Propylene glycol (RV antifreeze)

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BetterSense

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I made a heat exchanger out of copper pipe and froze the whole thing into a block of ice in my freezer. The idea was that I could run propylene glycol through it, and route the hoses out of the freezer and into a heat exchanger in my beer fermentation chamber.

It was a great idea, but it turns out the RV antifreeze I bought freezes solid inside the thing. The jug says "protection to -50F!" so I figured I was surely safe at the what, 10F in my freezer. Not so apparently. This confuses me. Car antifreeze surely doesn't freeze that easily. Is RV antifreeze that much worse than car antifreeze? Is there anything else I could use? I didn't want to use car antifreeze because of the whole kidney failure thing. Would it help to dilute it with methanol or something?
 
Read the instructions again. You might be missing a step. Antifreeze needs to be mixed with water. Some stuff you buy is already mixed, other stuff you have to mix yourself. The right mixture with water actually lowers the freezing point.
 
RV antifreeze will "slush" up but not freeze and break things at temps below freezing, thus offering burst protection to a low temp.

There are propylene glycol antifeezes for heating systems like Cryotek -100 that will offer flow at lower temps and still be nontoxic.
 
RV antifreeze isn't just propylene glycol, there's several other things in it. But as Lechien said, the protection they mention to -50F is just that it will slush up that cold. The jugs that I have even mention that at temps near 0F it will start to slush.
 
BetterSense said:
I made a heat exchanger out of copper pipe and froze the whole thing into a block of ice in my freezer. The idea was that I could run propylene glycol through it, and route the hoses out of the freezer and into a heat exchanger in my beer fermentation chamber.

It was a great idea, but it turns out the RV antifreeze I bought freezes solid inside the thing. The jug says "protection to -50F!" so I figured I was surely safe at the what, 10F in my freezer. Not so apparently. This confuses me. Car antifreeze surely doesn't freeze that easily. Is RV antifreeze that much worse than car antifreeze? Is there anything else I could use? I didn't want to use car antifreeze because of the whole kidney failure thing. Would it help to dilute it with methanol or something?
Click to expand...

was there water in the copper pipe that froze?
 
Is it true that the freezing point is lower when mixed with water? I'm skeptical.

I thought about trying a mix of the RV antifreeze and alcohol. Do you think pure alcohol would work?
 
BetterSense said:
Is it true that the freezing point is lower when mixed with water? I'm skeptical.

I thought about trying a mix of the RV antifreeze and alcohol. Do you think pure alcohol would work?
Click to expand...

I don't think it is. The reason for mixing water into antifreeze in your car is the boiling point not the freezing point.

Alcohol would help. But do you really need it that cold? Why not warm it up a bit and use more volume?
 
How can I warm my freezer up? I mean I can turn the thermostat up, but if the glycol freezes now I just somehow doubt that I can turn it up enough to ensure it won't freeze; it's not like the thermostat is on -50F now.
 
I'm still using the freezer for food! I don't want my food to thaw out. That's the whole point of using a heat exchanger...I want to have my freezer and use it to chill my beer too.
 
can you just use water? Obviously you can't leave the water in after you're cooling but if the water is constantly moving and going into the boiling wort trying to cool it down. it wont freeze while its moving.
 
There is no boiling wort. I'm using this to cool my fermentation chamber.

You are right that if I kept the water moving, I probably could just use plain water. But I have to turn the water flow on and off to regulate the temperature of my fermentation fridge. Keeping the water flowing constantly would be overcool.
 
Oops sorry. I guess I have been reading too many glycol threads today.
 
I agree with others that you may not have mixed it. A mixture of 40% water/ 60% glycol is required to achieve -55F freezing temps. This works because the glycol prevents the bonding of the hydrogen structures in water, hence the reason the mixture is required.

BTW: Propylene glycol (100%) freezes at approximately 10F.

