LG Mini split Invertor heat pump - Charging questions

[dsoxman]

I have an LG mini split invertor heat pump with three indoor units. I installed the unit myself and it worked good for about 6 months and slowly started to notice an issue when it was winter last year. We had someone look at it (didn't seem to know much about the mini split systems) and they looked for a leak but couldn't find anything, and then charged it back up. It worked again for about 6 months, and is now almost winter and we're noticing a lack of heat again. It's blowing out about 90 degree air, but should be around 130 i think. I ordered a new set of manifold gauges, a leak tester (sniffer) and a tank of 410a. I figured I'd rather learn how to service this myself since I don't think there's many people around here familiar with these. I just wanted some general advice on how to charge 410a in this unit. Can i charge it on heat pump mode? I believe the manifold on the outdoor unit says "gas" and "liquid" for the service ports. Do these change when in heat pump mode? Is there any trick to using the sniffer more efficiently? Any info would be appreciated. Thanks.

[al]

God knows how many laws you're breaking there man(although it is the land of the free so maybe not any?)!! Do not charge in heating mode. The refrigerant is at quite high pressure and in liquid form will give very nasty and extensive burns. Please call a fridge man, by all means seek the leak yourself and identify it to the repair man, the first caller should have found the leak and fixed it, simple as.

al

[dsoxman]

If you have to charge in AC mode, is it ok to do that in temp's under 60 outside? From the temp/pressure chart, it says that at 60 degrees, my pressure should be around 170. I assume that chart is for A/C mode. I don't see how I'm breaking any laws, I'm not draining my system or releasing anything into the air. The last guy didn't seem to know anything about the system and his leak tester didn't seem to function very well so he couldn't find any leaks.

[monkey spanners]

These systems can run at 600psi on the high side, connect the gauges/tank wrong or in the wrong mode and you could be staring at a pine lid from the wrong side.

Phone LG and ask for their recommended installers, they should be conversant with mini split systems. Failing that try recommended techs for other mini split makes, they are all pretty similar in operation.

The leak needs fixing first, its a critically charged system so the superheat or subcooling method most techs are used to cannot be used on these.

[dsoxman]

I've tried reaching out to LG for some support and recommendations of local installers but they were no help.

Is there anything different, charging wise, with the inverter style mini split compared to a standard A/C system with 410A? I know you charge 410 in the liquid form in A/C mode, but i've read mixed things about weather to charge it in the high side or low side. Which of these is correct?

[Kev The Tool]

LG tech support are sh*t worldwide mate so don't beat yourself up over it. you really do need a proper engineer though, this is not something you can do,you should be a trained tech as the system could throw you some weird readings, how you deal with it is where you're training comes in, that also does not take away the fact that there are also a lot of sh*t "engineers" as well. so choose carefully.

[install monkey]

charge it in the low side,charge to the factory charge then check the installation manual for additional charging ino based on the total length of piperun from outdoor to each indoor

ps you will need to buy a vac pump too[
QUOTE=dsoxman;267171]I've tried reaching out to LG for some support and recommendations of local installers but they were no help.

Is there anything different, charging wise, with the inverter style mini split compared to a standard A/C system with 410A? I know you charge 410 in the liquid form in A/C mode, but i've read mixed things about weather to charge it in the high side or low side. Which of these is correct?[/QUOTE]

[chilliwilly]

Are you sure its a leak? If it seems to work ok in the cooling mode but not in heating, it may be the reversing valve not shuttling all the way across. And possibly still partially cooling the indoor units.

Have you checked the temperature of only one ahu running and comparing it to the others when they're running? If theirs no difference then the amount of refrigerant must be ok.


I would have thought that 90 deg F (30+ deg C) would have been a satisfactory air off temperature for a heat pump anyway.

[dsoxman]

Are you sure its a leak? If it seems to work ok in the cooling mode but not in heating, it may be the reversing valve not shuttling all the way across. And possibly still partially cooling the indoor units.

Have you checked the temperature of only one ahu running and comparing it to the others when they're running? If theirs no difference then the amount of refrigerant must be ok.


I would have thought that 90 deg F (30+ deg C) would have been a satisfactory air off temperature for a heat pump anyway.


There's definitely a small leak somewhere. It worked great when I installed it and was blowing 130 degree air last winter. It slowly got down to around the 90 degree mark at the end of the winter and in the summer, I had it charged by a local tech. It was then blowing out nice cold air for most of the summer, and again started fading off near the end. It's now only blowing 90 degree air again in the early stages of winter. I've checked all indoor units and they're all blowing the same air temp .

You said to charge it in the low side, but I read that charging in the low side in liquid form is a sure way to ruin the compressor? Is that accurate?

Doug

[Gary]

What are the air in and air out temperatures on the outdoor unit?

Any frost on the outdoor unit?

[chilliwilly]

Charging liquid on the low side should be left to the experienced engineer/tech. You would normally charge almost full capacity on the high side, but in the case of topping off after a leak repair. You would charge liquid or gas on the low side.

When you charge liquid on the low side the volume of liquid is throttled down somewhat compared to the volume with charging with gas. If you have a sight glass on your manifold you can meter the amount of liquid by making sure the gas bubble/liquid ratio is about 50:50. If there's no bubbles and only liquid you will hear the pot start to grunt and potentially damage it, if you haven't already destroyed it.

What part of the US do you live in? Because even in the Southern parts its not unusual for the back up heaters to switch in when in heating mode when the outdoor temperature drops, or when the outdoor unit is defrosting. Maybe there could be a defrost problem or the back up heaters aren't working, but then again if its struggling to cool your system may have a leak as you suspect.

[airconair]

I reckon you should have got it installed by a licensed installer... That knows how to use a vac pump... Sounds like non-condensibles is your problem