[DIYOkie]

It looks like the first mini split we put in and hired a tech to charge has lost all of its coolant. I had a bad feeling about the guy, and I should have trusted my gut, but I was desperate, very little money....eh, bad decision.

I have spent the past few days reviewing the process of installing mini splits at the point where refrigerant lines are connected, then pull a vacuum, make sure no leaks, release the coolant, etc. I wish I would have just gone to the trouble to learn this the first time.

I feel very confident in the ability to properly torque the refrigerant line connections, per the documentation, and then evacuate and confirm no leaking, and add in the 29.63 oz on the plate for a 16' line, then an additional 17' of line @ .16oz per foot = 32.35 total oz of R410A for our system with a 33' line set.

My question is on the compressor. Is it likely dead? Before realizing there was a leak, we tried turning the system on and the compressor never started. That's when I started looking closer and found oily wet residue around the fittings at the condenser. Is it maybe in a protected mode or am I probably looking at buying a new outdoor unit?

 

[roughneck]

Compressors probably ok. Does the unit have a low pressure switch?
This is why the nitrogen leak check and use of a micron gauge while performing the evacuation are so important. These steps were also left out of your description.

 

[Porsche986S]

I would think the compressor didn't come on due to lack of refrigerant . When I had a " pro " finish a rough install on a mini split I was quite surprised how tight he made the connections he really reefed on them . And I think he also put a thin coat of nylog on the face of the flare fitting . Results were no leaks . Good luck with yours . Please post final results .

 

[DIYOkie]

Compressors probably ok. Does the unit have a low pressure switch?
This is why the nitrogen leak check and use of a micron gauge while performing the evacuation are so important. These steps were also left out of your description.

I'm not sure if it has a low pressure switch or not, but it likely does. I say this because this was bought in September 2019, and the current models feature the low pressure switch. I'm digging through my manuals and I'm not finding this part, yet.

I haven't seen any procedure using nitrogen and the use of a micron gauge. Been sticking to mini split specific procedures, and most of them seem to be good ole boy DIY'ers.

I would be happy to use them though, if I can. I guess I could look at other system types to see how they're used and then adapt them to the mini split system. I was also surprised to see this procedure covered in my installation manual and it only lists a manifold gauge, vacuum pump, and gas leak detector. That's it. They also only have you wait 5 minutes to see if you have a leak after the vacuum step.

I would think that should be a long, long wait.

 

[roughneck]

Samsung and Mitsubishi equipment requires 600 PSI nitrogen pressure test for 24 hours. Others require similar tests.
The suction gauge on a manifold isn’t for measuring the quality of an evacuation. I don’t even use a manifold gauge to pull vacuum.
On that gauge are readings for inches hg. 1” of hg is worth 25,400 microns. Atmospheric pressure on the micron gauge is 760,000 microns. I usually pull systems to 200-250 microns holding. So if you do the math you can see you cannot even see a decent vacuum using the suction gauge.
DIY or not the right tools and procedures need to be used to do things right.
These off brand minis are notorious for crappy support and instruction. If you release the refrigerant and find you have a leak, then what? Can’t release it into the atmosphere. Most DIYers don’t have a reclaimer to go grab to pump the charge out and fix the leak.

 

[roughneck]

Not that it’s for the average DIYer, this is my evacuation setup.

Appion vacuum rated core removers on the ports, connected to Appion 1/2” vacuum rated hoses straight piped to the pump via a vacuum tree, using a Yellow Jacket micron gauge for measurement.

 

[roughneck]

I’ll also say refrigerant is a terrible choice for leak checking.
All refrigerant has intense, quick, and extreme reaction to small ambient temperature changes. A change in just a few degrees could mean your system pressure dropped 10 PSI. But there’s no leak.
Nitrogen doesn’t have these swings. And can be released into the atmosphere once done.

 

[surferdude2]

Mini-splits are a neat way for DIY'ers and semi-pros to install systems without having to know much about refrigeration or have any of the expensive tools needed when doing in-depth refrigeration work. That's all well and good until something goes wrong and the charge is lost or some complex control circuit element fails.

