Hi guys

I have the following

Indoor-------FDY P250B7V1
Outdoor ----RYP250B7W1

I'm wrecked and I can't remember if it wasn F1 or F2 that kept blowing , it's the one that feeds the safety devices and the indoor unit. Anyway it was popping fairly regularly when I got to site, I went through the usual, disconnected the indoor everything ok , long story short I had the unit running for 4 or 5 hours while I was doing other work, I had bypass the 2 fan thermal overloads, not best practice Sue me , I had disconnected the crankcase heater so i still had the two pressure switches and obviously the indoor connected. After running for the 5 hours I heared a loud bang, the fuse didn't just blow it blew completely out of the fuse holder and tripped the main 3 phase mcd, can anyone shed some light on what's going on here, the only thing i did notice was that the cable for the indoors was a 3 core flex at the outdoor and ended up being a shielded cable like .5 or something, maybe even less. This has been running like this for over 10 years , I didn't get much of a chance to check this out , just to say there are 3 other systems identical to this sharing the same remote, U5 faults all day when the fuse popped seemed to shut everything down any ideas ????!