HVAC Installers - Looking for advice on new install

[jdcompman]

First off, let me say that I am not an HVAC contractor by day, but I've been researching and purchasing the tools for this project for months before actually starting the install.

Right now I'm in the last stages of installing my new Rheem gas furnace and HP system. I've finished the install and now am working on the final step of evacuating the lines before releasing the refrigerant into the lines. I'm running into a couple of issues...

The first issue is this...

The positioning of the piping inside the HP doesn't allow me enough room to get the Appion valve core removal tool on the service valve, let alone enough room to pull out the valve core.

Here is how I have things hooked up right now to evacuate the system; which is not ideal since I have to go through the valve core.

How do you guys get around situations like this?

Second question
Using the above setup, I can easily pull the system down to about 540 microns but can't really get any further, I'm guessing this is because of the valve core still being in the system on the low side. When I valve off the system I get a quick rise up to around 700 microns and after 30 minutes I'm at around 950.

Now some information I read, says that my evacuation is sufficient with these results but other things I read says I should be able to stabilize and not see a rise above 500.

After a few hours of having the system valved off I am up around 1600 microns.

Now my gut reaction is that I still have some moisture in the system and that I should sweep the system with inert gas and vacuum again.

Any insight you could provide would be greatly appreciated. TIA

 

[brewchief]

The valve core being in will affect how fast it will pull down but not how much, how long did you have it on the pump?
Is the oil in the pump fresh?
I would sweep it again and hit all the fittings with soap bubbles while it has 250psi in it, check the fittings on the hoses as well.
I set my vacuum gauge up on the center hose on my gauges so it never needs to see pressure.

Gauge hoses are not rated for vacuum in most cases so some rise from them isn't uncommon.

 

[jdcompman]

The valve core being in will affect how fast it will pull down but not how much, how long did you have it on the pump?
Is the oil in the pump fresh?
I would sweep it again and hit all the fittings with soap bubbles while it has 250psi in it, check the fittings on the hoses as well.
I set my vacuum gauge up on the center hose on my gauges so it never needs to see pressure.

Gauge hoses are not rated for vacuum in most cases so some rise from them isn't uncommon.

Thanks! That was going to be my approach going forward here. I did a couple of different sessions, each having the pump on for a couple hours each time. I changed the pump oil twice now, just to make sure that wasn't affecting things.

I know the gauge hoses aren't rated for Vacuum but it seems that the only downside is that they will outgas for a while when new and account for some rise, but shouldn't ultimately affect the ability to properly evac the system.

Again thanks for the help. I definitely don't know it all and don't pretend to, just trying to learn along the way.

 

[usa#1]

You probably have already done this, but I would hook the micron gage directly to the vacuum pump through the manifold to see what vacuum I could pull. This will assure that your pump and hoses are working properly and will actually pull below 500 micron.

 

[jdcompman]

You probably have already done this, but I would hook the micron gage directly to the vacuum pump through the manifold to see what vacuum I could pull. This will assure that your pump and hoses are working properly and will actually pull below 500 micron.

Thanks! Yep, I've already done that. Vacuum pulled down to 20 microns in about 10 seconds.

 

[Gerald O]

Does your vacuum pump have a gas ballast port? If you pulled a lot of moisture out of the lines you might need to crack the ballast open and let the water vapor vent off from the pump, then close it and continue. Might need to repeat this cycle a few times until it gets really dry.

 

[jdcompman]

Does your vacuum pump have a gas ballast port? If you pulled a lot of moisture out of the lines you might need to crack the ballast open and let the water vapor vent off from the pump, then close it and continue. Might need to repeat this cycle a few times until it gets really dry.

Thanks for the tip! In each of my evac attempts I started with the ballast port cracked open until the pump quieted down or until around 2000 microns. Then I would close it and continue down to the 540. I'm hoping That sweeping the system again will get me down to where I need to be.

I only have 15' of line so I feel like it shouldn't be that difficult.

Any other tips?