Why not test it out? Remove a small amount of the antifreeze, mix it 60% with 40% water in a plastic bottle (with head space), throw it in the freezer and see if it freezes. If it doesn't, you'll know what your problem is. If it does, you have a whole different problem (possibly cheap antifreeze that wasn't premixed correctly).

For future reference, 'non-toxic' on the label doesn't mean food safe. If it were me, I would consider getting rid of the anti-freeze and buying USP grade propylene glycol.
 
@ itsme6582 -- RV antifreeze is designed to be pumped into RV systems during the winter months to prevent pipe bursting while the RV is not being used. It is NOT poisonous. Ethylene Glycol is poisonous - RV antifreeze is Propylene Glycol. Different animal.

@FSR402 - you're in Michigan ! surely you know antifreeze is also valuable for protecting radiators and engine blocks from freezing during the winter months!

@ BetterSense - I think Pygon is correct, but have not tested it out - 40/60 mixture...
Some of the RV brands come pre-mixed 50/50, so something other than undiluted is required. I, too, run my glycol to cool my fermentation chamber, but it's in my keezer at a nice 38F, and pumped on demand to keep the water bath cool. It took some volume, however. I did not reach an equilibrium (glycol worked at first, then gradually got warmer, and keezer ran longer and longer) - until I reached a volume of 5 gallons.

good luck!
 
itsme6582 said:
It's poisonous
Click to expand...

LOL. Propylene Glycol is in many foods, including flavor extracts and is used to thin medicines that can't be cut with water. It is NOT poisonous.

OP: look for food grade or USP(pharmaceutical) grade PG. You can find it on amazon by the quart or gallon.

I should add that I would only bother with this if you are using a submerged chilled. If you are chilling a water bath for your carboy, your rv antifreeze should be fine in the proper mix ratio. Like I said, I would experiment with 50/50 or 60 pg/40 water ratio in a 20oz bottle just to see if it resists freezing.
 
I'm not cooling a water bath; my fermentation chamber is insulated and I have a heat exchanger in there (cold exchanger?) with a fan and a thermostat.

According to DOW's tables and my hydrometer, my RV antifreeze is 50%
propylene glycol. Gravity is about 1.042 which is less than the curve turnaround point.

Which still surprises me that it slushed, but it did. Maybe my freezer is turned down really low. Right now I have 50% ethanol/glycol, 50% Vodka/glycol, and 25% vodka and glycol solutions in the freezer to experiment.
 
Pygon said:
I agree with others that you may not have mixed it. A mixture of 40% water/ 60% glycol is required to achieve -55F freezing temps. This works because the glycol prevents the bonding of the hydrogen structures in water, hence the reason the mixture is required.

BTW: Propylene glycol (100%) freezes at approximately 10F.

Why not test it out? Remove a small amount of the antifreeze, mix it 60% with 40% water in a plastic bottle (with head space), throw it in the freezer and see if it freezes. If it doesn't, you'll know what your problem is. If it does, you have a whole different problem (possibly cheap antifreeze that wasn't premixed correctly).

For future reference, 'non-toxic' on the label doesn't mean food safe. If it were me, I would consider getting rid of the anti-freeze and buying USP grade propylene glycol.
Click to expand...

+ 1 for mixing with water
 
BetterSense said:
I'm not cooling a water bath; my fermentation chamber is insulated and I have a heat exchanger in there (cold exchanger?) with a fan and a thermostat.

According to DOW's tables and my hydrometer, my RV antifreeze is 50%
propylene glycol. Gravity is about 1.042 which is less than the curve turnaround point.

Which still surprises me that it slushed, but it did. Maybe my freezer is turned down really low. Right now I have 50% ethanol/glycol, 50% Vodka/glycol, and 25% vodka and glycol solutions in the freezer to experiment.
Click to expand...

you might look closer at the ingredients in your antifreeze, I know the stuff I got my hands on also includes alcohol. It too would start to freeze to the evaporator in my chiller (I use direct cooling on mine)
 
BetterSense said:
According to DOW's tables and my hydrometer, my RV antifreeze is 50%
propylene glycol. Gravity is about 1.042 which is less than the curve turnaround point.

