You have started out with " This is not a DIY, rather I'm just curious to learn something:" through the entire process of A/C instalation and diagnostics and some theory. You sure you haven't been piecing this thing together? lol

Some do have a small thud sound when shutting off but I wouldn't say it is loud by any means. If it is really loud you probably have big problem. Call a pro.

 

No, I'm just a homeowner so have not enough experience or gear to do any DIY to speak of even if I wanted to. I will be having a pro look at the system soon, just a question of who.

Yeah, it's loud.

 

Not picking on you Sonic, but just an oppinion from me. Many people express a "loud noise" from their AHU or CU that is completly normal. I dont get it. A CU scroll compressor wrapped in a blanket is noisy outside your bedroom window. I understand that, but it is what it is. What is excessive noise for a CU? Yes, you are going to hear it turn on and off. It is a mechanical device under liquid\vapor pressure. Listen to a home type air compreser in a garage, loud start, loud stop. No one complains about that, an AC window unit, same thing. I think the manufacture's should design a CU that can work underground.:grin2: I've been on call's where the HO complains about the next door neighbors CU starting up and bothering them. Geesh. I'd say, get a fuel fired furnace and fuel fired AC unit.:angel: As to your "clunk" noise when the compressor shut's off, think about it, it is under load, the Tstat is satisfied and dis-connect's power from it. If you know the suction pressure and the discharge pressure at the time of shutoff, this may equate to the differance in the noise level depending on several conditions. A clunk vrs a LOUD clunk. Either way, not a problem with the operation of the equipment in most cases. Same thing upon start up, does it have a TXV or Orifice\piston? I bet a sensitive person in this scenario really hate's the reversing valve\defrost mode in the winter.

 

Not picking on you Sonic, but just an oppinion from me. Many people express a "loud noise" from their AHU or CU that is completly normal. I dont get it. A CU scroll compressor wrapped in a blanket is noisy outside your bedroom window. I understand that, but it is what it is. What is excessive noise for a CU? Yes, you are going to hear it turn on and off. It is a mechanical device under liquid\vapor pressure. Listen to a home type air compreser, loud start, loud stop. No one complains about that, an AC window unit, same thing. I think the manufacture's should design a CU that can work underground.:grin2: I've been on call's where the HO complains about the next door neighbors CU starting up and bothering them. Geesh. I'd say, get a fuel fired furnace and fuel fired AC unit.:angel:

The stopping noise is something I'm honestly not sure how long has been there actually, it wasn't there during Winter when in heating mode, but it might be "normal" for cooling mode for all I know. What is not normal though is a low-end hum and randomly loud condensor starts that began immediately after a TXV swap (on the evap coil side of things). I don't understand why, nor has the installer acknowledged anything is operating incorrectly, but something definitely pissed off the outside condensor. Lineset is vibrating more since as well. Personally I suspect something is wrong with the charge or something got inside the lineset (moisture or carbon oxidation, etc). The clowns who did the work did not bleed nitro while brazing, didn't use a wet rag to protect the TXV, didn't use a micron guage to check the vacuum, and didn't even change the filter drier. I don't know if I'll ever get to the bottom of what's wrong because I would guess half the "pro's" who came to listen to the system would think it was within the realm of normal, but I know for a fact something happened during that TXV swap that has caused this noisier behavior. No doubt about it. Identifying and correcting the issue remains the big challenge.

I don't suppose there's any way to check the integrity of the refrigerant?? Or would any issue show up in the pressure & temp readings? All that has been done so far is basic temp and pressure readings. Installer says subcool is good, therefore things are working fine.

 

Sounds like your compressor is damaged. Willing to bet it has had to pump some liquid a few times along with some "black candy" to coat the internal pump housing.:gah:

 

Would a second opinion be able to actually tell me anything though? I sat and watched the techs take the pressure and temp readings and they do indeed correspond to the proper subcooling. So taking that away, what is left that somebody would be able to test if it were indeed an issue with what's floating around inside the lines, or damage to the inside of the compressor?

Can you guys elaborate a bit so if I do hire a 3rd party contactor that I can at least ask questions in advance if as to if they have the ability to peform certain specialized tests?

 

Have any of the techs actually seen or heard the noises?