 

[brewchief]

Make sure the caps on the service valves are tight, I've also had service valves that leaked refrigerant from the unit but only on units that were pumped down.

 

[acmikee]

do you have a nitrogen? pressurize it to 150lbs and and soap up your joints and hoses and look for leaks.

 

[JackDiddly]

I have had to use a similar process to pull vacuum on certain equipment because manufacturer's don't all seem up to speed on modern day evacuation techniques. However, I would suggest moving your core tool in between the gauge manifold and your vacuum hose, thus allowing you to leave the micron gauge open to both high and low side when you cut the vacuum out to see where it stands(as it looks in your pic you are just reading through the high side which is probably affecting the accuracy of the micron reading). There are a few other factors to consider. When you installed the new Evap coil was it still under pressure from the factory? Yes you can pull to a proper micron level with the schrader valves in place,it will just take a little longer. I have been pulling vacuum on new systems down to like the 220 micron range on my gauge and when I cut out the vacuum and isolate the gauge to the lines it slowly climbs back up and eventually holds at 500. What size pump are you using CFM? If you are watching your micron gauge and you see it start to climb really slow when the numbers get smaller that is normal(you might see a little fluctuation up and down as its pulling). Did you replace the lineset? you may have already said I know you mentioned they were only 15' or so. Are you using all new hoses on your gauges bad seals on your hoses will make you rip out all your hair. Another thing that can affect your ability to get the number low enough is going to be the temperature, here its been mild, but the colder it is outside the harder it is. The process of pulling the vacuum drops the temps inside of the pipe and sometimes it is necessary to break your vacuum with nitrogen and then vacuum again.

 

[Ohmthis]

Sometimes you can't use all the nice tools. I use vacuum rated hoses on my rig and don't use my gauges. The less fittings and connections the better. After you pull down, it will rise a little over time, but will level. This is a degradation of the vacuum and is ok to about 10% (550 microns on a 500 micron pull). If you pull down to 500 and it goes to 750-800 microns for example and levels off and stays it still has moisture. If it continues to rise and doesn't level off you have a leak. Fill the system with nitrogen and check for leaks. Every manufacturer has a different psi they want to see. It will be in the Installation manual. If it is taking over two hours to pull a vacuum and rising I want to say your hoses and or a leak are causing your problem. Good luck

 

[jdcompman]

Make sure the caps on the service valves are tight, I've also had service valves that leaked refrigerant from the unit but only on units that were pumped down.

I'll check, definitely a good thing to check.

do you have a nitrogen? pressurize it to 150lbs and and soap up your joints and hoses and look for leaks.

Yes I have nitrogen, that I used for backpurging while brazing the lineset. I didn't however sweep the lines before trying to pull a vacuum. I'm assuming this is where I went wrong. I'll try to do that tonight or tomorrow.

I have had to use a similar process to pull vacuum on certain equipment because manufacturer's don't all seem up to speed on modern day evacuation techniques. However, I would suggest moving your core tool in between the gauge manifold and your vacuum hose, thus allowing you to leave the micron gauge open to both high and low side when you cut the vacuum out to see where it stands(as it looks in your pic you are just reading through the high side which is probably affecting the accuracy of the micron reading).

This is a great idea! I never even thought to do that.

There are a few other factors to consider. When you installed the new Evap coil was it still under pressure from the factory?

Yep it still was pressurized when I pulled the plugs on it. Made the familiar "woosh" I'm used to when replacing automotive AC coils.

Yes you can pull to a proper micron level with the schrader valves in place,it will just take a little longer. I have been pulling vacuum on new systems down to like the 220 micron range on my gauge and when I cut out the vacuum and isolate the gauge to the lines it slowly climbs back up and eventually holds at 500. What size pump are you using CFM?

Thanks! This gives me a better idea of what I should be seeing. I have a JB DV-142N pump. It's 5CFM.

If you are watching your micron gauge and you see it start to climb really slow when the numbers get smaller that is normal(you might see a little fluctuation up and down as its pulling).

