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tgarde
05-12-2003, 08:04 PM
Greetings,

I am a lay person who likes to take things apart just to see how they work. Kind of like when you were a kid but now, when you put them back together, most of the time it still functions. In my firestation, we have a fridge that froze everything in the refrigerator. Obviously the thermostat was stuck in the on position. When we had a service tech come out he replaced the thermostat. We proceded to take apart the old part too see how it worked. And here is where I decided to ask the experts to see how the damn thing works. Keep in mind that the fridge was at least 10 yeast old.

The insulated tube(copper wrapped with a silver metal), attatched to the diaphram(?) Had a pressurized gas in it. Was that just air?

We assumed that when the gas in the tube absorbed heat, it expanded and pushed the diaphram(attatched to a inverted copper plate) which pushed a pin which closed a circuit to then turn on the compressor. Were we close with that assumption?

By turning the knob on the front, the distance between the copper plate and the pin got larger or smaller. This of course ment the compressor would come on faster or delay a little for a warmer invironment. How close were we on that one.

We did notice that there was some black charing to the circuitry in the insulated plastic switch (which looked like it plugged into something). A copper plate in that unit had a hole burned through it from the contact point next to it. There was the problem I am assuming.


Thank you for taking the time to answer my questions. There are probably a lot of different thermostats out there but I am hoping that this one sounds familiar to someone.

Todd

chemi-cool
05-12-2003, 10:05 PM
hi todd,
what kind of a fridge is this, one door with asmall freezer isside at the top or is it a two doorswith the freezer at the top?
where is the end of the thermostate connected to?

chemi

tgarde
05-12-2003, 10:48 PM
It was two door with the freezer on the top and a seperate thermostat for the freezer. As far as where the end of the thermostat was connected, I am not sure as we only saw the removed part.

Thanks!

Brian_UK
05-12-2003, 11:17 PM
Originally posted by tgarde
The insulated tube(copper wrapped with a silver metal), attatched to the diaphram(?) Had a pressurized gas in it. Was that just air?

No, the gas in the tube was a refrigerant that would expand when warmed to activate the switch.


We assumed that when the gas in the tube absorbed heat, it expanded and pushed the diaphram(attatched to a inverted copper plate) which pushed a pin which closed a circuit to then turn on the compressor. Were we close with that assumption?
Yup, spot on.


By turning the knob on the front, the distance between the copper plate and the pin got larger or smaller. This of course ment the compressor would come on faster or delay a little for a warmer invironment. How close were we on that one.
My word, we'll have you trained up yet :D , another correct answer.


We did notice that there was some black charing to the circuitry in the insulated plastic switch (which looked like it plugged into something). A copper plate in that unit had a hole burned through it from the contact point next to it. There was the problem I am assuming.
Yes, it looks like the switch contacts welded togehter after years of switching the compressor start up load. Nothing too uncommon with that I'm afraid.

Depending on the type of thermostat the 'plug-in' bits are probably meant to accept push-on wiring terminals.

Anyway Todd, I hope you enjoyed your little science project and that the beer is at the correct temperature again now. ;)

tgarde
06-12-2003, 01:50 AM
All is well and thanks for the confirmation!

Todd