You already know that a refrigeration pipe circuit should only include refrigerant and oil. The presence of even a little quantity of moisture, air, or a mixture of non-condensable gases may wreak havoc on the efficient operation of your system. Every time the system is opened and exposed to outside factors, it is essential that the refrigerant circuit be evacuated properly to preserve its integrity. It is required by the EPA that systems be evacuated to a depth of at least 300 microns, but what equipment should be used to accomplish this?
The purpose of evacuating a system is to get the pressure down to as near to zero as feasible from the atmospheric pressure of 14.7 PSI (760,000 microns). Standardization at or above 300 microns is usually necessary. You’ll need a device that can create a strong vacuum to drag the system into it. It can only be done if the system is leak-free (or “tight”). There will be no way to get the system low enough if it is leaking.
Do a dry run on the pump before you start the evacuation procedure. Check if your pump can effortlessly draw down to 50 microns by attaching a micron gauge directly to it. If you’re having trouble getting the reading below 50, make sure there are no air leaks around the connection ( I like to use a little Nylog). Verify the hose gaskets are in excellent condition and use fresh oil. Put a few drops of denatured alcohol into the gauge port of your micron gauge with an eyedropper if you think it could be broken. For best results, let the alcohol rest for a few seconds, then gently tilt the gauge up and down a few times before discarding it. If you suspect that oil or anything else is contaminating your gauge sensor, you should repeat this operation many times. You should re-test it and, if you have access to other micron gauges, compare the results.
Hoses designed for use in an emergency evacuation
To avoid damaging your charging manifold, avoid using it to draw vacuums. A standard charging manifold has a restricted diameter (often 1/4″) and several other constraints, such as core depressors. In addition, the vast majority of hoses found on charging manifolds are not designed to be used under pressure, making them useless in the event of an evacuation. If the micron level fluctuates much from the above test, or if the level instantly increases after the pump is separated, you know that there is a leaking spot in your arrangement and should investigate more. Get a separate set of hoses just for vacuuming, as suggested by yours truly. Appion hoses have served us well, and I urge my assistants and trainees to invest in them. You’ll be grateful to me afterward.
These hoses are great since they are 3/8″ in diameter all the way through, have a 3/8″ female connection on one end that can be screwed into your pump, and have a 1/4″ female connection on the other end that can be used with a wide variety of pumps and other devices. For evacuating big tonnage units, I have found that utilizing these hoses significantly shortens the time required.
Tool for Extracting the Core
How does this arrangement function if there are no core depressors? you may be asking yourself at this time. The core removal instrument is necessary at this stage. The fastest feasible evacuation can only be achieved with the least restricted setup. Shrader cores and hose depressors must be removed for this. Whilst I have experience with both the Appion and yellow-jacket core removal instruments, I have found that the Appions are superior for actual evacuation. Two of the yellow jacket tools have leaked on me when placed in a vacuum, although it may simply be my bad luck.
If you have never used one of these before, you thread the tool onto your 1/4″ Shrader core port and then draw back the core removal section of the tool. You can tell it’s properly aligned onto the Schrader core by pressing the removal portion back in and towards the core. You may now remove the core by unscrewing it, pulling the remover part out of the tool body, and then closing the isolation valve.
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With this helpful device, you may remove leaky cores for evacuation and replacement without having to withdraw the charge. For each available port, I have two of these gadgets in my emergency kit. Using these tools during your evacuation has the extra advantage of isolating them from the refrigerant system entirely. It is no longer necessary to second-guess whether a growing micron level is the result of a leaking hose or if there is still a refrigerant leak if you have your micron gauge directly on the system, as you should.
The blank-off isolation valve undoubtedly leaks on your Vacuum Pump if it’s anything like the pumps I’ve used. The isolation valves in these pumps don’t appear to be very sturdy and always end up leaking. Nevertheless, the Tez 8 pump shown above does not have a safety shutoff valve. Before I upgraded to the Tez 8, I used a JB pump and this yellow jacket evacuation manifold. With the evacuation tree, not only do you get a valve that holds, but you also get two 3/8″ evac hose connections and a 1/4″ port.
The Tree’s base is a standard half-inch (0.5″), making it compatible with the vacuum pump’s greatest connection point; a reduction fitting from 1/2 to 3/8″ is also included for use with vacuum pumps that lack a 1/2-inch inlet. While the 1/4″ port at the top of the tree is a perfectly acceptable location for some people to run their micron gauge, I find it far more convenient to attach mine to one of the side ports of the Schrader core removal tool, as we covered previously.
Scale in Microns
A good Micron gauge comes in last. This is a crucial instrument for judging whether the system has been sufficiently evacuated from moisture and gases. Throughout the years, we have tested a wide variety of micron gauges, some of which proved to be entirely unreliable and prone to leaks, while others proved to be excellent. In my opinion, a yellow jacket is a must-have item. If you want accurate readings from your gauge, you need to be careful not to get oil on the sensor. Never attach it at a downward slant, since this will increase the likelihood of oil getting into your sensor.