Liebert TM-10098 Fan Alarm / Fan settings, High Pressure Cutout, Suction Pressure Transducer

iCOM Controls Training and Service Manual

Fan Alarm / Fan settings

The fan operation is controlled by two (2) digital devices: the Loss of Airflow differential pressure switch and the Main fan Overload motor protection. The time delay at the unit start is always 5 seconds shorter than the control delay.

High Pressure Cutout

The control uses high head lockout functionality. If one compressor trips or is locked out on high head, the other compressor turns on when the space temperature increases 1°F. Pressing the alarm button on the display twice can reset high head Alarm. A lockout condition occurs on the third trip and must be

reset by turning the main power switch to off then back on.

Suction Pressure Transducer

The suction pressure transducer operation is only on air conditioning products (not chiller applications). Transducer measurements are made at least once every 1 second. With all other operating times for all compressors, additional measurements, shall be taken based on operation “at limit conditions” for 5 seconds and shall not include readings taken during Pumpdown or Winter Start

Kit (WSK) timeout.

Call for Cooling

The following applies for both R22 and R407C systems and applies to all compressor types. The call for cooling opens the Liquid Line Solenoid Valve (LLSV). Note: on units with Digital Scroll Compressors the unloader is energized

0.1second before the compressor contactor is energized. On air-cooled units with fan speed type condenser (FSC) the low pressure start threshold is 35psiG (50psiA). On air-cooled units with lee-temp control (LT) and all fluid cooled units the low-pressure start threshold is 60psiG (75psiA).

All compressorized units use the following start sequence:

Open LLSV, if WSK is set to 0, wait for suction pressure to reach setting, then start compressor and freeze protection timer.

If WSK is set greater than 0, operate the compressor for the WSK override time and monitor suction transducer value.

If pressure is achieved the compressor is allowed to operate, and the freeze protection timer is started.

If pressure is not achieved, turn compressor off and leave LLSV open.

If pressure is achieved within next 30 seconds the compressor is allowed to operate, and the freeze protection timer is started.

36