How to add R410a without losing vacuum

[motterpaul]

This probably seems stupid but I cannot find the definitive answer. Let's say you have a mini-split that is low on R410a, so you pull a vacuum and you are ready to add coolant.

You do not want to lose the vacuum, but it isn't like the installation procedure where the coolant is already inside the outdoor unit. You have to connect a tank (on a scale, etc.) How and where do you connect the hose from the R410a tank to the supply port without breaking the vacuum?

I am assuming we are using the setup as seen in those AC Service Tech LLC YouTubes where you have the 5/16" VCRT connected to the service port and the 1/4" VCRT connected to the 5/16" ball valve of that VCRT. Okay, the vacuum is finished so we can disconnect the micron gauge, and we have shut off with the 5/16" VCRT ball valve.

Do we connect the R410a tank to the port previously occupied by the micron gauge and then open the tank and the 1/4" ball valve to flow the coolant into the vacuumed lines?

 

[jjrbus]

Good question, what I cannot be 100% sure of is when to turn the mini on. Will the vacuum pull the 2.09 lbs into the mini without turning it on? Can putting liquid into the system harm the compressor if it is running?

 

[Jackfre]

From what I have seen, this kinda puts you in the “hit and hope” category. If the unit isn’t cooling yoou have lost quite a lot of the 410a. These problems typically show in the heating mode as the required pressures are so much higher. I think you might be better to bite the bullet, find the leak, repair and recharge to what the manuf claims is a “critical charge.”

 

[danski0224]

This probably seems stupid but I cannot find the definitive answer. Let's say you have a mini-split that is low on R410a, so you pull a vacuum and you are ready to add coolant.

You do not want to lose the vacuum, but it isn't like the installation procedure where the coolant is already inside the outdoor unit. You have to connect a tank (on a scale, etc.) How and where do you connect the hose from the R410a tank to the supply port without breaking the vacuum?

I am assuming we are using the setup as seen in those AC Service Tech LLC YouTubes where you have the 5/16" VCRT connected to the service port and the 1/4" VCRT connected to the 5/16" ball valve of that VCRT. Okay, the vacuum is finished so we can disconnect the micron gauge, and we have shut off with the 1/4" VCRT ball valve.

Do we connect the R410a tank to the port previously occupied by the micron gauge and then open the tank and the 1/4" ball valve to flow the coolant into the vacuumed lines?

This is always the problem.

NEVER disconnect anything from a Schrader port without an intermediate valve while under vacuum. Air will ALWAYS get in. Schrader valves are NOT designed to hold in a vacuum.

One option is to put an additional valve (VCRT) or core depressor valve between the micron gauge and the gauge port on the core removal tool. Not all valves are vacuum rated. Some that are, will leak anyways. More connections = more possible leaks.

Many micron gauges can handle limited pressure. The vacuum can be "broken" with refrigerant, then remove the micron gauge as refrigerant is added. It's a guessing game as to when to pull the micron gauge if gauges/manifold is not being used. Then there is only a slight loss of refrigerant, not sucking in air.

Refrigerant is added to the port that the vacuum pump is connected to on the core removal tool (VCRT). When the valve is off, the switch can occur.

Purge the hose from the tank to the VCRT with refrigerant. The hose can be mostly connected (VCRT valve still closed) then open the refrigerant cylinder valve (a little bit) to purge the air with refrigerant vapor, tighten hose to VCRT.

 

[motterpaul]

Thanks for the replies. Here is the situation. I have already done nitrogen and vacuum and everything looks good. I just never saw a video where R410a was added from a tank at this point rather than the outdoor unit. However, I did find this, which is different from what I said but is the same principle I believe:

In fact, it isn't a big deal but I don't understand why he leaves his micron gauge vulnerable to possible coolant contamination for so long. I am thinking adding the coolant hose to the 1/4" VCRT after removing the micron gauge is a better idea, or maybe even the side port (which has a Schrader) after you cap off the top opening. You can leave the ball valve closed until you purge the air and are ready to load coolant. If you see an error in my thinking feel free to let me know.

 

[danski0224]

The side port on a VCRT is on the system side of the ball valve.

