the presently disclosed compound condensing unit is invented by applying the operation principle and combining all the components having a cooling tower , a water - cooled condenser , a compressor , controlling components into one single unit as shown in fig1 in a cylindrical tower or a rectangular tower where the tower is divided into several floors having the components in each floor shown in fig1 and fig3 , as follows : floor s 1 : having a compressor 1 and controlling components ; floor s 2 : is a cylindrical water reservoir 4 , at the bottom of the reservoir there is a water pump 2 to circulate water within the system for cooling , and a floating level switch 10 for controlling the water level in the reservoir by turning on and off the electric valve 1 to fill water in to the preset level ; where water reservoir 4 can be designed differently as in fig5 . floor s 3 : is the refrigerant conduit 5 functions as water - cooling condenser occupying the whole area of a round sieve 9 having pores at the bottom to allow flow of water through as shown in fig2 ( a ), ( b ), ( c ) and ( d ); floor s 4 : is an empty cylinder with enough height , having a lot of holes 8 all along its wall with air - filter along the wall to allow flow of air through ; floor s 5 : consists of cooling pads 7 filling the whole space to splash water on to increase surface area for evaporation of water ; floor s 6 : consists of a sprinkler 6 to sprinkle water throughout the cooling pad 7 ; floor s 7 : consists of a fan 3 to draw air from floor s 4 to flow up against the direction of water droplets which drop down in floor 5 to cool down the water droplet and lower the water temperature to dew point where air is sucked out by the fan at the top of the tower of this compound condensing unit . as shown in fig3 , valve v 1 is turned on to allow water to fill the water reservoir 4 where water level is controlled by level switch l 1 by controlling the turning on and off of valve v 1 . once the air - conditioner is on , compressor 1 , water pump 2 and fan 3 are turned on simultaneously . compressor 1 compresses refrigerant to flow into conduit 5 to cause increase in temperature of the refrigerant , while water pump 2 pumps water from reservoir 4 up to sprinkler 6 to sprinkle water to cover cooling pads 7 to drip downward against the direction of air flow upward by sucking action of fan 3 through holes 8 to expel out at the top of the tower . this decreases the temperature of water to dew point at that particular time point . water droplets then drip down to cool the refrigerant conduit 5 where it turns into warm water and flows out through sieve 9 back to reservoir 4 to complete the cycle . water pump 2 then pumps water up to sprinkler 3 to start the next cycle . fig4 shows how floors s 1 and s 2 as of fig1 are combined to make floor s 1 . 2 to reduce the height of the tower . by designing the water reservoir having its lower part as half cylinder and its upper part is full cylinder about 2 - 3 inches in height to be able to receive all the water drips down as shown in fig5 . the lower half cylinder space is to install the compressor and all other controlling devices . the height of floor s 1 . 2 is shorter than the sum of floors s 1 and s 2 , thus helps decreasing the height of this compound condensing unit shown in fig6 . the feature and operation of the compound condensing unit of the present invention , using water at low - temperature ( i . e . at dew point ) to cool down the warm refrigerant is more efficient than air - cooling . using the fin coil refrigerant conduit is thus not necessary . the ordinary copper coil with much shorter length can be used . this reduces the cost of manufacturing . in addition , the low temperature at the dew point of water is much lower than that of the ambient temperature of air thus allows decrease of pressure of refrigerant in the system . the compressor operates at lower load thus electrical consumption is reduced , this lengthens the life of compressor , in addition to maximizing the efficiency of the cooling system . the build of the compound condensing unit as rectangular box lies horizontally is shown in fig7 , 8 , 9 and 10 . fig7 is front view of the unit installing a fan where to the left is a chamber installing a compressor and controlling components . fig8 is back view of the unit . all the components are arranged and operate as follows : floor f 1 is a tray having cross - section area ( width × length ) sufficiently enough to receive all the water drips down from floor f 2 and is high enough to contain all the water needs to circulate in the system , where the left side end is extended to the anterior having the same width and height but just enough length to install the water pump , level switch and water inlet controlled by an electrical valve which is controlled by a level switch as in fig9 and fig1 . floor f 2 consists of a refrigerant conduit functions as a water - cooled condenser placed in a sieve - bottom rectangular tray having area large enough to receive all the water drips down from floor f 3 and with enough height that water does not splash out , and that water can flow through the pores at the bottom of the sieve - tray . floor f 3 consists of cooling pad filling the total area large enough to allow complete cooling of the warm water drips down from floor f 4 to reduce temperature of water to dew point before reaching floor f 2 . the cross - section of the compound condensing unit is thus equal to the cross - section area of the cooling pad . floor f 4 consists of sprinkler installed to sprinkle water to cover the whole area of cooling pad . fig9 is the left - side view of a compound condensing unit showing how air is sucked by fan to cool down water droplets where the extended area of tray to contain water of floor f 1 to install water pump , level switch and water inlet . this also shows how water is pumped by the water pump to sprinkler at floor f 4 , the thickness ( width ) and the height of each floor and the positions the components are installed sidewise of the compound condensing unit . the top view of the unit is shown in fig1 , showing the length of the tray of floor f 1 with its extending part to installed water pump , level switch , water inlet and water valve and the layout of the components as a whole of the disclosed compound condensing unit . the principle of operation of the rectangular type horizontally arranged compound condensing unit is similar to that of the cylindrical type or rectangular type vertically arranged . fig1 is the rearrangement of the components of compound condensing unit of fig1 or fig6 by moving floor s 3 to a position between floors s 5 and s 6 , operation is then switching from ; first , cooling down the temperature of water then lower the temperature of refrigerant later ; to first , cooling the refrigerant and later cool down water . yet , the outcome is similar . similarly , floor f 2 as in fig8 can be moved to a position between floor f 3 and f 4 , shown in fig1 resulting in similar outcome as described in fig1 . as shown in fig1 , components of fig1 are rearranged by deleting the sieve - tray of s 3 and move refrigerant conduit 5 to place under the water at the bottom of water reservoir of floor s 2 , where operation is the same as floors s 2 and s 3 are combined to be floor s 2 . 3 . fig1 shows how floor f 2 is deleted and refrigerant conduit 5 is placed under the water at the bottom of water reservoir of floor f 1 , where operation is the same as floors f 1 and f 2 are combined to be floor f 1 . 2 . it is to be understood that the following claims are intended to cover all of the generic and specific features of the invention as described herein , and all statements of the scope of the invention which , as a matter of language .