Mini Split -Lineset Nitrogen Pressure Test Or Not

[TTTTTT]

Hi,

Just installed a new precharged 18,000 BTU Seer21 system. I would like to do the evacuate and charge the 16' lineset part myself which I don't see any issues with. I don't have the access to high pressure nitrogen though to do a pressure test. I have torqued the connections properly and will of course check for leaks. I know when I do the evacuation I will also get an indication of leaks as well. And after releasing the charge also check for leaks although shouldn't be any at that point. I was very careful when doing the connections to leave the shipping caps on until I was doing the final connections. i could get an HVAC tech out to do it, but where I am hard to get someone at this time.

Thoughts,

Thx Dave

 

[Git]

I installed a Mr Slim a couple of years ago and paid a tech to come out to start it up since I was in a similar situation. Also, it was needed to satisfy the requirements of the warranty

I am thinking about adding another indoor unit - I have two now, but there is room for a third. From what I understand your going to want to do the nitrogen test, but I am sure the *experts* on the forum will weigh in.

What I did was take one of my welding tanks - a 40 cu ft and had it refilled with nitrogen. Cost me about $20, now if I decide to proceed, I just need to buy a regulator for the nitrogen tank/pressure test - I have been looking at these:

800 psi regulator, $89
or
400 psi regulator $60

hose $21

(From what I have read - the Mr Slim can pump all the freon back into the outdoor unit but I need to look into it further)

So, another option - could you just rent a nitrogen tank locally? It would probably be cheaper then calling in a tech

 

[rlitman]

From what I understand (and I too will defer to the real experts), if you're using a micron gauge when evacuating, you will know for sure if there are any leaks.

Nitrogen pressure is good for FINDING leaks though, if you know you have them.

 

[theoldwizard1]

Just installed a new precharged 18,000 BTU Seer21 system. I would like to do the evacuate and charge the 16' lineset part myself which I don't see any issues with.

Aren't those line set "pre-charged" ? If there is a leak, you are going to loose refrigerant as soon as they are connected.

 

[Jackfre]

You have a substantial investment. To protect it, do it correctly and find the nitrogen and gauge. Doing so make any mistakes made easier to find and correct, regardless of how careful you were. Inverter/410a units are all critical charge. If, however unlikely, there is a leak there is no option but to recover the remaining charge and weigh in the correct amount of refrigerant. I can tell you from experience that it is time consMing and absolutely no fun.

 

[TTTTTT]

From what I understand (and I too will defer to the real experts), if you're using a micron gauge when evacuating, you will know for sure if there are any leaks.

Nitrogen pressure is good for FINDING leaks though, if you know you have them.

That is what I was thinking.

Aren't those line set "pre-charged" ? If there is a leak, you are going to loose refrigerant as soon as they are connected.

Sent from my HTC One M9 using Tapatalk

 

[TTTTTT]

You have a substantial investment. To protect it, do it correctly and find the nitrogen and gauge. Doing so make any mistakes made easier to find and correct, regardless of how careful you were. Inverter/410a units are all critical charge. If, however unlikely, there is a leak there is no option but nto recover the remaining charge and weigh in the correct amount of refrigerant. I can tell you from experience that it is time consMing and absolutely no fun.


Yes you are right on that. That 's one reason I posted. Get some experienced reply's.

Thx

Sent from my HTC One M9 using Tapatalk

 

[tab2]

I had my Mitsubishi dual zone vacuumed and nitrogen tested at 300 psi. When the tech came back after the weekend there was still 300 psi so he released the refrigerant. I didn't pay for it, but I wouldn't do it any other way next time. I sent him Omaha Steaks for Christmas, but I would have had no problem paying him a few hundred for it.

I was into the whole thing about $4k, which included some new tools. A vacuum pump wasn't one of them. Do you have access to one already? Then nitrogen and a regulator might be cheaper then having a tech come out.

 

[mhejl]

I installed a Gree 18k in my new shop about a year ago using the same equipment I've used on hundreds of cars - just with the appropriate adapter. Manifold is a billet aluminum SnapOn (overkill) and the pump a ~$200 RobinAir. Pulled vac for an hour (only about 15 ft of lineset) and then let sit an hour before releasing charge. No micron gauge or nitrogen but I do use Nylog and proper flare nut wrenches on all the fittings and even cut/flared one end. Still runs perfectly.

