Technical data

23
Refrigeration pipework
Skill requirements
All interconnecting refrigeration pipework must be
installed, tested and commissioned by a specialist
refrigeration contractor, who should provide for each
operator, Certificates of Competence regarding the Brazing
of Refrigeration Copper Pipework, and the Safe Handling
of Refrigerants.
Material
Only refrigeration quality seamless copper pipe must be
used. This must conform to the requirements of BS2871
– Part 2, being of suitable quality for use with refrigerants.
Full details of maximum allowable pressures for pipework
and fittings are detailed in ‘The Engineers Guide’ published
by 3D Air Sales Ltd.
Pipework site management
To minimise the number of joints, coiled copper should
be used in preference to straight lengths. Brazed joints
should be used in preference to flared joints. All pipework
must be square cut using a propriety pipe cutter to give
a clean cut, without copper fragmentation. Hacksaws
must not be used. Tubes must be capped to avoid ingress
of moisture and dirt.
Brazed joints
When brazing all pipework must be purged with nitrogen
(low pressure oxygen-free), providing positive pressure
in the pipe, preventing the formation of cooper oxide
particles and scale. An annulus must be used between the
feed pipe and the refrigerant pipe, to eliminate the ingress
of air, at the point of entry. The formation of scale and
particles will result in valves and capillaries becoming
blocked. Particles entering the compressor may cause
a reaction with the refrigerant oil, resulting in acidic
decomposition of the compressor motor windings.
Pipework support
Copper pipework must be supported correctly, by suitable
clamps, or in perforated cable tray. Where clamps are
used, the pipework must be supported at the maximum
centres stated below:
Pipe sizes
It is essential to use the pipe diameters stated in the
Engineering Data tables relevant to each system. The
stated sizes must be used for all pipe lengths up to the
maximum length.
Traps
Do not use traps anywhere in the refrigeration pipework.
Maximum pipe length
Do not exceed the maximum length and vertical separation
between the indoor and outdoor units, as stated in the
specification data table.
Flared joints and pipe bends
Place the flare nut on the tube prior to flaring. Use a
good quality proprietary flaring tool. Lubricate the tool
and the copper pipe with refrigerant prior to flaring.
Inspect the flared copper carefully, ensuring there are no
cracks or flaws in the copper.
Pressure testing
Ensure that outdoor unit service valves remain closed for
pressure testing. Perform pressure test with dry nitrogen,
up to 15bar. Inspect all joints for leakage. Check for any
deviation in pressure.
Position the pipe and
flare nut, and tighten
to the following limits:
FIXING CENTRES - SOFT TEMPERED COPPER TUBE
o.d. “ 1/4 3/8 1/2 5/8 3/4 7/8
HORIZONTAL 0.8 1.0 1.2 1.2 1.5 1.5
VERTICAL 1.0 1.2 1.5 1.5 1.5 1.8
FIXING CENTRES - HALF HARD COPPER TUBE
o.d. “ 1/4 3/8 1/2 5/8 3/4 7/8 11/8
HORIZONTAL 0.8 1.0 1.2 1.2 1.5 1.5 1.5
VERTICAL 1.0 1.2 1.5 1.5 1.5 1.8 1.8
TUBE DIA (o.d. in) 1/4 3/8 1/2 5/8 3/4 7/8
TORQUE kg/m
min 1.6 4.0 4.0 9.0 10.0 12.0
max 2.0 5.0 5.0 12.0 14.0 16.0
A
nnulus between o/dia. of nitrogen pipe and internal dia of
refrigerant pipe, sealed with rubber plug or similar.
This is to ensure complete purge of air from refrigerant
pipework.
Set nitrogen flow meter to 0.05m
3
/hr, OR (if no flow meter) set
pressure reducing valve to 0.2 Bar.
From Nitrogen Cylinder
Oxygen Free
Nitrogen gas