Hiya.
Had a call to a heat pump this week.
Lp alarm.
Heat pump runs for approx 1minute before it trips on lp alarm.
Pressure in system is fine 8 bar approx at 2oc.
Sight glass shows system dry.
Start it up high side goes up straight away 20bar + low side falls rapidly to 1 bar and trips out.
I cant really get it to run long enough to check temperatures across the filter dryer but i think it is reading a difference.
Seems like a near total blockage at the dryer.
Took off the txv bulb and made no difference, also opened up the txv but that made no difference.
When i turn it off the 4 way valve de energises and the system pressure equalises.

So looking at blocked filter dryer i think.
Delonghi heat pump approx 4 years old.
No problems till now, we regularly service it and no repairs done to refrigeration side.
Any help appreciated.