Which still surprises me that it slushed, but it did. Maybe my freezer is turned down really low. Right now I have 50% ethanol/glycol, 50% Vodka/glycol, and 25% vodka and glycol solutions in the freezer to experiment.
Click to expand...

Good thought on the specific gravity, and you might be right on the freezer temp -- most start 0F and go down from there, but probably not -55F.

All that said -- your original post mentioned that it froze solid but here you say slushed? I ask because the issue could be that your pump is a low-pressure pump than just can't handle moving the slush along (unlike an engine that uses larger hoses and warms up before it starts circulating with a much more forceful pump). Most fountain pumps are of the HVLP variety, made to move gallons not provide pressure, and is the reason they tend to have smaller amounts of vertical travel capabilities.

You will probably get better results from only alcohol than with a glycol mixture -- given the slushing potential of glycol at a higher temp than just alcohol (may lower the freeze point, but may raise the point at which it slushes).

So, here are the ideas I'm left with in the order I would personally try them (if it were me):

1) Unfreeze the copper tube and insulate it lightly (no more ice block). Give it the ability to retain slightly more heat but still be cooled by the freezer over time. Possibly try switching to a plastic or rubber with less thermal conductivity -- might take longer to cool your ferm, but you might avoid these issues when it's off.

2) Use 40% or better cheap vodka, pure ethyl, methyl or isopropyl alcohol. None are going to be cheap, but you probably won't have the slushing / pump issue.

3) If money was less of a concern -- build a split side ferm chamber. Use a low flow/low power pump (or throw yours on a rheostat) running constantly to cool a small area with a temp activated fan to circulate that air into a larger area.

4) If money was even less of a concern - use a dorm fridge combo for the cooling, hooked into a temp controller in a similar setup as above.

5) If money was no object... buy a brewery and have others worry about keeping it cool. ;)
 
All that said -- your original post mentioned that it froze solid but here you say slushed? I ask because the issue could be that your pump is a low-pressure pump than just can't handle moving the slush along
Click to expand...

The RV antifreeze slushes to a consistency somewhere between Sno-Cone and ice cream. There's no way it could be considered "flowable". My pump does not run constantly; I'm kicking the pump on and off to control the fermentation chamber temp, so I need the ability for the coolant to not slush even when it's sitting still for an extended period. There's no way I would build this so that if the pump fails or is off for too long, the mixture freezes in the freezer requiring a complete teardown and thawout. I definitely need a coolant that will not freeze/slush at freezer temps, period.

My 50% ethanol/RV antifreeze mixture did not slush, but my 50% vodka/50% RV antifreeze mixture did. Ethanol is pretty dang expensive because of taxes; isopropyl would be super cheap but if I have a leak in my freezer I don't want to have to toss all my food.

There's also the issue of what alcohol will do to my pump. This is the pump I'm using; it's not explicitly designed for pumping alcohol:

http://www.harborfreight.com/158-gph-miniature-submersible-fountain-pump-68396.html


Of course it would be more time and cost effective just to buy a dorm fridge and use a controller, but then it would me more time and cost effective to just buy commercial beer.
 
when you get into pumping alcohols, you run into issues with both the chemistry of plastics in the pump and the lower viscosity possibly possibly damaging it (its almost like running a pump dry- which all the lables always say not to do). also there is safety hazards of flamable substances which you need to consider.

if your fairly confident you dont have leaks and your design is sound, you could use either regular antifreeze (ethylene glycol), or windshield washer fluid designed for cold weather (contains largely methanol). other options would be organic or synthetic oils, which will get progressivly thicker with cold, but wont freeze solid. depends on the pump though.

I have a heat exchanger in there (cold exchanger?)
Click to expand...
fun fact- there is no such thing as "cold", scientifically. "cold" is really just an absence of heat. and that heat exchanger is still exchanging heat, just in the other direction.
 