Old fart disclaimer: I still have an R-12 manifold, too.

 

[tyme2par4]

I'm planning to install a Fujitsu 3 head unit this spring so I was looking through the install manual.
The manual lists too different methods of leak checking. Vacuuming or Nitrogen pressure test. It doesn't say anything about having to do both.

 

[softailtom]

I installed a Gree 18k in my new shop about a year ago using the same equipment I've used on hundreds of cars - just with the appropriate adapter. Manifold is a billet aluminum SnapOn (overkill) and the pump a ~$200 RobinAir. Pulled vac for an hour (only about 15 ft of lineset) and then let sit an hour before releasing charge. No micron gauge or nitrogen but I do use Nylog and proper flare nut wrenches on all the fittings and even cut/flared one end. Still runs perfectly.

Old fart disclaimer: I still have an R-12 manifold, too.

I was fixing to ask you if you used 134A manifold. I still have my r12 manifold with almost no hose left on it.

 

[TTTTTT]

I'm planning to install a Fujitsu 3 head unit this spring so I was looking through the install manual.
The manual lists too different methods of leak checking. Vacuuming or Nitrogen pressure test. It doesn't say anything about having to do both.

i was thinking of that as well.

Thx

 

[Radix2]

The idea is that the system works under pressure, so testing with vacuum alone may not show all leaks - because the leak seals when the pressure is higher outside or because the max pressure across the seal is only the 14psi of the atmosphere, not the 100+ psi of an operating system.

I have welding equipment, so I used argon and only had to buy a pressure regulator. Others have used co2 to pressure test.

 

[TTTTTT]

The idea is that the system works under pressure, so testing with vacuum alone may not show all leaks - because the leak seals when the pressure is higher outside or because the max pressure across the seal is only the 14psi of the atmosphere, not the 100+ psi of an operating system.

I have welding equipment, so I used argon and only had to buy a pressure regulator. Others have used co2 to pressure test.

Thx, that does make sense. Had also heard of using argon. May be a possibility.

 

[bacr619]

i was thinking of that as well.

Thx

Ok guys some times this why you would want to consider using an expert. You CAN NOT use R12 or R134a gauge sets. The gauge manifolds needs to rated for R410A. Reason being r12 condensing at 80 deg is at 80 psi r134a at 80 deg condnesing is 85 deg and r410a at the same is 230 and can will be higher according to outside temps. Before evacuating leak check with nitrogen or argon to 450 psi over night. Then evacuate system. This ensures all fittings are good and tight as welk as the piping. Do not cut corners on the leak check or evacuation.

I installed a Mr Slim a couple of years ago and paid a tech to come out to start it up since I was in a similar situation. Also, it was needed to satisfy the requirements of the warranty

I am thinking about adding another indoor unit - I have two now, but there is room for a third. From what I understand your going to want to do the nitrogen test, but I am sure the *experts* on the forum will weigh in.

What I did was take one of my welding tanks - a 40 cu ft and had it refilled with nitrogen. Cost me about $20, now if I decide to proceed, I just need to buy a regulator for the nitrogen tank/pressure test - I have been looking at these:

800 psi regulator, $89
or
400 psi regulator $60

hose $21

(From what I have read - the Mr Slim can pump all the freon back into the outdoor unit but I need to look into it further)

So, another option - could you just rent a nitrogen tank locally? It would probably be cheaper then calling in a tech

Sent from my SAMSUNG-SM-J320A using Tapatalk

 

[LS6 Tommy]

I've said it before and will have to say it again,

YOU CANNOT LEAK TEST WITH VACUUM. PERIOD.

Tommy

 

[600SL]

I've said it before and will have to say it again,

YOU CANNOT LEAK TEST WITH VACUUM. PERIOD.

Tommy

No you cannot but what the original poster proposed was exactly my plan. Evacuate the lines charge with N2 check for leaks and re-evacuate. If it were up to me I would have done this twice, checking for leaks with both vacuum and pressure.

But I was not confident with my brazing skills. So I hired an HVAC guy to braze and commission the system and I know not to tell him how to do his job but I did request him to go by the book and bring the system down to 250 micron which was over the 20 min vac period he was suggesting. So he vacuumed it then realized he had to put the covers on the air handler anyway. But the time we were done with that it was just down below 100 micron. Then he opened the valves and everything turned out fine.

