User Guide
|
Intelligent Purging System (IPS 8) for Ammonia - Technical data, installation and use
© Danfoss | DCS (ms) | 2020.01
BC306932151284en-000201 | 7
Working cycle
The Danfoss IPS 8 operates in 24-hour cycles, of
which 45 minutes are dedicated to an R452A pull
down. At power on, the pull down is initiated
immediately. If no NC gases are detected during
the 45 minute pull down, the system will close
the solenoid valve at purge point 1 and open the
solenoid valve at point 2. After a cycle time of 24
hours/N (Number of purge points), the
compressor will pull down again condensing the
ammonia. After 24 hours, all purge points have
been vented one time.
To identify NC gases, the controller utilizes upper
and lower thresholds for R452A evaporating
temperature. If, during pull down, the
temperature continues decreasing and the lower
threshold is passed, the controller considers
this to be a high concentration of NC gases
and opens the purge solenoid valve. The purge
valve will stay open until sufficient condensing
ammonia is present to lift the R452A evaporating
temperature above the upper threshold.
The compressor will continue running and if the
temperature again decreases below the lower
threshold, a new purge will be performed. This
process will be repeated until the R452A heat
exchanger temperature stays above the lower
threshold for >45 minutes following the previous
closure of the purge valve.
Fig. 2 - Power on & Cycle at no NC gases present: CST (compressor start time) and PDT (pull down time) are configurable
* Cycle (CST) = 24 hours/N (number of purge points)
Cycle (CST) *
Purger
Pull
down
(PDT):
45
mi
n
Cycle (CST) *
Purger
Pull
down
(PDT):
45
mi
n
Time
Power on
Purger
Pull
down
(PDT):
45
mi
n
On
O
ff
On
O
ff
Compressor
Purge valve
Fig. 3 - Purging procedure - Low R452A evap. temperature detected during PDT: Thresholds are configurable
* If low evaporator temperature is detected (passing lower threshold), the purging procedure will be repeated immediately
Time
On
O
ff
On
O
ff
Compressor
Purge valve
Evaporator Temp. (Tsat452)
Upper Threshold (VClseT)
Lower Threshold (VClseT)
Non condensables has been purged
- new cycle starts *
