SPC DERV Installation, Operating And Maintenance Instructions page 8

No thinning of the flare tube material
•
No cracked or split tubes
•
No longitudinal scoring or tool marks
•
Correct torque setting used to match diameter of nuts
•
After having completed the pipework the system should be pressure tested to ensure that there
are no leaks. Dry nitrogen up to a maximum pressure of 10 bar should be used and all joints
should be tested using leak detection spray or detergent.
4.3.2 Coil connections
For DERVDX size units 150 and 250 the evaporator coil in the indoor unit is equipped with a
capillary type expansion device. This device is factory brazed onto the coil within the casing of the
indoor unit. The liquid and vapour connections terminate outside the casing of the unit and are
sealed; the coil contains a holding charge of nitrogen which should be heard escaping when the
connections are opened with a hole cutter.
For unit sizes 375 and 500 the indoor units are supplied with a loose thermostatic expansion
valve. The valves must be fitted outside the casing of the unit and should be installed in line with
the instructions supplied with the device. When brazing the TEV into the liquid line it is important
that the valve is protected using wet rags so as to avoid any damage to same. The TEV should
be fitted as close as possible to the liquid connection on the coil.
4.3.3 Evacuation
After leak testing, the pipework should be evacuated before any of the valves are opened. The
vacuum pump should be connected to both the high and low side of the system and a deep
vacuum drawn to 500 microns. Triple evacuation is recommended if the vacuum pump cannot
achieve such deep vacuum levels.
4.3.4 Refrigerant charge
The outdoor unit is shipped with sufficient refrigerant for operation of the system with up to 5m
liquid line distance between the indoor and outdoor unit. The required system charge will be
indicated on the charging chart inside the access cover of the outdoor unit.
If the length of the liquid line exceeds 5m then additional charge should be added according to
the diameter of the liquid line. For 3/8" diameter pipe refrigerant should be added at a rate of 60
grams/metre and for ½" diameter pipe at a rate of 120 grams/metre.
If the unit is supplied without refrigerant or the refrigerant recovered and the whole system
evacuated then the full charge as shown on the charging table will need to be added.
4.3.5 Oil traps
To ensure adequate oil return to the compressor it is recommended that oil traps be fitted with at
least one trap for every 3m of vertical height. When the outdoor unit is above the indoor unit the
traps should be fitted in the suction line, if the indoor unit is above the outdoor unit then the traps
need to be fitted in the liquid line.
QA/IOM/63 ISSUE 2 - DERV Page 8 of 19