Sterling 30RA010-055 manual Operating Limitations

COMPRESSOR OIL

SIGHT GLASS

Fig. 39 — Compressor Connections and Oil Sight Glass Location

5.Allow unit to operate and confirm that everything is func- tioning properly. Check to see that leaving fluid tempera- ture agrees with leaving set point (CSP.1 or CSP.2), or if reset is used, with the control point (CTPT) [Run Status, VIEW].

6.Check the cooler leaving chilled water temperature to see that it remains well above 32 F (0° C), or the brine freez- ing point if the unit is a medium temperature brine unit.

7.Recheck compressor oil level (see Check Oil Charge section).

Check Refrigerant Charge — All 30RA units are shipped with a complete operating charge of R-22 and should be under sufficient pressure to conduct a leak test after installa- tion. If there is no system pressure, admit nitrogen until a pres- sure is observed and then proceed to test for leaks. After leaks are repaired, the system must be dehydrated.

All refrigerant charging should be done through the ¼-in. Schraeder connection on the liquid line. Do NOT add refriger- ant charge through the low-pressure side of the system. If com- plete charging is required, weigh in the appropriate charge for the circuit as shown on the unit nameplate. If partial charging is required, operate circuit at full load and use an accurate tem- perature sensor on the liquid line as it enters the TXV. Use the Temperatures mode on the Scrolling Marquee display to show the circuit saturated condensing temperature (SCT.A or SCT.B). Charging is most accurate at saturated discharge tem- peratures of 120 to 125 F (49 to 52 C). Block condenser airflow as required to reach this temperature range. Add refrigerant un- til the system subcooling (SCT.A or SCT.B minus liquid line temperature entering TXV) is approximately 15 to 17 F (–9.4 to –8.3 C). Refrigerant VAPOR only may be added to a circuit through the 1/4-in. suction Schraeder connection on the com- pressor. This connection is located in line and to the left of the compressor junction box for the SM110 compressors and to the

lower right of the compressor junction box for all other com- pressor models.

Never charge liquid into low-pressure side of system. Do not overcharge. Overcharging results in higher discharge pressure, possible compressor damage, and higher power consumption. During charging or removal of refrigerant, be sure water is continuously circulating through the cooler to prevent freezing. Damage caused by freezing is considered abuse and may void the Sterling warranty.

Operating Limitations

TEMPERATURES (See Table 41 for 30RA Standard Tem- perature Limits)

Do not operate with cooler leaving chiller water (fluid) temperature (LCWT) below 40 F (4.4 C) for the standard units, or below 15 F (–9.4 C) for units factory built for medium temperature brine.

High Cooler Leaving Chilled Water (Fluid) Temperatures (LCWT) — During start-up with cooler LCWT above approx- imately 60 F (16 C), the unit expansion valve will limit suction pressure to approximately 90 psig (620 kPa) to avoid overload- ing the compressor.

Low Cooler LCWT — For standard units, the LCWT must be no lower than 40 F (4.4 C). If the unit is the factory-installed optional medium temperature brine unit, the cooler LCWT can go down to 15 F (–9.4 C).

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