The paper deals with the description of the laboratory of large-scale radiant systems and the experimental measurement of the operation of the air/water heat pump in connection with three large-scale radiant systems in cooling mode. The measurements showed that the average cooling performance of the ceiling radiant system of 28.56 w/m2 compared to the wall radiant system of 31.56 W/m2 and the floor radiant system of 25.02 W/m2 did not reach the highest value, but it was able to ensure the most favorable indoor air temperatures. Radiant systems achieved satisfactory results in the cooling mode in terms of ensuring the average indoor air temperature. The efficiency of the heat pump in the cooling mode indicated by the manufacturer with an EER value of 4.52 was compared with the calculated SPF value of 5.06 during the measured period and it can be concluded that the efficiency of the HP declared by the manufacturer agrees with the calculated efficiency of the HP and even exceeds it.