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					Originally Posted by  Wayne
					 
				 
				What kind of failures might occur with the contollers? Do they have backup safetys? 
			
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 They can be as simple or as complicated as you want. I was able to pick up a Tunze ATO used for a steal a few years ago but I run it plugged into my Neptune controller for some extra protection. I also use a kalkwasser reactor and there is some risk of raising the pH too high so I came up with this: 
Max Change 030 M      Then ATO OFF
If pH    > 08.60       Then ALM ON 
If pH    > 08.40       Then ATO OFF
If Switch1  OPEN       Then ATO OFF
If Switch1  CLOSED     Then ATO ON 
If Timer KAL = ON       Then ATO OFF