coil.  Most often the motor will be 480 volts 3 phase and the  
voltage for the coil and switch will be 120 volts.

While the numbers I am giving out are made up as I don't want to look  
them up, you may have a size 1 starter rated from 1/2 amp to 30 amps, a  
size 2 rated from 20 to 50 amps, and so on. You install the heaters in  
that range to match the load.



Re: 60's-vintage motor overload heaters

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Measure the resistances!


--  

John Larkin         Highland Technology, Inc
picosecond timing   precision measurement  

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