Thanks Frank
the noise is like a waterfall not just a slight hissing.
when I did the compressors the refrigerant was weighed out and weighed back in to the correct amount.
rather than a hard re-set I just meant a reboot of the system, I know some manufacturers recommend powering back up in a specific order I.e. outdoor then bs boxes then indoors?
is there anyway of when I’m working on this I can block the controllers as people kept changing stuff while I was working, it on a ITM & I’m using a service tool