Then it's time to call someone who has been in the trade long enough to know the ropes and have the tools to fix it right. If you want to learn, good for you, watch them and ask questions. If they have to braze any joints, see to it that they bleed nitrogen through the lines while doing it, so as not to create copper oxide slag and other element that can poison the system and doom it for premature failure. When they get the leaks repaired and hook up their vacuum pump, see to it that they have a thermocouple micron gauge (or digital equal) attached and that they pull the system down to at least a 500 micron reading. If the tech tells you that neither of those procedures is really necessary, insist on it anyway and if he can't do it, dismiss him without full pay and get someone better equipped and more knowledgeable.

I'm not saying you or anyone else can't do this work but noone can do it properly without the proper tools... and they are generally too costly for occasional use. I will add that learning all the ropes for doing this kind of work takes more time than most people will be willing to give, especially if you don't intend to pursue a career in it. Paying a well trained pro is a bargain if you only need the service occassionally.

However, it's good to know enough to recognize when a tech you hire isn't doing things right. You should do that if you expect to need such service occassionally

Sealed systems should last for decades if built and maintained properly... they will fall short of that considerably if not created and maintained with respect to system purity.

 

[DIYOkie]

Thanks for the replies, fellas.

You're right, I cannot afford these tools. And I cannot afford to wait all summer to save up the hundreds and hundreds of dollars I've been quoted to check for leaks and add 33 oz of R410A.

So I'll be doing it, and not using the good tools. I'll have to follow the procedure that came in the manual. I need A/C, summer is coming, we're already getting humid in the house and I don't have the money to spend on a tech to do it right.

So it's DIY. And it will have to be with a manifold gauge set, a vacuum pump, a leak detector and some R410A.

Sucks, but that's my only choice. I will try to see if they rent those micron gauges and attempt the best procedure I can, but I doubt they rent them.

 

[roughneck]

Do you have a scale?
How will you leak check with refrigerant? You can’t put refrigerant in and then release it to the atmosphere.

 

[surferdude2]

Go for it... It's not the best way, but so what. If you have that equipment and are dead sure you have the leak repaired, you can get it going. The standard charging hoses aren't very good for extremely low vacuums but your pump may not be capable of that anyway. You won't need a micron gauge since you won't likely get it pulled down that low anyway.

Pull a vacuum for 30 minutes and then break it with the system refrigerant to zero pressure... repeat that process three times... at the third time finish by charging the system with the refrigerant container in vapor mode (upright) until it quits. Close the charging manifold valve and start the system running. Hopefully you have a temperature/pressure chart for your refrigerant and have charged systems in the past based on optimum pressure at specific ambients while observing the suction pressure/temperature relationship and the system superheat as measured at the evap outlet and the compressor suction inlet.

Since you are not doing this as a dealer but as a homeowner, you can avoid being prosecuted for allowing a small amount of refrigerant vapor to escape while doing this 3 step avacuation/purge process. You are not required to have an EPA certificate unless you are a professional dealer.

However, you can't escape being roundly criticized by the true professional that will snipe on you for doing this. Thirty years ago it was common practice I won't judge you but would prefer that you call a pro and get it done the right way... if for no other reason than it will/might have a longer service life.

Good luck.

 

[surferdude2]

I see the spell checker invented a new word for me in the above post... avacuation. Interesting. lol

 

[DIYOkie]

Go for it... It's not the best way, but so what. If you have that equipment and are dead sure you have the leak repaired, you can get it going. The standard charging hoses aren't very good for extremely low vacuums but your pump may not be capable of that anyway. You won't need a micron gauge since you won't likely get it pulled down that low anyway.

Pull a vacuum for 30 minutes and then break it with the system refrigerant to zero pressure... repeat that process three times... at the third time finish by charging the system with the refrigerant container in vapor mode (upright) until it quits. Close the charging manifold valve and start the system running. Hopefully you have a temperature/pressure chart for your refrigerant and have charged systems in the past based on optimum pressure at specific ambients while observing the suction pressure/temperature relationship and the system superheat as measured at the evap outlet and the compressor suction inlet.

Since you are not doing this as a dealer but as a homeowner, you can avoid being prosecuted for allowing a small amount of refrigerant vapor to escape while doing this 3 step avacuation/purge process. You are not required to have an EPA certificate unless you are a professional dealer.

