What effect does the addition of glycol to a heating system have on the compression tank's acceptance volume?

The correct choice indicates that the acceptance volume would increase when glycol is added to a heating system. This is primarily due to glycol's properties as a heat transfer fluid. When glycol is introduced, it often serves to reduce the freezing point of the liquid in the system, allowing for safe operation in colder environments.

The addition of glycol changes the thermal expansion characteristics of the liquid. Glycol has a higher thermal expansion coefficient compared to water. As a result, when the system heats up, the volume of the glycol-based fluid expands more than that of water would under the same conditions. Therefore, the compression tank must accommodate this increased volume of fluid without causing excessive pressure to build up in the system.

In summary, the presence of glycol causes an increase in the system's fluid volume under heat, leading to an increase in the compression tank's acceptance volume to effectively manage these changes without impeding the system’s operation.