To save the space in the underground counting rooms during the ATLAS phase II upgrades, a
project dedicated to the study of the impact of installing taller racks within the counting rooms
was launched, analysing its cooling performance and the impact on the cooling infrastructures.
A new 63U prototype rack equipped with three ATCA shelves, with open-bottom to top airflow,
high-power dissipating load blades, three new prototype 2U heat exchangers and various sensors
was installed in a lab. The impact on the cooling performance of stacking three ATCA crates
within a rack was checked, along with other critical aspects.