If you close the valve, there is still vacuum (or pressure) at the side port.

If you remove the micron gauge from the side port while under vacuum, air WILL leak in.

Virgin refrigerant will not harm a micron gauge. Some micron gauges have a pressure limitation. Pulling the micron gauge from the side port shortly after beginning to add refrigerant does not pose a problem for the micron gauge. It is also one less connection.

Note that because the side port has a Schrader valve, adding a valve to isolate the micron gauge poses additional issues, and not all valves are vacuum rated.

If the same hoses are used for recovery and evacuation, or if the system is undergoing repair (not a new system from the factory) there is the possibility of oil contamination of the micron gauge. Most micron gauges can be cleaned with rubbing alcohol. Some may get damaged. You have to know your tools to decide what to do.

 

[fitter30]

Since minis have only one port for service with your gauge manifold connect high hose to vac pump, micron gauge to low hose and the common hose to unit. Both manifold valves open for evac, for charging close micron gauge off, close pump valve off, connect refrigerant tank to vac pump hose, connect to tank purge hose ( tank on hose at manifold loosen hose for few seconds tighten hose) weight charge in add 3 - 4 oz for when the unit hose is disconnected. Wear gloves when disconnecting hose from unit.

 

[danski0224]

It isn't recommended to pull a vacuum (or recover refrigerant) through the gauge manifold and hoses any longer. Certainly hasn't been for the last few years, that I'm aware of.

 

[motterpaul]

Good question, what I cannot be 100% sure of is when to turn the mini on. Will the vacuum pull the 2.09 lbs into the mini without turning it on? Can putting liquid into the system harm the compressor if it is running?

This is a good question. I don't see why the refrigerant has to be "pulled in" to the lines. I assume it is under pressure in the tanks. I don't hear him say anything about turning the compressor on, and in fact, the power is not even connected. I guess that if you have the right amount of coolant in the system that it will "know it" when you turn the system on. You turn it on as soon as you have the correct amount of coolant loaded.

I am just guessing, though, but I know the compressor is off when you load R410a from the outdoor unit, and you turn it on after that is loaded (I tend to get the electrical out of the way much earlier).

 

[danski0224]

Good question, what I cannot be 100% sure of is when to turn the mini on. Will the vacuum pull the 2.09 lbs into the mini without turning it on? Can putting liquid into the system harm the compressor if it is running?

It could be possible to dump the entire cylinder into that mini-split, if it's large enough. But you probably don't want to do that.

This is where ADDING bulk refrigerant through a gauge manifold and through hoses with core depressors will slow you down.

It isn't just the vacuum, the pressure in the cylinder (which is dependent on the outdoor temperature for the most part) will force liquid refrigerant into the system.

In this case, given a small system, it should pull the entire 2.09 lbs through hoses and a gauge manifold (with cylinder pressure doing most of the work). Warming the cylinder to 100 degrees F (using hot water or a cylinder heater, don't be stupid and use a torch) will certainly do the trick.

If it pulls in 1.75 lbs by itself, then adding the rest during operation will also work. Make sure you are adding to the correct side of the system.

Do NOT add liquid to a running system fast enough to slug the compressor.

Yes, 410A must be added as a liquid from the cylinder, but the feed rate is throttled down with the system running.

I'd also wait 3-5 minutes to turn it on after putting the initial charge in while under vacuum.

 

[danski0224]

I guess that if you have the right amount of coolant in the system that it will "know it" when you turn the system on. You turn it on as soon as you have the correct amount of coolant loaded.

No, and do not do that.

 

[Aileron]

It isn't recommended to pull a vacuum (or recover refrigerant) through the gauge manifold and hoses any longer. Certainly hasn't been for the last few years, that I'm aware of.

Been in the business for 40 years, its done everyday. Pull the vacuum thru the center hose if you have a two valve system. Shut the gauges off when your done and remove the vac pump from the center hose. Put the ref tank on the center hose and do a small purge to bleed the air up and out at your mainfold connection. Open usually the high side and let er fly until your scale indicates its in. If you cant get it all in, you can start the system and add it to the low side ( meter it in 10 or 20 psi above suction pressure) or put a drum heater on the tank to warm it up with the system still off.

