The best HT fluid

oldsolar

I have heard that some glycols leave a gummy film. I know that low temp RV type is sticky. The last thing I want in drainback (that I don’t dare use water in) is to have each cycle leave a gummy film. There seem to be many manufacturers and grades of solar HT fluid glycol. Any help on which HT fluid is the best or might dry the cleanest would be great.

Kevin_in_Denver_2

Gumminess is water soluble

Anything left on the inside of the pipe after drainback is by definition water soluble.



Therefore, the next time a gylcol-water solution is pumped through that pipe, it will dissolve.



You may worry that the gummy film would dry out and leave a residue. Don't.

Kevin_in_Denver_2

dp

hot_rod

In the Euro solar magazines

I see ads for chemical cleaners to remove baked on glycol sludge from collectors. They seem to learn solar and hydronic lessons a few years ahead of us I doubt they would develop and market a product if there wasn't a need for it.



A flat plate collector can reach 325 f or higher temperatures. Sending a slug of glycol to a hot surface like that doesn't seem like a good idea. Even the extreme temperature Tyfo brand glycols, formulated for evac tube stagnation, probably would not be happy under those conditions.



There should be a way to make plain water drainback systems work properly, they have been used for many years in extreme cold conditions.



I've been running a NexGen u tube style evac tube system on my small greenhouse for several years now. Plain water fill, we see temperatures below zero for a spell every winter. I mounted them landscape with a 1/4" to the foot slop to the array.



I was more curious about summer time stagnation and how the header insulation would handle that condition.