DIYbanter - View Single Post - 60's-vintage motor overload heaters

Ralph Mowery

In article -
september.org, 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 wi 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.