Daikin VRV III Oil Recovery Function

[Iliketolearn]

Hi Everybody,
I'm very new for RE.
I would like to know more information about VRV III for oil recovery function.
Normally how frequent the oil recovery operate? and how long for each operation?

Thanks in advance.....

[Peter_1]

And what exactly are the machine's doing while they're in oil return mode?
The sumps aren't connected with each other and still they maintain a correct oil level in each parallel compressor. How they avoid that one is getting all t he oil (mostly the longest running VFD controlled one )
Questioned this myself several times.

[Brian_UK]

I thought Daikin did connect the compressor sumps together, they used too, I'll have to read up on that one.

edit:

Just been to the Daikin extranet and found a piping diagram for a three compressor set, 1 x inverter and 2 x fixed speed.

What they have done is pipe the return pipe from the oil separators back to a different compressor.

As in:- Comp 1 oil sep returns to comp 2; comp 2 oil sep returns to comp 3 and comp 3 returns to comp 1.

This link may not work if you are not registered.
http://extranet.daikin.co.uk/MDM/ima...W27275-1_E.pdf

[Gingerair]

Scratched my head over this one myself..
The oil sep return also discharges into the suction of a different comp..?!?!?
No wonder they fall over if the ref-necks arn't in the correct plane...

VRVIII where are you ???......

Have asked Daikin technical to explain this to me before, but think i may as well of waved a dime bar infront of the techies face...

It's also almost impossible to get an oil sample without unbrazing a comp & pouring some out of the suction port...

[Mentallist]

VRV III oil recovery is written in the sofyware as being every eight hours. It can however activate more frequent oil recovery operation if there are prolonged periods of high compressor output. For example: If all standard compressors are in operation and the inverter compressors are operating at high frequency, the software may decide to activate an oil return. It is also possible for the VRV system to calculate oil loss, these calculations are based on frequency of inverter compressor, operating pressures and temperatures. It also calculates the temperatures of the scrolls (This is called the Htdi temperature), by similar calculations, therefore, if it deems the scrolls are too hot, the software will also activate an oil recovery operation.

I hope this helps

[Peter_1]

I was aware of this 'vice/versa' system Brian_UK but it still confuses me how they can manage correct oil levels in the compressors, especially if you think that one is speed controlled, one of two others just on/off and if you then think what we have to do in a pack to stabilize oil in the compressors (floats, oil reservoir, oil safety switch in case of ...) And it becomes in my opinion even more difficult if compressor 1 sends his oil to 2 and 2 to 3. What if the system is running for a long time only on the main VFD compressor? Low speeds in the lines, all the oil going to 2,.... They regularly performs an oilreturn cycle (all EEV 's open and compressor at full speed) but even then...

[VRVIII]

I was aware of this 'vice/versa' system Brian_UK but it still confuses me how they can manage correct oil levels in the compressors, especially if you think that one is speed controlled, one of two others just on/off and if you then think what we have to do in a pack to stabilize oil in the compressors (floats, oil reservoir, oil safety switch in case of ...) And it becomes in my opinion even more difficult if compressor 1 sends his oil to 2 and 2 to 3. What if the system is running for a long time only on the main VFD compressor? Low speeds in the lines, all the oil going to 2,.... They regularly performs an oilreturn cycle (all EEV 's open and compressor at full speed) but even then...

Hi Peter,

If you look at the actual piping inside the unit you will see the compressor suction lines are slopped away from the compressors then turn down into a vertically mounted Y section.
The oil return lines from the oil separators connect in to suction line on the slopped section.
When only 1 compressor is operating the oil is returned to non operating compressor suction line, as this comp is off gravity will cause the oil to fall back to the Y section where the velocity of suction gas will carry oil back to the operating compressor.

This is slightly different for a unit with 3 compressors as std 1 is never allowed to operate alone.