I'd like to investigate & debate the various methods used to control head-pressure in rhvac systems.

The simple ones first:
1. Fan speed control for air-cooled condensers;
2. Water flow control for water-cooled condensers.

There are number of others. I'd be interested in exploring the merits of the various methods, in terms of effectiveness, ease-of-control, stability, reliability, energy usage, cost.

A few questions to kick off:
a. What happens if the ambient temperature is very cold & cools the condenser too much, resulting in a low discharge pressure at startup?
b. Can head-pressure control result in rapid swings in condensing temperature/pressure?
c. What happens if a temp/pressure sensor controlling water pump speed, is overly sensitive?
d. What happens if the water pump cavitates - what effect does this have on the condenser?