What I'm seeing around 1000 microns is the gauge will go up say 40 or 50 very quickly and go down 45 or 55 and repeat, all very quickly. I thought that was strange but attributed it to pulling a vacuum on the high side without the schrader valve and through the schrader valve on the low side.

Did you replace the lineset? you may have already said I know you mentioned they were only 15' or so. Are you using all new hoses on your gauges bad seals on your hoses will make you rip out all your hair. Another thing that can affect your ability to get the number low enough is going to be the temperature, here its been mild, but the colder it is outside the harder it is. The process of pulling the vacuum drops the temps inside of the pipe and sometimes it is necessary to break your vacuum with nitrogen and then vacuum again.

New lineset, new hoses and new gauges.

Sometimes you can't use all the nice tools. I use vacuum rated hoses on my rig and don't use my gauges. The less fittings and connections the better. After you pull down, it will rise a little over time, but will level. This is a degradation of the vacuum and is ok to about 10% (550 microns on a 500 micron pull). If you pull down to 500 and it goes to 750-800 microns for example and levels off and stays it still has moisture. If it continues to rise and doesn't level off you have a leak. Fill the system with nitrogen and check for leaks. Every manufacturer has a different psi they want to see. It will be in the Installation manual. If it is taking over two hours to pull a vacuum and rising I want to say your hoses and or a leak are causing your problem. Good luck

Thank you very much! That helps me a lot knowing what I should be seeing. I'm going to pressurize and check for leaks and sweep the system in the next day or two. I'm sure one or both of these is my problem.

 

[jdcompman]

So I got back to this, this last weekend and I'm still being defeated. I checked to make sure the service valve caps are tight. I then pressurized the system and left it overnight. When I came back in the morning, my gauges hadn't moved. So it seems like I'm down to simply moisture left in the system.

I depressurized the system and swept it for 5 minutes on a low flow of nitrogen, coming in the vapor line and exiting out the valve core removal tool on the liquid line. I then checked my vacuum pump to make sure it was working well still. Hooked the micron gauge right on the pump and easily pulled down to 14 microns in just a few seconds.

I hooked my gauges up, low side through the schrader valve (since I can't get a removal tool on there as explained above), high side on the output of the removal tool, and put my other removal tool on the charging port on the manifold with my micron gauge attached to it. After running the pump for about 1 hr I was pulled down to 520 microns but it seemed to have stalled there. So I valved off the system and it quickly rose to 800 and after an hour was at 1200. Ugh.

I tried to then break the vacuum with nitrogen again, sweep the system and vacuum again. Still no change at all.

I'm at a loss... I don't know where I'm going wrong. Any suggestions?

 

[Gerald O]

How are the temps there? If there is water in the lines it may be freezing when you pull the vacuum, especially if the lines are cold already. Ice will take a very long time to gas off. It may help if you can warm the lines and / or the indoor unit.

 

[jdcompman]

How are the temps there? If there is water in the lines it may be freezing when you pull the vacuum, especially if the lines are cold already. Ice will take a very long time to gas off. It may help if you can warm the lines and / or the indoor unit.

I was wondering the same thing, but the temps were in the 60's and I even tried to warm the lines down by the coil (lowest point in the system) with a heat gun. Seemed to have no effect.

I'm beginning to think that pulling vacuum through my manifold is the issue, or where I'm permeating. I just had a thought that I should test everything outside of my system (my equipment). I should valve off the vapor and liquid hoses (compact ball valves at the ends) and pull a vacuum through the manifold and then valve off at the pump and see if it holds. This will tell me if my setup is to blame, or if there is indeed just moisture in the lines.

 

[Gerald O]

Don't need the manifold for this procedure. You can connect your pump directly to the service valve without the manifold.

 

[jdcompman]

Don't need the manifold for this procedure. You can connect your pump directly to the service valve without the manifold.

