Controlling a boil with a PID

bgrubb7 · May 9, 2008

I have read a lot of posts talking about operating an Electric Boil kettle using a PID in manual mode by adjusting the duty cycle up or down to control a boil. Why can't you just set the temp at 212 or a little higher, and let the PID do the work?

mr x · May 9, 2008

If you set it over 212 in an mlt, it will never shut off. Setting to manual and picking an output once you know your equipment is a better way to go if you want to boil.

That should read 'If you set it over the boiling point...'

lustreking · May 9, 2008

Boiling is boiling. You can't control the temperature of a boil, simmer to full-rolling should be the same temperature. What you want to control is the rate of the boil.

bgrubb7 · May 10, 2008

That's sort of what I originally thought. A boil physically cannot be hotter than 212. Then why do I get different results with my analog thermo? At a 212 reading, I have a gentle boil, but I can crank my flame up for a vigorous boil, and then get a 215 to 220 reading. I do calibrate my thermo to ice water before I brew. Is my thermo just not accurate or am I missing something here?

littlehop · May 10, 2008

You're not brewing in death valley are you?

Bobby_M · May 10, 2008

I suspect maybe your thermo is reading 3 degrees too high.

mr x · May 11, 2008

bgrubb7 said:
That's sort of what I originally thought. A boil physically cannot be hotter than 212.

You're talking about pure H20 at sea level air pressure(1 atmosphere). Anything else will yield different numbers.

Controlling a boil with a PID

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Controlling a boil with a PID

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