Daikin vrv III heating fault

[grovecoooling]

Hi Chaps
wondered if anyone could help me.
I have a problem with a Daikin vrv system which has 21 indoor units each with BSQV boxes.
At present we have only been to site for a quick look and they have reported 1 unit not heating,the unit is furthest away from the condenser,the only unit on the ground floor.
when we attended site during the day most the other units were in heating mode and although it was only a quick visit they seemed ok (no report otherwise)
the unit in question was running but not heating.
I attended site the next morning and the unit was running fine in heating mode but after a while it stopped heating, this problem apparently happens all the time, heating one minute and then not the next.

I have 2 ideas, either low gas charge, maybe when there is more demand from other fan coils this unit is starved of refrigerant or faulty solenoid/bsvq box.

I am due to re visit site shortly to thoroughly check the system,
Obviously i want to try to avoid reclaiming and recharging the system.
Does anyone know how to carry out a test on the BSVQ box or any other advice

thanks

[VRVIII]

Hi,

I would suggest turning off 6~12 indoor units then test/monitor the problem indoor.

If the unit then works ok I would suggest checking:
1/ Refrigerant charge



2/ The pipe work run lengths are within limitations

Outdoor to furthest indoor <165m (<190m equivalent)
First refnet to furthest indoor <40m
Level difference between indoors <15m
3/ The correct size pipe work has been installed

Outdoor to furthest indoor >90m equivalent (usually works out about 70~75m actual) liquid line must be upsized.
4/ Refnets joints installed correctly

Horizontal +/- 30o
5/ Check capacity of all indoor and verify system diversity/connection ratio

If unit still fails to heat correctly I would check:
1/ if something is influencing the return air sensor and if the sensor is out of calibration, you can check this in code 41 – 01=controller sensor value / 02=return air sensor value
(you can also check which sensor is being used for thermostat control in field setting 20-2-? 01=combination of RemCon&RetA / 02=RetA only / 03=RemCon only
2/ Use a temp probe and check for a temp drop across bs box pipes when problem occurs.
3/ connect a service checker, monitor system operations for any abnormalities.