4th wire on Daikin VRV inverter compressor.

[Markie]

Hi,

I have a Daikin VRV RXYQ8MW1B that is tripping its main mcb intermittantly. The inverter compressor has the usual red, white and black wires going onto the U,V,W terminals but also has a brown wire going onto an N terminal.
I found a post on an old closed thread on here that identifies this wire as not a neutral but a feedback to the inverter so that the pcb knows the rotor position. I called Daikin help and the guy I spoke to said this is correct but didn't have any more info on this. My questions are how exactly does this work? What fault/s could this feedback wire show if something's wrong with the compressor? Should there be no continuity from this N terminal to U,V,W? (I'm assuming so) and why has this particular series got this feedback to the pcb when all other previous and models don't?
I'm pretty sure this is not causing this particular issue but I've never seen this on an inverter before and it's bugging me!

Cheers,

Markie.

[Brian_UK]

Can't really answer this one, sorry but looking at Daikin service manual SiUS39-601 on page 243 they give some check readings across those terminals.

https://www.daikinac.com/content/resources/manuals/service-manuals/vrv-systems/

Download the REYQ_M manual.

[frank]

It allows the pcb electronics to measure the rotation speed. It's called a Tacho output.

On the newer EC fans motors which have an inbuilt inverter pcb, there is an output RPM wire available for connection to a third party control or measuring circuit also.
http://www.ebmpapst.com.au/media/content/publications_downloads/product_flyer/news_articles_-pdfs/EC_motors_and_speed_control.pdf

[Markie]

Thanks for replies guys. That's a great help especially the fact that the manual shows what the resistance readings should be between N and N3 and P3 on the IGBT, which I can now check for future reference.
I'd managed to get the RXYQ-M manual from daikin but only because I called tech help and asked them to email it. As quite often happens I found that when I searched the Daikin extranet with the specific model number it didn't show any service manuals only a technical data manual. In general I find the Daikin website to be rubbish when it comes to finding stuff and usually end up on a third party website like daikintech.co.uk for service manuals. If anyone knows of any other sites that are good for that please let me know!
Cheers ;)

[narkom]

https://www.digikey.com/en/articles/techzone/2013/jun/controlling-sensorless-bldc-motors-via-back-emf

[VRVIII]

Hi,
The N wire provides a feedback signal to the inverter board which is used to detect the rotor position.
It’s unlikely a problem with the inverter circuit would result in the MCB tripping intermittently.
I would suggest you check the solenoid and reversing valves coils, crank case heaters etc. Also check the wiring for signs chaffing particularly against the sides of the electrics box.

[r.bartlett]

Hi,
The N wire provides a feedback signal to the inverter board which is used to detect the rotor position.
It’s unlikely a problem with the inverter circuit would result in the MCB tripping intermittently.
I would suggest you check the solenoid and reversing valves coils, crank case heaters etc. Also check the wiring for signs chaffing particularly against the sides of the electrics box.

long time, glad you're still alive!

cheers

Richard