High Pressure Internal Counter; Suction Pressure Transducers; Call For Compressor (Cooling Or Dehumidification) W/Transducers; Non Digiscroll Compressors - Emerson Liebert iCOM Training And Service Manual

iCOM
Controls Training and Service Manual

High Pressure Internal Counter

The internal counter can have 4 states 0, 1 and 2 are OK states, no alarm will
show up. If a "Situation", which caused the counter to increase by 1 becomes
older than 12 hours, the value of the counter will be decreased by 1 again.
3 is alarm state: it shows as "1" on the S302 or S303 counters and locks out the
compressor.

Suction Pressure Transducers

The new DS units use pressure transducers on the low side of the system instead
of low pressure switches. Parameter A116 Low Pressure Device Type should be
set to ANALOG. The transducer pressure measurements are read at 1 second
intervals. During all other operating times for the compressors additional pressure
measurements are read based on operating at "at limit conditions" for 5 seconds
and shall not include readings taken during Pumpdown or Winter Start Kit (WSK)
.
timeout

Call for Compressor (Cooling or Dehumidification) w/Transducers

Note: The following applies for both R22 and R407C refrigerant systems with all
compressor types.
When the compressor starts, the low-pressure value is ignored for a selected
period of time. This time value is set to 3 minutes (factory default) on air-cooled
units and to 0 minutes (factory default) on water and glycol cooled units.
After a Call for Compressor
a) With Low Pressure Delay Time (LPDT) set to = 0: the Liquid Line Solenoid
Valve (LLSV) opens, after one reading above Threshold 1 the compressor
starts (earliest 1 second after LLSV opens). Flow moves to Phase 2 for all
compressors.
b) With Low Pressure Delay Time set to ≠ 0: the LLSV opens, 1 second later
the compressor starts. The "flow" is now in Phase 1.

NON DigiScroll Compressors

The compressor(s) continue to run for LPDT value. If any single reading during
the LPDT is above Threshold 1 "and" the last reading (when LPDT elapses) is
above the pump-down cut-out value, the "flow" is now in Phase 2. The very first 6
minutes of phase 2 ignores all thresholds, except the Loss of Charge threshold.
After 6 minutes the "flow" changes into Phase 3 and starts check about NOT being
below Low Pressure Threshold 2 continuously for 240 seconds (the average value
of 3 minutes is used). If so, continue operation.
Note: Semi-hermetic (4-step) compressors shall run @100% (capacity valve off)
during the whole LPDT sequence.
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