Mini-split noise

[ollie76]

Evening all,

Got two LG Inverter series 12K mini splits installed this past summer. One for the upstairs and one for the downstairs. I must say, they have been fantastic so far. We shall see how they hold up.

One issue I have noticed, however, is an odd ringing sound when they are powered off. Both units do it, however, they don't always do it. It's quiet, but in a silent room you'll hear it.

So when running as required, they don't make the sound (at least I can't hear it anyway) and everything seems perfect. But, if you power them down after a couple minutes you'll hear a very subtle ringing sound coming from the indoor head. Kinda annoying. I did a little troubleshooting and if I switch the circuit breakers off, the ringing stops immediately.

Anyone familiar with this?

 

[Jackfre]

Check to see if the fan is running very slowly on the interior unit when powered off. Our idea of "off" and the engineer who wants the unit to be sensing all the time may be at variance.

 

[ollie76]

Yes you could be right. It doesn't sound like a fan though......I could be wrong. It's a high pitched ring (almost sounds like old school dial up modem noise)

 

[LS6 Tommy]

It could be the high side and low side pressures equalizing.

Tommy

 

[ollie76]

Yeah? It doesn't always do it.......seems like 75% of the time it will do it, 25% it's silent.

 

[ollie76]

Thinking about it though, I can't see it being pressure related. If I get my wife to stand next to the indoor unit when it's ringing and I go down and open the breaker. The noise immediately stops. When I close the breaker, the ringing will start almost right away.

This is of course with the unit set to the off position.

 

[LS6 Tommy]

Well, then it's definitely electrically related. I looked at some generic LG mini split wiring diagrams and didn't see anything that I would suspect could be noisy...

Tommy

 

[ollie76]

Yeah, got a feeling it's a normal thing. Was just talking with a friend of mine who just got the same machine installed and hers is doing the same.

 

[LS6 Tommy]

The only thing I can figure is there's a step down transformer mounted on a circuit board inside the indoor unit that is resonating something inside the unit.

Tommy

 

[Ohmthis]

It could be a faint whine almost like a motor at locked rotor hums. The motor could be turning very slowly and the motor would (because of harmonics from the frequency) quietly sing. I can also see a bearing very faintly squeal, but I would emagine it would get louder with more speed.

 

[bzinsky]

Never heard this noise on any of my 9kbtu inverter LG splits, which is very similar to the 12k

Usually when I have electric noise coming from a box or something, I just wait until I hear the noise and put my finger on random places around it to see if I can stop the vibration.

 

[builtin1894]

Evening all,

Got two LG Inverter series 12K mini splits installed this past summer. One for the upstairs and one for the downstairs. I must say, they have been fantastic so far. We shall see how they hold up.

One issue I have noticed, however, is an odd ringing sound when they are powered off. Both units do it, however, they don't always do it. It's quiet, but in a silent room you'll hear it.

So when running as required, they don't make the sound (at least I can't hear it anyway) and everything seems perfect. But, if you power them down after a couple minutes you'll hear a very subtle ringing sound coming from the indoor head. Kinda annoying. I did a little troubleshooting and if I switch the circuit breakers off, the ringi+ng stops immediately.

Anyone familiar with this?

My one year old lg mini split system has always exhibited the same ringing issue you've described. I have six indoor units connected to two outdoor units. The ringing problem only occurs on three units (white smart inverter wall mount units). These three are connected to one breaker on the electrical box and I believe the same outdoor unit. The other three indoor units (picture frame style units) do not suffer from this ringing issue.

I've had some success silencing the ringing by switching the system to heat mode with the temperature set to the coldest setting (so it doesn't actually engage), but I stopped doing this because I felt it put unnecessary stress on the system.

 

[Jackfre]

Speak with your contractor. Ask him to get the local LG rep to your home for inspection. I am saying the "factory" rep, not necessarily the distributor rep, although it is good if you have all three there. At the same time have your serial/model numbers handy and call the tech line at LG. Make sure you get a case number. You have substantiation that your issue is not a one-off deal. Ask how they intend to rectify the situation. Stay calm Report back. I think I would have the contractor confirm that all electrical connections are properly done and the grounds are secure. I'd also ask him to make sure all the connections on the pcb are properly set. Do that first and then follow up with the rep if the problem continues. Oh, and get the best technical guy from the Rep agency if they come out. If the units were purchased on-line you may not have the same access to Rep support, but if purchased through local distribution you should have that level of support. I represented Fujitsu for 14 years and that is the way tech calls were answered. When we had an issue we couldn't figure with the factories help we could, in extreme cases, get one of the Japanese engineers out for a look. That was very rare, but they wanted to know what was happening. Again, please report back on how this goes.

 

[PoorOwner]

Some of the bigger Mitsubishi units use about 50w to keep the compressor warm it’s called preheat to avoid Freon to all collect at the compressor due to cold temperatures.
Could it be your LG have that feature and you are hearing the noise being transmitted?
I guess you could turn off the breaker to verify if it produce that sound.

 

[Voi]

Subscribed for future reference. Just got power to my Fujitsu mini split and noticed a resonating sound during heat mode. Hope to fiddle with it more this weekend.

 

[Hugemoose]

I know this is an older thread, but our 18 month old LG system also does the same thing. The sound only emits from one unit of our 3 head system. It also sounds electrical, and immediately stops if I turn the breaker off. During the summer months if I don't use the AC at any given time, I just leave the fan on low so the noise isn't there. During winter months the breaker gets shut off.

It is annoying, but I'm glad I'm not the only one experiencing this problem!

 

[Lar]

Re: Mini-split noise - Solved

I had the same issue. I called LG tech support. They said it was due to the control board in the wall unit looking for a wireless connection - even though I don't have that option. It caused it to make a high pitch noise when powered on.

You need to replace the control board. Not too difficult. Mine was covered under warranty. When I replace the board the noise stopped.

Lar