But while pumping with N2 might seem like the cheap thing to do, a leak that cannot be detected with vacuum will be very difficult to find with N2 with the exception of certain fitting designs usually involving O rings. On the other hand vacuuming, which has to be done anyway, waiting for a short period to see if it wont hold the vacuum followed by charging the lines and checking with a leak detector will be more likely the most cost effective method.

My main reason for wanting to charge with N2 was merely to flush lines of moisture and whatever.

It kind of boils down to if you are a professional, your joints should be good enough to trust that you can go right to charging after vacuuming and in the long run that should pay off. If your a weekend warrior by all means fill with nitrogen over night and attempt to find a leak if you have a problem before charging.

 

[Ohmthis]

No you cannot but what the original poster proposed was exactly my plan. Evacuate the lines charge with N2 check for leaks and re-evacuate. If it were up to me I would have done this twice, checking for leaks with both vacuum and pressure.

But I was not confident with my brazing skills. So I hired an HVAC guy to braze and commission the system and I know not to tell him how to do his job but I did request him to go by the book and bring the system down to 250 micron which was over the 20 min vac period he was suggesting. So he vacuumed it then realized he had to put the covers on the air handler anyway. But the time we were done with that it was just down below 100 micron. Then he opened the valves and everything turned out fine.

But while pumping with N2 might seem like the cheap thing to do, a leak that cannot be detected with vacuum will be very difficult to find with N2 with the exception of certain fitting designs usually involving O rings. On the other hand vacuuming, which has to be done anyway, waiting for a short period to see if it wont hold the vacuum followed by charging the lines and checking with a leak detector will be more likely the most cost effective method.


My main reason for wanting to charge with N2 was merely to flush lines of moisture and whatever.

It kind of boils down to if you are a professional, your joints should be good enough to trust that you can go right to charging after vacuuming and in the long run that should pay off. If your a weekend warrior by all means fill with nitrogen over night and attempt to find a leak if you have a problem before charging.

It's not about being professional, the engineers that designed the equipment need a certain type of installation to ensure that the equipment performs as it should for the duration that it should. Hell, you already have the nitrogen hooked up if you are brazing right? The correct way to install is to make said connections (be it braze or flair), leak test with nitrogen (to the pressure the manufacturer requires), then when that is found to be leak free, vacumm with a micron gauge to ensure you have removed the moisture. Then release the refrigerant and charge by the manufacturers requirement.

 

[LS6 Tommy]

It's not about being professional, the engineers that designed the equipment need a certain type of installation to ensure that the equipment performs as it should for the duration that it should. Hell, you already have the nitrogen hooked up if you are brazing right? The correct way to install is to make said connections (be it braze or flair), leak test with nitrogen (to the pressure the manufacturer requires), then when that is found to be leak free, vacumm with a micron gauge to ensure you have removed the moisture. Then release the refrigerant and charge by the manufacturers requirement.

Well put.

Tommy

 

[TTTTTT]

It's not about being professional, the engineers that designed the equipment need a certain type of installation to ensure that the equipment performs as it should for the duration that it should. Hell, you already have the nitrogen hooked up if you are brazing right? The correct way to install is to make said connections (be it braze or flair), leak test with nitrogen (to the pressure the manufacturer requires), then when that is found to be leak free, vacumm with a micron gauge to ensure you have removed the moisture. Then release the refrigerant and charge by the manufacturers requirement.

Thx for all the responses. Just want to make the informed decision. Probably leaning to getting an HVAC tech to do it but I have some time if I want. Would always like to do most things but sometimes you have to cut your losses.

 

[600SL]

It's not about being professional, the engineers that designed the equipment need a certain type of installation to ensure that the equipment performs as it should for the duration that it should. Hell, you already have the nitrogen hooked up if you are brazing right? The correct way to install is to make said connections (be it braze or flair), leak test with nitrogen (to the pressure the manufacturer requires), then when that is found to be leak free, vacumm with a micron gauge to ensure you have removed the moisture. Then release the refrigerant and charge by the manufacturers requirement.

Certainly close off the N2 bottle and it leaks down right away no need to go any further. The N2 will find gross leaks quickly but it will not find the tiny leaks Freon can find in a short amount of time. So how long will a professional wait for pressure to drop before moving on. I'm saying for a pro this should be so rare of an event that going on to vac and charge as a standard practice, will be the least time wasting over his career.

