Hi Everyone. I am new to the site but have been reading a number of threads and am finding them very useful. My background is in construction but I decided to branch out and start installing ductless mini-splits. I completed my first install and performed a 40 minute pressure test @ 250psi. I proceeded to the last step of vacuum pump down and this is where I ran into problems. My vacuum setup is as follows: two Appion core removal tools, an Appion 1/2" vacuum hose and CPS vacuum gage. I pulled down under 500 microns quickly and closed the valve to isolate the vacuum pump from the system. The value immediately went up to several thousand and slow increased so I re-opened the valve and allowed it to pump down awhile longer. After several attempts I got it to remain initially at 400um. It didn't stabilize however and kept creeping up around 20-40um per minute. I wasn't sure if it was my system leaking or my connections so I brought my equipment home to see if I could hold a vacuum with a simplier setup. This setup involved one Appion core removal tool, a vacuum gage, a T-valve and about 3' of 1/4" line with plugged flares. I would post a pic but am too new to do so. This time I pressure tested my setup at 620psi for 24 hours. Pressure was good after 24 hours so I released the nitrogen. I started Pulling a vacuum and again when closing the valve the value would creep up. I don't understand why I can't hold a vacuum after holding 620psi after 24 hours. I am not sure if my vacuum gage is the issue or something else. Anyone have any ideas on what I could try next? Your help is appreciated.
Problem holding a vacuum after pump down
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shaggs2broke
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Here’s a screenshot of initial leak testing on a VRF. Note this is not a regular minisplit.
I was wrong. They want 594.6 PSI.
I’ll have to look for in service pressure testing, I think my other book is in the truck.
IIRC Mitsubishi specs 600 PSI for their stuff.
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I was wrong. They want 594.6 PSI.
I’ll have to look for in service pressure testing, I think my other book is in the truck.
IIRC Mitsubishi specs 600 PSI for their stuff.
Rider, where does it say that's OK for a pressure test involving the compressor?
I already stated the lineset and coils are fine with that pressure.
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This is excellent advice. I just assumed my equipment was good because it is all new. After hooking up appion valve core tool directly off vacuum pump outlet and adding vacuum gage I still couldn't hold vacuum so knew it was either the valve core tool or vacuum gage. Borrowed a different vacuum gage and could hold vacuum after properly pumping down. Lesson learned verify all your equipment regardless of whether it is new or not.
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I am new to all of this but I can't imagine people leaving equipment hooked up overnight at customer site and returning the next day to verify no pressure drop. What are practical times people actually wait when running a pressure test?
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Yes I have had training. Definitely wouldn't attempt installing these without any knowledge. I took Fujitsu 101 in person class and took a handful of classes on their online portal. I also have my EPA 608 type I and II certificate. I also have a bachelors in mechanical engineering so have had thermodynamics classes etc. None get into these types of specifics but you do learn about refrigeration cycles.
Unit was purchased from RSD.
I think I have pinpointed my problem, the vacuum gage I purchased new appears to be defective. I suspected it after my overnight 620psi pressure test with no drop. i felt I should be able to hold vacuum with same setup but vacuum gage in place of pressure gage but couldn't say for sure until I used another vacuum gage. I pulled down to 20 microns and held it under 500 microns through 3 feet of 1/4" tubing for over an hour. As soon as I added my other vacuum gage and tried again it wouldn't hold at all. Damn CPS and their vacuum gages!
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Yes um is micron sorry for the confusion. Where I work we use um and micron interchangeably.
Good deal shaggs ! Welcome, and hope you grab a chair and stick around.....
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I already gave the answer. Look. A one man band, who lets the customer know the deal beforehand, can surely leave it pressurized and come back the next day. That is understood.
But I am a realist. No company with employees in their right mind will do this nor do they do this on 99% of installs. Anyone can come on here and tell me that's wrong or this is wrong or whatever crap they want to preach. I am telling you realistic expectations based off of 25 years installing, servicing, and maintaining equipment. An overnight pressure test just isnt going to happen in order to keep multiple vans moving and profitable.
I looked through every piece of literature I have on Samsung and found no answer to your question.
Which doesn’t surprise me as their information is directly translated from Korean. Some is written very generically.
So I emailed tech support. And they confirmed the outdoor units are capable of a 590 PSI standing pressure test.
This isn’t limited to a specific unit. Or line.
It’s just not directly noted in their literature.
On a personal level, I’ve found many leaks myself going north of 500 that otherwise didn’t show up at lower pressures.
Back in my startup days, if the installer didn’t confirm to the installation instructions, the install was failed and we didn’t return until the pressure test was done per the manual.
OK; that's great. Samsung makes a more robust compressor shell than most, in that case.
Copeland specifically states that 360-ish figure concerning the low-side of the system.
Alls I'm saying is you gots to be careful.
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Copeland specifically states that 360-ish figure concerning the low-side of the system.
Alls I'm saying is you gots to be careful.
Sent from my Moto Z (2) using Tapatalk
It’s not *quite* as critical as it used to be. Thankfully the industry seems to be heading away from flair fittings everywhere. VRF wise a lot of the fittings seem to be going to sweat. Which is saving a lot of headaches on small weepers on flair fittings.
Still sucks to get a leak.
You aren’t kidding about being careful.
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Thanks everyone for the input. I find this forum both fascinating and informative.
So when running overnight pressure tests per manual are you factoring in temperature to the pressure reading? I would think pressure readings with that much time in between will likely also have temperature differences to take into account.
What kind of pressure drop would you consider a failure on a system? it seems to me any drop is unacceptable but I don't think I could readily spot tiny drop on an analog gage set especially with a night in between readings.
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Just as an addage to this thread. Daikin states 550 psi for a minimum of one hour, 24 hours recommended. And l will reiterate that in a perfect world that 24 hours would be adhered to, but practicality wins in my world.
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Much simpler explanation, the vacuum takes time to equalize hi to low side if a single service port. If 2 service ports pull off the larger 1 or both for faster equalization. Check cores, many clear style collect a small chunk of debris from brass cap threads that are unseen. I pull my cores and replace with robinaire after my evacuation. A core only allow .5cfm when left in- a 48k could take 12 hours at that pace. When core removed you are limited by hose size for cfm. To achieve fast deep vacuum use at least a 5cfm vacuum pump, pull core, use 1/2 diameter hose, ***triple evacuate***, a lost failsafe I still do, pull down to 2k, break with nitrogen, 1k, break with nitrogen, 500, break with nitrogen then actually pull the deep vacuum, dry lines won't creep and robinaire cores don't leak.
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After 4 1/2 years?
I enjoyed this post. It covered a lot of bases in short order. Shows intellect and potential.
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