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Persistent problem with AC compressor unit fans on split-ACs. Any help much appreciated.


GammaGlobulin

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Here is the persistent problem with several ACs....

 

aa.  This problem involves the OUTDOOR unit of a split-AC system of 20,000 BTU.

 

bb.  The AC is new.

 

cc. The problem is caused by a noisy fan which pulls air through the cooling coils of the outdoor unit and expels the heated air out the front of the compressor unit.

 

dd.  The noise problem occurs only at mid-range RPMs.  (This is an inverter AC, and so the compressor and fan speeds vary from very slow to very fast.)

 

ee.  Fan speeds and noise:

 

1.  At lower fan RPMs, the sound from the fan is quite normal.  At these fan speeds, the "noise" from the fan is easily tolerable, expected, and typical of most new AC units.

 

2. At higher fan RPMs, the sound from the fan is quite normal.  At these fan speeds, the "noise" from the fan is easily tolerable, expected, and typical of most new AC units.

 

3.  However, at mid-range RPMs, very suddenly, the sound of the fan becomes much louder.  The sound is difficult to describe, but it is sort of a much higher pitched "rattling" sound, as if something might be loose, even though I doubt that there is anything loose.

 

At mid-range RPMs, the sound of the outdoor unit suddenly becomes quite noticeable indoors, even though the windows are tightly shut.

 

ff.  So then, my question is whether or not the fan motor, or fan, suddenly becomes "unbalanced" at certain mid-range RPMs?

 

I would liken this to tires on a car being out of balance, for example.  At some RPMs, there is a definite shimmy or vibration.  And, at other speeds, the tires rotate without vibration.

 

gg.  What might be causing this, and what to do?

 

The machine is still in warranty.  However, trying to explain this to some of the AC technicians here is quite difficult.  They do not understand the concept of RPM, and may not know that a rotating object, such as a fan or an auto tire can vibrate at one rotational speed, but not at another.  Maybe they do understand but just do not know what to do about the problem.

 

hh.  As to what I might do:

 

1.  Should I try to get the AC manufacturer to replace the fan-motor/fan assembly?

2.  What can I do to convince the technicians that the operation of the fan is not normal?  (Why should the highest fan speed be much quieter than the medium-range fan speed?  This is crazy.)

3.  Or, is this problem normal?

4. I have other AC machines made by the same manufacturer.  Another of the machines I used in the past had a fan that was extremely quiet at all RPM states.  That machine was the same cooling capacity as this new machine.

 

5.  I also question whether or not the fan-motors/fans on newer AC machines that are being supplied by this company might be manufactured with cheaper fans and manufactured to less rigid tolerances.

 

ii.   Nobody here would drive a car with wheels that shimmied at certain RPMs and not at others.  And, similarly, why would a manufacturer intentionally produce an AC with a compressor unit fan which made excessive noise at mid-range speeds, and which was much louder than the noise at lower RPMs or much higher RPMs?

 

Any thoughts about this, any help with this, much appreciated.

 

No doubt, there are several here on the forum who have long-term experience with HVAC systems and with split-air-conditioner systems.

Hopefully, one of these experts will reply to this query....

 

Thank you.

 

(If this is not the correct forum for this AC Topic, then please kindly move to a more appropriate forum, more concerned with AC issues.  Thank you.)

 

 

Edited by GammaGlobulin
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It is clear from your description that there is a harmonic vibration at certain speeds.  Yes the first step should be the installation company followed by the maker. 
 

Were this an older unit the answer would be different and would involve some or all the following, adding bracing, adding different shock absorbent mounts, tightening all bolts, adding very small weights (many higher end fans come with these) on to the blades to move the harmonic, adding rubber sheet to the casing, moving the outdoor unit in relation to the wall. etc. 

 

As to the cause it’s difficult to be sure as the drive is to reduce energy use and what you consider to be cheaping out on materials is not doing that but saving energy. The fan may well be faulty as for sure the original design will not have had this problem.

 

FWIW while HVAC people may have a good understanding, it’s a fluid dynamic problem 

Edited by sometimewoodworker
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31 minutes ago, sometimewoodworker said:

It is clear from your description that there is a harmonic vibration at certain speeds.  Yes the first step should be the installation company followed by the maker. 
 

