Mitsubishi Electric PUHY-P250YNW-A Service Handbook page 5

[4] Piping Work
Piping Work
Operate the service valves carefully. Refrig-
erant may spurt out and cause frost bite or
other injuries. If leaked refrigerant comes in
contact with an open flame, toxic gas may
be generated.
Use pipes with adequate wall thickness. Re-
quirements for pipe wall thickness vary with
the refrigerant used, pipe diameter, and
pipe material. The use of the wrong type of
pipes may result in damage to the pipes, re-
frigerant leakage, and oxygen starvation.
Vacuum dry the refrigerant circuit using a
vacuum pump. Do not attempt to purge the
existing refrigerant out of the pipe with an-
other type of refrigerant. Doing so may re-
sult in pipe bursts and explosion.
To prevent explosion, do not use oxygen,
flammable gas, or a refrigerant containing
chlorine for pressurizing the system. Chlo-
rine will deteriorate the refrigerant oil.
To prevent explosion, do not heat the unit
with refrigerant gas in the refrigerant circuit.
Any substance other than the specified re-
frigerant, such as air, may cause abnormal-
ly high pressure in the refrigerant lines,
resulting in bursting of the pipes or an ex-
plosion.
Drain piping must be installed by a dealer or
qualified personnel in accordance with the
Installation Manual to ensure proper drain-
age. Improper drain piping may cause water
leakage, resulting in damage to the furnish-
ings.
To prevent the risk of water damage to the
furnishings, provide a separate trap for the
backup drain piping, and do not connect the
main drain piping and the backup drain pip-
ing in the upstream of the trap for the back-
up drain piping.
Ensure proper drainage. Improper drain pip-
ing may cause water leakage, resulting in
damage to the furnishings.
To prevent refrigerant leakage that can pose
a risk of oxygen starvation, use the flare nut
with a hole (supplied with refrigerant ser-
vice valve) to make flare connections.
Check for refrigerant leaks. If the refrigerant
leaks, oxygen starvation may result. If the
leaked refrigerant comes in contact with a
heat source, toxic gas will be generated.
To prevent the risk of failure to detect refrig-
erant leakage that can lead to oxygen star-
vation, perform air tightness test before
insulating the pipe connections. Refrigerant
detector may not be able to properly detect
refrigerant leak from pipe connections cov-
ered with insulation.
Before brazing connecting pipes, make sure
to remove them from the service valve. Fail-
ure to do so may heat up the valve, resulting
in unit malfunctions, wire burn damages,
and refrigerant leakage that can pose oxy-
gen starvation.
To prevent damage to the piping and resul-
tant refrigerant leakage that can pose oxy-
gen starvation, do not let the edges of the
parts come in contact with the adjacent pip-
ing.
Check if some water is retained in the drain
trap at periodic inspection. Water shortage
may cause water leakage, resulting in dam-
age to the furnishings.
To keep the ceiling and floor from getting
wet due to condensation, properly insulate
the pipes.
iv