PG25 Is Getting the Headlines. But It Isn’t the Only Cooling Loop in the Data Center.

Talk about data center cooling today and the conversation quickly turns to PG25, direct-to-chip liquid cooling and the thermal demands created by AI infrastructure.

That attention is justified. DOWFROST™ LC 25 is an inhibited propylene glycol coolant specifically engineered for direct-to-chip cooling systems, including systems with high-surface-area copper components—and those chips are expensive and critical to servicing the growing compute demand for AI and other uses.

But there is another cooling challenge that mechanical contractors, water-treatment professionals, and facility teams cannot ignore:

The rest of the data center still needs to stay cool. 
In other words, think of the humans too!

Server rooms, electrical rooms, mechanical spaces, offices, and other occupied areas continue to depend on central HVAC infrastructure. Pumps, chillers, heat exchangers, piping, and outdoor equipment still have to operate reliably regardless of what is happening inside the cold plate.

That is where DOWFROST™ HD Heat Transfer Fluid enters the data center cooling conversation.
Dow specifically identifies DOWFROST™ HD as a solution for primary circuits in data center facilities, while DOWFROST™ LC 25 is positioned for direct-to-chip cooling.

In other words, PG25 may be cooling the chips. DOWFROST™ HD can help support the facility cooling infrastructure around them.
 

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Two Cooling Jobs Require Two Different Fluid Conversations

As data center cooling architectures become more sophisticated, it helps to separate two fundamentally different applications.

Technology cooling and direct-to-chip loop

This is the loop circulating coolant close to high-performance processors and other electronics. Materials compatibility, particularly with copper-containing components, fluid cleanliness, and thermal performance are major considerations.

DOWFROST™ LC 25 was specifically formulated for this environment and is supplied as a ready-to-use 25% propylene glycol solution. 

Primary or facility cooling loop

This is the broader building-side thermal system supporting chillers, heat exchangers, air-handling equipment, and other HVAC infrastructure.

Dow positions DOWFROST™ HD for these primary data center circuits and states that the fluid is designed to provide corrosion protection, microbial control, and extended fluid life.

The terminology used for “primary,” “secondary,” and “facility water” loops can vary by system design. The important distinction is the application: DOWFROST™ LC 25 is designed around the datacom equipment cooling system, while DOWFROST™ HD addresses the larger facility-side heat-transfer system.

That distinction matters when specifying fluid.

Why Not Just Use Any Propylene Glycol?

Propylene glycol is the base chemistry. It is not the entire heat transfer [SS1.1][BM1.2]fluid formulation.
DOWFROST™ HD is a formulated inhibited heat transfer fluid containing approximately 94% propylene glycol concentrate plus a package of industrial corrosion inhibitors. Dow also manufactures the product using PuraGuard™ propylene glycol USP/EP, with purity greater than 99.8%.

That matters because a closed-loop HVAC system is not simply a container of glycol and water.

Over years of operation, the fluid can interact with:

• Piping
• Pumps
• Valves
• Heat exchangers
• Metals and alloys
• Seals and other wetted materials
• Makeup water
• Environmental contaminants introduced during installation or service

For the mechanical contractor or water-treatment professional, the real question, therefore, should not be:
“Do we need propylene glycol?”

It should be:
“What fluid formulation do we want managing this system for the next several years?”
 

1. Corrosion Protection Is Part of the Fluid Selection

Adding propylene glycol to water provides freeze protection, but glycol by itself should not be considered a complete corrosion-management strategy.

DOWFROST™ HD incorporates a specially designed industrial corrosion inhibitor package and is intended for heating and cooling applications, including HVAC systems. Dow now specifically includes the product within its data center primary-loop coolant portfolio. 

For critical infrastructure, that distinction is important.

The objective is not simply to prevent the loop from freezing. The objective is to maintain a reliable heat transfer system while helping protect the equipment carrying that fluid.
 

2. Data Center Reliability Extends Beyond the Server Rack

Data center uptime discussions understandably focus on processors, servers, and electrical infrastructure.
But cooling reliability is a system problem.

A high-performance direct-to-chip coolant cannot compensate for a poorly maintained facility loop, unreliable pumps, degraded heat exchangers, or problems elsewhere in the central cooling system.

For contractors and operators, that creates a useful design principle:
Choose the coolant based on the job each loop actually performs.
 

3. Fluid Purity and Formulation Are Different from Buying “PG”

There can be a tendency during bid review to reduce glycol selection to concentration and price per gallon.
Twenty-five percent PG is 25% PG. Thirty percent is 30%. Why pay attention to the name on the drum?
Because concentration only describes one part of the formulation.

DOWFROST™ HD is made with high-purity Dow PuraGuard™ propylene glycol combined with its industrial inhibitor system. The product is manufactured as a purpose-built heat-transfer fluid rather than simply supplying raw propylene glycol for field formulation.

That does not mean every alternative inhibited PG fluid is unsuitable. System materials, design temperatures, required freeze protection, OEM requirements, water quality, and operating conditions should all be evaluated when selecting a fluid.

It does mean that contractors and water-treatment providers should be cautious about treating every product labeled “propylene glycol” as functionally interchangeable.

4. Leak Detection Is a Small Feature Until You Actually Have a Leak

DOWFROST™ HD is available dyed fluorescent yellow-green to support leak detection.

In a large mechanical system with extensive piping, pumps, valves, and heat exchangers, easier identification of fluid leakage can simplify troubleshooting and maintenance.

It is not the feature that usually drives a data center cooling specification.
It is the kind of feature operations teams tend to appreciate later.

5. Think About Lifecycle Cost, Not Just the Initial Fill

Mechanical contractors are understandably under pressure to control project costs.
Water-treatment companies are often asked to provide a glycol recommendation at the lowest acceptable installed cost.

Procurement sees another line item.

But the initial fluid fill is only one part of the lifecycle of a primary cooling system.
DOWFROST™ HD provides prolonged fluid life and lower total cost of ownership. That is really the bottom line data center owners and mechanical contractors should consider.
 

Need Help Selecting a Heat Transfer Fluid for a Data Center Project?

ChemPoint works with mechanical contractors, water-treatment providers, engineering teams, and data center operators to help evaluate DOWFROST™ products based on the actual cooling application.

Whether you are sourcing DOWFROST™ LC 25 for a technology cooling system or evaluating DOWFROST™ HD for the primary HVAC loop, talk to ChemPoint about your system requirements, concentration needs, availability, and next fill.