Leaddog,
Thanks for the information. My 80 also runs a delta of about 10* from the Controller to the water output virtually all the time. I do believe that I've solved my problem. I feel kinda stupid chasing this problem for almost a year and the solution was so simple.
I have one really big question for you, or anyone really. I have two 1000 gallon tanks sitting in my detached garage, right next to the boiler room. They are not hooked up yet. Convince me that I really need to hook them up for storage. I've just not gotten around to it and I can say that I'm really happy with my system without storage. I'm eyeing up the garage space I could free up if I got rid of these tanks.
Bill the Dog
What do you have the setpoint for the boiler set at?
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Glad you figured out the overheat problem, but ah... did you read my post, last year?