Hitachi RAS-3-HVNC - Refrigerant Charge

3. Piping work and refrigerant charge
72
SMGB0079 rev.0 - 01/2013
3.4 Refrigerant charge
C A U T I O N
• Donotcharge OXYGEN,ACETYLENE,orotherammableandpoisonousgasesinto the refrigerant, as an
explosioncouldoccur.Itisrecommendedthatoxygenfreenitrogenbechargedforthesetypesoftestcycles
whenperformingaleakagetestoranairtighttest.Thesetypesofgasesareextremelydangerous.
• Insulatetheunionsandare-nutsatthepipingconnectionpartcompletely.
• Insulatetheliquidpipingcompletelytoavoidadecreasedperformance;ifnot,itwillcausesweatingonthe
surfaceofthepipe.
• Chargerefrigerantcorrectlyfollowingtheproceduresofthemanuals.Overchargingorinsufcientcharging
couldcauseacompressorfailure.Insulatetheunionsandare-nutsatthepipingconnectionpartcompletely.
• Checkforrefrigerantleakageindetail.Ifalargerefrigerantleakageoccurred,itwouldcausedifcultbreathing.
• Ifthearenutistightenedtoohard,thearenutmaycrackafteralongtimeandcauserefrigerantleakage.
Follow the next procedure to charge the R410A refrigerant inside the indoor unit:
1 Connect the gauge manifold using charging hoses with a nitrogen cylinder to the outdoor unit check joints of the liquid
line and the gas line stop valves.
2 Supply power to the indoor unit and switch the DSW1-2 ON of its PCB1. Thereby the indoor unit SV1 and SV2 open to
allow the vacuum and refrigerant charge operation inside the indoor unit. Very important to remind to switch the DSW1-
2 OFF when nishing the whole procedure.
3 Check for any gas leakage at the are nut connection by using nitrogen gas inside of the eld-supplied piping to increa-
se the pressure at 4.15 MPa.
4 Connect the vacuum pump to the gauge manifold and operate it for 1 to 2 hours until the pressure decreases lower than
a pressure of 756 mmHg in vacuum.
5 Fully open the outdoor unit gas and liquid stop valves.
6 Operate the outdoor unit in cooling operation for more than 10 minutes to circulate the refrigerant through the whole
circuit.
Thermal insulation
Gas line
Cover the are nut and union
of the piping connection with
thermal insulation
Liquid line
Liquid stop valve
Gas stop valve
Nitrogen tank
(For air Tight test
& Nitrogen blow
during brazing)
Vacuum cylinder
Manifold
gauge
Outdoor unit
Insulate the liquid pipe for
prevention of the capacity
decrease according to the
ambient air conditions and
the dewing on the pipe sur-
face by the low pressure