 

[Ohmthis]

Certainly close off the N2 bottle and it leaks down right away no need to go any further. The N2 will find gross leaks quickly but it will not find the tiny leaks Freon can find in a short amount of time. So how long will a professional wait for pressure to drop before moving on. I'm saying for a pro this should be so rare of an event that going on to vac and charge as a standard practice, will be the least time wasting over his career.

Yes, you are correct that you can quickly find a standard leak. I like to use big blue bubbles on all of the joints when leak testing. They cling to the joint well and will show a very small leak. The biggest aspect is just as you've mentioned, how long do you leak test? Some people say 30 min, some over night, each has there own ideals. One thing to think about, depending on what metering device is being used it may take 30 min or more for the pressures to equalize between liquid and vapor lines. So if you only did so for 30min, you might not have even got the same pressure on both sides of the metering device. I like to fill with nitrogen and start wiring, cleaning, organizing, etc. this lets me get things done while I'm waiting. Then I take my baseline reading and continue with more work while starting the actual test. YMMV

 

[Git]

When I installed my Mr Slim a couple of years ago, I came across this brochure that Mitsubishi puts out that talks about "Triple Evacuation" which I think is intended for commercial units, but the procedure was interesting

The importance of thorough evacuation:
It is vitally important to thoroughly evacuate any refrigeration system in order to prevent the following harmful effects:
> Any non-condensible product left in the system can cause the pressure in the condenser to increase and in turn, the compression temperature to rise.
> Moisture will result in adverse reactions in the refrigerant circuit.
> The polyester oils used in the R410A refrigeration systems are hydroscopic, which means that they absorb moisture from the air. To prevent chemical reactions in the system, any moisture must be removed at all costs.
> Oxygen (air) reacts with the refrigeration unit oil and can lead to faults such as compressor failure.

Leak Testing in 3 easy steps:
Step 1 45 PSI (N2) - Test for a minimum of 3 minutes
Step 2 220 PSI (N2) - Test for a minimum of 3 minutes
Step 3 450 PSI (N2) - Test for a minimum of 24 hours (if using R410A)

Triple evacuation in 6 easy steps:
Step 1 Evacuate the system to 1000 microns from both service valves. To measure the vacuum a vacuum gauge must be used at all times - do not use a system manifold gauge
Step 2 Break the vacuum with O FN to 14 PSIG
Step 3 Evacuate to 500 microns
Step 4 Repeat Step 2
Step 5 Evacuate to the lowest pressure that the pump will achieve (200 microns for a minimum of 1 hour)
Step 6 The rise test must then be carried out for a minimum of 30 minutes

http://www.mitsubishielectric.ca/en/hvac/PDF/city_multi/brochure_City_Multi_R410A_Installation.pdf

 

[motterpaul]

Aren't those line set "pre-charged" ? If there is a leak, you are going to loose refrigerant as soon as they are connected.

But assuming you have done a vacuum and it holds for a good amount of time with no loss, and then you release the refrigerant and you do another bubble test - if you THEN find a leak you can quickly recover the refrigerant in the outside unit again and fix the leak.

I would assume a leak found that way (under the full pressure of the R410a) would hopefully be small enough that the amount lost in the few minutes you have the line set loaded would not be a significant enough amount to ruin your install. Just fix the leaks and let the refrigerant go again.

I am NOT a pro though, just a person hoping to do an install. I am reading my install manual and it does not mention a nitrogen test. I DO understand the value of doing one, but since I plan to redo all flares and do the install by the book, I am thinking I can still do a good install as long as I check for leaks with Blue Bubble after the R410a is loaded and fix them right away.

 

[LS6 Tommy]

But assuming you have done a vacuum and it holds for a good amount of time with no loss, and then you release the refrigerant and you do another bubble test - if you THEN find a leak you can quickly recover the refrigerant in the outside unit again and fix the leak.

I would assume a leak found that way (under the full pressure of the R410a) would hopefully be small enough that the amount lost in the few minutes you have the line set loaded would not be a significant enough amount to ruin your install. Just fix the leaks and let the refrigerant go again.