I know, it was just an easy way to connect everything you know. I'm realizing I may just have to build my own little "manifold" out of standard fittings, to hook the hoses up. Maybe get some larger diameter hoses. I'm just trying to make sure I do everything 100% correct. There are people talking about holding 300 microns for 24hrs on a system. Right now I'm nowhere close to that...

 

[Trey T]

Before I installed my first mini-split, I benched tested the HVAC manifold and I can't seem to pull below 500micron. I tried it twice, about 45min each. I leaked tested the manifold and the pressure holds.

I bought a dedicated vacuum-rated hose and I did not bench test it. During the day of install, I did a straight vacuum from pump to core removal tool and it pulls down to about 200 in less than 30min. Same pump same oil as during bench test.

I don't know what to tell you other than get a dedicated vacuum hose and don't use the HVAC manifold at all. Appearantly, a lot of tech on youtube do it like that w/o the manifold hose.

 

[jdcompman]

Before I installed my first mini-split, I benched tested the HVAC manifold and I can't seem to pull below 500micron. I tried it twice, about 45min each. I leaked tested the manifold and the pressure holds.

I bought a decidated vacuum-rated hose and I did not bench test it. During the day of install, I did a straight vacuum from pump to core removal tool and it pulls down to about 200 in less than 30min.

I don't know what to tell you other than get a dedicated vacuum hose and don't use the HVAC manifold at all. Appearantly, a lot of tech on youtube do it like that w/o the manifold hose.

Great to know! I was suspecting this... How low did you pull your system down to and what did you hold it at and for how long? Did you have a picture of your vacuum setup? I have a general idea of what to build but pictures always help

*edit* nvm I went and looked back through your thread and answered most of my own questions. It looks like you only vacuumed through one of the lines and not both simultaneously, thus eliminating the need to make a manifold to hook both lines up at the same time.

 

[JackDiddly]

I don't know how much this will help but here is a little info straight outta my JB Vacuum Pump Manual.
"Charging lines have been used for many years for the vacuum end of air conditioning and refrigeration servicing. Charging line use stretches back as far as when Inches of Mercury (inHg) was the way measuring of a vacuum was taught. A charging line hose can be vacuumed to 50 microns if it is clean. New Environmental hoses, fresh off the shelf, will only reach about 300 microns until they are cleaned out with alcohol and vacuumed for awhile. Why is this? First the charging lines are mostly gaskets made for positive pressure. Second, they are permeated. Third the compound of the hose inside will outgas when under a vacuum until it is cleaned out, as discussed earlier."

I pulled a Vacuum today (with my gauges) on a system that would not allow for the core removal tool on either valve at the condenser. Around 65 degrees outside today. On this particular system the lineset (7/8-3/8) is between 75-80 ft. I ran the pump(6cfm) for probably around an hour and the Micron level at that point was near the 500 range, isolated the lines and it quickly raised to over 800 - not done yet. Turned the pump back on for probably another good hour (I don't sit and watch it while its running I will carry on with other tasks and check on it periodically) Once I came back and saw the microns just about to 200 on the gauge I again isolated the system to the vacuum gauge where it slowly climbed and then held at 480 microns for a period of time before charging.

 

[jdcompman]

I don't know how much this will help but here is a little info straight outta my JB Vacuum Pump Manual.
"Charging lines have been used for many years for the vacuum end of air conditioning and refrigeration servicing. Charging line use stretches back as far as when Inches of Mercury (inHg) was the way measuring of a vacuum was taught. A charging line hose can be vacuumed to 50 microns if it is clean. New Environmental hoses, fresh off the shelf, will only reach about 300 microns until they are cleaned out with alcohol and vacuumed for awhile. Why is this? First the charging lines are mostly gaskets made for positive pressure. Second, they are permeated. Third the compound of the hose inside will outgas when under a vacuum until it is cleaned out, as discussed earlier."

