Support
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switch mounted on the pump. Check that the on/off switch is the
only source of ignition in the pump. If this is the case, the vacuum
pump can be safely used with flammable A2L-refrigerant if the
on/off switch is not used:
• Move the switch to the on position and plug the pump into
a socket outside a minimum 3m radius from the unit and
control the vacuum pump from this socket. •
•
In Addition, keep the vacuum pump in a well-ventilated area
or outside. The flammable refrigerant discharged by the pump
should be able to safely disperse and should not result in a
flammable situation.
Vacuum pumps with a brushed motor should not be used
because of the high energy sparks they create within the motor. Recommended procedure for recovering Hydrocarbon
refrigerants from small refrigeration units:
SERVICE TOOLS
In general, all service tools that are being used for HFCs can be
used for hydrocarbon refrigerants.
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•
•
RECOVERY MACHINES
Standard recovery machines cannot safely recover flammable
refrigerants and therefore must not be used. Unlike vacuum
pumps there are several sources of ignition (on/off switches,
relays, pressure switches).
A leak would result in a flammable zone around the machine.
As these hazards cannot be avoided; the correct recovery
machine must be used. Again, currently these machines are not
freely available from South African suppliers.
It is important to note the following:
•
•
•
•
•
Evacuate the recovery cylinder to remove air before filling it
with flammable refrigerant.
Do not mix flammable refrigerants with other types of
refrigerant in a recovery cylinder.
When recovering hydrocarbon refrigerants, do not fill the
recovery cylinders with more than 45% of the HFC safe fill
weight.
Label the recovery cylinder to show it contains a flammable
substance.
A2L synthetic refrigerants (as HFOs and R32) must be
recovered as with the HFC refrigerants and not vented to
the atmosphere.
LEAK DETECTION
Most electronic leak detectors used for HFC and HCFC leak
detection are not safe or sufficiently sensitive for use with
flammable refrigerants. This of course means that we will need to
use electronic detectors specifically for flammable gases.
Flammable refrigerant systems must be leak-tested using a
method that is safe and sensitive: for example, service cylinders.
The standard for Hydrocarbons used is:
• A red shoulder (donating: flammable gas).
www.hvacronline.co.za
Left hand thread (an adapter piece is required to connect
manifold).
Minimum test pressure = 4800 kPa.
Fill rate for recovery cylinders should be noted as they differ
from HFCs, HCFCs.
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•
•
•
•
•
Ventilation fan 3m from the working area and position at
floor level.
Recovery unit 3m from the working area to recover the
hydrocarbon refrigerant.
When the desired low pressure is reached or the low-
pressure lamp illuminates, switch the unit to low pressure
override and allow it to run for two minutes (to remove
refrigerant from the oil).
Pressurise the system with nitrogen to just above
atmospheric pressure.
Using an HC sensor, check that no hydrocarbon refrigerant is
in the air before using the brazing torch.
Open or cut the connections and complete the service
operation.
Braze back the connections.
Cylinders for flammable refrigerants have left thread
connections. They differ from the traditional HFC refrigerant
cylinders to avoid use of the incorrect fittings and underline
the type of refrigerant being used.
Recommendations for vacuum, recovery and leak checks for
A2L-refrigerants are valid for A3-refrigerants.
For small quantities of hydrocarbons to be evacuated from
a system, normal practice recommends venting, but always
refer to national legislation. Regardless, venting needs to be
conducted in a well-ventilated area, away from any ignition
source.
TRANSPORTATION
Chris this brings us to the next aspect and that is the transport of
flammable gases in cylinders and equipment.
Let us consider both the transport of flammable gases in
cylinders, for example by the contractor, and the transport of
refrigeration and air conditioning systems which are charged
with flammable refrigerants. The most common requirements
of service companies and manufacturers are covered as follows:
Continued on page 55
RACA Journal I February 2020
53