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two power resistors as element

B

Bruce Raymond

Jan 1, 1970
0
One thing missed in all of the discussions so far is that once
the water reaches 100 degC you have to dump in a *lot*
more heat to change its state from liquid to gas. I'm too
lazy to go look up the energy required for the state change,
but it's substantial.

- Bruce Raymond
 
N

nospam

Jan 1, 1970
0
I'd not expect
any design to get much beyond perhaps 10:1 (you were pushing 26:1 with your
experiment...).

Well yeah I know I was pushing it, some here seem to think the resistors
will vaporise as soon as you switch on.

I already ran the same resistor at 10 x rated in water and predicted it
would eventually fail from lead corrosion.

For 26 x rated I figured there would be too much localised boiling so went
for oil which likely offers significantly less cooling.

The resistor is wire wound on something then coated with a thin layer of
cement or ceramic loaded paint or something.

I would like to have tried one of the green glazed ceramic types, but
didn't have a suitable value and power supply kicking around.
 
R

Roger Hamlett

Jan 1, 1970
0
nospam said:
Well yeah I know I was pushing it, some here seem to think the resistors
will vaporise as soon as you switch on.
Yes. You will see, that with the right resistors, I am one of the people who
believe it is probably possible, though like you, also expect corrosion of
some form to be the most likely failure if the overload is 'reasonable'.
I already ran the same resistor at 10 x rated in water and predicted it
would eventually fail from lead corrosion.
Fair enough.
For 26 x rated I figured there would be too much localised boiling so went
for oil which likely offers significantly less cooling.

The resistor is wire wound on something then coated with a thin layer of
cement or ceramic loaded paint or something.

I would like to have tried one of the green glazed ceramic types, but
didn't have a suitable value and power supply kicking around.
You should try a much bigger one (evil grin - pictures of a person boiling a
300 gallon oil tank, with a couple of hundred watt 1 ohm resistors in
series, connected directly to the mains...). :)

Best Wishes
 
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