Were this an older unit the answer would be different and would involve some or all the following, adding bracing, adding different shock absorbent mounts, tightening all bolts, adding very small weights (many higher end fans come with these) on to the blades to move the harmonic, adding rubber sheet to the casing, moving the outdoor unit in relation to the wall. etc. 

 

As to the cause it’s difficult to be sure as the drive is to reduce energy use and what you consider to be cheaping out on materials is not doing that but saving energy. The fan may well be faulty as for sure the original design will not have had this problem.

 

FWIW while HVAC people may have a good understanding, it’s a fluid dynamic problem 

 

Thank you.

 

YES, I agree this might very much involve harmonic resonance induced noise/vibration.

 

However, the sound, the "high-pitched" rattling sound, makes me think that there is something more to this than just harmonic vibration, or resonance....

 

Anyway, thank you.

 

If you might have any further thoughts..then...please add if you have time.

 

(As stated above:  Two out of three of these ACs have had this problem of excessive vibration, and excessive noise, at only certain RPM.  However, just try to explain this to some local technician.  This is an almost impossible proposition. I wish I could just swap out the fan on the new AC for another fan, and then test to see what happens.  But, how to get the locals to do this, is not going to be easy.)

 

 

 

 

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31 minutes ago, Banana7 said:

What's the make and model of the AC. How is the compressor mounted/secured? Any photos?

 

a.  I think it might not be good for me to mention the brand/manufacturer.

b.  The outdoor unit, the compressor unit, is sitting on adequate rubber feet.  This is not the problem.  In fact, the machine is quite heavy.  And, the "outer case" of the outdoor unit is rock steady, and does not vibrate.

c.  The only vibration, or noise, seems to be coming solely from the compressor unit fan.  AND, the compressor sound is quite normal.  The issue is not the compressor.

d. I would provide photos, if needed.  But...then...photos of what?  I would need to open the case of the outdoor unit to take a photo of the fan.

e.  The AC  was purchased new, about four months ago.

f.  This AC brand is similar to the premium brands, such as Hitachi.  But, this is NOT a Hitachi.  Neither is it a Daikin.  And, neither is it Mitsubishi.

 

Perhaps Important:  This machine was manufactured in Malaysia.  

 

 

Edited by GammaGlobulin
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a. The best solution would be to solve the fan problem.

 

b. The next potential "solution" might be to move the compressor unit about 10 meters from the window of the room in which the indoor evaporator unit is located.

 

c.  However, it is my understanding that there might be some loss in efficiency by extending the length of copper pipe from the evaporator unit to the condenser unit, due to heat loss from the extended coolant pipe.  (maybe only marginal efficiency loss, but IDK)

 

Try explaining this, in Thai, to your local AC service person, why don't you?

This will really put hair on your chest.

 

 

 

 

 

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18 minutes ago, moe666 said:

What brand of a/c is it. This could happen without an inverter. 

 

Yes.

This could happen with an AC that is not an inverter unit.

However, the reason I pointed out that this is an inverter unit is because....

With an inverter unit, the fan speed progresses in very many "steps" from lowest RPM to highest RPM.

And so, the lower range of RPM speeds are not a problem

The higher range of RPM speeds are not a problem.

 

It is only the mid-range of RPM speeds which are loud and noisy and "rattling".

Also, the machine will often just stay at the mid-range RPM speeds, and this becomes unacceptable, in a very short time.

 

 

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28 minutes ago, simon43 said:

Has someone hacked into GG's account and made this sensible post?

 

No Simon!

 

There is a time and place for everything, under heaven.

 

This is my time for a very serious post.

These AC issues are driving me CRAZY.

I am unable to communicate with the local service people in any adequate way.

They just do not get anything!

They look at me with vacant stares....and it's unnerving; please believe me.

Am I in the Twilight Zone?

 

It is the VERY RARE times like these that I wish I were back in Taiwan, where the technicians were from planet Earth, and not from Neptune.

 

Anyway, Simon....

 

At my wits end, I am now even thinking of buying some type of premium aftermarket fan, of identical specs, and installing it myself, just to prove my point to these local service guys, and even to the company itself...because....

 

This machine is manufactured in Malaysia.

