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Old 12/05/2007, 06:07 PM   #1
kenargo
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Join Date: Jan 2007
Location: Redmond, WA
Posts: 8,151
AC3 Best practices

After reading some recent threads I thought that this may be appropriate; a collection of best practices to ensure a health and happy tank.

I'll start with a few that I use:

Rule: Program with failure in mind - You should avoid code with open ended conditions

Bad:
If Temp > 80 Then COL ON
If Temp < 77 Then COL OFF

Better:
If Temp > 80 Then COL ON
If Temp > 84 Then COL OFF // Something may be wrong
If Temp > 83 Then ALM ON // Notify me
If Temp < 77 Then COL OFF

Reason and Fix: When a condition is open ended then the sky is the limit on the damage that can be caused. Since, under most conditions a tank should not get so out-of-wack that readings are off-the-scale of what would be reasonable add code to handle the unexpected (e.g., if you keep your tank between 75-77 then it would be VERY unlikley that the temp would ever reach < 72 or > 80 so code as such. Add code to handle the unexpected; (using the above example) if the temp > 80 then it may be more likley that something has failed, shutting down things may be the best solution and let the human figure it out.



Rule: Adjust heaters/chillers (if adjustment is possible) to have a threshold slightly more/less than the AC3.

Reason and Fix: If a timer gets stuck in the ON state then the device may be able to assist in keping the tank under critical conditions. A stuck heater, set slightly above AC3 setpoint is less likley to cause a problem than a heater set to 90 and stuck on.



Rule: Use an alarm timer

Reason: An alarm is active notification; something gets turned on (a buzzer, a light, email, pager, etc). An alarm gives that tank an ability to yelling when something may not be quite right.


Please add the things that you do to protect from tank meltdown!


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