Bigger Tonnage Cooling Tower

Here is an example.

Suppose that the ambient wet-bulb temperature is 20°C. A 5° approach means that the condensing temperature of the chiller is 25°C; 10° approach ≈ 30°C; 15° approach ≈ 35°C; etc.

Now, consult the capacity/power data for the chiller. At 25°C condensing temperature, it consumes X power (hp or kw); at 30°C it consumes maybe 1.2X power; at 35°C, maybe 1.4X power.

Closer approach = lower condensing temperature = less chiller power.

Lately, i parallel my redundant cooling tower to bring down the condensor approach temperature.Return water temperature to cooling tower previously was 98F and now is 88F. By doing this, i can see a lot of difference on running load amp. At least 20amp drop from previously but i don't know how to relate this to the theory behind od condensor approach temperature.

What's the local wet-bulb temperature, on a daily basis?

our wet bulb here is 29c

Please reread post 1; it tells you how this works. The closer approach/lower condensing temperature equates to lower condensing pressure, so the compressors don't have to "push" as hard.