Daikin VRV 'K' Series

[philpsy]

I am having major issues with a 'K' series VRV I system. Running in a Hotel with 21 head units on it (19 x 3kw underceiling cassettes and 2 x 15kw ducted). Condenser has numerous modules in a rack, (1 inverter module, 2 standard modules and a function box) six compressors in total.

We came into the building in 2009 and since then we have changed the inverter compressor numerous times with no real luck in finding out exactly why they are failing. They are mechanically seizing (we assume due to poor oil return) but generally when we come to the failed compressor there is sufficient oil inside. We have had Daikin come through on the last two failed compressors and they cannot determine the cause. Today we have had another compressor fail, only lasted 7 months!!!

Anyone got an ideas???

[r.bartlett]

We have a site with 5 systems the same as above.To make matters worst they were installed outside spec which has increased the compressor failures. We first got involved when the inverter compressor failed 3 times in as many months. We changed the eevs and uprated the cch's (which was a recommendation by Daikin) make sure the jackets go back on as they often get left off or fall to bits after a compressor change.

However we now only use new (reclaimed) R22 as we suffered more failures when reusing the old. (60kg a time :-)

We have had a few DUK chaps out including our VRVIII here who is really really good . The K-Plus is a beast and there are not many engineers who really know-or want to know- the unit. I assume you have the manuals etc?

It sounds to me as it's a liquid return issue. However these units cannot de diagnosed via a forum. Connect a service checker to the PCB on the function box as this gives greater detail of what is happening in the condensers/function box. The F1 F2 isn't as good for in depth analysis.

The top VRV guy is a called Alain De Lille based in Ostende. He can assist via email if he has sufficient data.(see above) DAU should be able to contact him he's always flat out busy with the problem children of VRV..

[philpsy]

Yes we have the manuals, and we purchased a service checker last year but we generally only look/record from F1 F2, I will check out connecting to Function box PCB tomorrow. Numerous lots of data have been sent to Daikin Techs in Sydney and they have said everything looks good and is operating as it should (eg oil returns) - and now we have compressors failing again??

We have found that the sump temps on the compressors get very cold after oil return cycles which points to big floodback - I know they are supposed to flood a little to get the oil back but the sumps are getting to less than 5 degC, this seems too low to me. Was this the reason you uprated the CCH? Why did you replace the EEVs?

This condensing unit is on Level 12 of hotel, serving units on Ground, 1st and 2nd floor (nearly 40m riser), Daikin say they can do 50m rise but this seems a long way to get the oil back up?

What is DAU? and is Ostende in Belgium?

Since Daikin have reviewed the data and confirm everything looks ok, I am concerned that we are not doing something correct in our compressor changes? We have installed suction and liquid line shells with valves so we can remove cores after cleanup, we have confirmed oil quantity and quality. we have replaced inverter PCB, capacitors on Inverter comp, run contactors. Function box PCB is new. Pressure test for 5 days and triple vac system. There is a tag showing refrigerant charge and this amount has been confirmed by us by calculating liquid line length. Anything else we need to check???

[r.bartlett]

DAU = Daikin Australia. Yes Ostende is the EU HQ and manufacture ring plant. Alain is the most technical guy on VRV. The CCh's were uprated as Daikin suggested they were undersized from new. Sadly they are no match for liquid flooding but helps keep the oil warm. We get colder times than you (depending upon where you are but either way you should be heading into warmer months..)

The F1F2 doesn't give as much information on what happens on the outdoor than the PCB connection. When you start up checker remember to select PCB then scroll down to the bs box number. You do far more than we do as we don't fit suction driers and a down time of 5 days+ is totally out of the question when the hotel is full.

when we change a comp we just isolate that module and dump the charge across to the system. Then change the compressor and PLT vac that out. we are done in a long day.
if the compressors are getting cold then that shows the oil return is working. way back then we had a lot of flooding during various times and these pic's are taken during a DUK trip: note the ice on the (new) compressor

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the chap you can see is from DAU.

Most problems seem to be charge related. During the first few months we lost 3 systems out of 5 which was 87 bedrooms out of 140 with no heating.. Boy we had some sleepless nights I can tell you... Now for some strange reason we haven't any failures in ages and not lost one room night to an unexpected breakdown.... Of course the hotel now forget what it was like and assume that's 'normal':mad:

I have a report from DUK about liq flood back which I can pass on..

[Neddy]

Did you get an oil pack with the invertor compressor? Ive changed a compressor on the normal K series ( one invertor and standard compressor) and it came with an oil pack. Four litres of oil and a metal tin to connect a vac pump to suck the oil out of the standard compressor. Not sure if this should apply to you but worth asking the Daikin the question. Are your crankcase heaters working ok off cycle?

[philpsy]

Richard: Thanks for sending through this report I will take this on board and check some of these when we startup the system again - it is lucky for us at the moment the ambient temp is comfortable, but we are coming into summer and have to have this sorted very soon.