When you call the local multi-national office/company headquarters in BKK, they seem to know NOTHING. In fact, for any technical question, the BKK guys must send emails to Malaysia just to get a reply about any simple technical issue.  So, in truth, the BKK office is nothing more than a sales and importing group, and not a technical/manufacturing group.

They tell you that they will contact the manufacturer in Malaysia, their manufacturing site.

And then, you need to wait for a reply, from Malaysia, passed through the guys in BKK.

It's like....

It's like a game of CHINESE WHISPERS:

image.png.65f5b628f22c495452552cbbeb0c8797.png

 

 

 

It seems that most of the manufacturing/tech people have been moved out of Thailand.

This company stopped producing ACs in Thailand, several years ago, according to my understanding.

 

So, Simon....

Thank you for your reply.....!

 

(Also, here on TV, I will not name the manufacturer.  There is no point or benefit in doing so.)

 

 

 

 

 

Edited by GammaGlobulin
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A friend had the same issue in a split only 4 years old badly installed by the developper in the over costly pool-villa developpement in Hua Hin in Hin Lek Fai.

 

The whole installation was badly done  like many other parts of the finishes of the house, as of course none of the falang developpers did any final checking before delivering the property to the lesee owner.

 

The owner also mentioned that the developpers usually took 8 to 12 months to take action, and that too,  only after multiple reminders

Edited by SingAPorn
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5 minutes ago, SingAPorn said:

A friend had the same issue in a split only 4 years old badly installed by the developper in the over costly pool-villa developpement in Hua Hin in Hin Lek Fai.

 

The whole installation was badly done  like many other parts of the finishes of the house, as of course none of the falang developpers did any final checking before delivering the property to the lesee owner.

 

a.  It might possibly be an installation issue.

 

b. My belief is that it is a manufacturing defect issue, and production QC issue with the fan manufacturer, and the testing of the fan before assembly in Malaysia with the AC, on the production line.

 

c. One commenter has already stated that this noise issue is not as intended in the original design of the machine.  Therefore, the fan needs to be replaced, I guess.

 

However, how to communicate this to the importer of the ACs manufactured in Malaysia?  I do not know.

 

As I have stated:

 

This multinational has a large group in Thailand, and a manufacturing site in Malaysia where the ACs are built.

 

Trying to communicate with these groups, and also trying to communicate with the local designated service center, which is not part of the multinational, is very difficult.

 

Also, another compounding factor seems to be lack of adequate understanding and poor communications due to lack of English language skills, even though, as we know, a multinational should realize that the English language is sort of the Lingua Franca for conducting international business.

 

Welcome to the Kafkaesque world of HVAC in Thailand, I guess....BIG TIME.

 

 

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8 hours ago, GammaGlobulin said:

Thank you.

 

YES, I agree this might very much involve harmonic resonance induced noise/vibration.

 

However, the sound, the "high-pitched" rattling sound, makes me think that there is something more to this than just harmonic vibration, or resonance....

 

Anyway, thank you.

 

If you might have any further thoughts..then...please add if you have time.

 

At this point you have 2 real options.

1 make the instal technician return giving a little information as possible so they can witness the problem, claim that there are more different problems you can’t describe so they must attend. 

 

2) play around with fan blade weights to change the harmonic

 

It is absolutely a problem of a harmonic vibration, however just because the fan is producing the vibration does not mean that something else is not responding to the movement of the fan. 
 

The  "high-pitched" rattling sound, is either a loose component or 2 components that are rubbing due to the vibration. The self cure is to discover exactly where the noise originates and put a block or rubber/foam between them. 
 

to locate the sound use a mechanics stethoscope. 
 

Option 1 is preferable

in reality there probably is no real guarantee beyond the “its working” and you are on your own. 
 

Unfortunately you have discovered why buying one of the big names is worth the extra money they cost. 

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17 minutes ago, sometimewoodworker said:

At this point you have 2 real options.

1 make the instal technician return giving a little information as possible so they can witness the problem, claim that there are more different problems you can’t describe so they must attend. 

 

2) play around with fan blade weights to change the harmonic

 

It is absolutely a problem of a harmonic vibration, however just because the fan is producing the vibration does not mean that something else is not responding to the movement of the fan. 
 

