Brazing Work Considerations; Refrigerant Piping Work Considerations; Water Pipe Work And Connection; General Notes - Hitachi RWM-(H)FSN3E Technical Catalogue

9 Piping work and
refrigerant charge

9.5.4 Brazing work considerations

C A U T I O N
• Use nitrogen gas for blowing during pipe brazing. If oxygen, acetylene or fluorocarbon gas is used, it will cau-
se an explosion or poisonous gas.
• A rust coating will appear inside of tubes if no nitrogen gas blowing is performed during brazing work. This
film will be flecked off after operation and will circulate in the circuit, resulting in clogged expansion valves,
etc, and the compressor will be affected.
• Use a reducer valve when nitrogen gas blowing is performed during brazing. The gas pressure should be
maintained within 0.03 to 0.05 MPa. If excessively high pressure is applied to a pipe, it will cause an explosion.

9.5.5 Refrigerant piping work considerations

C A U T I O N
• Do not charge OXYGEN, ACETYLENE, or other flammable 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 flare-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.
• Check for refrigerant leakage in detail. If a large refrigerant leakage occurred, it would cause difficulty with
breathing or harmful gases would occur if a fire were in the room.
• If the flare nut is tigthened too hard, it may crack over time and cause refrigerant leakage.

9.6 Water pipe work and connection

9.6.1 General notes

• Install the factory supplied Shutdown Valves for connecting the Water Inlet / Outlet pipes as close as possible to the
Indoor Unit, in order to minimise flow resistance and, if necessary, for water flow regulation.
• It is advisable to use flexible joints after the Shutdown Valve for the water Inlet / Outlet piping to prevent the transmis-
sion of vibrations.
• Proper Water pipe inspection should be performed after piping work to assure there is no water leakage in the circuit.
Fill in the heating circuit (refer to
• The Indoor Unit is equipped with an air purger (factory supplied) at the highest location of the Indoor Unit (Electric
Heater top). If this location is not the highest of the water installation, air might be trapped inside the water pipes,
which could cause system malfunction. In that case additional air purgers are provided (field supplied) to ensure no
air enters the water circuit.
• It is advisable to insulate the water pipes, joints and connection in order to avoid heat loss.
• When the unit is stopped during shutdown periods and the ambient temperature is very low, the water in the pipes
and the circulating pump may freeze, thus damaging the pipes and the water pump. In order to prevent this, the unit
has a self-protection mechanism which should be activated (refer to
C A U T I O N
When connecting the water piping to the indoor unit, it is necessary to install 500mm of flexible water piping
from the indoor unit, in order to avoid metal expansion problems due to temperature. After these 500mm install
copper Piping.
N O T E
The maximum piping length depends on the maximum pressure availability in the water outlet pipe. Please
check the pump curves.
120
TCGB0070 rev.3 - 04/2012
Circuit Water Filling-in chapter) and open inlet and outlet Shutdown Valves.
Available optional functions chapter).