Why can pressure controls not be used as the sole source of temperature control in outdoor temperature climates?

Pressure controls are designed to monitor and regulate the pressure within a refrigeration system, but they are not adept at accurately controlling temperature on their own, particularly in outdoor environments with varying temperatures. In these scenarios, pressure may not rise sufficiently to activate the control because the ambient temperature outside may be low. If outdoor conditions do not allow the pressure to reach the set point, the system could fail to engage properly, leading to inadequate cooling performance.

For example, if the outdoor temperature is significantly low, the pressure of the refrigerant may not increase as expected, which would prevent the pressure controls from responding appropriately to maintain the necessary cooling temperature. This dependence on pressure to reflect temperature can result in situations where refrigeration systems do not operate efficiently or effectively in colder climates.

In contrast, factors like pressure control reliability in extreme temperatures and the need for frequent calibration would undermine pressure controls in determining temperature control under specific circumstances, but the underlying issue of temperature influencing pressure response is a more fundamental limitation.