 

[danski0224]

Been in the business for 40 years, its done everyday. Pull the vacuum thru the center hose if you have a two valve system. Shut the gauges off when your done and remove the vac pump from the center hose. Put the ref tank on the center hose and do a small purge to bleed the air up and out at your mainfold connection. Open usually the high side and let er fly until your scale indicates its in. If you cant get it all in, you can start the system and add it to the low side ( meter it in 10 or 20 psi above suction pressure) or put a drum heater on the tank to warm it up with the system still off.

I'm not saying that it isn't done. I also have done it that way.

However, if you choose to look at other options, you will see that there are better ones, and they take less time.

No big deal to me either way.

 

[motterpaul]

@danski0224 - I appreciate your input and I guess I should expect that some people will take me literally. Of course, the system doesn't "know" anything, but it operates correctly if the right amount of coolant is loaded before you start it. I assume you are saying the coolant has to stabilize and make its way through the lines before you turn it on and thanks for reminding us. You also want to purge any air out of the hoses first, of course. In the video (referenced above) he had longer than normal line sets and needed to add 4 oz of R410a. He did it right after he had loaded what was in the new compressor unit, by doing the math and putting the container on a scale. He did it all before he started the compressor.

We are talking about mini-splits where there is only one service port.

 

[jjrbus]

Great responses, greatly appreciated!

 

[Aileron]

All service tech my ***! who sands new clean pvc before solvent welding it.

 

[fitter30]

It isn't recommended to pull a vacuum (or recover refrigerant) through the gauge manifold and hoses any longer. Certainly hasn't been for the last few years, that I'm aware of.

Want to know why? How much volume is in a system that holds 5 lbs or less. Tell me how when most minis only have one service port on the suction port in cooling there's a better way without spending $500 - $600 on the correct manifold and hoses. A decent gauge manifold and hoses like yellow jacket get below 500 microns.

 

[jjrbus]

Want to know why? How much volume is in a system that holds 5 lbs or less. Tell me how when most minis only have one service port on the suction port in cooling there's a better way without spending $500 - $600 on the correct manifold and hoses. A decent gauge manifold and hoses like yellow jacket get below 500 microns.

Made me go look! I'll be there is a manifold for mini's!! I shop in different places, the one I saw was $27 LOL

 

[Dagny]

4 valve manifold.

 

[LS6 Tommy]

The cylinder should have already been attached to your manifold charging line and the line should have also been under the same vacuum. You don't evacuate the unit, THEN hook up to the cylinder...

Tommy

 

[motterpaul]

The cylinder should have already been attached to your manifold charging line and the line should have also been under the same vacuum. You don't evacuate the unit, THEN hook up to the cylinder...

Tommy

Where do you connect the refrigerant hose to the system if the vacuum hose is also already connected?

That was my original question.

The cylinder has an open flare (no Schrader) - so you need to fit the other end of the hose to a Schrader since that is how most hoses are made. I assume you can add a second VCRT (a 1/4" to 1/4", the same one used for your micron gauge) and use the side port of that with the Schrader valve in it for the refrigerant hose. That way you can hold your vacuum and also feed in new refrigerant.

The YouTubes say to put in a little refrigerant and then replace the Schrader at the mini-split adapter so you can disconnect the vacuum hose and connect the refrigerant hose to the same spot. I agree this seems overly complicated, especially if the unit has no coolant for you to put in before you replace the Schrader.

 

[danski0224]

Where do you connect the refrigerant hose to the system if the vacuum hose is also already connected?

That was my original question.

The cylinder has an open flare (no Schrader) - so you need to fit the other end of the hose to a Schrader since that is how most hoses are made. I assume you can add a second VCRT (a 1/4" to 1/4", the same one used for your micron gauge) and use the side port of that with the Schrader valve in it for the refrigerant hose. That way you can hold your vacuum and also feed in new refrigerant.

The YouTubes say to put in a little refrigerant and then replace the Schrader at the mini-split adapter so you can disconnect the vacuum hose and connect the refrigerant hose to the same spot. I agree this seems overly complicated, especially if the unit has no coolant for you to put in before you replace the Schrader.

