LG ductless charging...

[Nubicon]

This is mostly regarding a line from the install manual, page 30, and how it relates to my first LG install.

"Ensure the difference between the intake temperature and the discharge is more than 46.4*F(8*C)(cooling) or (heating)."

Then they give an example "for reference" that states if you have a 95*F ambient you should have a vapor side pressure between 120~130 psig. This is the total charging information for the system (aside from the .22 ounce per foot of 410-a for each foot over the 25' precharge).

My install turned out to have EXACTLY 25' of lineset, the only cut I made was to get rid of a burr on the factory end. That said I neither added nor removed any 410 as the factory charge should be perfect (and it seems to operate perfectly as is).

It's running at 125psi vapor, putting out 47* air from the discharge, the intake/return air temp is 69.4* and the outdoor ambient is currently 71*. It is dehumidifying at an impressive rate, normally a good sign! The question here is how is a 46.4 split even possible? Is it a misprint? Is it badly worded? How in the hell would this or any other system ever discharge 23* air?

So does anyone have experience with LG that can verify this is operating properly? Is my supply air temp within the range of your prior experience? Thx :confused:

Oh- it's an LG 1 ton HP, model lsn120he with corresponding condensing unit.

[barty]

The temperatures you're seeing corresponds with what we see over here.

I saw on another thread that the spilts were much lower but local guy's here said they were ok??

I have seen off coil temps of below zero which is a result of winter over condensing due to the fact that most of these systems are rated at 48 deg's c -a temp not seen in the UK for a wee while.

125 psig on 410a is just about right. Measure the suction at the port and it should be between 1 to 5 deg's c

Cheers

Richard

[Nubicon]

4.4*C currently. Keep in mind that the sun is setting and all the other stats have changed.

House is now approx. 66*-68* return air and outside ambient is 67.8*.

I'm gonna call it good for now, it seems to work well. I wish they would come up with some kind of charging chart instead of relying on weighing completely. And that 46.4* split across the evap just cannot be for real (anyone?....)

Now if only the cat would stop standing on the remote!:D

[waterdawg]

If you suspect a problem with the charge the only way to check is to reclaim and weight in the charge. The delta t over the coil is a guide only and there are no S.H. guidlines that I'm aware of. And yes the manual needs a lot of work to make sense. it was Korean translated into english without much success.

[royc]

I just recently installed one of those in my office/shop. The install manual is a bit goofy at times due to it being translated. I had to recharge mine cause I had a small leak on the low side condenser flare, its a bit hard to put a wrench on the service valve, and tighten the flare. After I retighten it I added gas to get the proper superheat using ODT, WB and DB and ended up with 15 superheat if my memory serves me right, and yes those pressures you stated was about where mine ended up at.

Put that thing in dehumidify and it will freeze you out of there..lol

Roy

[royc]

If you suspect a problem with the charge the only way to check is to reclaim and weight in the charge. The delta t over the coil is a guide only and there are no S.H. guidlines that I'm aware of. And yes the manual needs a lot of work to make sense. it was Korean translated into english without much success.

Its a cap tube system with the cap tube at condenser. It can be charged using regular superheat procedures.

Roy

[Nubicon]

Thanks for all the responses everyone. This may turn out to be a good tech discussion after all!

Royc- you mentioned the cap tube system (which is indeed true) and traditional superheat methods. Are you referring to the old school rule of thumb where if you have no actual printed info then try to achieve 15* superheat? I have been told ductless units do not fall into the superheat charging constraints because they do not actually have true vapor/suction lines. Going way back, I believe the instructor told us they are far more condensed into liquid than a traditional split system on the vapor side.

I guess what this comes down to is that I feel way more confident charging systems with actual superheat numbers or subcooling numbers than I do by weighing it in and hoping it's right on. What if you go by the book, install say a 30' lineset, and add 1.1 oz of 410. The system doesn't work at all. With nothing else to fall back on where would this leave the installer? (maybe this goes back to the traditional charging/superheat methods....:cool: )

[royc]

To be honest I'm not sure if the install instructions are correct. It wants a 46 TD, thats crazy. If my intake temps, which I just checked, are 76 and they want a 46 td, thats would make my leaving temp 28..lol

I looked at it just like any other split system with a fixed orfice. So I took the regular superheat calcs and applied, and it came to 15, so thats where I put it. Whats interesting is that I now have about a 20 split, just the same you would expect, and the pressures are just what they claimed.

I think someone needs to rewrite that manual, or explain to me how a 28 degree leaving temp is possible.

Roy

[barty]

Thanks for all the responses everyone. This may turn out to be a good tech discussion after all!

Royc- you mentioned the cap tube system (which is indeed true) and traditional superheat methods. Are you referring to the old school rule of thumb where if you have no actual printed info then try to achieve 15* superheat? I have been told ductless units do not fall into the superheat charging constraints because they do not actually have true vapor/suction lines. Going way back, I believe the instructor told us they are far more condensed into liquid than a traditional split system on the vapor side.

I guess what this comes down to is that I feel way more confident charging systems with actual superheat numbers or subcooling numbers than I do by weighing it in and hoping it's right on. What if you go by the book, install say a 30' lineset, and add 1.1 oz of 410. The system doesn't work at all. With nothing else to fall back on where would this leave the installer? (maybe this goes back to the traditional charging/superheat methods....:cool: )


This is a very strange argument. The "what if" assumes the manufacturer hasn't carried out tests on the longer line sets. HE HAS which is why they give you a oz/foot additional. Just charge as per manual and it WILL work.It appears you're trying to outsmart the maunfacturer-sorry bud but it ain't you..


Cheers


Richard

[Nubicon]

And with that response it it lucidly cleaer that you have not read the installation manual for LG ductless products. It is like it was written by a Korean 5 year old and then translated by a second year foreign language student into English.

And then there are the instructions telling you to charge until you acheive a 46.4* split across the evap coil? We all know this is normally impossible. So what leads you to this blind faith in the manufacturers info? And with most scales charging accurately at 1/5th an ounce is also exceedingly difficult (with liquid 410 at that).

Why do their instructions give you an example at 95* ambient telling you it should run at ~125psi suction.....when it runs there at 70*.....and 88*. Hell, it doesn't ever seem to change!

[royc]

Lol..yea thats why I just ignored it, they need to re-translate that thing. But one needs to remember its a split HVAC with a fixed metering device. If you do your WB, DB and OAT, you will charge it with superheat, just like any other unit. I dont think the high side copper when insulated will effect it enough to worry about.

Roy