I pulled a Vacuum today (with my gauges) on a system that would not allow for the core removal tool on either valve at the condenser. Around 65 degrees outside today. On this particular system the lineset (7/8-3/8) is between 75-80 ft. I ran the pump(6cfm) for probably around an hour and the Micron level at that point was near the 500 range, isolated the lines and it quickly raised to over 800 - not done yet. Turned the pump back on for probably another good hour (I don't sit and watch it while its running I will carry on with other tasks and check on it periodically) Once I came back and saw the microns just about to 200 on the gauge I again isolated the system to the vacuum gauge where it slowly climbed and then held at 480 microns for a period of time before charging.

Jack,

That definitely helps! Thank you very much for your response. Since this is my first system I've done, I think I'm mostly suffering from not knowing what to expect. Some of the stuff I read, says "x" number of rise over a period of time means everything is good. And other things I read (like your post) tells me that it should rise and eventually stop rising all together. This is what i'm expecting. I'm thinking I should be able to pull down to 2 or 300 hundred and get the system to level off below 500 microns. At this point, I've never even been able to get below 500.

 

[Trey T]

First of all, you have to understand that vacuum is primarily to remove moisture. If you can't pull below 500micron-Hg, there's still good amt of moisture. Therefore, purge it with nitrogen and vacuum again and cycle that all over again; the industry call this "triple vac" or "triple vacuum".

I believe triple vac WAS popular because ppl were doing them w/o micron guage. What they do is pull down to 30in-Hg for 15min and then hold 30min w/ nitrogen, and you do that couple more times to ensure 99.9% of moisture is removed. It was very prescriptive.

Ppl often curious if micron guage is a required tool. No if you do the triple vac.

 

[HAP]

If you have the time, let it run for longer. It is not uncommon for some systems to require longer evac times. I was able to get down to 62 microns after about 2 hours of continuous vac. It wont hurt to try extended evacuation...

R,
HAP

 

[danski0224]

The techs that are pulling down to really low numbers and holding them are using flared soft copper tube (or the special flexible stainless steel lines) for vacuum use only and no manifold.

Some older Carrier residential equipment had back-seat valves without Schrader cores and these valves are found on mostly commercial stuff. Old York R22 automotive compressors had the same type of valves. These valves make easy work of connecting to the system without the Schrader core. Getting the Schrader core out used to be more of an emergency repair- few had the tools to pull it without evacuating the system first. While it may have been common in industrial/commercial applications, it was not (and is not) common in many residential installs where hackery and "good enough" reigns supreme.

Your hoses leak, the hose crimps leak, the manifold valves leak, all of the hose fitting connection points on the manifold are potential leaks, hose end leaks, hose end gasket leaks, O-ring in the core tool leaks... Nylog at all connection points can help. So will vacuum rated hoses.

That BluVac is incredibly sensitive. Any small change in a small closed system will change the readings by a lot.

Just operating the core tool ball valve will cause the BluVac to fluctuate.

It can take hours to clear out a small residential system like yours.

Appion makes 3/8" ID hoses with 1/4" flare ends for rapid evacuation. Supposedly, it makes a big difference.

At some point, you need to know and understand the limitations of your equipment and balance that with the realities of an installation outside of a laboratory. You are already doing better than 90% of any residential HVAC contractors in my working experience to date (including some big names in my area, and those that claim to do it properly).

 

[LS6 Tommy]

If there is water in the lines it may be freezing when you pull the vacuum, especially if the lines are cold already.

Water BOILS under a vacuum. That's more or less the whole point of evacuating the system in the first place...


Tommy

 

[danski0224]

Water BOILS under a vacuum. That's more or less the whole point of evacuating the system in the first place...
Tommy

And the water can freeze if the vacuum level increases (temperature drops) before the water boils off.

Interesting experiment, I'm sure there are videos out there of it happening. I saw it in real life in a glass beaker.

That is the other purpose of the "triple evac". When the vacuum is broken with dry nitrogen, any potentially frozen water would liquify again.

 

[jad3675]

And the water can freeze if the vacuum level increases (temperature drops) before the water boils off.

Interesting experiment, I'm sure there are videos out there of it happening. I saw it in real life in a glass beaker.

