R404a water cooled condensing unit with 8oC cooling water

[wta12]

Take the hottest temperature you will ever see for the water supply, add 5 to 7 K and use this to calculate your compressor and your expansion valve.
Regulate your valve in winter for the hotter conditions you will see in summer and it will save you a lot of energy.
And, your HP will be stable the whole year long.

Please clarify for me the Hotter condition is the HP - discharge gas condensing temperature, Isn't it ? and why we need higher in winter cause i use chilled water with extremely stable 8oC (12 oC max but seem to never happen) ? All of my unit with cold room inside building so weather have very tiny affect.
Regards