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TVP Manual (full) March 2007 CE rev 03.doc
CAUTION
Most leaks are found at the connections of refrigerant lines, pay particular attention to these
areas. These joints should be checked regularly throughout the life of the installation.
Check all brazed joints for any leaks.
Check valve bodies in the valve box.
If a leak is found at a Parker coupling, ensure that the joint is fully tightened. If the leak
persists the joint will have to be disassembled and re-seated. Parker fittings may be
re=surfaces using 1200 grade wet or dry paper mounted on a glass or "Tufnol" block.
Leaks on a brazed joint must be repaired using hard solder. Open the manifold valve and
release the gas from the refrigerant line and cryo-coil before attempting a repair.
CAUTION
Failure to identify and repair leaks before operation will lead to poor performance system
contamination and in extreme cases total system failure.
2.10 Preparation of cryo-coil and refrigerant lines
It is essential a two-stage vacuum pump capable of better than 3 x 10
-3
mbar is used.
Standard refrigeration manifold lines and an oil free reclaim unit are essential. Always start
from the position of having all of the valves on the manifold and the TVP closed when carrying
out any service or installation work.
Evacuate the refrigerant lines and cryo-coil through the system access valve to 0.005 mbar or
less. As evacuation refrigeration lines are severely conductance limited a minimum evacuation
time of at least two hours is recommended. Close the TVP unit’s access valve while the
vacuum pump is still running. Close all hand valves and isolate the system before turning the
vacuum pump off.
If the system pressure is greater than 235psi back filling of the line will probably not be
required unless they are very long. The common return cool and defrost hand valves maybe
opened ideally in that order.
Your objective is to achieve a static system pressure at ambient with the hand valves open of
210 to 235psig. Above this value the system may trip it’s over pressure trip and below this
range full cooling capacity may not be realised. If the system pressure is outside this range
use a top-up charge to increase system pressure or reclaim unit to reduce the pressure.
2.11 Connection of external temperature sensors
To optimise the cycle time for any given system it is good practice to use the remote sensors
and place them on the refrigeration lines as close as possible to the vacuum feed-through as
possible.
A TVP uses PT100 platinum resistance sensors, which offer greater stability, accuracy and
durability than thermocouples. External sensors with 6m leads are included in the package;
they maybe extended to 12m with low impedance wire, with no loss of accuracy.
To connect the remote sensors remove the blanking connector and insert the remote sensors
supplied. The system will automatically switch to the external sensor. See diagram 9 for
location and connector
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