That is the other purpose of the "triple evac". When the vacuum is broken with dry nitrogen, any potentially frozen water would liquify again.

Yes, that is true for liquid water...but I think the amount of moisture in a lineset is small enough that it would boil off before it froze. It's not like there's a 10cc slug of water in the lineset.

John

 

[PWC Repair]

Ppl often curious if micron guage is a required tool. No if you do the triple vac.

Wrong, especially with a hydroscopic oil like 410a uses. And good practice is to ALWAYS triple evac. There is absolutely no possible way of knowing whether you've pulled good vacuum without a micron gauge. Evacuating down to 29" eliminates 97% of all air but less than 5% of any moisture. The difference between pulling microns low enough to boil off moisture is 29.72" (5000 microns) and 29.88" (1000) microns. You just can't get this accurate on a manifold gauge set, therefore you NEED a micron gauge. If you pull vacuum that remains less than 1000 microns AND stays for at least 10 minutes then you have successfully removed any moisture from the system. If the level rises above 1000 but stays below 5000 microns then there is STILL moisture remaining in the system. If you see it rise above 5000 microns then there is definitely a leak in the system or your hose connections.
First thing I would suggest would be to hook your pump directly to the system with only a tee and micron gauge. Hoses, fittings, and gauge valves commonly leak under vacuum but not pressure. If it holds, you're good to go. If not, then try another hose and repeat. You may also want to remove the king valve caps one at a time and place your thumb over the top as the system is being evacuated. Does it start sucking your thumb in? Although this would be rare on a new system it DOES happen on older ones periodically. I just replaced a compressor due to a locked down indoor TXV on my system this past March and mine was sucking air through the high side valve, microns wouldn't stay stable as you are describing.

 

[Trey T]

Who said anything about accuracy or inaccuracy using manifold? It's the entire "triple vac" procedure that matters. The manifold vac pressure will always bottom out on the manifold. Already, you're making a lot of assumptions here.

If you read some earlier Carrier install manual - just google it - and you'll understand why ppl did triple vac long ago AND IT NEVER SAYS ANYTHING ABOUT USING A MICRON GUAGE. I don't know if the procedure was invented by Carrier's engineers/scientist or not but Carrier had it in their install manual or other literatures for long time.

Again, triple vac is a prescriptive procedure because techs were able to vaccum the system almost blindly. Today with handheld-size micron guage and affordability, techs use them with more confidence for their installations w/o spending so much time doing the "triple vac". LET ME ASK YOU THIS: HOW DID THEY COME UP WITH THE "TRIPLE VAC" PROCEDURE?

If you're in the industry and that's what you do everyday, micron guage is not a "REQUIRED" tool. Again from beginning, I NEVER said anything about not recommending it. Just to be clear, I do recommend it. As a matter of fact, I own a Fieldpiece SVG3.

 

[Milton Shaw]

Nobody has mentioned this but all systems I have seen come with a new dryer somewhere in the outdoor unit. Those dryers are rated for moisture removal by drops of water they will hold. If you can get the system to hold below 1000 microns that shows you don't have a leak, the dryer will take care of any moisture that remains in the system. So charge the new system after 1000 microns hold and you should not have any problems from moisture.

 

[LS6 Tommy]

And the water can freeze if the vacuum level increases (temperature drops) before the water boils off.

Interesting experiment, I'm sure there are videos out there of it happening. I saw it in real life in a glass beaker.

That is the other purpose of the "triple evac". When the vacuum is broken with dry nitrogen, any potentially frozen water would liquify again.

Before we get too involved, evacuating a system will NEVER remove "water", only water vapor (moisture).

That being said, if you decrease pressure & temperature stays the same, the water boils off. If you decrease temperature and pressure stays the same, water will freeze. Decreasing pressure does not decrease temperature. You will never create ice from water by decreasing pressure. At least not at the temperatures seen in normal atmospheric conditions.

Somebody isn't studying their pressure laws...

