Thermostats

[mjoekingz28]

Can anyone explain to me how these operate? Is it mercury that reacts to temperature?

I can google, but I enjoy Bob's view on things.

Thx

 

[eljefino]

Wax that softens and a spring then opens the trap door.

 

[Kuato]

Depends on the model, but many use a bimetal strip - the two metals shrink or expand at different rates, tripping the circuit to turn the system on or off.


Mercury has dwindled in new stuff due to environmental concerns.

 

[440Magnum]

Originally Posted By: mjoekingz28
Can anyone explain to me how these operate? Is it mercury that reacts to temperature?

I can google, but I enjoy Bob's view on things.

Thx


What kind of thermostat? Car cooling system? Home heating/cooling system?

Car thermostats use a wax pellet that melts, expands, and pushes a plunger out to open a poppet valve and let coolant flow.

Home HVAC thermostats use everything from bi-metallic springs that tilt mercury capsules, bi-metallic springs that activate microswitches, to semiconductor sensors that signal a microprocessor to turn a system on or off.

 

[Pop_Rivit]

Wax melts at a specific temperature, expands, and pushes a rod out of a cylinder, opening the valve.

 

[djb]

Note that the mercury you see in old house thermostats are part of the level switch. The bi-metal coil reacts to the temperature by uncoiling, changing the orientation of the glass bulb. The mercury flows down and closes the electrical contact between the two posts.

The is completely different than the use of mercury in bulb thermometers, where the thermal expansion forces the metal up the very thin tube.

 

[OneEyeJack]

Mercury is magic.

 

[Pop_Rivit]

Originally Posted By: 440Magnum

What kind of thermostat? Car cooling system? Home heating/cooling system?

Since it's in the "automotive" general topics, I assumed the original poster was discussing automotive thermostats.