Because YOU mention VCRT, I ASSUME that you are using one of those, correct? VCRT = Vacuum Core Removal Tool or Valve Core Removal Tool.

With the VCRT, the Schrader is removed from the mini split access port- that is the point of using a VCRT.

The VCRT has a ball valve and (2) 1/4" SAE flare ports. One of which, the side port, is typically used to connect the micron gauge.

First order of business is to do a leak check with the VCRT installed and no micron gauge. Leak check = pressurized nitrogen NOT vacuum.

Once that is done, blow the nitrogen charge out of the open end of the VCRT (or through your gauges), but not quite all of it. Leave a little bit in there, just a couple of PSI so the piping doesn't **** air. Gauges are used for this, but do not need to be used later.

The vacuum pump will remove that little bit of nitrogen.

Pull the vacuum. Once done, close the valve on the VCRT and do NOT remove the micron gauge yet.

Valve is closed on VCRT, micron gauge is still in place, connect hose to refrigerant cylinder and loosely connect the other end to the VCRT. With the cylinder upright, crack open the valve and purge the air in the hose with refrigerant vapor. It only takes a little bit. Tighten the hose end to the VCRT. Fully open refrigerant cylinder valve.

Make note of factory fill of refrigerant and add whatever is needed for lineset length. Add a couple of ounces for hose length.

Turn the cylinder upside down on a scale and zero scale. Valve is open on refrigerant cylinder. Valve is closed on VCRT, system should be under vacuum. Leak check was done with nitrogen, NO NEED to wait once vacuum is done.

Open valve on VCRT. Refrigerant goes into system. After a few seconds, remove micron gauge while adding refrigerant.

Watch scale.

Close valve on VCRT once desired weight is reached (note: weight will be "negative" because scale started at zero). Close valve on refrigerant cylinder.

Re-install Scrader core using VCRT. Putting in a new one is a good idea.

Let system equalize for 5 minutes.

Turn it on (assuming service valves are open). NOTE: some manufacturers require a 24 hour "power on" time (no heat/cooling call) to warm up compressor oil before normal operation.

At no point is a gauge manifold required to put refrigerant into the system. Depending on the refrigerant capacity, a gauge manifold can hurt you because the refrigerant can be added faster through 1 hose than through 2 + the manifold and valves.

 

[fitter30]

Made me go look! I'll be there is a manifold for mini's!! I shop in different places, the one I saw was $27 LOL

No just a regular 3 hose two valve manifold. Then a 5/16 to 1/4" adaptor or a 1 /4 x 5/16 hose for hook up to the mini.

 

[jjrbus]

No just a regular 3 hose two valve manifold. Then a 5/16 to 1/4" adaptor or a 1 /4 x 5/16 hose for hook up to the mini.

https://www.homedepot.com/p/Pioneer...-Gauge-Hose-Set-Port-PGML-5-16B1-4Y/315648967

 

[motterpaul]

@danski0224 Thank you for the reply. What you described is also what looked logical to me, but I was watching videos and most people were using the end flare of the 1/4" VCRT instead of the side one. That had me confused, but I got my splits working last week and they are running very smoothly - sorry that I took a break and did not thank you before.

 

[b-nasty]

My trick for doing this is to connect the vac to the high side of the manifold and tank of 410 to the service (yellow line)

After the pressure and vac decay tests are done with the VCRT valve closed, attach the low side of the mani to it, open all mani valves and run the vac. This pulls all the air out of the mani, hoses, and the end of the VCRT. Close high side to isolate vac, and now you can own the tank to replace the mani and hose vac with refrigerant. Zero the scale and use the VCRT valve to feather in the juice. If you don't have the extra VCRT to isolate the micron meter (which has stayed connected to the VCRT top port) you can now remove it with the positive pressure in the lines.

The only downside to this method is the extra time to vac the hoses and the guaranteed loss of 1-2oz of refrigerant in the mani and hoses vs a single hose from VCRT to tank.

Purging the open end of the VCRT with refrigerant, like is commonly recommended, is hacky. There's no way to get all the air out of the end of the VCRT, and that precious sub 300 micron is a lie at that point.