Disclaimer: This is to be used as guide. This is to be used by someone who has knowledge of A/C systems. If you follow this guide and something goes wrong there is no implied or actual warranty. The only person who is reasonable if something goes wrong is You. PS If something goes wrong do not blame me.
Equipment required:
1. Valve Core removal tool (VCRT). Here is a great little video about using one:
2. Two stage vacuum pump
3. Hose that is vacuum rated (from the VCRT to vacuum pump)
4. AC manifold or pressure hose with suitable connectors, typically ¼ inch (from nitrogen regulator to VCRT)
5. Nitrogen tank (with gas)
6. Regulator for nitrogen
7. Digital Micron gage.
8. ¼ inch brass extension from micron gauge to VCRT port
Some general tips:
All the ports will have covers over them. They must be removed to connect the charging hoses. There is a cover over the valve that releases the refrigerant that must be removed. Once removed a hex driver is used to open the valve. Don’t open the refrigerant stop valve until the lines are attached, have been tested, and you are reasonably sure there are no leaks.
The nitrogen is used both as a pressure test and to remove any moisture in the system.
Don't use the charging hoses to pull a vacuum unless they are also vacuum rated. Many inexpensive hoses will work perfectly well under pressure, but may leak under vacuum. You don’t want to waste your time chasing vacuum leaks in your hoses and connections. Get a vacuum rated hose.
When pulling a vacuum and doing the hold test, make sure there are no hoses used to connect the micron gauge to the VCRT. Use only brass fittings.
Don't use just any old ball valve as it is likely to leak under vacuum. Use a valve core removal tool as a ball valve. The valve in the VCRT is usually better under vacuum.
Practice removing and replacing the valve core with your Valve core removal tool (VCRT) before you starting doing anything. Especially the replacement part, because at the end of this procedure, you will be doing it on a system containing refrigerant.
The VCRT has a movable end (stem) that can unscrew the valve core and pull it backward. Once stem is all the way back the valve on the VCRT can be closed. Once the valve is closed the stem can be removed from the main body. The end of the VCRT can be used as a port.
Watch videos of all these steps before you attempt them. There are lots of different approaches, it is well worth your while to view several, to get an idea of what is going on.
Initial setup:
1. Valve Core removal tool (VCRT) connected to service port. Leave the schrader valve in the side port.
2. Remove valve core in the service port using the VCRT. (Yeah, you could have removed it before you put on the VCRT, but it is good practice for a DIYer who doesn't do it every day).
3. Put the micron gauge on the side port (don't use a hose; use all brass connections with shortest possible path).
4. Connect a Vacuum-rated hose from back port on the VCRT to the vacuum pump. I put an optional ball valve on the vacuum pump end, to avoid blow back of oil when I turn the pump off (we'll call this the pump ball valve).
First vacuum of the system:
1. Turn on vacuum pump, open pump ball valve and the VCRT ball valve, and pump it down to medium vacuum (4000 microns or so).
2. Close VCRT ball valve.
3. Close pump ball valve.
Most of air & moisture in the line sets should be removed. Now we do a pressure test, and at the same time pick up most of the remaining moisture into the nitrogen.
Pressure test:
1. Remove vacuum hose from back port of VCRT (you have the VCRT ball valve closed, right?)
2. Set the nitrogen regulator pressure to 0 initially.
3. Setup hoses as follows:
Nitrogen -> middle port on service gauges.
Low pressure (blue) service gauge closed (don't need that side).
High pressure side (red) connected to outbound
High pressure service gauge valve closed for now.
4. Turn up nitrogen regulator up to 5 PSI (very small positive pressure).
5. Open VCRT ball valve.
6. Remove micron gauge, it might not be qualified for high pressure. ( Note that if you have the schrader valve core in the side port of VCRT, and the core depressor set correctly, there should be little gas exchange when you do this. Since you already gave it a light positive pressure of nitrogen, no air should be reintroduced in the system when you do so.)
7. Slowly open high pressure service gauge valve.
Check for gross initial leaks. If none, slowly increase pressure on regulator to your target. For me, it was 350psi. Close the service gauge high pressure valve. This will isolate the system under test from the nitrogen regulator.
Note the pressure on the service gauge. Wait for your desired hold time. An hour seems about right. During that time check for leaks with bubble test (Note: There are Leak Detector solutions on Amazon that will help to find leaks). If the pressure drops noticeably in an hour, you have a big leak. But even if the pressure does not appear to drop, you might have a tiny leak. Watch carefully for bubbles, this is what shows tiny leaks. Think about it, suppose the actually pressure dropped ½ of a psi in an hour. You wouldn’t notice it on the gauge. But in 200 hours you could have lost 100 psi. No bubbles after your hold time? Probably good to go. Don’t rush through this step, if you missed something and release the refrigerant into a system with even a tiny leak, you will regret it. Next step is vacuum purge.