My 50% ethanol/RV antifreeze mixture did not slush, but my 50% vodka/50% RV antifreeze mixture did
Click to expand...

strait ethanol is going to be a 200 proof liquid. vodka is usually 80-100 proof.
so in the first mixture you have 50% alcohol and 50% antifreeze,
in the second you have 25% alcohol, 25% water, and 50% antifreeze (not accounting for the water in the RV antifreeze), so obviously it should have a higher freezing temp.

edit- hah, i bought that same harbor freight pump on sale the other weekend. i can tell you that methanol will probably destroy it, same with ethanol (vodka), so i wouldnt do that. rubbing alcohol should be ok (short- or mid- term atleast), though i dont know what all the components are made from.

ethylene glycol will work fine with it, as that is exactly what im using it for.
 
BetterSense said:
The RV antifreeze slushes to a consistency somewhere between Sno-Cone and ice cream. There's no way it could be considered "flowable". My pump does not run constantly; I'm kicking the pump on and off to control the fermentation chamber temp, so I need the ability for the coolant to not slush even when it's sitting still for an extended period. There's no way I would build this so that if the pump fails or is off for too long, the mixture freezes in the freezer requiring a complete teardown and thawout. I definitely need a coolant that will not freeze/slush at freezer temps, period.
Click to expand...

I would agree -- it's not going to be considered 'flowable' through 1/16 or 1/8th lines. 1/2" lines though, with higher pressures from a much more powerful pump, and the fact that it only needs to move far enough to be heated -- well, that's why we don't buy new engines/cars every spring.

BetterSense said:
Of course it would be more time and cost effective just to buy a dorm fridge and use a controller, but then it would me more time and cost effective to just buy commercial beer.
Click to expand...

Well of course, but we don't do it cause it's cheaper, right? ;)

I'm afraid that if your concern is food safety, you're stuck with alcohol. You could probably disassemble the pump and replace the o-rings with ones more tolerant to alcohol (given the o-rings and sometimes washers are almost always the problem with running alcohol through that type of pump), but you'll also have to accept potential for what is essential a mini-bomb/lighter to possibly burn something down if anything goes horribly wrong.

Otherwise, I'm going to have to agree with audger that if you insist on this system as-is, food safety is out and you'll probably need to go with a different chemical.

Of course, I'd rather replace some freezer food than potentially my house, if it were me. At least, in theory, since in practice I'm using frozen salt-water 2 liters and a fan on a thermostat to keep my ferm chamber temps fairly constant, changing them out between twice a day to once every two days (depending on the stage of fermentation).

Anyway, I think that's about all the input I have to give on the subject -- good luck my friend.
 
Otherwise, I'm going to have to agree with audger that if you insist on this system as-is, food safety is out and you'll probably need to go with a different chemical.
Click to expand...

I still think that propylene glycol will work if I mix it up stronger. I just don't know where to buy it locally.
 
BetterSense said:
I still think that propylene glycol will work if I mix it up stronger. I just don't know where to buy it locally.
Click to expand...

Call your nearest tractor/farm supply. It's not going to be "food grade" or "USP grade" (then, neither is RV antifreeze).

It is used to prevent ketosis in cattle/goats.
 
BetterSense said:
I still think that propylene glycol will work if I mix it up stronger. I just don't know where to buy it locally.
Click to expand...

If you can get pure propylene glycol, you can mix it such that it won't slush.

I use it in a chiller system at a local brewery to prevent ice on the evaporator.
 
Chemical Engineer here. Here's some info on PG. First, when it's food grade, it is 100% non-toxic. You can drink it, bathe in it, mix it with your food, even atomize it and breathe it in and it won't hurt you. Second - In a pure state, it freezes (or melts for that matter) at -74 F. No more, no less. As you add water, that temperature goes up.

Here are some other data points, First is the Temperature (in degrees F), the second is the % PG (the rest is water):
-60F/60%; -50F/57%; -40F/54%; -30F/50%; -20F/46%; -10F/42%; 0F/36%.

