Daikin RSEYP10K7W1 3 pipe system keep getting LC fau

I've recently been working on the above system, I've had the pleasure of putting a unit back together that an engineer had left in pieces, I've put 2 new condensing fan motors, another small board linked to the main PCB board, crankcase heater, main PCB board, after fitting these I cleared the controllers of the old faults and reset the system from the outdoor unit by holding reset for 15seconds, I tried to run system up but it faulted LC which indicates there's a communication error between the main PCB board and the inverter board, I reset the system a few time and still had the same fault, I reset it one more time and this time it ran up, I ran the system on full cooling for 25 minutes all ok, I then ran system on heating for a good 20 minutes, I had one of the outdoor fans blanked of with cardboard as I'm still waiting for a fan blade, the system eventually cut out on high pressure, I reset system again and now I just keep constantly getting the LC fault, has anybody had this issue before? I've made sure everything's plugged in the right ports and there's no loose connections, gas pressures were fine when system was running!

Have you checked the insulation resistance on both the inverter compressor and the fan motor?

Both fan motors are brand new, I'm just confused to why the system would run for nearly an hour and then bring this fault up again! I locked out the inverter compressor aswell through the outdoor board and ran system up again on the other compressor it ran for about 5 mins but again then faulted LC which baffled me as this means a comms error between main PCB and the inverter PCB, even though I've locked the inverter out

Quote:

---

Originally Posted by Nicholasdjones

Both fan motors are brand new, I'm just confused to why the system would run for nearly an hour and then bring this fault up again! I locked out the inverter compressor aswell through the outdoor board and ran system up again on the other compressor it ran for about 5 mins but again then faulted LC which baffled me as this means a comms error between main PCB and the inverter PCB, even though I've locked the inverter out

---

Do you have the service manual because there are quite a few things that can cause this fault other than comms error.

if youve swapped the main board then u need to perform the wiring check and auto charge function via the pushbuttons on the outdoor

Nah no service manual mate, is that pretty standard thing to do when changing a board on a daikin install monkey, will give this ago tomorrow morning mate thanks, will get on the phone to daikin to take me through it, been on the phone few times to Daikin one of the engineers said he had a guy with a similar problem and even though it was a comms error between main and inverter he changed the board tht controls some of the mag valves and tht sorted it! But think I will try what u said first mate with wiring check, what's the reason with doing the auto charge function?

when u power up a daikin from install you have to perform a wiring check- first see if the outdoor can see all indoors and all bs boxes- then do wiring check,
the auto charge function on a vrv3 and prob vrv4 - calculate the additonal charge- add approx 80% of it then do auto charge where it will take gas until it decides it has enough- but reading about your comms issue maybe its due to defective lead from main to inv pcb - or inverter pcb may be faulty- this can be disabled via the setting mode, maybe unplug the fan motor without the fan blade, but keep the 2 pin plug for the fan thermistor connected think its q1t or q2t-

Yeah ive already locked the inverter compressor out and still got the LC fault coming up its a bit of a strange one! I had it running for an hour but when it cut out on high pressure and I tried to re run I'm just constantly getting LC!

If anyone has any other ideas as what to try please let me know