However, you can't escape being roundly criticized by the true professional that will snipe on you for doing this. Thirty years ago it was common practice I won't judge you but would prefer that you call a pro and get it done the right way... if for no other reason than it will/might have a longer service life.

Good luck.

I have watched procedures that use superheat to gauge how much refrigerant to add. But that was with central systems that use a TXV at the evaporator.

I couldn't actually find what the evaporator uses on a mini split, and in searching for it found that all videos and procedures I can find do not mention anything about it, and don't even use the high pressure hose in the process.

They seem to be putting in whatever amount the label says on the condenser. Mine says 29.63 ozs. Then .16 ounces per addition line set foot, which is 17, so added altogether should be 32.35 ozs.

This makes sense to me since the unit is shipped with that quantity and the procedure in the manual simply has you release it into the lines. So it's acting like that's the perfect amount of refrigerant. It would seem I simply need to add whatever it came with.

Am I wrong on that? All the mini split procedures I find seem to make that assumption. But then...they're all DIY'ers really so....

 

[surferdude2]

By all means, go with the label amount and the additional for the line set as needed. Since it's down to a 2 place decimal it would seem to be inferring that it's very accurate.

Then take the time to see that it isn't flooding back too much... a cold suction line entering the compressor is fine but a cold compressor dome is not fine. Some compressors need a little cooling from the return vapor but too much can wash the lubrication away or slug the compressor with liquid. Spend the extra 30 mins run time and see that the compressor dome isn't cold just to be sure.

With 401a, I'd expect to see something around the 130's +- (assuming room temp in the mid 70's) for suction pressure at the compressor and no surging or fluctuations of the gauge needle.

 

[DIYOkie]

I'm using this procedure as a guide. This looks like the right way, and bit more precise than the DIY stuff I've run into.

In this one, he's adding just enough for the line set extra length. In my case, I have to add all 32.35 ozs, so I'm going to have to be careful on that part.

 

[surferdude2]

It sounds like you have a handle on this and I expect you to report back your results so we can all toast you by hoisting a recently re-introduced stubby Coors in your honor. That stubby bottle was introduced the year I was born, 1936... I don't insist it was to honor my birthday though. lol

It's good that the manufacturer passed along the exact amount of charge for that unit. I'm not used to such nice treatment and back in the day spent lots of time sneaking up on the proper charge for small systems by vapor charging slowly until it optimized. The newer refrigerant mixtures make that process less than desirable and vapor charging is rarely used now. I didn't consider that when I outlined the process for you earlier since I was ad libbing from past experience. Fortunarely I retired from the trade before it took a truckload of refrigerants to be well equipped enough to handle whatever came up.

 

[roughneck]

Pretty much all minis are charge by weight/lineset length.
Its next to impossible to charge a variable speed mini in the field using traditional means of charging and system measurement.

 

[surferdude2]

@roughneck Yeah, the trade is much tougher now that they have it all jacked up with the regulations, gasses, recovery gear and extra record keeping. It took all the fun out of it and made it more expensive all the way down to the customer level and more gruesome for the repairman.

If I'm fortunate enough to live much longer, I'll probably end up having to hire someone to fix my AC... that'll be the day! lol

 

[user_12345a]

@roughneck Yeah, the trade is much tougher now that they have it all jacked up with the regulations, gasses, recovery gear and extra record keeping. It took all the fun out of it and made it more expensive all the way down to the customer level and more gruesome for the repairman.

the regulation and required record-keeping may be pain, but necessary to stop people from venting refrigerant.

laws are stricter outside the us - topping off leaking systems is illegal in canada (and rightfully so) unless there's a risk of loss of product i believe.

i just wish they wouldn't phase out most current hfc's due to the gwp concerns.

 

[DIYOkie]

I'm still confused about a couple things on the vacuum part.

One, I thought the deep vacuum down under 500 microns was to help us detect leaks, so do I really need to do a nitrogen test in my case? If I do, that's fine, I'm just trying to understand why I would.

Two, professionals clearly pull vacuums down under 500 microns, often from 100 - 200, yet my manual has me using manifold gauges...it doesn't sound like this vacuum is very specific? I guess I would have thought some exact value of negative pressure in the lines would be required before releasing refrigerant. But we can just be 130 microns, or -76cmHg...whatever?

Anyways, thanks for your help. Really.