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Glycol lowers the freeze point of the fluid circulating through an Advantage chiller loop, which is what makes sub-freezing process temperatures and outdoor winter operation possible in the first place. As a rough guide, around 25% glycol protects to roughly 15°F, around 40% protects down to roughly 0°F, and 50% or more gets into the -30 to -40°F range depending on the specific glycol type - these are general, rounded figures for planning, not a substitute for confirming the right fluid and percentage with us for your process.
The tradeoff is that glycol doesn't carry heat as efficiently as plain water, and the higher the concentration, the more pronounced that effect becomes - heat transfer drops and the pump needs more horsepower to move the same flow rate through the loop. Running a higher percentage than the process requires costs performance and energy for no benefit.
The right approach is to size around the minimum glycol percentage that protects against the actual lowest expected temperature or process requirement - not the highest percentage available or a round number picked out of habit. If the process fluid itself needs to run below 32°F, that required temperature (not the ambient outdoor low) is usually the number that sets the percentage; if the concern is purely outdoor freeze protection during winter shutdown, the ambient design low is the relevant number instead.
Propylene glycol and ethylene glycol behave differently at the same concentration and have different suitability depending on the process, so confirm which one applies before finalizing a percentage. Propylene is the standard choice anywhere food, beverage or pharmaceutical contact risk is a factor, since it's non-toxic; ethylene glycol is more common on purely industrial loops with no contact risk, since it costs less and transfers heat slightly more efficiently at a given concentration. Mixing the two fluids in one system, or on one site across separate loops that could ever cross-connect, is a mistake worth designing against from the start. See Glycol Chillers for the Advantage indoor and outdoor packages built to run these solutions.
| Approx. Glycol Concentration | Approx. Freeze Protection | Notes |
| ~25% | ~15°F | Light freeze protection, minimal effect on heat transfer |
| ~40% | ~0°F | Common for moderate sub-freezing process or winter outdoor duty |
| ~50%+ | ~-30 to -40°F | Range depends on glycol type (propylene vs. ethylene); pump sizing impact is significant |
PROPYLENE VS ETHYLENE
Which Glycol Type Applies
The type question comes before the percentage question, since the two fluids don't perform identically at the same concentration and aren't interchangeable once a system is filled. Propylene glycol is the standard for any loop with food, beverage or pharmaceutical contact risk, or anywhere a leak could reach a process, product or people - it's non-toxic, which is the deciding factor regardless of cost. Ethylene glycol is more common on purely industrial loops with no contact risk, where its slightly lower cost and marginally better heat-transfer performance at a given concentration make it the more economical default.
Once type is settled, percentage follows from the lowest temperature the loop has to survive - whichever is colder between the process fluid's required setpoint and the site's outdoor freeze exposure, if the unit is outdoors. Send us both numbers and your glycol type preference (or contact-risk requirement) and we'll confirm the exact mix for your Advantage chiller.
Send Us
- Required leaving fluid temperature, if below 32°F
- Outdoor ambient design low, if the unit is outdoors
- Any food, beverage or pharmaceutical contact risk
- Existing glycol type in the loop, if this is a refill or top-off
