If rapid cycling of the capacity steps occurs, the deadband setting is too low and should be raised to the point that rapid cycling will cease.
If a cooler design range other than those shown in Table 5 is desired, determine the setting by using the fol- lowing formula and Table 6:
Minimum Required Unit Deadband:
Minimum Deadband = (Cooler Design Dt ÷ (2 x no. of Capacity Steps)
=F (C)
The lights on the temperature controller will indicate the status of the control. If the green light labeled ABOVE SET POINT is illuminated, the controller will add steps of ca- pacity, if additional steps are available. If the yellow light labeled BELOW SET POINT is illuminated, the controller removes steps of capacity.
The temperature controller also has a red light labeled OUT OF RANGE that indicates the system load was reduced faster than the controller could remove stages. If this occurs, the unit shuts down to avoid cooler
Once the temperature rises back into the control band, the unit restarts automatically. This also occurs if the therm- istor fails in the open mode. In the case of a thermistor fail- ure, the unit does not restart until the thermistor is replaced.
On medium temperature brine units, the brine must be properly mixed to prevent freezing at a temperature of at least 15 F (8.3 C) below the
All units have the following 2 modes of
1.The temperature controller protects the system from
2.The
COMPRESSOR GROUND FAULT SENSOR Ð The ground fault sensor accessory (Part No. 30HW900004) monitors all
phases of the
NOTE: Two accessory packages are required for 30HK, HL units.
UNIT OPERATION
Capacity Control and Operating Sequence Ð
The 30HW units have a
afourth step available as a
At initial
30HK,HL UNITS Ð Close the compressor circuit breaker and turn the
In approximately 5 minutes, the lead compressor starts and the unloaders are energized (compressor unloads when com- pressor unloader solenoid is energized). On 30HL units, the liquid line solenoid valve will remain closed for the ®rst 10 seconds of compressor operation. The
Approximately 30 seconds (high setting) or 3 minutes (low setting) later, depending on the sample rate setting, the lag compressor starts and the unloaders are energized (compres- sor unloads when compressor unloader solenoid is ener- gized). On 30HL units, the liquid line solenoid valve will remain closed for the ®rst 10 seconds of compressor opera- tion. The
Approximately 30 seconds (high setting) or 3 minutes (low setting) later, depending on the sample rate setting, the lead compressor is loaded (unloader solenoids deenergized).
Approximately 30 seconds (high setting) or 3 minutes (low setting) later, depending on the sample rate setting, the lag compressor is loaded (unloader solenoids deenergized).
When the load is satis®ed and the leaving ¯uid tempera- ture falls below the set point, the last stage activated is dropped immediately. If the leaving ¯uid temperature still remains below the set point, then the control drops an additional stage every 30 (high setting) or 180 (low setting) seconds, de- pending on the sample rate setting.
30