To HVAC pros with mini split A/C experience

[grow nerd]

Previously I've worked primarily with packaged "no-name" (Shinco, Klimaire) mini-split A/C's with included linesets, stated to be the intended length for the pre-charged (R410A) refrigerant. I used the included lineset, which so far has been long enough for the installation, and didn't add any refrigerant. Just a DIY vacuum job using a manifold gauge (to ensure it holds vacuum, as well as the soap test) and a cheap Harbor Freight vacuum pump (and a mini-split fitting adapter). It's always worked fine and never gave me any problems.

Now I'm looking at a LG LSN240HSV LSN240HSV 2-ton mini-split that doesn't come packaged with a lineset, but with multiple different lengths of linesets available as an optional purchase from the distributor.

Looking at the manual, it states the "standard length" to be 25ft. for 5/8 + 3/8 linesets (page 11):

http://www.appliancefactoryparts.com/content/pdfs/148643-2.pdf

Does this mean that the outdoor unit is pre-charged with enough refrigerant for exactly this length x diameter (25' x 5/8" + 3/8"), and that as long as I don't use a shorter (i.e., 15') or longer (i.e., 30' or 50') lineset, that I can get away with not having to add or remove additional refrigerant?

Capacity is based on standard length and maximum allowable length is on the basis of reliability. Additional refrigerant must be charged after 7.5m(25ft).

 

[Guest 18340]

Yes, exactly.
Not a pro, but have the same experience with mini's that you do. Started out with cheap Amcor and Shinco and finally stepped up to a Mitsubishi.
I do my own installs, vacuum jobs, etc. But yeah, you got the right idea about the Lg specs when it comes to line sets.
I commend you for reading the fine print when it comes to the specs. A lot of guys end up with useless mini's because they rely on the dealer to sell them the correct accessories and don't do any research for themselves.

 

[trichy]

Would you buy one of those cheap splits again? If not, why?

 

[RedRain]

bingo...after 25 ft you must add refrigerant at a weight of 35 grams per meter

you will have to evacuate some refrigerant if you used only 15 ft. it clearly states that the unit it charged with enough r410 for the standard length of 25 ft.

so now u need a large and very accurate scale to weigh the r410a, a bottle of refrigerant, and a bottle of nitrogen to purge any air from you manifold before adding a vapor charge to the unit.

r410 is a very picky refrigerant, you must vac down to at least 500microns before running the system. I would leave your vac pump on for almost a day, especially if you have a cheap one. It cant hurt. Refrigerant is an amazing thing when it under the correct conditions.
If you need to run in excess of 25 ft you can always go to a local HVAC company and ask them to install sealed brass quick connects onto your lineset and indoor and outdoor unit. They will pressure test, and vac down, and add the correct amount of refrigerant that u need.

take the time to measure twice and order a line as close to a run as possible. When you have a bunch of a line set coiled up, you risk oil logging in the line and starving the compressor.

 

[grow nerd]

How much of an impact is there by not doing a nitrogen purge? Particularly if I leave the lineset protected by not opening the caps until seconds before connecting (minimum air exposure).

I've seen some linesets claim that they've been "pre-charged" (with nitrogen, they claim), does that make a difference? How much?

In previous DIY vacuums on no-name mini-split's, I would simply pull vacuum using a cheap R134 automative gauge from Harbor Freight, a mini-split adapter, and a cheap 2.5cfm single stage vacuum pump also from Harbor Freight. Run pump for about 15-30 minutes, leave manifold attached to see that it holds vacuum, do the "soap test", and move on to the electrical.

How much of a difference is there to use an automotive manifold gauge only to measure vacuum prior to releasing the R410A, if I don't have a refrigerant bottle added or anything else (i.e., measuring pressure) vs. using a proper R410A gauge which isn't (AFAIK) any different as far as vacuum is concerned? I'm using manifold gauge for checking vacuum, primarily, since I'm not HVAC-trained and don't know what pressures I should be reading for what ambient temperature, etc.

I'm obviously going to get the "standard" length x width lineset, according to installation manual, to keep things extra simple.

 

[RedRain]

Hey grow nerd,

I mentioned the nitrogen to purge your manifold of any air, if you have to add refrigerant to your system.

If you were to use your flared lineset, keep the lines sealed until you are ready to connect, and use 2 wrenches to tighten. Connect your vaccuum pump and let it run for 24 hours before you open the valves to release the refrigerant into the lines. Be sure to disconnect the vaccuum pump line to the lineset, while the vac pump is running to avoid allowing any of the enviorment to be let inside the line.

Without a vaccuum guage I would let the pump run for hours. I use a ported, balanced deep vaccuum pump with 1/2" hoses and it takes me 30-45 minutes to bring a 500 micron vaccuum on a line.

When you pull a vaccuum and do a soap test you are doing nothing. The soap test is used to find leaks when you have a system charged with nitrogen. If you had a system under vaccuum that was leaking, it would pull in the water/soapy mix.

You simply cannot have any contaminates inside the line to run at maximum BTU and get a good life from your compressor. I would bring the unit to a qualified HVAC technician and have them install brass quick connects, and properly purge, vaccuum and charge if needed.

I like doing things the right way and I dont half ass things, so obviously my choice is to take it to a professional who knows what they are doing.

I am sure you can get it going with your tools, but who knows and you probably wont have it running at 100% efficiency. I use yellow jacket/ ritchie guages and manifold and hoses, nothing else.
R410a is a different beast than r22. It is much more picky, and synthetic. Bigger head pressure, faster veloicty requirements, stricter installation guidelines. You cant have mistakes with R410a.


Feel free to ask me anything else. Hope this helps.

