The use of “Oxygen Free and Dry Nitrogen” (OFDN)
Flushing the system and providing a “Holding Charge” of
OFDN to the system:
After HC refrigerant removal (venting and recovery by vacuum pump) from the
system, the empty refrigerant circuit should be flushed with OFDN in order to
assure that there is no remaining HC in the system but also to blow-out other
possible contaminants including humidity. In case of no further actions to the
system e.g. disassembly of indoor and outdoor unit for transport to the compa-
nies repair shop or an on-site specific components replacement at a later date,
an OFDN holding charge should be supplied to the refrigerant circuit. This is in
general to avoid that air or humidity will be introduced into the system and cause
contamination.
Provide a filled Nitrogen Cylinder (containing OFDN gas) equipped with reliable
pressure regulator and Nitrogen transfer hose (N), having a ¼” SAE female
adapter and with Schrader valve core depressor. Secure the cylinder!
The warning sign is still placed in the work-area because we are now handling a
pressurised (about 250 bar) cylinder and OFDN gas is intentionally blown off
from the system to the ambient area!
L
N
Never switch
ON the AC
system if
charged with
OFDN!
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