Daikin compressors

[weidit]

Hi guys

could anyone explain or point me in the right direction for the following.

when you have to vrv condensers linked together or a single unit with 2 x comps

How do they run....
ie does one run full time and other help? and at what loads or stages does the other one help?

if the second compressor doesnt need to be used often there will be more wear on the first compressor?

Many thanks

[bill1983]

Since inverter compressors became common vrv or vrf systems have been manufactured with one of each. The inverter compressor runs at variable speeds to match the required load, with the single speed compressor only being used when the inverter is at or approaching 100% speed.
If for example the system was installed for a series of rooms, lets say 10 rooms all the same size then if all the rooms systems were calling for cooling or heating, then both compressors would run fairly constantly. if however over half the rooms systems were switched off, then the inverter would modulate to match the reduced demand.
as regards wear on the compressors, the wear rate would be higher on the compressor that runs the most as is normal on any system. as long as the system has been designed to match the required load and is maintained well, wear rates should not differ that much between the 2.
have you a problem on a system or is this a general question?

[weidit]

Bit of both to be honest as I have a system at the mo that's asking for full load and master comp isn't coming on. But we are having someone check flow rates into units as is a watercooled system. But the whole thing go me thinking about slave and master units...

On Daikin systems when you link to condenses via q1 and q2 and pipework is also linked. One will be set to master and other as slave. Would the master be the one doing that runs mainly and get help or the slave?

Many thanks

[bill1983]

they probably alternate to even out the run hours; mitsi do the same. on the other hand if only one system has an inverter then the inverter comp will always be the lead comp with the standard comps alternating to share the rest of the duty.

[weidit]

In this example both units that are joined are same models and both inverters.

[bill1983]

in that case the software will alternate the inverters 1st and the standards 2nd to ensure equal load sharing but the inverters will always take priority, unless of course the load is always high. ie over 50% of the total. after that the inverters will share the remaining load alternately.
daikin probably publish something about this, but if you follow logical rules then the above will always be true.
you really need to interrogate the system to find the inverter demand to see if it is approaching 100%. i don't know enough about daikins to help you on that i'm afraid, but keep coming back, someone on here will educate us both.
if you are dealing with daikin systems most of the time, get yur boss to send you on a course, take hundreds of pages of notes all the way through. ask your questions and get the manuals.

[VRVIII]

Alec,

If you download the appropriate service manual from Daikin extranet, this explains compressor capacity control and compressor priority sequence. The control varies between VRV2, VRV3 & water cooled VRV etc.