Hitachi PMML0524 Instruction Manual page 5

Additional safety manual for R32 refrigerant air conditioner and heat pump according to IEC 60335-2-40:2018
3. Repairs to sealed components
• If it is absolutely necessary to have an electrical supply to
equipment during servicing, then a permanently operating
form of leak detection shall be located at the most critical
point to warn of a potentially hazardous situation.
• Particular attention shall be paid to the following to ensure
that by working on electrical components, the casing is not
altered in such a way that the level of protection is affected.
• This shall include damage to cables, excessive number of
connections, terminals not made to original specification,
damage to seals, incorrect fitting of glands, etc.
• Ensure that apparatus is mounted securely.
• Ensure that seals or sealing materials have not degraded
such that they no longer serve the purpose of preventing the
ingress of flammable atmospheres.
• Replacement parts shall be in accordance with the
manufacturer's specifications.
NOTE: The use of silicon sealant may inhibit the effectiveness
of some types of leak detection equipment.
Intrinsically safe components do not have to be isolated
prior to working on them.
4. Repair to intrinsically safe components
• Do not apply any permanent inductive or capacitance loads
to the circuit without ensuring that this will not exceed the
permissible voltage and current permitted for the equipment
in use.
• Intrinsically safe components are the only types that can
be worked on while live in the presence of a flammable
atmosphere.
• The test apparatus shall be at the correct rating.
• Replace components only with parts specified by the
manufacturer.
• Other parts may result in the ignition of refrigerant in the
atmosphere from a leak.
5. Cabling
• Check that cabling will not be subject to wear, corrosion,
excessive pressure, vibration, sharp edges or any other
adverse environmental effects.
• The check shall also take into account the effects of aging
or continual vibration from sources such as compressors or
fans.
6. Detection of flammable refrigerants
• Under no circumstances shall potential sources of ignition be
used in the searching for or detection of refrigerant leaks.
• A halide torch (or any other detector using a naked flame)
shall not be used.
7. Leak detection methods
• Electronic leak detectors shall be used to detect flammable
refrigerants, but the sensitivity may not be adequate, or may
need re-calibration. (Detection equipment shall be calibrated
in a refrigerant-free area.)
• Ensure that the detector is not a potential source of ignition
and is suitable for the refrigerant used.
• Leak detection equipment shall be set at a percentage of the
LFL of the refrigerant and shall be calibrated to the refrigerant
employed and the appropriate percentage of gas (25 %
maximum) is confirmed.
• Leak detection fluids are suitable for use with most
refrigerants but the use of detergents containing chlorine
shall be avoided as the chlorine may react with the refrigerant
and corrode the copper pipe-work.
3 PMML0524 rev.2 - 01/2021
7. Leak detection methods
• If a leak is suspected, all naked flames shall be removed/
extinguished.
• If a leakage of refrigerant is found which requires brazing,
all of the refrigerant shall be recovered from the system, or
isolated (by means of shut off valves) in a part of the system
remote from the leak.
• Oxygen free nitrogen (OFN) shall then be purged through the
system both before and during the brazing process.
8. Removal and evacuation
• When breaking into the refrigerant circuit to make repairs –
or for any other purpose –conventional procedures shall be
used. However, it is important that best practice is followed
since flammability is a consideration.
The following procedure shall be adhered to:
• remove refrigerant
• purge the circuit with inert gas
• evacuate
• purge again with inert gas
• open the circuit by cutting or brazing
• The refrigerant charge shall be recovered into the correct
recovery cylinders.
• The system shall be "flushed" with OFN to render the unit
safe.
• This process may need to be repeated several times.
• Compressed air or oxygen shall not be used for this task.
• Flushing shall be achieved by breaking the vacuum in the
system with OFN and continuing to fill until the working
pressure is achieved, then venting to atmosphere, and finally
pulling down to a vacuum.
• This process shall be repeated until no refrigerant is within
the system.
• When the final OFN charge is used, the system shall be
vented down to atmospheric pressure to enable work to take
place.
• This operation is absolutely vital if brazing operations on the
pipe work are to take place.
• Ensure that the outlet for the vacuum pump is not close to
any ignition sources and there is ventilation available.
9. Charging procedures
• In addition to conventional charging procedures, the following
requirements shall be followed.
– Ensure that contamination of different refrigerants does not
occur when using charging equipment.
– Hoses or lines shall be as short as possible to minimize the
amount of refrigerant contained in them.
– Cylinders shall be kept upright.
– Ensure that the refrigeration system is earthed prior to
charging the system with refrigerant.
– Label the system when charging is complete (if not
already).
– Extreme care shall be taken not to overfill the refrigeration
system.
• Prior to recharging the system it shall be pressure tested with
OFN.
• The system shall be leak tested on completion of charging
but prior to commissioning.
• A follow up leak test shall be carried out prior to leaving the
site.