It's very difficult, if not impossible, to give definitve figures for what you request. However, I used to work in the industrial water treatment industry supplying products and services for the control of corrosion, deposition & biofouling but it was some time ago! My advice may be a little out of date but here goes....
As general rule, problems of one sort or another will be encountered if no conditioning controls are employed.
1. Start as already advised by examining raw water quality and system operational characteristics (temperature range, max temperatures, local environment, materials of construction, any local discharge limits, current problems, etc)
2. A useful tool for determining the likely problems that you may encounter can be the Langelier Saturation Index or the Ryznar Index. This will indicate the likely scaling / corrosion potential of the system and allow a conditioning treatment progrqamme to be tailored
3. From the above, you can also then determine the max COC (Cycles of Concentration) allowable - remember, the prime function of a cooling system is generally not to cool water but to save water by recycling! If water were free we'd all be using "once through" systems.
4. The greater the COC the lower the water & chemical bill - treatment chemicals (except biocides unless applied continuously, viz possibly chlorine / bromine) concentrate in the process stream as do other dissolved / suspended materials.
5. Best to contact a number of suppliers regarding an inhibitor programme
6. TYPICAL (emphasised) ranges for the determinands you request:
pH - usually between 6.5 to 8.5. Lower potentially increases corrosion risk but reduces scaling, higher favours scaling. Higher ph reduces efficacy of chlorine (hypochlorous acid is the effective biocidal component. A high pH may also reduce the protection offered by certain forms of treatment (e.g. zinc products)
Cond - (or Total Dissolved Solids). Higher can increase risk of corrosion but ususlly just considered as indicator of system concentration. Figures of around 2000 to 2500 uS are probably a typical max.
T Hardness - Calcium generally more of a problem due to more ready ppt'n of calcium carbonate. Actual value of Ca hard used in Langelier calc. Actual permissable values would vary considerable depending upon nature of the system and other ions present (e.g. a CaCl2 brine system would be very high indeed due to the high solubility, CaSO4 predominant would lead to typical figures of around 2000 max applied, CaCO3 a lot less dependant mainly on system temp)
T ALk - indicator of temp hardness. Again no actual max usual, but used in Langelier calcs
Cl2 - very useful indicator of cycles of conc as usually unaffected by environment of the system. Only really an issue with suseptable materials present (e.g. stressed stainless)when levels of 200 max might be applicable.
Si - not normally an issue unless particulate thaen becomes part of sus solids / turbidity consideration w.r.t errosion & deposition potential. Silca based corrosion inhibitors can be used.
Fe - undesirable due to indicator of corrosion within ferrous systems and considered as an essential nutrient for some biofoulants. Consider that a potable water system would operate at 50 ppb target with MAC 200 ppb. probably means that a system value of 1 to 2 ppm would be OK
Trust this helps
