Daikin Inverter Compressor Issues

[garyjh24]

Unit Details: Model REYQ16M8W1B

Original call out was system not working. On arrival found system main breaker tripped and inverter board had failed.

Checked inverter compressor windings resistance checks and insulation test, all ok.

Replaced the inverter board, on system trying to run the inverter compressor the inverter is energised and provides voltage to the compressor, a whining noise can be heard at the compressor, approx. 1.4amp at each phase is measured. The power from the inverter then drops off and the process starts again. The compressor will not run. Suspected compressor seized so replaced inverter compressor.

With new inverter compressor installed and new inverter board installed, commissioned system, once again, on inverter board energising , a whining noise can be heard at the compressor, again, approx. 1.4amp at each phase is measured. The power from the inverter then drops off and the process starts again ( approx. 30 seconds later). The compressor will not run.

Performed various tests:

Inverter - Power transistor check mode performed
Fan Motor – resistance values checked all ok.
Noise Filter – voltage output
Contactor K1M working
Output from all boards correct

With all checks performed compressor is still not operating ( again, inverter board energising, providing voltage to compressor, whining noise can be heard then power drops off).

To be sure all components are working, we have an identical system on the site, so I have swapped boards with this system.

Unit with the compressor not working now has the working units noise filter, fan motor PCB, fan motor and inverter board – compressor still not running.

Unit that was working now has failed units noise filter, fan motor PCB, fan motor and inverter board installed, system all working well – thus none of the boards/fan are causing this issue.

I have not replaced the main PCB with all the sensors connected to date.

The technical team seem to think I have been provided with a faulty compressor, but I am not so sure, especially as it seems to be doing exactly the same as the original compressor, am I missing something that could be holding this compressor off?

Additional Notes:
The inverter compressor has 4 cable connections, the fourth being the N connection that I believe is used to measure the compressor rotation.

No fault codes are being providing by the system.

The new inverter board that was fitted with the old inverter compressor has been tested on the other system and works

Any help would be appreciated.

[seanf]

What about disconnecting the compressor from the pipework, and with the suction and discharge pipes open to the air try and run it and see what it does?

Phase rotation check?

[Peter_1]

Gary, You described almost exactly the same as what I have come across... and also a similar installation on this site and all PCBs swapped with no result.
With all that you have already measured and performed because apparently you know very correctly what you are doing, it can hardly be other than that you got a wrong compressor. But as a final test you might want to swap the mainboard between them. Wasn't the original compressor with 3 connections and dne new one with 4 connections? Didn't you accidentally connect something wrong there? With the compressor with 4 connections, this is just the star point that one brings out. I read tis is indeed for rotation check but I think they it use it also to inject a controleld DC voltage on the windings that then acts in this way as a cranckcase heater. But with like what you have already done - many would have given up long ago - I would also start to suspect the compressor.

[Peter_1]

can this help you? https://www.youtube.com/watch?v=fGYNrZ-x9PQ

[garyjh24]

Gary, You described almost exactly the same as what I have come across... and also a similar installation on this site and all PCBs swapped with no result.
With all that you have already measured and performed because apparently you know very correctly what you are doing, it can hardly be other than that you got a wrong compressor. But as a final test you might want to swap the mainboard between them. Wasn't the original compressor with 3 connections and dne new one with 4 connections? Didn't you accidentally connect something wrong there? With the compressor with 4 connections, this is just the star point that one brings out. I read tis is indeed for rotation check but I think they it use it also to inject a controleld DC voltage on the windings that then acts in this way as a cranckcase heater. But with like what you have already done - many would have given up long ago - I would also start to suspect the compressor.

Thanks Peter 1, the original inverter compressor had the four terminal connections as does the new. I have done an inverter check and also swapped the inverter board to the second unit of which it all works well.

[coldflow]

Recently, I specifically thought about improving my renewable Scalar control in the house. Since time is of the essence and evolving, I decided to try Variable Frequency Drives, which I found on the internet. What do you think about it, very interesting to hear your opinion

[kanchi]

what is the error code?

[daveca]

It is mandatory to test this with a digital storage oscilloscope on the compressor power leads. A DVM is useless

The forum SW deleted my comment...

Thisis a problem of compressor overloading the drive, and the drive is switching on and off quickly trying to control the output current and voltage, that switching at high speed is what youre hearing at the compressor.

It is bad design to use a vfd to start a compressor. Switching supplies do not like high startup currents and MUST be sized for start winding current, not run current.

Overload and startup foldback will destroy such a supply.