High Discharge Temperature Control Ð If the discharge temperature increases above 160 F (71.1 C) (PSIO Software Version 09 and higher) or 180 F (82 C) (PSIO Software Version 08 or lower), the guide vanes are propor- tionally opened to increase gas ¯ow through the compressor. If the leaving chilled water temperature is then brought 5° F (2.8° C) below the control set point temperature, the con- trols will bring the chiller into the recycle mode.
Oil Sump Temperature Control Ð The oil sump tem- perature control is regulated by the PIC which uses the oil heater relay when the chiller is shut down.
As part of the pre-start checks executed by the controls, oil sump temperature is compared against evaporator refrig- erant temperature. If the difference between these 2 tem- peratures is 50 F (27.8 C) or less, the start-up will be delayed until the oil temperature is 50 F (27.8 C) or more. Once this temperature is con®rmed, the start-up continues.
PSIO SOFTWARE VERSION 08 AND LOWER Ð The oil heater relay is energized whenever the chiller compressor is off, and the oil sump temperature is less than 140 F (60 C) or sump temperature is less than the cooler refrigerant tem- perature plus 60° F (33.3° C). The heater is then turned off when the oil sump temperature is: 1) more than 160 F (71.1 C); or 2) the sump temperature is more than 145 F (62.8 C) and more than the cooler refrigerant tem- perature plus 65° F (36.1° C). The heater is always off dur- ing start-up or when the compressor is running.
PSIO SOFTWARE VERSION 09 AND HIGHER Ð The oil heater relay is energized whenever the chiller compressor is off and the oil sump temperature is less than 150 F (65.6 C) or the oil sump temperature is less than the cooler refrig- erant temperature plus 70° F (39° C). The oil heater is turned off when the oil sump temperature is either 1) more than 160 F (71.1 C); or 2) the oil sump temperature is more than 155 F (68.3 C) and more than the cooler refrigerant tem- perature plus 75° F (41.6° C). The oil heater is always off during start-up or when the compressor is running.
When a power failure to the PSIO module has occurred for more than 3 hours (i.e., initial start-up), the oil sump is heated to 100° F (56° C) above the evaporator refrigerant temperature or 190 F (88 C), whichever is lower. Once this temperature is reached, the oil pump will be energized for 1 to 2 minutes or until the oil sump temperature cools to below 145 F (63 C). The normal heating algorithm is now followed once ramp loading has been completed.
After a 3-hour power failure, the oil temperature must rise to the higher oil temperature. The controls will delay the start of the compressor until this temperature is met.
Oil Cooler Ð The oil must be cooled when the compres- sor is running. This is accomplished through a small, plate- type heat exchanger located behind the oil pump. The heat exchanger uses liquid condenser refrigerant as the cooling liquid. A refrigerant thermostatic expansion valve (TXV) regu- lates refrigerant ¯ow to control oil temperature entering the bearings. There is always a ¯ow of refrigerant bypassing the thermostatic TXV. The bulb for the expansion valve is strapped to the oil supply line leaving the heat exchanger and the valve is set to maintain 110 F (43 C).
NOTE: The TXV is not adjustable. Oil sump temperature may be at a lower temperature.
Remote Start/Stop Controls Ð A remote device, such as a time clock which uses a set of contacts, may be used to start and stop the chiller. However, the device should not be programmed to start and stop the chiller in excess of 2 or
3 times every 12 hours. If more than 8 starts in 12 hours occur, then an Excessive Starts alarm is displayed, prevent- ing the chiller from starting. The operator must reset the alarm at the LID in order to override the starts counter and start the chiller. If Automatic Restart After a Power Failure is not activated when a power failure occurs, and the remote con- tact is closed, the chiller will indicate an alarm because of the loss of voltage.
The contacts for Remote Start are wired into the starter at terminal strip TB5, terminals 8A and 8B. See the certi®ed drawings for further details on contact ratings. The contacts must be dry (no power).
Spare Safety Inputs Ð Normally closed (NC) digital inputs for additional ®eld-supplied safeties may be wired to the spare protective limits input channel in place of the factory- installed jumper. (Wire multiple inputs in series.) The open- ing of any contact will result in a safety shutdown and LID display. Refer to the certi®ed drawings for safety contact ratings.
Analog temperature sensors may also be added to the options modules, if installed. These may be programmed to cause an alert on the CCN network, but will not shut the chiller down.
SPARE ALARM CONTACTS Ð Two spare sets of alarm contacts are provided within the starter. The contact ratings are provided in the certi®ed drawings. The contacts are located on terminal strip TB6, terminals 5A and 5B, and terminals 5C and 5D.
Condenser Pump Control Ð The chiller will moni- tor the CONDENSER PRESSURE and may turn on this pump if the pressure becomes too high whenever the compressor is shut down. CONDENSER PRESSURE OVERRIDE is used to determine this pressure point. This value is found on the Equipment Service1 LID table and has a default value (Table 4). If the CONDENSER PRESSURE is greater than or equal to the CONDENSER PRESSURE OVERRIDE, and the ENTERING CONDENSER WATER TEMP (Temper- ature) is less than 115 F (46 C), then the condenser pump will energize to try to decrease the pressure. The pump will turn off when the condenser pressure is less than the pressure override less 5 psi (34 kPa), or the CONDENSER REFRIG (Refrigerant) TEMP is within 3° F (2° C) of the ENTERING CONDENSER WATER temperature.
Condenser Freeze Prevention Ð This control algorithm helps prevent condenser tube freeze-up by ener- gizing the condenser pump relay. If the pump is controlled by the PIC, starting the pump will help prevent the water in the condenser from freezing. Condenser freeze prevention can occur whenever the chiller is not running except when it is either actively in pumpdown or in Pumpdown Lockout with the freeze prevention disabled (refer to Control Test table, Pumpdown/Terminate Lockout tables).
When the CONDENSER REFRIG TEMP is less than or equal to the CONDENSER FREEZE POINT, or the ENTERING CONDENSER WATER temperature is less than or equal to the CONDENSER FREEZE POINT, then the CONDENSER WATER PUMP shall be energized until the CONDENSER REFRIG TEMP is greater than the CON- DENSER FREEZE POINT plus 5° F (2.7° C). An alarm will be generated if the chiller is in PUMPDOWN mode and the pump is energized. An alert will be generated if the chiller is not in PUMPDOWN mode and the pump is energized. If in recycle shutdown, the mode shall transition to a non- recycle shutdown.
