60's-vintage motor overload heaters

[DaveC]

http://imgur.com/yIx0dC6

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.

 

[DaveC]

On 1 Jun 2016, Ralph Mowery wrote:

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.

You are correct! (c;

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

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

Thanks.

 

[Ralph Mowery]

In article <0001HW.1CFFE1A000174A8F114D213CF@news.eternal-
september.org>, not@home.cow says...

http://imgur.com/yIx0dC6

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.

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.

 

[Ralph Mowery]

In article <0001HW.1D00060A001FD374114D213CF@news.eternal-
september.org>, not@home.cow says...

On 1 Jun 2016, Ralph Mowery wrote:

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.

You are correct! (c;

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

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

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.

 

[John Larkin]

On Wed, 01 Jun 2016 20:38:08 -0700, DaveC <not@home.cow> wrote:

http://imgur.com/yIx0dC6

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.

Measure the resistances!


--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com