Tommy

 

[Gerald O]

Before we get too involved, evacuating a system will NEVER remove "water", only water vapor (moisture).

That being said, if you decrease pressure & temperature stays the same, the water boils off. If you decrease temperature and pressure stays the same, water will freeze. Decreasing pressure does not decrease temperature. You will never create ice from water by decreasing pressure. At least not at the temperatures seen in normal atmospheric conditions.

Somebody isn't studying their pressure laws...

Tommy

When the water vaporizes the temperature of the remaining water drops. This is because it has to give up energy to those water molecules entering the vapor phase. Basic principle of swamp cooler.
Somebody isn't studying their thermodynamics laws.

 

[danski0224]

In the experiment I saw, the thermocouple thermometer attached to the beaker indicated a decreasing temperature. Strangely enough, it was somewhere around 32*f when the ice appeared...

It's been a while, but the temperature did decrease.

 

[elfshadow]

Interesting discussion.

Ok, while decreasing pressure, AKA, pulling a vacuum, will cause water to boil at a much lower temperature, the change of state from liquid to gas will not occur without adding energy.

As Gerald points out, this additional energy comes from the rest of the water in the system, and the air around the system and will lead to a severe temperature drop. This can potentially lead to freezing.

When you have frozen water under a vacuum it will not melt. It goes through a process called sublimation where solid turns directly to gas. This takes a long time as there is very little energy remaining in the ice. This where triple evac comes in. Breaking the vacuum with nitrogen raises the pressure of the system to allow the ice to melt rather than sublime. Melting is a much faster process then sublimation. We use dry nitrogen to avoid adding any additional moisture to the system.

That being said, the only way to tell if you have the moisture content low enough in a HVAC system is with a good vacuum gauge. Triple evac is best practice because it saves time, not because it insures that you have all the water out of a system

The POE oil used in newer systems is hydroscopic. This is a major problem as it turns acidic when exposed to high temperatures and moisture. This leads to compressor burnout.

 

[Trey T]

Saves time as in short-term (during install) or long-term (possible issue that resulting a call-back)?

For short-term, triple vac is a very time-consuming procedure that may take up to 4hrs. Again, there's actually a SPECIFIC PROCEDURE PUBLISHED.

What you're thinking is deep vacuum method using two stage pump, nitrogen, and monitor w/ micron guage.

If you're using a micron guage to monitor the moisture level, technically that's not a "triple vac" method. I believe the "triple vac" was invented because back then they didn't have a portable or commercially available micron guage for techs to use on-site; therefore, the tech have to rely on the overkilled vacuum method that somebody came up with (perhaps from laboratory testings). W/ the equipment available today (2-stage vac pump, core removal tool, large vac hose, etc...), any smart HVAC tech will know that they will lose money/time if they do "triple vac."

http://www.trutechtools.com/Vacuum-Training_c_1100.html

Interesting discussion.
...

That being said, the only way to tell if you have the moisture content low enough in a HVAC system is with a good vacuum gauge. Triple evac is best practice because it saves time, not because it insures that you have all the water out of a system

....

 

[LS6 Tommy]

When the water vaporizes the temperature of the remaining water drops. This is because it has to give up energy to those water molecules entering the vapor phase. Basic principle of swamp cooler.
Somebody isn't studying their thermodynamics laws.

Interesting discussion.

Ok, while decreasing pressure, AKA, pulling a vacuum, will cause water to boil at a much lower temperature, the change of state from liquid to gas will not occur without adding energy.

When you have frozen water under a vacuum it will not melt. It goes through a process called sublimation where solid turns directly to gas. This takes a long time as there is very little energy remaining in the ice. This where triple evac comes in.

Yes, I'm well aware of the thermodynamics of how a swamp cooler works. It doesn't lower the water temp, it lowers the air temp as the water vaporizes.

If you pull a vaccum on a container of water at room temperature it changes state without adding any additional energy. Three times. It boils until it no longer can give off enough energy to boil & it freezes. Then it sublimates. Liquid to vapor, liquid to solid, solid to vapor.

