Three pin refrigerator thermostats?
 

Can anyone explain the internal circuit of a 3-pin refrigerator
thermostat such as a WDF-18 ? Thanks.


https://www.amazon.com/s/ref=nb_sb_n...tor+thermostat

Three pin refrigerator thermostats?
 

Davej wrote

Can anyone explain the internal circuit of a 3-pin
refrigerator thermostat such as a WDF-18 ? Thanks.

https://www.amazon.com/s/ref=nb_sb_n...tor+thermostat

One terminal is the common. That is connected to one or other of the other
two
terminals depending on whether the temperature is above or below the set
point.

Three pin refrigerator thermostats?
 

On Monday, February 11, 2019 at 1:53:44 PM UTC-6, Rod Speed wrote:
Davej wrote

Can anyone explain the internal circuit of a 3-pin
refrigerator thermostat such as a WDF-18 ? Thanks.

https://www.amazon.com/s/ref=nb_sb_n...tor+thermostat

One terminal is the common. That is connected to one or other
of the other two terminals depending on whether the temperature
is above or below the set point.

Oh, so what would a refrigerator need to apply power to when
it shuts off the compressor?

Three pin refrigerator thermostats?
 

Davej wrote
Rod Speed wrote
Davej wrote

Can anyone explain the internal circuit of a 3-pin
refrigerator thermostat such as a WDF-18 ? Thanks.

https://www.amazon.com/s/ref=nb_sb_n...tor+thermostat

One terminal is the common. That is connected to one
or other of the other two terminals depending on
whether the temperature is above or below the set point.

Oh, so what would a refrigerator need to apply
power to when it shuts off the compressor?

It doesnt, its just the way thermostats are usually done.

You see the same thing with oven thermostats too.

Its more obviously useful with room thermostats.

Three pin refrigerator thermostats?
 

On Monday, February 11, 2019 at 4:26:47 PM UTC-6, Rod Speed wrote:
Davej wrote:
Rod Speed wrote:
Davej wrote:

Can anyone explain the internal circuit of a 3-pin
refrigerator thermostat such as a WDF-18 ? Thanks.

https://www.amazon.com/s/ref=nb_sb_n...tor+thermostat

One terminal is the common. That is connected to one
or other of the other two terminals depending on
whether the temperature is above or below the set point.

Oh, so what would a refrigerator need to apply
power to when it shuts off the compressor?

It doesnt, its just the way thermostats are usually done.

You see the same thing with oven thermostats too.

Its more obviously useful with room thermostats.

Hmmm, I've just removed one from a dorm-sized fridge and
there was a wire on every terminal.

Three pin refrigerator thermostats?
 

"Davej" wrote in message
...
On Monday, February 11, 2019 at 4:26:47 PM UTC-6, Rod Speed wrote:
Davej wrote:
Rod Speed wrote:
Davej wrote:

Can anyone explain the internal circuit of a 3-pin
refrigerator thermostat such as a WDF-18 ? Thanks.

https://www.amazon.com/s/ref=nb_sb_n...tor+thermostat

One terminal is the common. That is connected to one
or other of the other two terminals depending on
whether the temperature is above or below the set point.

Oh, so what would a refrigerator need to apply
power to when it shuts off the compressor?

It doesnt, its just the way thermostats are usually done.

You see the same thing with oven thermostats too.

Its more obviously useful with room thermostats.

Hmmm, I've just removed one from a dorm-sized
fridge and there was a wire on every terminal.

Some thermostats do have an internal heater.
That reduces the hysteresis in the thermostat.
Bit counter intuitive why that approach works.

Now that you have it out, easy to use a multimeter
to see how that one uses the terminals.

Three pin refrigerator thermostats?
 

On Monday, February 11, 2019 at 5:26:47 PM UTC-5, Rod Speed wrote:
Davej wrote
Rod Speed wrote
Davej wrote

Can anyone explain the internal circuit of a 3-pin
refrigerator thermostat such as a WDF-18 ? Thanks.

https://www.amazon.com/s/ref=nb_sb_n...tor+thermostat

One terminal is the common. That is connected to one
or other of the other two terminals depending on
whether the temperature is above or below the set point.

Oh, so what would a refrigerator need to apply
power to when it shuts off the compressor?

It doesnt, its just the way thermostats are usually done.

Not likely, I bet there is a wire connected to all three terminals.
It may be part of a design so that the defrost heater is only powered
when the compressor is off.




You see the same thing with oven thermostats too.





Its more obviously useful with room thermostats.

It's not useful there, of all places. I never had a thermostat that
was more than a simple on/off switch for a home heating system. Some
have two stages, but that's another story.

Three pin refrigerator thermostats?
 

trader_4 wrote
Rod Speed wrote
Davej wrote
Rod Speed wrote
Davej wrote

Can anyone explain the internal circuit of a 3-pin
refrigerator thermostat such as a WDF-18 ? Thanks.

https://www.amazon.com/s/ref=nb_sb_n...tor+thermostat

One terminal is the common. That is connected to one
or other of the other two terminals depending on
whether the temperature is above or below the set point.

Oh, so what would a refrigerator need to apply
power to when it shuts off the compressor?

It doesnt, its just the way thermostats are usually done.

Not likely, I bet there is a wire connected to all three
terminals. It may be part of a design so that the defrost
heater is only powered when the compressor is off.

Makes a lot more sense to do that in the controller, not the thermostat.