Carrier CDF-20Q7 Owner's Manual page 11

SAFETY PRECAUTIONS
(or any other detector using a naked flame) shall not be used.
11. 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.
12. 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.
13. 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 minimise 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.
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