The  "high-pitched" rattling sound, is either a loose component or 2 components that are rubbing due to the vibration. The self cure is to discover exactly where the noise originates and put a block or rubber/foam between them. 
 

to locate the sound use a mechanics stethoscope. 
 

Option 1 is preferable

in reality there probably is no real guarantee beyond the “its working” and you are on your own. 
 

Unfortunately you have discovered why buying one of the big names is worth the extra money they cost. 

 

As usual, your analysis is the best.

 

a.  I had also thought of using weights on the fan.

 

b.  Actually, I did buy one of the big names in ACs. Starts with a P, and ends with a C.  And, I have been buying, and only this brand, for over 25 years, but in other countries.

 

c.  Re: "It's working", and so what more do you expect...,mentality:     You are absolutely correct.  

 

============

 

Still, the best thing I gained from this discussion is knowing how to approach the manufacturer and also the service people.

 

From now on in, I will have only one refrain, which is....

 

"The compressor fan is not balanced properly."

 

If they do not balance the fan properly, then the original installation work was not done properly.

 

==========

 

I think you are correct that the high-pitched rattling is due to...   2 components that are rubbing due to the vibration

This is exactly what it sound like, in fact!

 

This is very helpful.

 

 

 

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Without naming names , is this a Chinese , Japanese  or Korean air conditioner  ?

 

MIL bought  a Chinese unit last year. At first it also made more vibration noise at some speeds. After about a month of this it settled down and the noise stopped occurring.

 

Other than that she is very happy. Cooler than our 9 year old Mitsubishi according to my wife.

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14 minutes ago, Denim said:

Without naming names , is this a Chinese , Japanese  or Korean air conditioner  ?

 

MIL bought  a Chinese unit last year. At first it also made more vibration noise at some speeds. After about a month of this it settled down and the noise stopped occurring.

 

Other than that she is very happy. Cooler than our 9 year old Mitsubishi according to my wife.

 

This machine is sold by the same manufacturer of the machine in question, in this Topic.

The machine here in the video is only 6-months old.

A new machine, basically.

 

This manufacturer seems to be providing ACs to the local market with excessive vibration, probably due to problems with the compressor fans.

 

I am no expert.

YOU decide.

 

 

Edited by GammaGlobulin
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1 hour ago, GammaGlobulin said:

From now on in, I will have only one refrain, which is....

 

"The compressor fan is not balanced properly."

@GammaGlobulin giving To much information 

 

“ The AC is not working” or “the AC is about to explode”

 

You know what the problem is but telling them is not going to help you. They have to realises it themselves and give a solution.

 

The problem is extreme noise at some fan speeds. They have to solve the problem 

 

Their solution maybe “replace the complete outside unit”

They probably can’t fix the real problem because they don’t have components. The “fix” may cost 100 x the real fix but that’s their problem not yours.

 

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Sounds like an unbalanced fan, fan motor mounting loose, bearing slop, or mounting frame not stiff enough so it flexes , at least to me. If the mounts have “rubber” vibration absorbing pieces, one could be damaged or missing.

 

All blowers, fans, have “critical” rotational speeds where the fan should not operate for long due to the natural resonance or they will damage bearings at minimum. Used to work with GE frame 5 gas turbines. It was always fun starting them up as you had to bypass vibration interlocks and get through the critical speeds as fast as possible to minimize wear. occasionally,  the startup firing would stall a bit and the gas turbine would not accelerate quick enough. Big pucker.

 

Just because you cannot hear the vibration at other speeds doesn’t mean the imbalance is not there.  Likely have to replace the fan blades or the whole fan plus motor plus mounts depending on how they do the parts. I would vote for replacing the whole assembly since it could also be driven by slop in the bearings.
 

Maybe send the recording to Malaysia ?

Edited by degrub
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4 hours ago, GammaGlobulin said:

 

 

This machine is sold by the same manufacturer of the machine in question, in this Topic.

The machine here in the video is only 6-months old.

A new machine, basically.

 

This manufacturer seems to be providing ACs to the local market with excessive vibration, probably due to problems with the compressor fans.

 

I am no expert.

YOU decide.

 

 


if the video is the extent of the problem the DIY fix is likely to function, be effective and reasonably easy to try.

 

if it’s the problem I will elaborate.

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