Daikin RSX10KA7W1 blowing PCB fuse

[eire1]

Hey folks, was at a callout this evening but couldn't complete due to poor light. It's a Daikin VRV. Another engineer was at it on Mon, a u4 fault and he found the mcb tripped and the 10A fuse on the control board blown. I called out today, replaced the fuse. The inverter board started to buzz and it blew the fuse. I then coded out the inverter. The fuse then blew again maybe 30 mins later, but never ran at all in that time. I swapped the Control PCB with a unit beside it and the same thing happened. Any ideas? Due back in the morning.

Thanks

[Tayters]

Is that a 407C version? Found a wiring diagram for a RSX10K7W1 (RSX10KA7W1 is yours) and if that's the same then do you mean fuse F1U on here (http://www.daikintech.co.uk/data/vrv-outdoor/rxyq/.../rsxp-k7w1_databook.pdf).

If so this fuse goes to the inverter board which although you may have disabled the inverter comp you still have power to the PCB. You said the inverter board buzzed, well, that's not a good sign unless is was just making that tinkling sound that inverters seem to.

Not a Daikin guru and hard to advise without seeing but it if my description is correct and diagram matches I'd be checking anything that is plugged into the inverter board, all the normal compressor checks (megger, windings resistance), diode test of inverter for what it's worth, correct neutral/supply, see where that takes you. From there be worth checking capacitors, diode module, standing pressure, just incase anything else is amiss. Have a good study of wiring diagram, see if the fuse feeds anything else as well as it does go into main PCB to feed overloads, HP switch, transformer so the issue might lie there.

Good luck!
Andy.

[eire1]

I'll have a look Andy, Thanks. No it's r22 from 2001. Thing has seen better days.

[Northy303]

Ohm out compressor and fan motor and make sure nothing is shorted then with the compressor leads off check for a balanced dc voltage output from inverter to compressor all 3 leads should be the same, then check the amp draw from the fan motor.
My money is on the outdoor fan motor.