Inhibited Propylene Glycol Preparation, Selection and Application

A majority of the chillers manufactured at G&D are atmospheric with a vent cap and fill port located on top of the reservoir. This is where you want to add your propylene glycol (or whatever secondary refrigerant applies) mix.

It is highly recommended that the system, mainly the process piping, is flushed with water before adding glycol to the system. This is especially important for plastic systems where debris can become trapped during installation and fitting. It would also be beneficial to flush the individual pipes before installing them.

City water pressure or the chiller’s process pump can be used to circulate and purge spent water (containing debris). It is important that the spent water not make it back into the reservoir. This can be accomplished by installing an isolation valve just upstream of the chiller return connection. This will remain closed and water can be purged through a wye strainer or purge valve installed just upstream of the closed valve.

When using propylene glycol, or any other heat transfer fluid, it is important to dilute the solution properly. The PG should also contain inhibitors (~3-5 % in the concentrate). It is also highly recommended to use distilled water when diluting the PG as minerals can break down the glycol overtime rendering the solution inert. For most systems, and this depends on the temperature the PG will be circulated at, the mix needs to be at 35% v/v, 2.0F, 24.75 Brix… for most applications. The dilution needs to be measured with a field refractometer, as a hydrometer that will not give an accurate reading.

When charging the system with a heat transfer fluid that needs dilution (most cases), it is highly recommended to calculate the total volume in all line sets, tank jackets and reservoir. Charts can be found online for vol./ft. calculations for various pipe ID sizes. It is recommended to leave a bit of head space in the reservoir and take your time with this step of the systems commissioning as it can become costly to over/under dilute the heat transfer solution.