Controlling a boil with a PID - Home Brew Forums
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Old 05-09-2008, 04:42 PM   #1
bgrubb7
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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?



 
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Old 05-09-2008, 04:48 PM   #2
mr x
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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...'


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Old 05-09-2008, 05:28 PM   #3
lustreking
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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.
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Old 05-11-2008, 01:01 AM   #4
bgrubb7
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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?

 
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Old 05-11-2008, 01:16 AM   #5
littlehop
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You're not brewing in death valley are you?
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Old 05-11-2008, 03:08 AM   #6
Bobby_M
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I suspect maybe your thermo is reading 3 degrees too high.
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Old 05-11-2008, 08:30 AM   #7
mr x
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Quote:
Originally Posted by bgrubb7 View Post
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.


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