Daikin VRV II REYQ8M7W1B Inverter E3 faults.

Hi,
I have been assisting a collegue by phone with the above VRV II system that is having E3 faults. It recently had a failed inverter compressor that was repalced along with the inverter pcb. The system will not run as it starts the discharge pressure quickly rises to over 34 bar and then goes into HP retry, as seen on service checker. After 3 attempts it goes to E3 fault (high pressure).
It seems that the reason for this is that the discharge stop valve solenoid is not being energised by the main pcb when the inverter compressor starts to run. There is no 240v output to Y5S from X11A on the maim board. With the system in full heating and hence both 4 way valves closed to upper and lower heat exchangers the discharge gas has nowhere to go as it cannot leave the outdoor unit via the dual pressure (hot gas) pipe. Interestingly, with the inverter coded out and the standard compressor running solo the hot gas solenoid does open, giving the same pressure readings at the discharge port inside unit and at the hot gas pipe service port and the system runs ok.
We tried swapping the main pcb with another working unit (same model number) and got the same result.
Daikin tech help said that the solenoid should open when the inverter runs in heating and could offer no explanation other than a faulty main pcb. This doesn't tally with the fact that with the pcb from another unit not experiencing the fault we get the same result.
We are going to look at the other system that's not having E3s to see what happens regarding when the solenoid gets energised in heating with inverter only running next. Unfortunately we ran out of time on site and cannot get back until next week.
In the meantime if anyone has and insight on this that would be a great help.
Cheers,
Mark.

REYQ is VRV IV unit not VRV II, is not it?

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Originally Posted by narkom

REYQ is VRV IV unit not VRV II, is not it?

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REYQ is used for VRV 2, 3, and 4. It’s the M series that means it’s a 2.

Have you checked 240v on X1A?

Attachment 15291

If there was no power to the main pcb the unit would simply do nothing which is not what I’ve described.

Hi Mark

When the VRV II heat recovery starts heating thermostat ON the HEX 2 (lower) begins with being a condenser before the main discharge solenoid (hot gas pipe) energises, so the head pressure is controlled via lower outdoor HEX initially, the expansion valve for this lower HEX will open fully to 2000 pulses but if faulty it doesn't open at all, leading to your symptoms, i'd unscrew expansion valve head and see if system operates in heating with out entering E3 error code but don't leave the system in this state. Good luck

Quote:

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Originally Posted by Asbolute

Hi Mark

When the VRV II heat recovery starts heating thermostat ON the HEX 2 (lower) begins with being a condenser before the main discharge solenoid (hot gas pipe) energises, so the head pressure is controlled via lower outdoor HEX initially, the expansion valve for this lower HEX will open fully to 2000 pulses but if faulty it doesn't open at all, leading to your symptoms, i'd unscrew expansion valve head and see if system operates in heating with out entering E3 error code but don't leave the system in this state. Good luck

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Hi Absolute, many thanks for your reply. Your diagnosis was correct. We found out a couple of days after my post that an engineer from our company had Swapped the main pcb with another system to check it and in doing so had plugged the expansion valves back into the wrong sockets. Hence when the lower hex 4 way valve was opening the upper hex expansion valve was operating and not the lower one.
Thanks again,
Markie 👍