Refrigeration 101

By: ssjwizard


As mentioned before there are a few ways you can do this using various setups and equipment IM going to start with the professional way and work my way down to the "ghetto" way.

Nanny boy way:

this is basically just hooking up your system and taking it to a refrigeration shop and having them charge it up for you can range from 15-40 dollars.

Pro way: for this you will need a few pieces of hardware:

01) a set of R-12/R-22/R134 standard gauges OR a set of automotive R134 gauges with a retrofit kit.
02) 1 vacuum pump any size(can be fabricated)
03) refrigerant
04) nitrogen
05) bucket of warm soapy water

The first thing you will need to do is connect your gauges. Yellow to the refrigerant, blue to low side(evaporator), red to high side(condenser). what we are going to do now is fill the system with nitrogen to check for leaks because you don’t want to be wasting potentially hazardous or expensive refrigerant. So connect your bottle of nitrogen up to your refrigerant line and open the low side valve on your gauge set and allow nitrogen to enter the system until its gets to about 250psi then close the valve. This is where the warm soapy water comes into play. Use a rag or similar to drip some over every joint and watch for bubbles as the system is cycling. Now at this point if you have leaks you need to fix them first lets get the refrigerant back into its bottle. So what you want to do is open the high side valve on your gauge as the system is running this will get most of the nitrogen back into its bottle. Now of course there will be some left just close the valves unscrew your nitrogen bottle and on to the next step. Now what we need to do is vacuum the system out if you go all the way down to 29.74 inches of vacuum all of the moisture should be out of the system while that’s optimal if you pull it that low you can also compromise the oils. At a minimum with a good vacuum pump you need to run at least an hour. So the way you do this is you hook the suction side of your pump up to the refrigerant hose(yellow) on your gauge set. Now you just click on your vacuum pump and open both the high and low side valves at the gauge. Let it run to your desired vacuum level then detach it from your system you are now vacuumed next step is to fill. Now in filling your system what you want to do is hook up your refrigerant bottle to the yellow line and open your low side valve this will add refrigerant.

OK watch your psi on the high side wait for it to get to about 150 psi then close the valve. Now at this point the low side pressure should be a bit high 30-40 maybe less depending on your system. Wait about 5 minutes for this pressure to stabilize check and see if the evaporator is cold it will at this point with most refrigerants. By this point hopefully your low side is low again (as close to 0 or under as possible) what we can do now it tweak the charge. If you want a higher heat load at the cost of a bit of coolant temperature then you want to add more refrigerant get it so the low side is as high as you can stand(under 50psi) while the high side is reasonable(220-250). if you added to much refrigerant or just want more of a vacuum at any cost let some refrigerant out to do this you open the high side valve it will force some refrigerant back into the storage container due to its higher pressure this will bring down your low side pressure reducing the coolants boiling temperature. In the above description you CAN forgo the step of nitrogen testing for a semi professional job it will work just fine. You can also forgo the use of the vacuum pump BUT that is in no way the recommendation of the writer but your system will function without it.

OK now for the following steps you will need various combinations of equipment to charge up your system. The steps of nitrogen testing and vacuuming in the above listed method are recommended throughout all of these methods though for everyone its not necessary possible and can be forgone if absolutely necessary

Method #1: you need the following hardware for this:

01) R134 self charge hose(9 dollars at Wal-Mart or similar)
02) 1 set of R12 to R134 auto retrofit adapters
03) 1 can of R134 or refrigerant of your choice

OK with this method you will take your main adapter and put it on the low side shrader valve and if using refrigerant other than R134 another to that access valve on that and connect it to the other end of the hose(about 1 foot long so choose wisely) now turn on your system and open the refrigerant valve allow refrigerant to flow into the system until the evaporator begins to get cold then stop the flow. Let it cycle for a few minutes and add a bit of refrigerant the temperature at the evaporator should get even colder due to a better flow of liquid freon and watch the temperatures until you get the highest temperature you are willing to stand for and disconnect hook it up to your system and if your heat load capacity is good and you want to try to bring down the temperature a bit use a pen or similar to press in the high side valve to let some out or hook your assembly up to the high side and open it Freon should flow back into the container. VIOLA you’re done!

Method #2: you need the following parts for this setup

01) 2 home air conditioning self test set or 1 test set and 1 charge boost set
02) refrigerant that fits the home refrigeration standard(not automotive R134 unless you feel like adapting it)

OK now take one hose and hook it up to your low side and attach your refrigerant bottle here. Take the little gauge provided with this kit and hook it up to the high side pressure this isn’t going to provide to much help but just a bit. Flow in refrigerant using the same instructions provided in last two methods until the little gauge tops off then let it cycle and detach it from the high side hook it up to your low side to test your lsp(low side pressure) you want this as low as possible but with still enough freon to handle the heat load so 20ish is ok and 30ish is good for heat load it will give up a bit of the low temp to do so though if your system was vacuumed it may read 0psi which means its 0 or in vacuum which can be great for temps if your system is big enough. You may want to add or remove refrigerant at this point till you get it to a charge you like.

Method #3(ghetto greatness): you need quite a bit of hardware for this but it’s a good end user solution:

01) 2 standard compressed air gauges preferably ones with a vacuum rating
02) 4 short steel or brass fittings to attach the gauges
03) flux coated brazing rods(if using other than brass fittings
04) any of the before mentioned connecting hardware(you can actually purchase a set of hoses for a gauge set without the gauges its about 30 bucks)
05) refrigerant(DUH!)

OK now what your going to need to do is install this stuff before you close your loop or cut your system open and attach this stuff. OK what you need to do is on either side of the shrader valves attach your gauge using the fitting and braze/solder it onto the standard piece of copper tubing your using simple stuff. To connect just slide the copper pipe inside of the gauge fitting and if you want crimp it shut and then fill the excess with solder or brazing compound do this on both sides and you permanently attached set of gauges. Now fill the system watching your pressures go up until they hit your optimum goal following the Pro method.

Any of these will work and will be reasonably easy/accurate to perform for your typical user pick the method that suits you best. As previously mentioned you will get better results if you vacuum and use a drier but they can be forgone if you situation demands it. Before I go here’s a common method used to adapt a bbq bottle to fill your refrigeration system.


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