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NS-AC06PWH1/NS-AC07PWH1/NS-AC08PWH1
• Checks to electrical devices
Repair and maintenance to electrical components shall include initial safety checks and component inspection
procedures. If a fault exists that could compromise safety, then no electrical supply shall be connected to the circuit
until it is satisfactorily dealt with. If the fault cannot be corrected immediately but it is necessary to continue
operation, an adequate temporary solution shall be used. This shall be reported to the owner of the equipment so
all parties are advised.
Initial safety checks shall include:
That capacitors are discharged: this shall be done in a safe manner to avoid possibility of sparking;
That there are no live electrical components or wiring exposed while charging, recovering, or purging the system;
That there is continuity in the grounding.
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Repairs to sealed components
• During repairs to sealed components, all electrical supplies shall be disconnected from the equipment being worked
upon prior to any removal of sealed covers, etc. 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.
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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.
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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.
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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.
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Leak detection methods
The following leak detection methods are deemed acceptable for systems containing flammable refrigerants.
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. 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.
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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.
