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Old 02-15-2011, 03:35 PM   #1
dtfeld
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I've blown a couple heater elements in my HLT by running it partially submerged or dry. Stupid. I want to put a little automatioin on it, but want some input.

I currently have a 10 gal cooler, so I thought about epoxying a capacitive prox to the inner wall and tuning it to "see" the water behind it.

However, going to an all SS 10 gallon system, and a capacitive prox won't work thru a metal wall. I'm thinking about something on a sight glass, but finding something small enough and mounting issues are problematic. I thought I could wire it in series with the main power heater relay to interupt power to the heating element if water goes below the set level.

Has anyone added this safety feature? What did you use and how did you wire it in? As always, pitures appreciated.

 
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Old 02-15-2011, 03:36 PM   #2
IrregularPulse
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You want a float switch wired in series with your control signal from the PID to the SSR.
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Old 02-15-2011, 03:38 PM   #3
Cpt_Kirks
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I never run the elements in my HLT when the drain valve is open. If you follow that rule, maybe some kind of switch connected to the valve?

ETA: Also, I have seen a two probe water level sensor that uses the metal pot as the common. I will look for the link when I get home.

 
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Old 02-15-2011, 03:39 PM   #4
dtfeld
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Float switch... Interesting. Have you sourced a food grade version?

Also, was trying not to have to cut another mounting hole in the thing. Prox switches are a "shoot through" solution.

 
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Old 02-15-2011, 04:16 PM   #5
bruin_ale
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Quote:
Originally Posted by Cpt_Kirks View Post
I never run the elements in my HLT when the drain valve is open. If you follow that rule, maybe some kind of switch connected to the valve?

ETA: Also, I have seen a two probe water level sensor that uses the metal pot as the common. I will look for the link when I get home.
Do you fly sparge? You don't lose heat during that? I haven't got my system up yet, but fully intend to run the HLT element while sparging to keep the temp of the sparge water where I want it. On my old propane system I only had a single burner, so while I was sparging I would move the burner to my boil kettle and get the boil started. By the time I was done sparging, the sparge water was probably 110-120 degrees at best.

 
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Old 02-15-2011, 04:19 PM   #6
bruin_ale
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Quote:
Originally Posted by dtfeld View Post
Float switch... Interesting. Have you sourced a food grade version?

Also, was trying not to have to cut another mounting hole in the thing. Prox switches are a "shoot through" solution.
http://www.oscsys.com/Stainless-Float-Switch.html

I think I've seen the same on e-bay for about $10..

 
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Old 02-15-2011, 04:20 PM   #7
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Quote:
Originally Posted by dtfeld View Post
Float switch... Interesting. Have you sourced a food grade version?

Also, was trying not to have to cut another mounting hole in the thing. Prox switches are a "shoot through" solution.
as in shoot through the wall of the cooler and detect water level? I admit I have limited experience with them, but have worked with them in the field and have never seen an application where a proximity switch shoots through a wall and sees something. It would see the wall and register. (In my limited experience)
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Old 02-15-2011, 04:25 PM   #8
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This one appears to be used in coffee urns so I would say food safe and likely temperature cooperative. Not a lot of info on it but you could probably get more details by contacting them.
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Old 02-15-2011, 04:26 PM   #9
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Quote:
Originally Posted by bruin_ale View Post
http://www.oscsys.com/Stainless-Float-Switch.html

I think I've seen the same on e-bay for about $10..
Wow cool find. You can get a dented (damaged) version for $8.99
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Old 02-15-2011, 04:34 PM   #10
carloski44
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This maybe what your looking for Kind of pricey at $135.00 from Automationdirect.com
http://www.automationdirect.com/stat...rox30mmuhz.pdf
A ultrasonic proximity sensor can measure fluid levels from the top down, would make a great little addition to an HMI screen to show liquid level in the HLT.
Let me know if you go that route how it works out for you I have played with them a little here and there but never actually used it in a application.

 
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