# mini split pressure test



## tallslenderguy (Nov 7, 2018)

Hi all,
I did a self install of a Daikin 9000 btu mini split. Originally, i'd intended to to the grunt work and have an HVAC company do the line hookup, pressure and vacuum. After lots of searching (most will not do it) I thought i had found a company to do that for $400, but after buying and installing the system, i called them back and they wanted to charge $1500. 

I bought all the tools, Yellow Jacket gauges, torque wrench, elliptical flare tool (very cool), vacuum pump, micrometer and various valves and connectors. Yesterday, i finally got a dry day to pull the vacuum and pretty sure i have the dreaded leak. I pulled down to 250 microns and when i isolated the vacuum pump, the vacuum ended up going to 1200 fairly quickly. 

I had been hoping to avoid a pressure test, but looks like that is out. 

Here's my question, since i am going to pull a vacuum anyway, why can't i use compressed air for the pressure test? Yes, i know it will have moisture in it, but I'm going to pull a vacuum after fixing any leak, so is it really necessary to use the drier nitrogen gas? I hate the idea of having to buy a nitrogen tank, etc. It's a new system, there is no refrigerant oil to worry about contaminating, just tubing. I figured i could pressurize and bubble check the flare fittings, then let it sit for a few hours to test for leaks? Am i missing something?


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## roughneck (Nov 28, 2014)

No, it still runs contamination risks. Not to mention that a proper leak test on your unit is over 400 PSI. 
Many new minis are requiring 600 PSI holding for 24 hours minimum.


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## jjrbus (Aug 28, 2009)

Recently installed a Daikin 9k, calls for 550 psi with 550 psi maximum, for minimum 1 hour 24 recommended. Because of this and that my pressure test lasted 3 days. 



Not fun paying the big bucks for special tools required, it is that or risk faulty install. The tank and gauge can be sold after to recoup some of the money.


Not mentioned much is mini's are sensitive to power surges and need a surge suppressor. I put a whole house one in, more $$$$$$$


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## tallslenderguy (Nov 7, 2018)

Okay, got a 40cf tank of N from Airgas... tank was $125 and the difference was the gas cost. 20 cf tanks are $100 on Amazon, sans gas, so it seemed competitive. The regulator I ordered on Amazon will go up to 800psi @ $65, so another $200 cost in addition to the Yellow Jacket gauges, vacuum pump and micrometer. All told, about $500 in tools, but still half the cost of hiring a company and i get to keep the tools. 
Funny thing, the instructions that came with my Daikin unit (model RXSO9LVJU pg 7) only say to vacuum for >15 minutes with a 25' line set. The pressure test is: "turn the liquid stop valve 90 degrees. Close it after 5b seconds and check for gas leakage."


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## jjrbus (Aug 28, 2009)

?? My manual also includes the gas release for 5 seconds, but that is after the pressure, vacuum test. 



Not the first discrepancy I have seen in Daikin manuals. I had to go to the electrical forum to figure one out.


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## supers05 (May 23, 2015)

Sometimes I wonder if they used Google translate to translate those manuals..... It can be interesting. 

OP. Pressure test to 50psi, check for leaks. Only do a full test after you think there's no leaks. Is even recommend an extra step at 100psi or so. It'll save you nitrogen if you have a leak. 

Cheers!


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## tallslenderguy (Nov 7, 2018)

Hey supers05,

That's great advice about starting with 50psi of N... pretty sure there is a leak given how quickly i lose my vacuum after shutting the pump down. 

Yeah, not sure about the instructions, usually the case with Chinese stuff, not so much Japanese. I built a 3d printer with parts from China and there were no written instructions at all, just pictures... which turned out to work for visual me lol.


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## viper (Jul 30, 2009)

Agree with Super. Super, are you sure you didn't steal my method or do we think alike? lol

Pressure up to a lower pressure and only when it holds, push it up. As the owner, you can afford the little extra time to play this game. 

Also, It is VERY common to see something hold pressure but not vacuum. Not the system but fittings and such. You really have to check this but I like pressure tests. N will have much less variance with temperature. 

Also, you can always rent the stuff to someone in need to help comp the cost. I know every time I need a special tool I don't have, I remember what someone else might charge me, and that cost is very quickly absorbed, AND you own the tool at the end of it. 

As for myself, I have a LOT of things I can use Nitrogen for. I have also found uses for CO2 that I used for my kegs. matter of fact, in a pinch I can use in HVAC.


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## supers05 (May 23, 2015)

viper said:


> Agree with Super. Super, are you sure you didn't steal my method or do we think alike? lol
> .


No comment....... Lol

PS. I probably wouldn't use CO2 in your system. It's much more reactive then nitrogen N2. It's great to put out fires though. 