I'm also aware of the theories behind triple evacuation. My point was you still will never form ice from the moisture (not water) in an A/C system. The moisture will boil off. If you have actual liquid water in your system, you're screwed. As I previously stated, a vacuum pump will not remove liquid water. That was my entire original point.

Tommy

 

[Gerald O]

Yes, I'm well aware of the thermodynamics of how a swamp cooler works.

Apparently not.

It doesn't lower the water temp, it lowers the air temp as the water vaporizes.

Yes it lowers the air temperature, and it also lowers the temperature of anything else in the ambient environment, including the liquid water that it evaporated from.

If you pull a vaccum on a container of water at room temperature it changes state without adding any additional energy.

Rubbish. Please study enthalpy of evaporation. The water cannot enter the vapor state without gaining energy. That energy must come from somewhere. Since the air has been removed it cannot come from the air. That leaves only the metal lines and any remaining liquid (or frozen) water.

It boils until it no longer can give off enough energy to boil & it freezes.

Now you are contradicting yourself--you now state that the water is giving off energy to "boil". Guess what; if it gives off energy it will become colder.

My point was you still will never form ice from the moisture (not water) in an A/C system The moisture will boil off. If you have actual liquid water in your system, you're screwed..

You're not making any sense now. Moisture is liquid water.

As I previously stated, a vacuum pump will not remove liquid water. That was my entire original point.
Tommy

Wrong still. The vacuum will remove liquid water in the lines by causing it to vaporize into a gas and then pumping out the gas.
That's how it works, really.

 

[LS6 Tommy]

OK, I oversimplified things. I said a lot of things that weren't phrased properly. I didn't contradict myself. I never said pulling a vacuum on water wouldn't make it colder. I said you didn't need to add any energy to make it boil under a vacuum and that was completely wrong & poorly stated. I SHOULD have said you don't need to raise its temperature to make it boil.

When the term "Moisture" is used in reference to a refrigerant circuit it does not mean liquid water. It means the water vapor contained in the air that the system was exposed to when it was open. I still stand by my original statement (& so does the RSES) that you cannot remove liquid water effectively from a system with a vacuum pump.

I never meant to sound argumentative, so I apologize if I came across that way.

I'm always willing to be shown my mistakes.

Tommy

 

[Gerald O]

Just about every training guide for EPA certification warns that rapid evacuation with a large capacity vacuum pump could cause any liquid water in the lines to freeze. They also state that nitrogen should be added in that case to re-pressurize and melt any ice. The reason I thought it was worth mentioning to the OP was his location in South Dakota suggested that the ambient temperature there might already be fairly low.

I agree that is impractical to remove large amounts of water by vacuum. A small amount of liquid water generates a lot of gas when it vaporizes and could keep the vacuum pump busy for many hours by sheer volume of gas produced, not to mention contamination of the pump oil.

I did find an interesting statement by one vacuum pump manufacturer about using charge lines for evacuation. They said that the lines are air permeable under high vacuum. This is not a problem for charging, but it will never be possible to hold a high vacuum with them because the air actually migrates through the rubber. For deep vacuum below 500 microns they recommend copper lines with soft copper flared connections.

This manufacturer states that basically, if you are evacuating through regular charge lines, expect the vacuum to gradually rise. If you get it to stay below 500 microns for 5 to 20 minutes then you've gotten all the water out. If it rises faster than that then there's either a leak or still some water in there.

 

[LS6 Tommy]

Well, to be blatantly honest, it's been almost 3 decades since I was an apprentice and there's absolutely no arguing the technology & methods have changed. When I was doing service work I almost always purged with nitrogen during lineset work and plumbed the vacuum pump in with copper, but the vacuum pumps I used were nowhere near big enough to make ice, let alone get liquid water out unless you let it run for about a month.

Back then 750 microns was condsidered to be a REALLY deep vacuum. We all know 750 is not considered deep enough these days.


Tommy