Product Overview
Table Of Contents
Figure 3: Functions for During operation
Pos. C: The lubricating oil pressure falls during operation to a value lower than the set/xed dierential. At point C,
safety circuit T1-T2 cuts in and the timer is activated.
Pos. D: The lubricating oil pressure reaches the set/xed dierential plus the contact dierential before the timer
period elapses. At point D, safety circuit T1-T2 cuts out and the timer is stopped, i.e. normal lubricating oil conditions
for the compressor have been established.
Pos. E: The lubricating oil pressure falls to a value lower than the set/xed dierential during operation. At point E,
safety circuit T1-T2 cuts in and the timer is activated.
Pos. F: The lubricating oil pressure remains lower than the set/xed dierential. At point F the timer cuts out
operational circuit L-M and the compressor stops. If a signal source is connected to terminal S, it will be activated.
Restart can only be performed after about 2 minutes by activation of the reset button, provided the cause of the
fault has been determined.
After start-up
It is important that a function check should be made to ensure that the dierential pressure control is operating as it
should.
This check can be made by pressing the test device (inside the unit on the left hand side).
When the test device is pressed down and held in this position, the compressor motor should stop after the release
time determined by the time relay has elapsed.
© Danfoss | Climate Solutions | 2021.02 AI211986438834en-000901 | 3
Dierential pressure switch, Type MP 54, 55 and 55A