Pull a Deep Vacuum Twice as Fast

How much would you pay for a vacuum pump that could evacuate a system in half the time of your current one? Think of how much time it would save you! The good news is you can probably cut your evacuation time in half just by changing your vacuum setup.  If you are like most techs, you are using ¼” hoses and your standard manifold while pulling through Schrader valves. And that is exactly the problem. The Schrader valves, gauge passages and small hoses all add up to a big restriction. No matter how wonderful your pump is you can’t pull a vacuum quickly through that setup. So the answer is not to get a new vacuum pump, it is to connect it with less restriction.

This will involve some financial investment in better equipment, but it will cost less than a new vacuum pump and yield far more results. First, I would purchase two core removal tools. They cost about $50 each. Removing the Schrader core while you evacuate the system is the single most important step in reducing the restriction and reducing the time it takes to evacuate a system. This $100 investment should cut your time in half, even if you don’t change anything else.

The next recommendation is to get a short ½” hose to connect to the ½” port on your vacuum pump. Appion makes a 6” hose with a ½” connection on one end and a 3/8” connection on the other. If you are using four port gauges with a 3/8” vacuum port, this short hose will connect right to it.  This costs around $35. So for $135 you can easily cut your vacuum time in half if you are already using four-port gauges with a 3/8” vacuum port.

You don’t have a 3/8” vacuum port on your gauges? If you are using valve core tools you don’t really need gauges to pull a vacuum. The valves in the core tools allow you to blank off after the vacuum is pulled and connect your charging hoses and refrigerant. With that in mind, put a 3/8” tee on the short hose which is connected to the vacuum pump. Finally, connect two hoses from the tee to the core tools. Appion makes ½” hoses with a 3/8” connection on one end and a ¼” connection on the other which will allow you to do this. These are about $75 each. Since you are using valve core tools, you can connect your vacuum gauge to the side port of one of the core tools.

A couple of final notes. Change the oil in your vacuum pump! Vacuum pump oil gets dirty every time it is used, and dirty oil reduces the vacuum pump’s ability to pull a good vacuum. Not to mention letting running the vacuum pump with dirty oil can shorten its life and you WILL need a new vacuum pump.  You should always start out with fresh oil every time you use your vacuum pump. For large jobs, or particularly dirty systems you may need to change the oil more than once. And of course, use a vacuum gauge. Without a vacuum gauge you don’t really know when you have a good vacuum. You can get a micro BlueVac vacuum gauge for around $100.

 

Sucking Through a Coffee Stirrer

Have you ever tried using a coffee stirrer as a straw? I have attempted to use a coffee stirrer as a straw when I was really thirsty, needed a straw, and none were available. After all, they do look like a straw: they have a small hole running up the middle. In fact, you can get a little bit through, but the process is slow and frustrating. The restriction created by the small hole in the coffee stirrer just will not allow very much through. When you connect your vacuum pump up through standard 1/4” hoses, leaving the Schrader cores in the Schrader valves, you are essentially forcing your vacuum pump to draw through a coffee stirrer. It’s not impossible, but very slow and frustrating. The restriction imposed by the Schrader valve and small diameter hoses restrict how much gas can come through, slowing the process down. You can dramatically reduce the time it takes them to evacuate a system by removing these restrictions. In fact, removing the restrictions will do far more than getting a bigger vacuum pump. The same pump you already own can probably evacuate systems in half the time you are accustomed to by simply removing the restrictions (assuming you keep the pump clean and change the oil). The biggest restrictions are the Schrader valve cores. You can buy two vacuum rated core removal tools and dramatically reduce your evacuation time, even using the same hoses and gauges  (so long as they don’t leak). The core removal tools allow you to remove the core, evacuate the system, charge the system, and then replace the cores. Next, you might want to use 3/8” or even 1/2” hoses to evacuate rather than 1/4” hoses that came on your charging manifold. That replaces the coffee stirrer with a properly sized straw. Finally, you should consider using a manifold with a larger bore. Any one of these improvements will make a noticeable difference; all together, the effect is close to amazing. Appion sells a Megaflow Speed kit that packages these three components together. Tru-Tech sells a Rapid Evac Kit that contains the hoses, valve core tools, and some Nylog vacuum sealer. They are both a little expensive compared to standard manifolds or 1/4" hoses, but they work much faster. Just ask yourself this – how much would you pay to cut your evacuation time in half.

If you teach air conditioning, you should contact Appion. They are giving away a vacuum pump to schools that purchase one of their Megaflow Speed Kits. While you are at it, ask for one of their recovery machines too. Note: this deal is just for schools – they are not giving away a recovery machine and vacuum pump with every gauge set sold. E-mail sharon@appioninc.com and ask for details on their educational program.

Warning: After you use better equipment you won’t want to return to your old coffee stirrers.

Does Your Vacuum Pump Suck?

For many technicians, the answer is no – which is bad. Vacuum pumps are supposed to suck. If you are using your compound gauge to tell you when you have a vacuum, you really don’t know what your vacuum pump can do because a compound gauge can’t tell you. The difference between a great vacuum and an awful vacuum just can’t be seen on a compound gauge. It is a little like trying to measure the distance of a millimeter using your car’s odometer. You need a micron vacuum gauge to check the vacuum your pump produces. It is not unusual for a vacuum pump to be in such bad shape that a vacuum gauge connected to it won't register anything. That is not because the gauge is broken, but because the pump does not suck. 

The reason many vacuum pumps in the field do not produce anything close to their rated vacuum or capacity is that their oil is not changed often enough. How often should it be changed? Basically, whenever it gets dirty, it should be changed. You might be able to pull a vacuum on several small, clean systems before changing the oil, or you might need to change the oil in the middle of an evacuation on a particularly nasty system. Vacuum pump oil should be clear. If it has become cloudy or discolored, it needs changing. It is never wrong to change the oil. You normally have several hundred dollars in your vacuum pump even if you got it on sale. Leaving dirty oil in it really does not make economic sense because the crud in the oil is eating up your machine.

The oil not only lubricates the mechanical parts, it also provides the vacuum seal. When stuff is dissolved in the oil, the oil produces a vapor pressure from all the stuff in it – water, refrigerant, flush solution. The vacuum pump cannot pull down any lower than the vapor pressure of the oil in it. So if you have 10W30 instead of vacuum pump oil, or your 10W30 is full of water from all the systems you evacuated this past month, your vacuum pump likely does not suck.  If you have a traditional rotary vane vacuum pump with the oil reservoir on the outside and a sight glass in the middle, you can usually remove that oil reservoir and clean it. We actually change our oil a lot at school – a whole lot more than usually happens in the field. But we still get a good layer of scum on the bottom.  We dismantle our pumps at school at least once a year and clean out all the crud that has collected in the bottom of the oil reservoir. Just pouring oil through does not get the job done. So if your vacuum pump does not suck, try cleaning it and changing the oil.