Oil return in VRF systems

Are there special piping requirements for VFR systems to ensure oil return? (I'm thinking of upgrading my split system to VRF). I read somewhere that IQDrive ramps the compressor up to full speed for 4 mins every half hour to ensure proper oil return. How do other systems handle it?

A little more info - in my case the compressor/condenser are roof mounted, the air handler is about 20ft below.

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Originally Posted by semb

Are there special piping requirements for VFR systems to ensure oil return? (I'm thinking of upgrading my split system to VRF). I read somewhere that IQDrive ramps the compressor up to full speed for 4 mins every half hour to ensure proper oil return. How do other systems handle it?

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Same!
Are you sure that you need VRF system? It is "litle" expensive for single home.

I'm thinking about modifying my current system by adding an inverter drive and an EEV - so I'm trying to learn all I can about what the issues are. At lower loads the refrigerant flow will be lower, so I'm concerned about oil return.

Quote:

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Originally Posted by semb

I'm thinking about modifying my current system by adding an inverter drive and an EEV - so I'm trying to learn all I can about what the issues are. At lower loads the refrigerant flow will be lower, so I'm concerned about oil return.

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That is not VRF. That is only simple inverter driven compressor system.

You really can't make a true VRF system without having all the software, hardware, and components in sync.

Regarding the oil return, Daikin losses more oil into the system than Mitsubishi.

I think you should not modify your system to VRF system.. It will cost very high..