Glycol

[jflaherty]

What is the best mixture for an ice bar which is a system designed to create a solid ice section of a bar. We have been told by the installer that the mixture of glycol and water should be 40/60 respectively. We were running on a mixture of 73/30 glycol/water but were told that this is wrong, can anyone help.

[Dan]

For such an application, 40/60 should be more than enough for a 0 deg F surface, which is likely colder than you need to frost the surface. No harm in adding more glycol, though, other than the minor additional expense.

But don't use a 73/30 mix. It spills all over the floor.

[Mike Hopkins]

I would get the specifications of the glycol used and follow their
reccomendations to obtain the proper mix for the application. Typically look for a freeze point about 20*F lower than what you are cooling. You can make the mix too rich which could actually raise the freeze point and cause high viscosity and resultant flow problems. After you figure it out test it on a regular basis or send a sample out to a lab for analysis. Even though it is a sealed system the mix can turn sour and create problems down the road. Also consider toxicity, the solution you are using may be toxic and or enviromentally unfriendly. If it is toxic what are the consequences if it leaks out on the bar ? Propylene glycol is considered non toxic although it is more expensive. What are you using?
Mike Hopkins

[Dan]

Mike, I was assuming a solid stainless cold wall plate where the fluid wouldn't be a concern. But a cold plate application shouldn't reflect a 20 deg F TD, should it? I assumed that a nice frost was what was desired.

Jim! What effect does your customer desire, and how is it displayed? My experience is limited to frosting surface displays. Perhaps you have something more demanding?

[Robert Rumpff]

Dan is right you should be OK down to zero with a 40/60 solution but I wouldn't go much over 60/40 as you start coming back up the scale as you get closer to 100 % glycol. 60/40 is good down to at least -40 F. and that should be plenty for what you are doing.

[hvac01453]

The maximum freeze protection is 69% glycol and as stated earlier the more glycol added the freeze point rises. The other consideration is heat transfer. When the glycol percentage rises heat transfer is reduces or slowed down. The other thing to think of is protecting the chiller barrel. The duo-check glycol tester will tell you your protection level.