Strange Resonating Ringing Singing Sound Carrier 40MPHA 38MPRA Mini Split Indoor Unit

[mgladden2]

Well here's an odd one. Brand new install, quality equipment, Carrier 40MPHA indoor paired with 38MPRA outdoor.

Everything works as usual, but each time the compressor cycles on, as the indoor unit begins cooling, it goes through a 1 minute ringing / singing / resonating sound that increases in pitch then goes away. Remains gone until the next cycle (reaches set point, compressor winds down, temp raises enough to trigger new cooling cycle).

Attaching zipped up mp3 recording of the sound. It's pretty bland for the first 30 seconds then really picks up around 45 with the pitch increasing, gone after about a minute.

Anyone heard of this before? It seems every noise known to man is covered in an article or video somewhere, but I've only found people with this kind of ringing on the line set. Lines are silent on this, outdoor unit makes only normal noises, indoor unit makes no other unusual noises except for this sound. It's coming from slightly to the right of center.

Cheers.

 

[Terry D]

Is the line set shorter than 10 ft

 

[mgladden2]

Is the line set shorter than 10 ft

No, it's 30 feet.

 

[Terry D]

Was the refrigerant added to the factory charge for the longer lineset

 

[mgladden2]

Was the refrigerant added to the factory charge for the longer lineset

Of course. 21 grams added.

 

[Terry D]

Does it do it in both cooling and heating modes. Did the installer come back and look at it

 

[mgladden2]

Does it do it in both cooling and heating modes. Did the installer come back and look at it

I'm the installer. Never had this happen before. In heating mode it eventually begins making a muted version of this sound and unlike in cooling mode it doesn't go away after 1 minute.

 

[Terry D]

What size is the unit. Just browsing the internet, looks like for the extra 5 ft of lineset, .8 ounces needed to be added. Which in not quite 23 grams. Doesnt look like a problem with the charge. I sure dont know what it could be

 

[mgladden2]

What size is the unit. Just browsing the internet, looks like for the extra 5 ft of lineset, .8 ounces needed to be added. Which in not quite 23 grams. Doesnt look like a problem with the charge. I sure dont know what it could be

I like to stay slightly under rather than risk over charge. Under you lose the smallest bit of efficiency. Over you risk damaging the compressor. But yeah, 23 vs. 21 isn't the issue. That's pennies.

Thanks for thinking about it. Strangest thing I've ever heard. It's a 9k.

Cheers.

 

[Gizzi]

Is the inverter causing ringing through the compressor, and it's resonating through the unit? I have seen what sounds like the ringing/whining of bad bearings come through inverter driven motors. I'm not familiar with Carrier mini splits, but I assume there is a test mode where you can ramp the condensing unit up and down. Maybe try that and see if it narrows things down?

 

[mgladden2]

Is the inverter causing ringing through the compressor, and it's resonating through the unit? I have seen what sounds like the ringing/whining of bad bearings come through inverter driven motors. I'm not familiar with Carrier mini splits, but I assume there is a test mode where you can ramp the condensing unit up and down. Maybe try that and see if it narrows things down?

Thanks for the ideas. I'll do more tests but I believe yesterday I heard no unusual sound at any location except for the middle right of the indoor unit. I believe I checked the outdoor unit and compressor area on the bottom right, plus the linesets but the sound only existed at the indoor unit itself. The test button's function is to put the unit into max mode, which the remote can also do at the lowest temp and max fan.

I thought about a fan bearing issue but the unit is new, so that seemed unlikely. Could be though. Factory defect or something.

Cheers.

 

[jjrbus]

Unfortunately new no longer means good! I have had several "new" products be bad and seems to be getting worse as time goes on. One guru claims that the Chinese manufacturers in an effort to conserve and keep prices down are not adjusting or replacing machinery as needed and putting out poor quality parts.

 

[yeldogt]

Did you find the problem?

It does sound like the inverter .... but, you say coming from the inside? If so it has to be some type of fluid resonance as the compressor modulates and changes the flow. I wonder if something is not tight and the exchanger is vibrating -- or if some isolation pad is not there and the exchanger is resonating through the case.

 

[zsjordan]

@mgladden2 off topic somewhat, how do you like this system? I'm looking at installing one but also trying to compare with the 40MAQ. Wondering if the additional cost for the Infinity 40mpha is worth it?

 

[Mr onetwo]

I just had a Mitsubishi 9K installed last week and the indoor unit has a bad bearing and has to be replaced.Very slight rattling sound...not like yours.I would check the indoor unit for anything rubbing or a loose screw. Just a wild guess...make sure service valves are all the way open and check for a kinked pipe internally in both units.The line set could be bad also.Good luck

 

[yeldogt]

@mgladden2 off topic somewhat, how do you like this system? I'm looking at installing one but also trying to compare with the 40MAQ. Wondering if the additional cost for the Infinity 40mpha is worth it?

Looks like the higher end unit has an eye like the Mitshubshi ...

Typically the outside units are either hyper heat or regular ..... some companies still make a value line that is just AC.

Inside there are often two heads available --- one will have split vanes and more occupancy adaptions for more money.

 

[fitter30]

Couldn't open your file but probably has something to do with the expansion valve & compressor probably doesn't start to ramp up for a minute by that time valve will start to close. Then refrigerant flow rate and ex valve are in sink. Wonder if the ex valve bulb is tight on the suction line. Carrier has factory help at their distributors. Who ever u purchased the equipment from might be able to talk with them.