Undercharged vrv system symptoms?!??

[weidit]

Hi guys
Have a vrv system this is not cooling rooms down but showing no faults.

Have been lead to believe that the additional charge to be incorrect by around 5kg! System runs and completes quick wiring and pipeing test with no problems.

Any advice would be much appreciated. Many thanks

[Peter_1]

What's SH on the indoor unit the most far away for the outdoor unit after switching on all the indoor units in continuous cooling mode (set to 17°C)?
Have you used a Service Checker? It can give you the readings of all the probes.
Recover everything, weight and recharge correct

[nike123]

Fastest solution is recover and weigh proper charge after verifying what correct charge should be by checking pipe lengths and instalation manual.

[weidit]

It's a water cooled vrv with 30 degree water supply in.
Was getting around 15 bar suction in full cooling. With room temps of 26 plus. And remotes set to 16 degrees we get air off 22 degrees at best.
It's a heat recovery 3 pipe
Affraid no service checker.

[chemi-cool]

Some electric valve is open when it should be closed?
Stuck 4way valve?

[al]

is 30degree water in too high? is it daikin vrv or other vrf? R410a presumably at the pressures given, why do you suspect an undercharge?

Alec

[multisync]

More like over indexed than undercharged...

[frank]

Check out page 76 on here

http://www.heronridge.co.uk/falt_cod...20training.pdf

[weidit]

Check out page 76 on here

http://www.heronridge.co.uk/falt_cod...20training.pdf

about thermistors? i thought that at first as the indoor units are in the mezz space 32 degree air on and duct into the air conditioned space.

it has a centralized controller which is showing the room temps at around 26/30 degree's so the condensing units must know that they are being asked for cooling.

There are 2 x condenser linked together and the slave seems to be the one doing all the work ie master compressor doesnt run. But is getting very very hot. altough it isnt on and pumping (not drawing amps) is has a liquid discharge off 34bar still.

the slave unit is producing 15bar suction pressure and 33 bar liquid. with indoor air off temps of no better than 20 degress when in full cooling.

any ideas guys? when should to compressors cut in and out?
and under full load they would both run wouldnt they?


many thanks

[weidit]

3 way valve problem maybe?
Many thanks

[Gingerair]

If it's undercharged the compressors can run with high discharge temps.
If the system detects its running out of parameters the comps may be unloaded to safegaurd against damage.
If you post the model no. of your units you'll probably get better info specific to your system..

There's loads of posts on here re the performance of VRV's, have a search..
I don't think your system is a Mits Elec but here's one recent post-
http://www.refrigeration-engineer.co...ad.php?t=25318

[weidit]

Sorry it's a Daikin water cooled...

[Gingerair]

Hi Alec, you got a year & model No. ???

[VRVIII]

about thermistors? i thought that at first as the indoor units are in the mezz space 32 degree air on and duct into the air conditioned space.

it has a centralized controller which is showing the room temps at around 26/30 degree's so the condensing units must know that they are being asked for cooling.

There are 2 x condenser linked together and the slave seems to be the one doing all the work ie master compressor doesnt run. But is getting very very hot. altough it isnt on and pumping (not drawing amps) is has a liquid discharge off 34bar still.

the slave unit is producing 15bar suction pressure and 33 bar liquid. with indoor air off temps of no better than 20 degress when in full cooling.

any ideas guys? when should to compressors cut in and out?
and under full load they would both run wouldnt they?


many thanks

Hi Alec,

Are you sure the master module has not been disabled via the outdoor unit pcb (field setting - mode 2 setting 38 )? This would prevent the master unit operating.

A liquid line pressure of 33 bar is excessively high, I suspect you have insufficient water flow through the condenser plate heat exchangers.
Have you checked the following:
1/ Head pressure (should be <30bar – limiting function will be active >29.5bar)
2/ Entering/leaving water temperatures (difference should be < 10 C)
3/ Water flow rate (nominal flow rate is around 90 l/min per unit)

Each unit should have an inlet water strainer and a flow switch connected across terminal Block X2 connections 3 & 4. I would suggest you check all water strainers and correct operation of the master unit flow switch this could also prevent the master unit operating.

[al]

alec

as per post 6 is your evaporative condenser ok?

al

[VRVIII]

alec

as per post 6 is your evaporative condenser ok?

al

Yeah yeah, what ever

[al]

you gotta have a sense of humour!!

It's like a customer ringing up, i have a cold room, it's white and not cooling, fix it over the phone for me!

more info would be great.

al

[weidit]

Master Compressor runs in test but not when full cooling? Has correct charge! Thermister problem maybe?

[weidit]

Is there somewhere you can check thermistors are Reading correctly? Is there a link or anything? Ie what in volts it means in bar for daikin vrv?
Many thanks