Antifreeze for hydronic systems

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Jackmartin

Excellent advice. Please do not mix éthylène and propylene glycol together. We had a fitter do that on a very large system and it took us three weeks to flush the black sludge it produced out of the system . The final bill 30 K so be careful. There are test strips you can get from the large water treatment companies that will tell you what kind of glycol is present, never assume anything
We had one fitter that thought he could just go to any automotive supply house and buy antifreeze " it is all the same"? He is in Heaven now and we all breathed a sigh of relief, may he rest in piece. All.the best Jack

John Abbott

Great advice I would add a few points, I by necessity used a lot of propylene glycol in closed loop geothermal systems the fluid temp at the heat pump would get below freezing as I learned when one tech didn't circulate the fluid enough to mix it thoroughly we used to buy it in 55 gallon drums some larger systems required over a hundred gallons.
There is a formula available on line to compute the amount of PG required and the size of the expansion tanks Extrol used to have a good online tool. NEVER use EG always PG many of the manufacturers give a conversion chart to correct your refractometer reading. There are three parameters on most charts and you must understand what they mean to better protect your system. The first is Freeze point which is generally defined as the temperature at which ice crystals are present in the mixture. The second is flow point which is the temp at which the fluid can be pumped and the third is burst point which is the temp at which damage will occur.My best advice is to not use more antifreeze than necessary to protect your system and check the PH yearly as others have advised.
Have a great and safe Holiday season!

MrStu02

Excellent article, well written. I have a little addendum.
I was doing solar in the mid ‘00’s, got to spend a week at Viessmann’s NA headquarters (best coffee ever). And we were using a new kind of anti freeze that started with propane-xxx-xxxx. It was explained that the anti freeze is what ushered in a new era of solar installations. It was able to withstand higher temperatures before breaking down.

MrStu02

PS- having read a comment on geo-thermal in the comments, that is where we got to use the best anti freeze. Because there is no heat exchanger between the two circulated fluids, we used methyl hydrate in the ground loop. A 25% concentration gives -40 protection, and it’s considerably less expensive. And having a 2hp mix cart made things go smoothly, we would recirculate until the water in the 26 gallon tank was clear again.

hot_rod

MrStu02 said:

Excellent article, well written. I have a little addendum.
I was doing solar in the mid ‘00’s, got to spend a week at Viessmann’s NA headquarters (best coffee ever). And we were using a new kind of anti freeze that started with propane-xxx-xxxx. It was explained that the anti freeze is what ushered in a new era of solar installations. It was able to withstand higher temperatures before breaking down.

Tyfo is a German brand of glycols and they have an ultra high temperature glycol, 350 F maybe?
Intended mainly for evac tube systems that see very high stagnation temperatures. One issue is those high temperature fluids may not meet the "low toxicity" rating requirements.

Rocky_3

A necessary evil here in the Great White North. We go through close to 1000 gallons of PG a year. Always the HD version, and always after cleaning and flushing the system with a well-known brand of cleaner, then yearly ph tests at the annual. We carry inhibitor in our service vans so that we can "refresh" the inhibitor on a yearly basis. I have a little cheat sheet that I send out with our techs. It is a formula I found in Dow's glycol manual. Tells you how to calculate how much glycol to put back in a system that has depleted its percentage, or, conversely, a formula for determining how much fluid to pull out of a system to drop the percentage. for instance, if you test and find you are at 18% concentration, but you want 40%, it tells you how much 100% to add back to the system to get it back to 40%. Local wholesalers carry a 60/40 mix of PG in 5-gallon pails, and we find homeowners or even home builders will add this to the system straight. So we get calls of low heat or system performance issues and find the glycol is way too strong. As mentioned here by others, most manufacturers of hydronic components have a max limit of about 50% glycol before issues arise. We don't recommend glycol to our clients unless they are prone to being gone from their homes for prolonged periods of time during the winter, or unless the property is a rental, or old and drafty. Whats the old saying? "the only good thing about antifreeze is that it doesn't freeze!"
Good article,
Rock