Cheers!


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## tallslenderguy (Nov 7, 2018)

viper said:


> Also, It is VERY common to see something hold pressure but not vacuum. Not the system but fittings and such. You really have to check this but I like pressure tests. N will have much less variance with temperature.


Thanks viper,
This too is helpful info. I have lots of experience in DIY, restored 4 historical houses doing the work myself, not afraid to try stuff. But, i do understand that someone who does something professionally is in a different class from me. Doing something daily for many years gives one much more skill and understanding just by virtue of practice and experience. 
Info like what you have provided about it being "VERY common to see something hold pressure, but not vacuum..." is a great example of long experience, thanks for providing it.


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## tallslenderguy (Nov 7, 2018)

jjrbus said:


> Recently installed a Daikin 9k, calls for 550 psi with 550 psi maximum, for minimum 1 hour 24 recommended. Because of this and that my pressure test lasted 3 days.


I got my regulator for my N tank yesterday. Started at 50, soap and no leaks. Then 100. Currently at 200 and holding just fine. Wondering where you found the "550 psi" number? It's not in the install manual i got, those instructions just employ letting the refrigerant into the line, but that isn't a very good pressure test since it is not running and compressed? Looked for the spec plate on the unit, not readily apparent where that is? I found a more extensive spec sheet here, but still no high side psi? it makes sense to me to test with N at the high side of operating psi first since that is a real pressure the system will be subjected too. https://resource.bakerdist.com/is/content/Watscocom/Gemaire/daikin_rxs09lvju_article_1395692849434_en_ss.pdf?fmt=pdf


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## jjrbus (Aug 28, 2009)

tallslenderguy said:


> I got my regulator for my N tank yesterday. Started at 50, soap and no leaks. Then 100. Currently at 200 and holding just fine. Wondering where you found the "550 psi" number? It's not in the install manual i got, those instructions just employ letting the refrigerant into the line, but that isn't a very good pressure test since it is not running and compressed? Looked for the spec plate on the unit, not readily apparent where that is? I found a more extensive spec sheet here, but still no high side psi? it makes sense to me to test with N at the high side of operating psi first since that is a real pressure the system will be subjected too. https://resource.bakerdist.com/is/c...9lvju_article_1395692849434_en_ss.pdf?fmt=pdf



Not an AC guy, just another homeowner trying to get by. The install manuals are flawed, even worse with the cheap off brands. 



Poking around the net on various brands I found from no mention of pressure on some models up to 550 on others. My Daikin calls for 550. From what I understand my Daikin 15 SEER can run pressures up to 600 psi! PG 8 in my manual.


I can't say too much more as I have no experience with your unit, the perils of DIY!


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## tallslenderguy (Nov 7, 2018)

jjrbus said:


> Not an AC guy, just another homeowner trying to get by. The install manuals are flawed, even worse with the cheap off brands.
> 
> 
> 
> ...


Thanks jjr,

I have a similar page in my manual, but it makes no mention of max pressures. I'm at 450 now and holding for an hour, will run it up to 500 for 24 hours, because that is the highest my high side gauge goes. So jazzed i have no leaks so far, the vacuum let go pretty quickly, but there were a lot more extraneous connections to leak, plus, it's a different dynamic. Very grateful to viper for the input that vacuum leaks are common vs pressure. 

Hope to do start up tomorrow after vacuum. Not a moment to soon, it turned winter here this week, should be a good test.


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## supers05 (May 23, 2015)

The manufacturer's instructions rule in this case, as there are a few variables. However, our code (B52) sets the minimum design pressure for R410A to 236 psig for the low side, and 444 psig for the high side. (design can be higher, but not lower.) Your test at 450 psi is probably just fine, but 500 shouldn't hurt it. Typically they are designed for 600 in order to avoid nuisance pressure trips. (high pressure cutout has to be below design pressure.) 

Let your pressure test sit for 24hrs, and then evacuate. Make sure that your vacuum pump caps aren't leaking. (some come with multiple ports, and the caps tend to leak when not secure.) 

Cheers!


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## tallslenderguy (Nov 7, 2018)

Pressure test held for 24 hours. Vacuumed the system down to 240 microns and it held a half hour at 260. Released the refrigerant and did a start up yesterday without any issues and the system is running great. Thanks for all the input, was very helpful info.


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## supers05 (May 23, 2015)

tallslenderguy said:


> Pressure test held for 24 hours. Vacuumed the system down to 240 microns and it held a half hour at 260. Released the refrigerant and did a start up yesterday without any issues and the system is running great. Thanks for all the input, was very helpful info.


Thanks for the feedback. Holding at 260 um for 30 min of great. (tolerance is up to 500 um) 

Cheers!


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