Nitrogen test necessary?

fugmin

Hi. First post here. I was reading mini split threads but couldn't find my question. Basically I want to skip the nitrogen test if possible and only do a vacuum test on a single head Fugitsu with 10ft lines. I asked 2 hvac companies if they would do the final hookup but understandibly both said no. I don't have access to nitrogen. I know it is the preferred method to purge and pressurize but what are my chances of skipping this step and not bricking my unit. Also, are factory line set flairs ok to use or should they be redone? Thanks for the help and I hope I didn't break any forum rules discussing DIY installs.

STEVEusaPA

Nitrogen is for leak testing.
Most professionals cut the factor flares and do their own, then do a nitrogen test, then pull a vacuum and check for it to hold (decay test).
Vacuum test is to remove all moisture from the lines.

fugmin

Thanks Steve. I tried local rental co. for nitrogen but no luck. I suppose I could go through the phone book looking for a willing tech for commissioning but I get the feeling its like bringing your own eggs to the diner. Not cool. I would actually prefer that route just to get the warranty on parts from Fugitsu.

Dave Carpentier

We get our nitrogen from a local welding/gas company.

Big Ed_4

First it is recommended to use the flair nuts from the unit . Normaly you would need to cut the lineset to discard the extra . The system should not have any oil traps . Coiling the lineset would have to be laid horizontally if run is shorter then the minimum . The vacuum is to remove any moisture . If you bypass the 500# leak check , running a vacuum pump with a leak would suck in contaminants .

fugmin

Big Ed_4 said:

The vacuum is to remove any moisture . If you bypass the 500# leak check , running a vacuum pump with a leak would suck in contaminants .

The vacuum wouldn't hold in that case right?

Big Ed_4

Slighest leak the pressure will not fall below the 500 microns needed but suck in moisture . . The pressure test of 500 # is really the leak check and can show you if there is a leak .. We use bubbles to find the leak if any . A good digital manifold will show the slightest leak. I would recommend keep asking around it would be good job for a old timer ....

fugmin

That's helpful, thanks.

pecmsg

It's listed in the manual, so it has to be done!

You purchased the equipment now want someone to do the start-up and commissioning? No contractor I know of will accept the responsibility for that unless for a family member of close friend!

ChrisJ

I don't think I'm entirely against not pressure testing. It'll suck if you have a leak, but you'll likely be able to figure it out while pulling a vacuum.

However, running a vacuum pump without a good properly working micron gauge I am completely against. I doubt you could even notice a small leak just using a cheesy analog gauge on a manifold set.

EdTheHeaterMan

EDIT: based on @ChrisJ's comment to follow the word Absorb has been replaced with ENTRAIN

Another thing that Dry Nitrogen does is to act like a sponge to ENTRAIN any moisture contamination. (look on the label of the nitrogen bottle, it is 99.4% or better, moisture free). Back in the day I learned a triple evacuation method and I used it until I retired. Fill with Nitrogen and test for leaks. Evacuate to 29.9" then charge with about one or two PSI nitrogen to absorb any lingering moisture. then evacuate to 1000 microns. This was the one I used for the vacuum static test for 10 minutes. If the vacuum rose above 1700 microns then you must find the leak. Then one final charge of 2 psi of nitrogen. Then the final evacuation to 500 microns or even lower at times

This was in my contract for every new install. So my mechanics had to do it. I'm proud to say that I never had a compressor burn out in all my years of contracting. Even if the mechanic tried to fudge the evacuation, the fact that he needed to put nitrogen in there 3 times helped to leave the system contaminant free.

Mr. Ed

ChrisJ

EdTheHeaterMan said:

Another thing that Dry Nitrogen does is to act like a sponge to absorb any moisture contamination. (look on the label of the nitrogen bottle, it is 99.4% or better, moisture free). Back in the day I learned a triple evacuation method and I used it until I retired. Fill with Nitrogen and test for leaks. Evacuate to 29.9" then charge with about one or two PSI nitrogen to absorb any lingering moisture. then evacuate to 1000 microns. This was the one I used for the vacuum static test for 10 minutes. If the vacuum rose above 1700 microns then you must find the leak. Then one final charge of 2 psi of nitrogen. Then the final evacuation to 500 microns or even lower at times

This was in my contract for every new install. So my mechanics had to do it. I'm proud to say that I never had a compressor burn out in all my years of contracting. Even if the mechanic tried to fudge the evacuation, the fact that he needed to put nitrogen in there 3 times helped to leave the system contaminant free.

