Glycol testing: Why so important?

glycol quality ground source heat pump

We previously wrote about the importance of biomass owners choosing the right fuel source for their boiler. Ground source heat pump owners need not worry about this, but would be well advised to check the quality of the glycol in their system prior to the onset of winter.

As the key heat transfer medium in a ground source system, it is vital that the glycol is maintained to a standard that allows for efficient heat transfer and minimises pump running costs. You can read more about the impact of glycol here.

In simple terms the glycol, whether it is alcohol or synthetic-based, is an antifreeze and water mix that continuously circulates through the collector array. Testing with specialised refractometers allows for the concentration of antifreeze to water to be established. A new install can have an antifreeze concentration as high as 33%, which allows for excellent thermal transfer. Over time there is the possibility that some glycols will degrade, so it is worth regularly checking the quality of the fluid that is circulating through your collector array.

A 25% antifreeze to water mix is acceptable. Below this level, it may be worth considering replenishing or replacing the glycol in order to maintain optimum efficiency from your heat pump system. Degraded glycol can become thicker, leading to losses in thermal transfer efficiency and increased wear on the circulation pumps.

Glycols should be replenished like-for-like, and in particular ethylene and propylene-based glycols should never be mixed. If it makes more sense to replace the glycol then this is also possible. Depending on the age of the system, this could make a lot of sense as glycols become more advanced and less environmentally damaging. We can advise on what the best solution for you would be, and have the capability to empty, clean and refill all systems, regardless of size.

If you have a maintenance contract with us, we will as standard check the quality of your glycol as part of our annual service. If you think that this is an area of your system that needs attention then please feel free to speak to one of our team, and we can offer friendly, impartial advice to ensure that you are gaining the maximum benefit from all aspects of your system.