working thermostats

[Boman]

Would someone explain to me why working thermostat will allow a dryer to get hotter when empty than it does when the dryer has a load in it?

I mean 155 degrees is 155 degrees, right? Why would the exhaust reach temps upward of 160/170?
I don't remember these things doing this a few years ago.

Now that I think about it, I had a hot plate I would test stats on. Good ones would open and close at the specified temps if I remember correctly.

[jeff1]

Would someone explain to me why working thermostat will allow a dryer to get hotter when empty than it does when the dryer has a load in it?

Wet clothing will absorb some of the heat, as the clothes become dry(er) the temp will change more like when running it with nothing.

jeff.

[Boman]

I understand moisture affects the heat, but still, 155 degrees is 155 degrees in my feeble old mind. I mean lokks to me like if a stat is rated to kick off at 155degrees, you pour 155 degree gravy, water, paint, etc on it and it should kick off a lot closer to the rated temp than what they do.

Just one of many things I may never understand

[jeff1]

Dryer thermostats are rated in degrees Fahrenheit which will be marked on the thermostat somewhere. This temperature will be identified by an "L" followed by the temperature rating. Eg. L130, L145, L155, etc. This is the temperature the normally closed contacts will open at. At room temperature, the main contacts will be closed and should show continuity when tested out of the circuit, if good.

Once opened by heat the contacts will remain open until it has cooled to a set temperature which will be dependant on the calibration it was designed to. This differential may also be displayed on the part and could be 10-40? or more. If displayed on the part, it would look something like L150-20, the 20 being the differential between cut out and cut in.

More modern dryers may use a SPST (single pole, single throw) thermostat for temperature control which may also contain a bias heater. On these, two terminals for the bias heater connection appears at the top of the thermostat housing and only perform that one function when powered of changing the temperature at which the thermostat operates.

jeff.