Recharging a VRV or VRF System

[Assad]

Regasing a VRF system which has 18 indoor units.

Unfortunately the commisioning documents have gone missing and there is no record of the correct refrigerant charge.

I know the proper way would be to calculate the pipe run and the amount of indoor units plus the outdoor unit factory charge but this may be more difficult than it sounds, as I’m not too sure of the pipe run.

I know the outdoor unit factory charge and I can find out how much each indoor unit holds. If I was to recharge the system with above information, would I be able to trim charge by running all the indoor units in cooling mode and checking I get a 10 degc split on the air on air off temperature.

Regards Assad

[laf100]

A colleague of mine has recharged a VRV by Subcooling, but you have to have a good load on the system, run all units in full cooling, and it is not accurate, only recommended if you cannot access the pipework at all.

Are you not able "guess-timate" the route the pipework will take by tracing indoor/outdoor pipe entry/exits & risers etc. then calc' as per the manufacturers install guide? This may get you closer to the correct additional charge required.