I am NOT a pro though, just a person hoping to do an install. I am reading my install manual and it does not mention a nitrogen test. I DO understand the value of doing one, but since I plan to redo all flares and do the install by the book, I am thinking I can still do a good install as long as I check for leaks with Blue Bubble after the R410a is loaded and fix them right away.

Here we go again. YOU CANNOT USE VACUUM TO LEAK CHECK. If you do enough work that you have a recovery unit, you should also have the nitrogen (and the common sense) to leak check it properly the first time.

Once you've opened the service valves on the system, if you find a leak you can't just recover the refrigerant "in the outside unit", repair the leaks and recharge. You must recover the refrigerant from the entire system, perform leak repairs, leak check again, evacuate the system again and then weigh in the proper charge.

Tommy

 

[motterpaul]

OK... if I could find out what kind of Nitrogen I need, I can do the nitrogen check.

It is not as if I don't understand the process, but as I said holding a vacuum is all my install manual requires, then it says to let the refrigerant go. There is no nitrogen step. If I do have a leak that I find when I load it, I assume it is leaking out (not in) so it is not as if the 410a is getting contaminated. I understand to have go back to the vacuum process before I recover and reload.

Happy to do the nitrogen step, but I truly cannot find out what I need to buy or where here in CA to do it.

 

[LS6 Tommy]

OK... if I could find out what kind of Nitrogen I need, I can do the nitrogen check.

You want dry nitrogen.

Tommy

 

[motterpaul]

Thank you - I appreciate that. I just got a detailed response of the same on another site so I feel a lot better about the N2 testing.

 

[motterpaul]

Aren't those line set "pre-charged" ? If there is a leak, you are going to loose refrigerant as soon as they are connected.

Only DIY line sets such as Mr. Cool brand have pre-charged line sets. Most mini-splits carry the coolant in the outdoor unit, not in the lines. Non-DIY units have flares that need to be remade and tightened, and they recommend a nitrogen test. DIY units do not have flares, the indoor units are preconnected to the line sets and the outdoor connections are more like a "clip-on" connection that releases the refrigerant from the pre-charged line sets into the rest of the system.

 

[theoldwizard1]

Most mini-splits carry the coolant in the outdoor unit, not in the lines. Non-DIY units have flares that need to be remade and tightened, and they recommend a nitrogen test.

Okay, so why is nitrogen "better" than pulling a vacuum and and seeing if it leaks ? Faster ?

Because nitrogen is a pressure test, isn't it possible to still have a leak under a deep vacuum ?

 

[motterpaul]

Okay, so why is nitrogen "better" than pulling a vacuum and and seeing if it leaks ? Faster ?

Because nitrogen is a pressure test, isn't it possible to still have a leak under a deep vacuum ?

Mini-split lines are very high pressure, as much as 500 PSI when in heat mode. That is internal pressure. A nitrogen test can get the lines up to similar internal pressure and then you can use bubbles to check for leaks,

A vacuum is kind of the opposite, it is external pressure because the lines are voided. It is possible a vacuum will not reveal or can even hide the kind of a leak that a nitrogen test reveals.

However, my unit installation manual does not even mention doing a nitrogen test. It is better if you have the assets and tools to do one, but they are not mandatory for a DIY install. If your DIY install fails, then you have the opportunity to buy the needed nitrogen and scales and extra R410a.

 

[old__man]

Can I use welding gas, argon/CO2 mix, instead of nitrogen? If so, anyone got a amazon link to the type of regulator and hook up I need to complete the test?

 

[LS6 Tommy]

Okay, so why is nitrogen "better" than pulling a vacuum and and seeing if it leaks ? Faster ?

Because nitrogen is a pressure test, isn't it possible to still have a leak under a deep vacuum ?

Let me approach from another angle. If the unit doesn't hold a vacuum there is indeed a leak, but a unit can hold a vacuum and still leak when pressurized. A vacuum can and will "hold" small leaks shut. I've seen it mulitple times.

Tommy

 

[jjrbus]

Old R22 units ran at much lower pressure, haphazard installs could be gotten away with, R410a runs up to over 600 psi. Daikin wants 625 psi nitrogen test!

Most mini split failures are due to improper installation.

Installing a mini split is not rocket science, but must be done right. A shoemaker installation might not fail in 2 minutes, it might take 2 years, 95% chance it will fail.