Vacuum purge
1. Remove hose from nitrogen supply to middle port of service gauges.
2. Slowly open the high pressure value on service gauges and bleed down to 5 psi or so.
3. Close VCRT ball valve, remove hose between back port of VCRT and service gauges (high side).At this point, your line set is lightly pressurized with nitrogen, held in by the ball valve on the VCRT.
4. Reconnect your vacuum hose to back port on CRT.
5. Turn on vacuum pump.
6. Open the pump ball valve. This evacuates all the air that is in the vacuum hose, plus the little bit in the outside part of the VCRT.
7. Reconnect the micro gauge. Again, you have a light positive pressure in system, so when you reconnect, no air gets into the system.
8. Open VCRT ball valve,
9. Pump down to a deep vacuum, around 300 microns.
10. On the way down, partially close and open the CRT ball valve to get rid of any gas stuck behind the valve.
11. Once it reaches 300 microns let the pump run for at least 15 minutes,
12. Monitor the micron gage and make sure it stays there or lower.
When you have established a stable low vacuum of 300 microns or lower, close the VCRT ball valve. You can expect a very slow rise, but it should not go higher than 500 microns in 15 minutes. If you have met this goal, you have successfully purged your system of moisture. If the pressure increases to more than 500 microns repeat the pressure tests.
Opening the refrigerant ports:
Keeping the VCRT ball valve closed, crack open the refrigerant valves a bit, this introduces refrigerant in vapor form into your vacuum. Now you need to put the valve core back into the service port. Note that the stem that you use to push the valve core back into position will be under pressure. Keep a steady push, but gentle, and you will get the job done. Note that in order to install the valve core, you needed to open the VCRT valve once you have the stem screwed to the VCRT body. To see if you are doing things correctly, you can pull the stem back, and reclose the VCRT valve. Remove the stem from back port of VCRT, look at it. If it still has a valve core on it, you messed up, try again.
If you completed all the above steps correctly, you should be able to remove the VCRT, and the system will hold pressure. Test the service port with bubble test. You might have to (gently) snug up the valve core.
Now open both your refrigerant valves fully, replace cover caps (three of them), and you are good to go. Enjoy your new system!
Equipment required:
1. Valve Core removal tool (VCRT). Here is a great little video about using one:
3. Hose that is vacuum rated (from the VCRT to vacuum pump)
4. AC manifold or pressure hose with suitable connectors, typically ¼ inch (from nitrogen regulator to VCRT)
5. Nitrogen tank (with gas)
6. Regulator for nitrogen
7. Digital Micron gage.
8. ¼ inch brass extension from micron gauge to VCRT port
Some general tips:
All the ports will have covers over them. They must be removed to connect the charging hoses. There is a cover over the valve that releases the refrigerant that must be removed. Once removed a hex driver is used to open the valve. Don’t open the refrigerant stop valve until the lines are attached, have been tested, and you are reasonably sure there are no leaks.
The nitrogen is used both as a pressure test and to remove any moisture in the system.
Don't use the charging hoses to pull a vacuum unless they are also vacuum rated. Many inexpensive hoses will work perfectly well under pressure, but may leak under vacuum. You don’t want to waste your time chasing vacuum leaks in your hoses and connections. Get a vacuum rated hose.
When pulling a vacuum and doing the hold test, make sure there are no hoses used to connect the micron gauge to the VCRT. Use only brass fittings.
Don't use just any old ball valve as it is likely to leak under vacuum. Use a valve core removal tool as a ball valve. The valve in the VCRT is usually better under vacuum.
Practice removing and replacing the valve core with your Valve core removal tool (VCRT) before you starting doing anything. Especially the replacement part, because at the end of this procedure, you will be doing it on a system containing refrigerant.
The VCRT has a movable end (stem) that can unscrew the valve core and pull it backward. Once stem is all the way back the valve on the VCRT can be closed. Once the valve is closed the stem can be removed from the main body. The end of the VCRT can be used as a port.
Watch videos of all these steps before you attempt them. There are lots of different approaches, it is well worth your while to view several, to get an idea of what is going on.
Initial setup:
1. Valve Core removal tool (VCRT) connected to service port. Leave the schrader valve in the side port.
2. Remove valve core in the service port using the VCRT. (Yeah, you could have removed it before you put on the VCRT, but it is good practice for a DIYer who doesn't do it every day).
