I am sorry for my long delay in replying. I want to thank you two, Hugo and Mlseim, your input was is very valuable and I appreciate your time.
I’m going to work on tapping existing thermistor lines in a week or two and I will let you know how it goes.
I’m using Sunearth TR0301 U controllers.
A very special thanks to you Hugo for making the Imp. I have been testing conversions of existing solar hot water systems to a more stable stagnation type, and having an imp in the attic sending me temps on piping while I sit in the mechanical room recording pressures has been a game changer for me. The imp is amazing.