Daikin RZQ125D7V1B

[Kirky]

Hi all hope everyone is well

Had a call out to a Daikin split serving a server room. Customer said unit is not cooling. On arrival sure enough server room very warm but not as hot as you would think without any cooling. Checked indoor coil cold at inlet but soon losing cooling about a quarter of the way round (cassette). faulty metering device, restriction, partially blocked filter drier, lack of refrigerant. At the outdoor unit the liquid line was sweating away, suction pipe nothing. Put gauges on 10 bar suction 11 bar liquid ?????? We are on R410A by the way. Discharge nice and hot into reversing valve (Heat pump on server room application) and then into condenser coil. Condenser coil not even warm almost feels cool off fans. Maybe not quite as straight forward as I thought. Liquid line not warm to the touch all the way to what I assume is a electronic expansion valve. Pipe sweating leaving the EEV. Decided to switch unit off and restart. On start up the suction pressure dropped to 4 bar before steadily creeping back unto 10 bar which is where I was before. Could it be a restriction in the condenser coil ?. At the minute I definitely think we have a restriction somewhere however the 10 bar suction pressure is puzzling me. Think I'm gonna put some temp cooling in and sleep on it. Any advise welcome and if anyone has a link to the service manual that would be great. Sometimes when your this tired you just tie yourself in knots. Cheers guys

[frank]

Sounds over charged

[install monkey]

run it in test heating see if pressure on suction pipe goes to 33 bar
go setting mode 41 read the air,coil sensor-hold test for 8 seconds- shows setting mode 10 then release and hold for a further 8 seconds then temp up (changes 40 alarm history to 41 sensor values)
any fault codes?

[The Viking]

OK,
Before you go too far down the troubleshooting route, what is the humidity like in the room?
If it is below 35% then your unit is likely to go in to "frost prevention" mode and therein lies your problem...

[Kirky]

The system has been in use since 2010 without problem. No work other than routine maintenance carried out. Charge is recorded as factory pre charge although the pipe run is prob only 5m. I will take a closer look tomorrow and check for fault codes. I will take a reading of the rooms humidity however it did feel over 35% but will check. Something which I failed to mention before was that the amber led H3P HWL was illuminated showing a fault approximately 10 mins after start up.

[Kirky]

I did check 40 alarm history when I arrived nothing shown. But will interrogate the controller further tomorrow now I have a bit more know how. Thanks

[install monkey]

http://www.mediafire.com/download/p8...bv5n/rzq_d.pdf
big manual- happy reading- hope its not one of my installs!!!

[The Viking]

The system has been in use since 2010 without problem.

OH, good.
Then there is no chance that their IT guys would have added more load.

Once I were called in to a site where another engineer had spent 2 days investigating why the CRAC units no longer performed. Over the years there had always been 3 units running and one unit in stand by but now not even with all 4 units operating could the room temp be maintained.
The facilities manager and the IT guys insisted that they hadn't added any new kit...
Well, come 5pm when the nightshift's IT manager came on duty the problem was solved in 5min flat.
The weekend before (this must have been on a Wednesday) they had upgraded all their servers to the latest generation blade servers. (=16 kW load per rack instead of the 4 kW of the old servers)

[r.bartlett]

http://www.mediafire.com/download/p8...bv5n/rzq_d.pdf
big manual- happy reading- hope its not one of my installs!!!

he did say it was still running

[AbsoluteWDJ]

Sounds over charged

Ditto this

[nick2ono]

i would remove and recharge with fresh refrigerant...

[marc5180]

Have you tried a pump down, this sounds like it could well be an inefficient compressor.

I had the same fault a few weeks ago.

The compressor was ramping up to about 70hz but suction pressure was still around 10-11bar on R410a, with an air onto the Evap of 26degC