 

They were more occupied with taking readings actually and didn't spend much time on the noises. But yes, without me even saying anything while we were standing outside the condensor shut off with a loud clunk and they both looked at each other and chuckled and commented how scrolls can be lound starting and stopping sometimes. Claimed it is normal, but I would expect them to say that regardless. One tech did take a moment to listen to the low end hum inside the home, didn't have any solid explanation. Part of him was sort of implying it was normal but I could just sense he knew it wasn't. But it was subtle enough that he wasn't about to spend time trying to hunt down the cause. He mentioned lineset noise transfer as one explanation but I sort of proved that theory wrong and then he then just said sometimes with 410a/scroll systems noises get into a home and it can be nearly impossible to resolve. So in that sense they did acknowledge the issue, but are trying to brush it off. In all honestly, I probably would accept the "it's normal" excuse had I not known the way the system ran (quietly) prior to the TXV service.

My quandry now is, I either need to focus on dampening the noise somehow, through a vibration pad under the condensor (and possible lineset dampening as well), and/or potentially put up a cement wall along one side of the condensor. OR else the system has a legitimate problem, and by doing the afformentioned all I will be doing is masking a bigger problem that is just going to bite me later. I'm struggling to get some guidance on what the case is so I know which path to pursue....but so far having a rough time. :gah:

 

Wow, it really sounds like you are trying to make this noise an issue,when it probably isn't. "you could just sense" that he thought it was unusual seems like a bit of a stretch. Maybe you have a problem , maybe you don't seems like the majority on here think not. Probably just the sound of refrigerant rushing back through the compressor on shut down, could be the TXV is non bleed as was said before. Did you even have a TXV before or a piston metering device? For your own peace of mind you may have to pay someone else to look at it, and actually tell them what you think the issues are, instead of sending them to check pressures and trying to read their minds.

 

Sonic, addressing the thrum noise. if your sure the CU is the issue this will not apply. If it's the AHU, I've seen solutions such as an inch or two of re-infroced rubber strapping used below the all thread when a AHU is mounted to the the stringers\rafters in an attic. Also, if mounted to the attic floor, the AHU shoud be isolated with rubber, or equivalent for noise isolation. Just My oppinion. Where is your AHU located and how is it mounted?

 

@ the two most recent replies:

Evap had a TXV previously (not piston). Also, it was suggested that if the charge is off in a 410a/scroll system, even slightly, it can sometimes cause the compressor to run louder - so they first wanted to make sure the charge & pressures were okay. Checking that stuff wasn't my idea, it was the techs.

The noises are for certain occuring at the outside condensor unit, the air handler is inside in a closet and is essentially silent. The stat is set for 60 second off delay on the AHU, so you can easily tell when the outside condensor shuts off, everything goes almost dead silent inside the home even while the AHU is still running. If you go outside you can hear the sounds, including the hum. What is happening is the low end hum is being transferred into the home through windows and then bouncing around inside. Single pane windows can't filter low end at all. The reason the hum is there to begin with is reverberation of the condensor (likely compressor). I *think* what has happened is something as a result of the TXV swap procedure caused the compressor to become irritated just enough that it's running a bit rougher, vibrating a bit more which is causing a resonance of the whole condensor, sort of like a drum, which is now eminating low end.

Then there's the loud starts. It's not every time, almost random from what I can tell, but seems to do it more prevalently if the system has been sitting idle for a while. It's a grinding sound that starts out loud and tapers off after 5 seconds give or take.

 

Have the compressor replaced and see if it helps or get rid of the cheap pad and bag the compressor.:grin2:

 

Do you guys think putting a rubber mat (vibration pad) between the pad and condensor would help reduce the compressor noise noticably? Or would that likely be a waste of time?

 

I have a unit with a scroll compressor and it makes some noise on start-up and shut down. I had an OEM start kit installed and that helped considerably with the start-up noise and it lowered the starting current as well. When it shuts off it makes a soft clunk and a soft rocking noise for a second or so. I think this is perfectly normal. Not being able to hear your hum I would check the coil on the contactor and reversing valve as I have heard some of them produce a loud, constant hum. Also, I have seen the CU cabinet make strange noises from vibration. Try temporarily loosening some of the cabinet screws to see if the noise changes or goes away. Good luck.

