[PeterLee1980]

Hello Everyone,

I wanted to make a (first and long) post about my LG mini split heat pump install since after much searching around, it looks like this forum is the best place to discuss DIY mini split installs. This is mostly to document and for anyone else looking for information.

This is actually the 2nd mini split I've installed. This one was actually to replace the old one I previously installed. I previously had a 12k BTU mitsubishi R22 mini split which lasted for just under seven years (I installed it in early 2005). The compressor grounded out on the unit (I assume, it was popping the breaker). The compressor surged when I reset the breaker and caused a hole in the condenser coil, which caused it to leak out all the refrigerant (very quickly!). I did have a tech come out and basically told me it was not cost effective to repair mini splits, especially the old R22 models, and it was better to completely replace. I was quoted $3700 to install a new Fujitsu 12k BTU.

With that I decided to do another install of my own. I combed the internet and ended up deciding on the LG 12k 20 SEER inverter model. I ordered the unit and all the tools (I sold all the tools from my last install) and went to work. I found lots of good tips from this thread like using Nylog, using crows feet to torque the flare nuts, and pressure testing with a bit of the R410a in the unit (I ended up using N2 though myself).

I did end up having one problem (see below), which we'll see how it works out and hopefully I don't end up having a $1300 door stop.

Couple of things I found when I was installing:

1) My manifold gauges and hoses don't seem to hold pressure or vacuum very well. I bought a brand new Imperial manifold with 60" 410a hoses. I found when I was doing the N2 pressure test, it would lose pressure from the manifold and hoses fairly quickly.

I ended up doing the N2 pressure test by putting a C&D ball valve (not the core removal tool) on my service port and then connecting up to my manifold;s low side. I then charged up the system to 150psi, closed the C&D ball valve and then disconnected the manifold hose (the ball valve seemed to hold pressure just fine). I left it for 48 hours, then I reconnected the low side manifold hose to the ball valve and recharged just the manifold and hose (leaving the ball valve closed) to 150psi. After the manifold and hose were charged to 150psi closed off the low side manifold valve, disconnected the N2 tank, and then opened the ball valve on the service port. I did this twice and it seemed to work as intended with slight (~1 psi) variations based on temperature.

I also of course did the bubble test on the flare fittings when it was pressurized.

2) I had similar problems when pulling a vacuum. I used a Robinair cooltech 6cfm pump and a Supco VG64 micron gauge. As a test, I connected the micron gauge directly to the low side manifold hose and the vacuum manifold hose to the vacuum. I ran the vac and it did pull down to 270 microns (it probably could have went further, I just got tired of waiting). I closed the low side manifold valve (the microns jumped up to around 450 from just turning the valve) and then microns continued to creep up to around 1100 microns after 10 minutes. It seems like it would just continue going up.

I even tried connecting the micron gauge directly to the vacuum pump, but the valve on the pump didn't seem to hold well at all since I got a much quicker vacuum rise in this configuration.

In the end, I did the triple evac, evacing down to < 500 microns, breaking the vac with about 15 psi of N2 and letting it sit for 10-15 minutes, then repeating the process and then pulling a final vacuum. The final vacuum I pulled down to 310 microns and released the refrigerant from the condenser.

If I had to do it again, I would buy the Appion 5/16" core removal tool with the extra side port and a micron gauge I could connect without any hoses the micron gauge port on the core removal tool.

As for the problem I had, the unit did fire up no problem and is currently working. I did notice the compressor was very loud though and had a noticeable rattle. After further investigation I found it would only make this noise when the compressor was at lower speeds (due to the inverter model). I found if I had it on max heat it would speed up and quiet down. If I brought the temp down to closer to the current room temp it would start getting loud and rattling again.

My first thought was liquid slogging the compressor. I used just the factory charge since my lineset was 15 feet exactly. In the manual it says it is charged for a 25 foot lineset, but no additional charge is required until 41 feet?!? Also, after some research it seems like the accumulator on these types of units is specifically designed to prevent liquid slogging the compressor in slight overcharge scenarios.

Anyways, it's hard to tell if the unit is overcharged without completely evacing the unit and weighing in the charge since LG doesn't supply any suction pressure tables for heating mode, only cooling! My service port pressures in heating mode are running 340 - 440 psi with an outdoor ambient temp of 50 degrees, depending on the inverter compressor's speed. It usually seems to run around 390-400psi. Compared to other unit's pressure charts, it doesn't seem completely out of whack.

What I ended up doing to "fix" the problem for now, I pulled the front panel off the condenser and found the rattling sound seemed to be caused by excess vibration and then metal parts vibrating against each other causing a rattling sound. I noticed the insulation around the compressor (and accumulator??) seemed a little loose (it's attached with velcro). I noticed as soon as I tightened up the compressor insulation, the vibration went way down and the unit is very quiet now.

So I have no idea if it genuinely was loose and needed to be tightened or if it's not supposed to be vibrating that much period and it's on its way to an untimely death. Since I did the full install myself (couldn't find a local contractor willing to startup a DIY system), I'm warranty-less.

My next step is to buy an ammeter and check the compressor current draw. Apparently if it's overcharged it may cause excessive current draw. And then if it works OK until summer I can check the suction pressure in cooling mode.

If I had to do it over again, I'd buy a unit with a better service manual, probably a mitsubishi again. We'll see though, this unit may be just fine.

Sorry for this really long jumping around post, but I wanted to document it for anyone else who might be considering doing a similar install and/or anyone else who might have similar problems!

Thanks for a great forum!