 

[grow nerd]

Thanks for the explanation.

When you pull a vaccuum and do a soap test you are doing nothing. The soap test is used to find leaks when you have a system charged with nitrogen. If you had a system under vaccuum that was leaking, it would pull in the water/soapy mix.

I meant after I open the valve for the R410A on the outdoor unit. I would see if there's anything leaking from the pressured lines.

I would bring the unit to a qualified HVAC technician and have them install brass quick connects, and properly purge, vaccuum and charge if needed.

What's a fair price for that? Or rather, how much difference would it make realistically?

I am sure you can get it going with your tools, but who knows and you probably wont have it running at 100% efficiency.

Kinda been my concern for a while. Luckily haven't had any "problems" yet or anything that's not taking care of the job for its BTU rating. But it would be nice to know that it's at it's 100% potential. Never really access to a "safe" HVAC guy with that type of equipment and skills so I've done it mainly out of necessity but with a side effect of low cost as well.

Hope this helps.

Thanks.

 

[RedRain]

refrigerant will not make soapy water bubble..only nitrogen will.

FYI -if u were to test a system for leaks you would recover the refrigerant into a recovery tank, and load the system with 200psi of nitrogen. You can then apply soapy water to find a leak. Some people use messy uv dye as well, but I dont like forgeign matter in the compressor crankcase, no matter what the product is other than POE oil and R410.

however since the oil for the compressor is carried through the lines with the r410, u will normally find an oil on the copper where a leak has been made.

It will probably cost you around $500 to get the taps, have them brazed on and the system vacc'd down and a few oz of r410added. I would say it should give you peace of mind knowing that the heart of your grow is working properly. I can assure you that I am not just making this up. there is a phase change happening, and it cant working at 100% effeciecy if there is foreign matter contamination. Which can lead to compressor failure, or simply put no cooling!!

Your tools may very well get u there, but you dont know for sure. Thats why I recommended running ur vac pump for several hours to ensure a low micron level.

No problem!! Glad I can pass on some knowledge to an open mind!

 

[Guest 18340]

..

 

[Midnight]

Thanks for the explanation.


I Never really access to a "safe" HVAC guy with that type of equipment and skills so I've done it mainly out of necessity but with a side effect of low cost as well.


Thanks.

Can you pm me regarding this? I can help you out.

 

[RedRain]

If you are bringing your unit to someone, there is no need for a safe AC guy. There are many reasons why you would want to have your mini split vaccuumed down and quick connect taps installed. Any HVAC company with half a brain can do this for you. Its a slow time right now so I am sure if you were to bring it into a shop with some cash you can get it done for a lil cheaper.

you also have the vaccuum pump. Just install the lines and run the pump for several hours to ensure you have a low micron level, since you do not have a vaccuum guage.

If you require more than 25 ft, go to a local HVAC company and inquire. Nothing is sketchy about getting this done, it happens every day.

 

[mg75]

http://www.youtube.com/watch?v=1ZapUDX3u8c&feature=player_embedded#!

 

[ClimateControl]

DIY Mini Split Installation

DIY Mini Split Installation

Yup, thats what I do:

 

[CaliKine]

You don't need to run your vacuum pump 24 hours, That's a little over kill. If you want to
do it by the book, you connect a digital vacuum gage to the system and run the vacuum until you read 500 microns. Close the valves and verify that the system holds around 500 microns for 15 minutes. The whole point of the vacuum is to boil off any moisture in the lines because moisture and Freon form acid and will eat away the shellac insulation on the compressor windings and cause compressor failure. If you can not reach 500 microns you have a leak. You can use nitrogen to pressurize the lines to 400 psi and any leak should be able to be found using soap bubbles.

 

[CaliKine]

If anyone wants to buy a micron gauge and is paranoid, buy it online. there are hundreds of sites.

 

[nightridda]

Question for my hvac guys out there. I want to build my own air conditioning unit. I have a bunch of peices. What main components for like a 2 ton would I need? And would any of these prices be of any help.

 

[queequeg152]

lol wtf thats an air compressor man. a good one too, id give you 100 bucks for it right now no questions asked.

im sorry dude, but if you are asking these questions you just dont have anywhere close to enough experiance to build and tune an ac system to run properly.

i mean at a min you will need the various acroutrements of your typical hvac technician... vacuum pump, micron gauge, recovery pump, acetylene torch etc.

you would also need various crimping tools and shit to make decent connectiions to what ever sequencing board you buy.

you would need a bending break to form some sort of enclosure for your coils at a minimum. some enclosures for your electronics etc.

its just never ever going to happen man.

 

[queequeg152]

those compressors look like freezer compressors lol. what capacity are they?

that coil in the second image looks like a single pass condensing coil? could be from a small ac unit? ice cream machine or something like that?
it looks new so idk. it could be anything to be honest. an oil cooler, water radiator etc.

regardless its going to be far far far too small to handle any appreciably sized system.

idk wtf the third picture is? some sort of plastic duct take offs?

last picture actually looks like a legit horizontal evaporator coil. it looks big too. it could maby handle like 3 tons? i have a similar 4 ton coil in my attic, its 4" thick, three passes and like 26x24? something like that.

all this shit is worth money. a decent amount of money. just sell it on ebay or where ever and take that cash and put it towards a real ac unit.

 

[nightridda]

All the stuff is in a warehouse for building air dryers and condensing units. My father owns he said if I can find anything I could use to make an AC unit I could have it.. so I just started snaping pictures of anything I saw that could be useful but I deff understand.

 

[nightridda]

And the black plastic think is a 12 inch fan shroud it's for a fan to push the air through a unit