Support
Stage 3 In stage three of this method the system must be evacuated to the same level as the deep vacuum method ( 500 microns ). The reason for this is that in this stage all the non-condensables as well as the remaining water vapour must be removed . This evacuation will take much less time than the evacuation in the deep vacuum method because there will be very little , if any , moisture left inside the plant .
Jabu , the following represents the equipment that you will require in order to draw a vacuum on a system :
• A two stage vacuum pump that can evacuate down to 50 to 100 microns
• Manifold gauges
• Refrigerant type hoses
• A special vacuum gauge that can indicate very low absolute pressures . ( Typically we use a micron gauge ) The very deep vacuum ( or the very low absolute pressure ) required for evacuation cannot be read on the normal manifold gauges .
• Mechanical gauges to measure vacuum are available , however , the more modern electronic gauges are more popular because of their ease of use and the fact that they are not as susceptible to damage .
Three types of vacuum gauges are available , these are : |
1 . |
The gauge with LEDs to show the vacuum reached , |
2 . |
The digital vacuum gauge , and |
3 . |
The analogue gauge |
The units used for indicating the absolute pressure on the vacuum gauge can be in microns , Pascal , mbar , Torr or mm Hg ( mercury ).
Jabu , let us have a look at the manifold sets that most technicians use .
We are all familiar with the standard three-pipe manifold sets , but they are limited in their efficiency for evacuation requirements . The long 6mm lines are restrictive and offer resistance which increases effective evacuation times .
We can improve on the standard manifold gauge lines by keeping your manifold lines as short as possible . There are shorter lines available (± 250mm long ).
On some manifolds there is an additional port for evacuation , with a larger 9.5mm yellow hose and hose connection . Internal ports are also larger on these sets . This is specifically for evacuation and reduces evacuation times considerably .
Although it is very convenient to use the manifold gauge to connect the pump and the gauge to the system it is preferable to use solid copper piping for the connection ( 6 mm for small
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RACA Journal I May 2022 www . hvacronline . co . za