 

Update:

I had another tech finally come out. This guy clearly seemed to know his stuff, a fary cry from the bafoons who installed my system. Anyway, he took a listen to the start, stop and running sounds and he said it's not normal. He is not wanting to get in the middle of the situation by touching anything while the unit is still in the 1 year labor warranty, but he said from his 20+ years experience the issue is either a slight over charge or something in the lines that shouldn't be. He said if it were up to him he would first retreive the refrigerant using a sterile container and then weigh it to make sure the charge was correct, making any adjustments necessary. And in the process he said he can hook up a filter drier of some sorts so the refrigerant is filtered (potentially removing some contaminants, if present). Lastly, performing a good vacuum and verifying it before releasing the refrigerant back into the system. If the issue wasn't resolved after that, he would assume it is a referigerant problem and completely swap out the refrigerant, replace the filter drier, do a vacuum/check and let it rip. He felt that approach would have a 90%+ probabilty of resolving the issues. A hard start kick might also assist but he feels that isn't the core issue in my case. Also some iso pads might help some too but that would again be putting a band-aid over the real underlying problem.

What are your thoughts? Does this guy's logic sound within reason?

 

He felt that approach would have a 90%+ probabilty of resolving the issues.

What are your thoughts? Does this guy's logic sound within reason?

I feel it has a 0% probability of success.

You asked.

 

I probably represented the explanation a bit incorrectly. In the second scenario it's not the refrigerant per-se in question but other things that shouldn't be in the lines along WITH the refrigerant is what I think the tech was trying to explain to me. At any rate, he felt that was less likely than the charge simply being off. He said it needs to be weighed in my case due to the fact the line temps are not "normal" because of the suction line missing insulation in the chase, so the only way to know the charge is correct is to weigh it. Being off by just half a pound could make the compressor run a bit rougher and also slug fluid at times (start and stop) is what I believe he was saying.

Anyway, the guy is 20+ years in the businesss, authorized servicer and NATE certified. So I did what the Pro's on the forum repeatedly recommended and went ahead and got somebody else to take a look at things. So if this guy doesn't sound reasonable then I'm not sure what else to do at this point.

Sonic

 

I can tell you that my own home has two Lennox units...both scrolls...and one has always made more noise than the other when it shuts down...and there is nothing wrong with either of them...9+ years and both are still going strong. We've had some pretty hot temps here in the DFW area this summer and both units are keeping the house 30+ degrees cooler than the outside temps.

So I wouldn't sweat the compressor noise, which was your original post.

You then brought up a "hum" that is bothering you. Based on what you said this last guy wanted to do...and you seem to agree with...why don't you call the original installer back out and get them to do what the guy suggested? I don't think it will solve your problem, but it would give you some peace of mind. If they don't want to do it then you can decide if you want to just forget about the remainder of the warranty on the TXV and just have the last guy do it.

 

Keep in mind, all these noises began immediately following the TXV replacment, it's not like they were there from the beginning. And to state again, I don't believe this is related to the TXV itself but rather the procedure involved in swapping the TXV.

None of the noises are consistent all the time. The hum is usually consistent, but there are a few times/conditions during the day I've noticed it is sometimes non-existent (for example when it's really hot outside typically between 3pm and 5pm). The stopping sound can range from a normal click off to a loud CLUNK (and I mean LOUD). Starting it can thump loudly, and also grind for a few seconds (and then taper off). The tech was explaining that it is very possible the unit is overcharged a bit which would explain why the noises are inconsistent because all the various operating conditions during the day impact temperature and pressure. Or something to that effect.

Sonic

 

If it's overcharged then the excess needs to be recovered. There's no justification for removing the entire charge. Explain the concept of subcooling to your technician.

 

In my experience, when scroll compressors grind at startup, the system is overcharged. I recently had a condenser doing this and I pulled over three pounds of refrigerant out. The compressor not only did not grind anymore at startup, the system cooled the house more effectively. Imagine that.

When the system is properly charged there may be a small noise when the compressor stops, especially if the system cycles on hot days. But IMO it should not be heart stopping LOUD.