3. Put the micron gauge on the side port (don't use a hose; use all brass connections with shortest possible path).
4. Connect a Vacuum-rated hose from back port on the VCRT to the vacuum pump. I put an optional ball valve on the vacuum pump end, to avoid blow back of oil when I turn the pump off (we'll call this the pump ball valve).
First vacuum of the system:
1. Turn on vacuum pump, open pump ball valve and the VCRT ball valve, and pump it down to medium vacuum (4000 microns or so).
2. Close VCRT ball valve.
3. Close pump ball valve.
Most of air & moisture in the line sets should be removed. Now we do a pressure test, and at the same time pick up most of the remaining moisture into the nitrogen.
Pressure test:
1. Remove vacuum hose from back port of VCRT (you have the VCRT ball valve closed, right?)
2. Set the nitrogen regulator pressure to 0 initially.
3. Setup hoses as follows:
Nitrogen -> middle port on service gauges.
Low pressure (blue) service gauge closed (don't need that side).
High pressure side (red) connected to outbound
High pressure service gauge valve closed for now.
4. Turn up nitrogen regulator up to 5 PSI (very small positive pressure).
5. Open VCRT ball valve.
6. Remove micron gauge, it might not be qualified for high pressure. ( Note that if you have the schrader valve core in the side port of VCRT, and the core depressor set correctly, there should be little gas exchange when you do this. Since you already gave it a light positive pressure of nitrogen, no air should be reintroduced in the system when you do so.)
7. Slowly open high pressure service gauge valve.
Check for gross initial leaks. If none, slowly increase pressure on regulator to your target. For me, it was 350psi. Close the service gauge high pressure valve. This will isolate the system under test from the nitrogen regulator.
Note the pressure on the service gauge. Wait for your desired hold time. An hour seems about right. During that time check for leaks with bubble test (Note: There are Leak Detector solutions on Amazon that will help to find leaks). If the pressure drops noticeably in an hour, you have a big leak. But even if the pressure does not appear to drop, you might have a tiny leak. Watch carefully for bubbles, this is what shows tiny leaks. Think about it, suppose the actually pressure dropped ½ of a psi in an hour. You wouldn’t notice it on the gauge. But in 200 hours you could have lost 100 psi. No bubbles after your hold time? Probably good to go. Don’t rush through this step, if you missed something and release the refrigerant into a system with even a tiny leak, you will regret it. Next step is vacuum purge.
Vacuum purge
1. Remove hose from nitrogen supply to middle port of service gauges.
2. Slowly open the high pressure value on service gauges and bleed down to 5 psi or so.
3. Close VCRT ball valve, remove hose between back port of VCRT and service gauges (high side).At this point, your line set is lightly pressurized with nitrogen, held in by the ball valve on the VCRT.
4. Reconnect your vacuum hose to back port on CRT.
5. Turn on vacuum pump.
6. Open the pump ball valve. This evacuates all the air that is in the vacuum hose, plus the little bit in the outside part of the VCRT.
7. Reconnect the micro gauge. Again, you have a light positive pressure in system, so when you reconnect, no air gets into the system.
8. Open VCRT ball valve,
9. Pump down to a deep vacuum, around 300 microns.
10. On the way down, partially close and open the CRT ball valve to get rid of any gas stuck behind the valve.
11. Once it reaches 300 microns let the pump run for at least 15 minutes,
12. Monitor the micron gage and make sure it stays there or lower.
When you have established a stable low vacuum of 300 microns or lower, close the VCRT ball valve. You can expect a very slow rise, but it should not go higher than 500 microns in 15 minutes. If you have met this goal, you have successfully purged your system of moisture. If the pressure increases to more than 500 microns repeat the pressure tests.
Opening the refrigerant ports:
Keeping the VCRT ball valve closed, crack open the refrigerant valves a bit, this introduces refrigerant in vapor form into your vacuum. Now you need to put the valve core back into the service port. Note that the stem that you use to push the valve core back into position will be under pressure. Keep a steady push, but gentle, and you will get the job done. Note that in order to install the valve core, you needed to open the VCRT valve once you have the stem screwed to the VCRT body. To see if you are doing things correctly, you can pull the stem back, and reclose the VCRT valve. Remove the stem from back port of VCRT, look at it. If it still has a valve core on it, you messed up, try again.
If you completed all the above steps correctly, you should be able to remove the VCRT, and the system will hold pressure. Test the service port with bubble test. You might have to (gently) snug up the valve core.
Now open both your refrigerant valves fully, replace cover caps (three of them), and you are good to go. Enjoy your new system!