When you say "if the compressors are getting cold then that shows the oil return is working. way back then we had a lot of flooding during various times and these pic's are taken during a DUK trip: note the ice on the (new) compressor" . How much flooding back is normal during and oil return cycle - we are thinking that during the oil return it is flooding too much and washing out all the oil and compressor is pumping liquid? It almost seems as though the system is overcharged as these sump temps are getting low even during normal cooling operation (worse when low load). But as I have mentioned before the charge is always weighed in and I have checked the piping distances against spec and the additional charge shown is correct. If it is okay with you can I send though some operating data from our service checker for you to have a look through?

Neddy: didn't get an oil pack with new compressor they come precharged with oil. Yes sump heaters are working in off cycle. The inverter compressor has two sump heaters, one of them works all the time and the other i think is engaged when oil temp is low? I have never seen this switch on, unless I disconnect(open circuit) oil thermistor.

[VRVIII]

Philpsy,

I would suggest you first check the liquid injection solenoid valves are operating correctly, i.e. not passig liquid when deenergised. You must also remove the filter drier cores after a few days operation as the addition pressure drop can cause problems (especially with long pipe runs).
Have you checked the suction superheat entering function unit form indoors, the suction and discharge superheats at each compressor? This would verify if liquid flooding is taking place at indoor side (i.e. indoor EV's passing when unit is off / blocked filters etc) or outdoor side (i.e. faulty EV or solenoid etc)
Has the system suffered mostly inverter or standard compressor failures? Have most failures been in one module (inv/std1/std2)?

[r.bartlett]

Philpsy,

I would suggest you first check the liquid injection solenoid valves are operating correctly, i.e. not passig liquid when deenergised. You must also remove the filter drier cores after a few days operation as the addition pressure drop can cause problems (especially with long pipe runs).
Have you checked the suction superheat entering function unit form indoors, the suction and discharge superheats at each compressor? This would verify if liquid flooding is taking place at indoor side (i.e. indoor EV's passing when unit is off / blocked filters etc) or outdoor side (i.e. faulty EV or solenoid etc)
Has the system suffered mostly inverter or standard compressor failures? Have most failures been in one module (inv/std1/std2)?

Nice to see you back here...at last someone who knows what they are on about :-)

as you see on my pictures the oil balance line is frosting which means the oil has been driven out of the sump. This is possibly where the failures occur, The oil is driven out of the comp to the std. Then it runs dry and fails. the unit switches off and the oil returns. Just a guess mind.. I don't think we got to the reason for this operating condition (I am sure the liq sol was not passing) but when we noticed it it caused a big panic I can tell you.


Again service checker data is vital for a full investigation. Buy a cheap laptop and set it on the pCB. let it run for a few days/weeks collecting data and ask VRV III if he fancies a week away in the sunshine :-)

[philpsy]

It is always the inverter compressor that fails. Today we started the system up and I noticed the suction line icing up from the outlet of the accumulator. (it must be full of liquid or oil?) Temperatures were good entering the function box - this is not visible while watching the service checker data as the suction sensor is before the accumulator, all you can see is the oil temp on the inverter getting lower and lower (suction line minus3deg, compsump 5 degrees) - I switched the unit off. Do I need to reclaim and empty out the accumulator for correct operation? will it just do this again?

Correct me if I am wrong, during the oil return cycle, it floods the evaporators and suction line to bring back all of the oil from the system back to the condenser. and I take it the accumulators are sized to handle the amount of liquid flooding back to protect the compressor. But the oil must run through the accumulator to get back to to the compressors? how does it do this? only two pipes at the top???

I also checked a few line strainers in the oil equalizing lines at the function box, but all were clean. Has anyone had any issues with strainers blocking up? there are too many of them in these units!

[philpsy]

When you say that most of the problems were charge related, were you under or over?

Yesterday we have had DAU out to run over the system completely, they have come up with it being an issue when only a few head units are running. What is the minimum amount of heads that should be on? And how do you control this in hotel rooms? I can lock them on with iManager but I am sure we will get many complaints about units not switching off. If this is the case then VRV is wrong application for hotel rooms in my opinion.

Do you have email address for Alain? I would like to send him some data for analysis.

[Brian_UK]

But the oil must run through the accumulator to get back to to the compressors? how does it do this? only two pipes at the top???
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Sorry about the poor spelling but it's not my picture. The oil gets sucked back via the orifice at the back of the pipe bend.

[Ross]

Hi Guys,

I know it has been a few months since anything but has the problems of INV compressor failures been solved??

It has been a few years since I worked for Daikin but I do recall a few INV compressor failures on the 'K' series using the function box. From my experience I had some cases due to the emergency backup mode being activated for too long in setting mode 2. Over time this would cause an inbalance of oil between the compressors and modules. The setting modes of the PCB can be confusing to understand and set. I would suggest checking with Daikin Tech support that the emergency backup is still not activated especially if you are continuing to have multiple compressor failures.

The oil balance issue was identified by Daikin R&D and rectified on the VRVII to ensure better oil balance across modules and compressors in normal operation and emergency backup.