I've been working on 3 heat pump systems each with 2 circuits seperate circuits.

However i'm having problems with system 1 + 2

Systems are 3 years old and have never worked correctly supposedly.

When i first got on site system 1 (circuit 1&2) both had LP faults and no refrigerant in the system, it was obvious others had been working on it.

System 2 (circuit 1&2) again both had no refrigerant in the system, pressure tested and found leaks on all systems and repaired. Vacced out and recharged.

Ran system 1 in heating and system began to pump itself down we looked at the TXV and found that it had been played about with.
After holding the bulb the pressure increased from 1/2bar to 1bar, we had 6k subcooling so i was thinking that a new TXV was needed.

I decided to put into cooling to prove the system would work if that TXV wasn't being used however after a few mins of running circuit 2 head pressure began increasing slowly until it got to 26bar and tripped.

On the condensor there is ductwork that comes off the top in order to reroute the air out of the room (the condensor is insidea building)but the ductwork doesn't have an inline fan to push the air along.

I thought this may be the problem so we took the ductwork apart so the air off blew into the room, this brought the HP down to 15bar where it stayed.

We tested several times replacing the ductwork and the pressure would rise, then we would take the ductwork off and the pressure would fall...to me proving that the ductwork is causing it to go off on HP.
But if that was the case then surely circuit 1 would be going off on HP as well which it wasn't, circuit 1 was running away happily with no problems.

System 2 circuit 1 is doing exactly the same and its got me baffled and it's been a long day!!

This should be a simple fault to fix but maybe it isn't just the 1 problem.

To Recap
System 1 circuit 2 on cooling faults HP
circuit 2 on heating faults LP

System 2 circuit 1 on cooling faults HP
circuit 1 on heating faults LP