Where it gets confusing, is that often PG mixtures (especially for RV Antifreeze) will list "Burst Protection". All this means is that it will freeze, but won't expand enough to burst a copper pipe. Per the Dowfrost Information Sheet (where I'm getting all this data), a -50 F "burst protection" requires 35% PG. As you look at the freeze protection (above), you see this mixture will freeze right around 0F - so it won't work as a circulating heat transfer fluid (at the temperatures you desire).

So what should you do? What I would do is buy pure PG and mix it 50/50 with water. So where do you get pure PG? Best bet (as mentioned by a previous writer) would be an animal supply store, such as Tractor Supply. They have the Ideal brand for $20 per gallon. I THINK it's pure (but could not read their label online). I would ask. Amazon is always an alternative, although a quick search gave me a price of $37 per gallon. Could you mix it with RV Antifreeze to "richen up" the RV Antifreeze? Sure, but one final warning about RV Antifreeze, sometime is includes Ethanol. Not harmful, but not as benign as PG. (Essentially, Ethanol is Grain Alcohol.)

I hope that helps!
 
Pygon said:
Call your nearest tractor/farm supply. It's not going to be "food grade" or "USP grade" (then, neither is RV antifreeze).

It is used to prevent ketosis in cattle/goats.
Click to expand...

Any vet supply place online should have it. It's 100% pure propylene glycol and is food grade. I think mine was ~$20/gallon.
 
packet said:
Any vet supply place online should have it. It's 100% pure propylene glycol and is food grade. I think mine was ~$20/gallon.
Click to expand...

I'll second this -- I use it for cutting nicotine for use in electronic cigarettes.
I haven't gotten dead from it yet (nor have I developed ketosis :cross:)

It is USP and about $20 per gallon from the local tractor supply store.
 
Subbed. I'm just wrapping up my DIY glycol chiller build and am trying to figure out what and at what mixture to use! This is useful info.
 
Attached is the Dowfrost data sheet with the freeze point chart for different solution percentages. If you are getting pure PG from the feed store then the numbers should be similar, but if someone can post up a brand I can double check. If you are using an ac or true chiller then shoot for 15* lower freeze point than what the refrigeration system suction is designed for to give a proper safety margin. So if you have your chiller set for a 25* suction use a 30% pg solution to give you a freeze point of 9.2*F. If you have a vat in your freezer that can get down to -10/-15* then go with something in the 45-50% range. If it's a vat in your freezer you can go a bit closer to the freezer temp compared to the 15* difference you need with a chiller. This stuff starts getting thick as the % solution goes up so keep that in mind when selecting a pump to circulate it.

View attachment Dowfrost.pdf
 
I just checked Tractor Supply, and they have a no name brand of PG 'full strength" for under $4 per gallon, store only. I which I had time to go there before the pending blizzardmageddon or whatever you want to call it, and before they realize the price is wrong, or so it seems. I did not find this last time I looked.

I'm still up in the air over my final design, but PG is a critical part. I picked up mini radiators used on CPUs (and more) that will mount to my 4" box fans I already have in my 4 chamber heated fermentation cabinet. I bought a generic transmission cooler that will mount 2 more 4" fans that will go in the bottom of the cooler. I also got surplus diaphragm type water pumps to circulate the coolant.

Already have 4 ST1000 controllers set up for heating, and will tweak them to drive the waterpumps and, via relay, the cooler fans.

Great plan, now I just hope it all works as expected.

Getting Lager fermenting temps should be no issue with the cooler temp around 35F, but not gonna get lagering temps this way. The cooler is actually a mini chest freezer (Redi Whip display case) so I can bring it down to zero no problem, but then it's a dedicated freezer, and not sure I need that capacity otherwise. Although if I do dedicate this as a freezer then I can skip the cooler fan and 'trans cooler' and just have a 10 gal reservoir at around 0F and use that for wort cooling too. It pains me greatly to use excess water for wort cooling, and this would eliminate that entirely. 10 gallons of PG at this price is much more affordable than I had found recently.
Decisions, decisions......


John
 

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