The Impact of Setting the Temperature Control Unit (TCU) to a Cycled Setting
What is the impact of the cycled setting? Modality Solutions has results to share. While running a series of controlled tests for a client, the temperature control unit (TCU) was inadvertently set to cycle mode allowing the company to compare and contrast the results of a continuous versus cycled setting.
Most, if not all, carriers of temperature-sensitive pharmaceutical products have clear instructions to set the TCU to run in continuous operation. Why? The fan and compressor unit remain active and operating at all times to minimise the temperature differentials within the trailer. But, the TCUs have an alternate setting for fuel saving.
In this mode, the fan and compressor will cycle off when the set point temperature is achieved. The TCU will wake up when the thermostat temperature reads between 3° and 5° from the set point.
The temperature of the air passing through the supply vent of the trailer is an indirect measurement of the mode of operation of the TCU. In continuous mode, the extreme in temperature variation is +/- 3° of the set point. In cycle mode, the lag time to activate the TCU can result in temperature spreads of more than 5° from the set point.
There is also an additional variance in the cycle mode because the fan operation contributes to the overall distribution of temperatures within the trailer.