Mr. Ed

Technically I do not believe N2 or air absorb moisture, like POE does for example. But you're still correct, it makes it much easier to pull out of the system.

But for someone that's DIY and doesn't have tools I'd still recommend a micron gauge over nitrogen any day if it's one or the other.

ratio

The factory 'flare' is only there to keep the flare nut on the line set—& as @Big Ed_4 noted above, use the nuts that came on the unit. I get nitrogen from the HVAC supply houses, you may be able to as well, depending on how much of a stickler for the rules they are (& how competent you appear); but you should be able to get it without restrictions from a welding supply store. You could use CO₂ or argon just as easily for a pressure test, but I suspect N₂ is the cheapest.

As for going without, if there's no leaks it's an extra step that just uses up time & money. If it were my house, meh, maybe I'd skip it. If it were Grandma's house, I'd do it for sure.

mattmia2

You can get a cracker and small disposable CO2 cylinders. There are also various solutions for the home brewing market that can get more than a tiny cylinder but less than a welding tank and regulator for CO2 and nitrogen. I know there are adapters for soda stream and paintball tanks.

fugmin

How much refrigerant usually escapes before the low refrigerant warning code flashes in your experience?

HVACNUT

fugmin said:

How much refrigerant usually escapes before the low refrigerant warning code flashes in your experience?

Well a one head ductless doesn't hold too much to begin with, so even a few ounces lost isn't good. Is this a box store system? The proper procedure is a triple vac using nitro between. 

fugmin

It is a Fujitsu from hvacdirect.com.

pedmec

Fujitsu with a J.

fugmin

Yeah with a J corrected

HVACNUT

I suppose nitrogen is not absolutely pertinent, but I would leave the pump running even hours after you hit 500 microns, then leave it for hours after to make sure it holds. Make sure the pump oil is fresh. 

EdTheHeaterMan

ChrisJ said:

Technically I do not believe N2 or air absorb moisture, like POE does for example. But you're still correct, it makes it much easier to pull out of the system.

But for someone that's DIY and doesn't have tools I'd still recommend a micron gauge over nitrogen any day if it's one or the other.

Explain relative humidity using your Technical Belief

Just askin' for a friend!

ChrisJ

EdTheHeaterMan said:

Technically I do not believe N2 or air absorb moisture, like POE does for example. But you're still correct, it makes it much easier to pull out of the system. But for someone that's DIY and doesn't have tools I'd still recommend a micron gauge over nitrogen any day if it's one or the other.

Explain relative humidity using your Technical Belief Just askin' for a friend!

I'd like to call @Jamie Hall to the witness stand.

heathead

Make sure you are using a torque wrench on the flair fittings. Don't Skip that step. Also look into the FlareMate Seal Kit for the flair nuts. Also make sure you are using the right flair fitting angle and eccentric flair tool. I wouldn't use it but KWIK-E-VAC Line Set Flushing Kit for Mini Split Air Conditioning Systems. The fact that you want to skip a step with a mini split, that can easily cause so many problems that can affect proper operations and electrical consumption over the life of the unit is not worth the risk. Keep looking for a company or individual to do it right.

DJD775

@EdTheHeaterMan @ChrisJ
https://hvacrschool.com/does-air-or-nitrogen-absorb-water/

mattmia2

so instead of using the vacuum pump they do have you are suggesting they just purge it with refrigerant?

(obviously don't do this. if you're feeling lucky evacuate it, break it with refrigerant, evacuate 2 more times. no longer a recommended procedure but it probably will work. of course the issue is that the non-cfc oils bond with moisture that mineral oil didn't)

EdTheHeaterMan

@ChrisJ FROM THE ARTICLEThis is the "Relative Humidity" I'm talking about. So Absorb is not the correct term, but it gets the point across. I will change my post from Absorbs to Entrains for the sake of accuracy. We all want to be correct without offending. LOL

@Jamie Hall has not answered your subpoena. Will he be held in contempt of Dead Men Court?

I rest my case.

ChrisJ

EdTheHeaterMan said:

@ChrisJ FROM THE ARTICLE This is the "Relative Humidity" I'm talking about. So Absorb is not the correct term, but it gets the point across. I will change my post from Absorbs to Entrains for the sake of accuracy. We all want to be correct without offending. LOL

I think my response was both accurate and respectful.

EdTheHeaterMan

ChrisJ said:

I think my response was both accurate and respectful.

I agree, But the thing about calling @Jamie Hall to the stand was hilarious. Thanks for the laugh! BTW. Read my edit!