I'm prepairing to fill my small (12 gallon) closed loop system here in Minnesota. I want to have freeze protection without draining the system if I choose to shut the system down for a season.
I have seen home radiant systems that are using RV antifreeze in them, others with small concentrations of propylene glycol based hydronic fluid, but they are suplemental systems with forced air as a backup. Freeze concerns are very low. The small system above does not have a backup heat system.
I have access to 99.9% ethylene glycol which if I mixed at 60% with RO water would give me freeze protection to -60F. Am I missing any modifiers or additives that I should be concerned with in this application? I would prefer ethylene based over propylene based since ethylene glycol has a better heat transfer at a given concentration. My pure ethylene glycol base fluid has no silicates in it. It is the same base that we use for a large process heat boiler system at work, just not at 60% concentration, being that freezing is not a concern at work.
i would suggest 3 gallons then the balance water and check it with a glycol tester for ranging borrow it from work.... don't want to do to much cause the heat transfering drops as you add it to the water....and as long as the fluid is being circ'd you will never freeze it.. ok maybe 2 gallons well insulated on perimeter walls no raw piping on the outer walls of the space