 

Mine was making a loud resonating, vibrating the line-set. Sounded like a a few amateurs attempting to play the trumpet:grin2:. Hard to describe. It was loud enough that when the unit shut off and made the noise, the neighbors from across the street would stare. Anyway, it turned out being overcharged a bit. Im not sure how much he let out, but it was an immediate fix. THe noise only happened right when the compressor shut off, and only happened in the hotter part of the day (from 2pm to 9pm). We also had 40 consecutive days of over 100 and a few 110f days, so it probably played a roll. Good luck

 

Ok Guys, FINALLY I have the sounds to share.

Due to limitations of the site's upload engine, you will have to rename the files to an .MP3 extension to listen to them. (Sorry)

I went through hell to record these, so hopefully, FINALLY you Guys can now distinguish what might be going on. Keep in mind, even these clips don't do full justice because there's more "thump" going on than transposes in the clips (and of course some of it is being transferred down the lineset into the home which obviously the clips don't portray).

What say you guys ????

Sonic

 

kinda read this whole tread and my thoughts tend to be different
first your link didn't work
has any of the techs you had look at the unit checked the fan blade
i have come across several units that would wake the dead on shut down and some time on start up
cause was the hub on the condenser fan blade was just slightly loose and causing a thump when the tourck of the motor was disengaged
ask them to pull the blade and check the hub
IMHO:angel:

 

I should have clariied: You need to right-click on the files and then "Save Target As", then rename the extension from .DOC to .MP3.

You're not the first person to mention the fan/hub as a possible cause of the noise at shutdown. Right now, I'm in the mode of trying to prove something probably isn't right, that's why I'm hoping some guys on the forum here can listen the files.

 

You have a Comfort Series condenser, correct?

The audio sounds perfectly normal to me. Maybe you should have sprung for an Infinity...

 

i am sure that one of the pros from this site could
be from your area that may be willing to look & listen.
if you were from my area i would be but it would be
only my opinion & let your previous guys do the work.

 

Apparently no pro forum members in my area, already checked into that.

Yes, Carrier Comfort Series.

I've listened to literally dozens of systems the last six months.... Trane, Lennox, Ruud, etc.. And have yet to hear ONE that makes noises like mine, or at least as loud anyway.

The challenge I placed previously with the installer and other doubters still stands: Point me to even ONE new (or relatively new) system like mine that makes noises of the type and magnitude mine is making and I'll be more than glad to drop the concern. So far nobody has been able to do that.

 

Have you listened to other Comfort Series of the same tonnage and match up?

Listening to other brands is like saying my F150 doesn't sound like that Dodge Ram...

 

Agreed, but using that logic, then after listening to new systems, older system, R410a systems, R22 systems, larger systems, smaller systems, cheaper systems and more expensive systems, if my system still stands out then it would imply the Carrier Comforts line is garbage from a noise perspective. Clearly outside the "norm" of other competitors since they also have models in that same price-tier. I personally don't subscribe to that logic. Not yet anyway.

I'd like to hear from others as to their opinion on the noises. Even the service techs raised an eyebrow when they heard the stop noise, but they were only there to check charge so they weren't about to investigate anything.

 

is this a case of buyers remorse or just trying to get a different unit because we are in no way able to find a problem over the net. I think you are better served by finding someone that can figure out the problem if there is one and fix it or not

as much as i would like to say what i think the noise is i cant because i am not standing there while it is happening

call your installer and just tell them you aren't happy with the noise and you want it resolved asap

sorry for being blunt but we are not the ones there

 

A lot of guys on the forum requested recordings of the sounds, so I just provided those. That's where we are at. Stop trying to insinuate alterior motives, there are none beyond figuring out what the cause of the problem is. As I said, while I suppose it's possible the equipment may be substandard from a noise perspective, I don't subcribe to that logic, yet. If that were indeed to end up being the case, rather than an actual underlying problem, then I might have buyer's remorse. But as of right now, no. I DEFINITELY have a case of installer remorse however.

For now, I'm just wanting opinions on the noises being normal for a new system or not. Those noises weren't there intially. That much I can say for certain. Or at least not as loud/obvious. This all started after a TXV swap. System otherwise seems to run okay.

In case this got lost somewhere in the discussion, I did have some other techs take a listen and they both generally felt the noises are on the fringe of what might be considered normal, but said a new and properly running system usually doesn't make that degree of start/stop noise, and furthermore they seemed most curious about the stop noise (although didn't elaborate).