CVHF help

[Industmech]

Hey guys I'm new and I need some help. I am trying to find out the design evap/cond approach on a CVHF570 S#L08B00859. I also need to know if any press/temp/IGV can be calibrated. The customer has reduced loads to keep it out of surge. This is a design level 3N manufactured in 08. It has .025" wall internally enhanced tubes.
Cond. Approach 7
Evap approach 3-4
Suction superheat 4-6 (Pipe skin temp no well)
Discharge superheat 16
IGV 50%
RLA 100%
Cond. diff P 7-8 psi should be 9
Evap diff P 15 psi should be 7
Cond delta T 13 which is design
Evap Delta T is 6 design is 9
I believe the tubes are fouled and it is low on refrigerant but the discharge superheat seems low. I cannot get any more water flow and have to wait until January for shutdown to inspect the tubes. At the same time to much chill water flow may be affecting the approach and suction superheat plus over working the condenser. If I new the design approach it would help.

[Magoo]

The condenser TD (K) or approach is the design saturated condensing temperature less the highest potential air on temperature. Wet bulb temperatures also influence evap condenser capacity, high wet bulb reduces capacity.

Have you checked system for non-condensibles, which will accumulate in evap/condenser, reduce performance and total heat of rejection.

[Industmech]

The drain leg temp equals sat temp for given pressure. I can't get my hands on the design refrig temps for evap/cond. I do have the design water temps

[jason09]

pressures and temperatures