HVAC Vibration Diagnosis & Repair

Q&A on HVAC Vibration Problems & Related Noises

Vibration Noises at HVAC Equipment, FAQs

Question: How do I Diagnose vibration at the HVAC Air Handler

Can a dirty cooling coil cause HVAC system vibration? Also the service policy & warranty I purchased is not being honored by the service company.

I have a question concerning the A/C unit. When the A/C Unit turned on (inside furnace located in hallway) had a noise (vibration on the A/C Unit) I have a warranty plan and they send a technician.

Technician checked the blower by sliding the blower from its position and stated blower was OK. Technician went on and check Other parts of the furnace and was unable to determined what was causing the vibration.

He had a device (camera) to check inside air handler and notice that the coils were dirty.

He stated that it is possible that dirty coils (A/C Unit still operating OK) could cause the vibration on the unit.

Technician stated that A/C unit must be pulled/removed from its location in order to clean the Coils, which would cost over $1000.00 to include cleaning coils plus the labor.

Unfortunately the Warranty plan does not cover cleaning the Coils (maintenance), the Warranty Company interpretation of dirty coils is "Clogged coils", which technician stated coils were not clogged just dirty.

My question is: Could dirty coils (unit still cooling & running OK) can cause the vibration? R.V. 5/11/12

Reply:

The assertion that a dirty coil caused the unit to vibrate leaves me baffled. How did the tech explain that?

Indeed if the coil is really dirty and blocked it may frost over or fail to pass enough air and your cooling air will be reduced, but that's not vibration.

Look for loose parts that move when motors or fans run, including a bad blower fan bearing, mounts, loose duct work, etc.

FIRST: a lost balancing weight on a squirrel-cage blower fan can cause vibration that may be described as "humming".

Fan counterweights are detailed

at BLOWER FAN ASSEMBLY CLEANING

At HUMMING NOISES from HVAC SYSTEMS HUMMING sounds from A/C or Heat Pump systems

I've collected what we know about humming noises in HVAC equipment

Why might the position of a blower squirrel cage fan (or "wheel") on the motor drive shaft make any difference in sounds from the air handler?

1. if the shaft and blower wheel are not properly aligned - which I've come across occasionally with pulley installations secured by a set-screw; this is unusual as most-often the clearance between motor shaft O.D. and squirrel-cage bearing and shaft I.D. is very slight; perhaps a third party motor shaft or blower wheel is being made to a different tolerance.

If this is the case when you tighten the set screw (e.g. an allen screw in a pulley or on a blower wheel) the wheel or pulley may be slightly mis-aligned.

In turn this may cause vibration, wobble, noise, and maybe early motor or bearing failure.

NEXT: Try pressing gently on components to see if the vibration stops - DO NOT GET YOUR FINGERS CUT OFF IN MOVING PARTS - so you may want to have a more qualified tech take a look.

See the diagnostics in these

Articles Diagnosing Vibration in HVAC Systems

• BUZZING SOUNDS & vibration sounds from A/C, heat pump or inverter or from other equipment in, or, or near buildings
• CYCLICAL REGULAR NOISES or vibrations from loose parts on HVAC systems - a section in HVAC NOISE-2 CHATTER CHIRP CLANK FAN GROAN
• RATTLING & VIBRATION NOISES from A/C or Heat Pump System.
• VIBRATION & HUMMING NOISES from HVAC SYSTEMS  - describes nearly all sources of vibration and the sounds it may cause

Reader Follow-Up:

Thank so much for your response. As I mention on my email below that the Warranty plan does not cover cleaning the Coils (maintenance), and their interpretation of the technician report that vibration is because of dirty
(clogged) coils.

I complained to the Customer Service Rep that the technician DID NOT correct the vibration problem and was not sure what Was causing it. Customer Service Rep suggested to contact the technician and re-submit a report on what could be causing the vibration.

I did contacted the technician, and explained to him that Customer Service denied the claim because of his report stating that the coils were 100% dirty. The technician contacted Customer Service but the claim was still denied based on this report.

As I stated to customer Service and the technician that the Vibration was not FIXED, I still have to PAY $75 Deductable (service Fee) and the vibration problem was not fixed.

My conclusion is that the technician stop searching to determined what was causing the vibration after he saw that the coils needed to be clean and stated that could cause the vibration and he stated that it should be cover under the warranty (technician estimate cost for cleaning the coils $850.00 submitted on his report).

Again, I mention to the technician that he did not fix the vibration problem.

I did read the Warranty Plan and it states that cleaning of the coils is not cover under the plan, but my point was to customer service and technician that the vibration problem was not fix. Again, thank you for your response. 5/31/12

Reply:

You can inform the customer service people that a dirty coil blocks airflow but does not cause vibration in the system. I would ask that a more qualified, experienced tech be sent to the job. It sounds from your description as if the tech you had knew that he could blame an excluded item and thus escape honoring the warranty.

Reader Follow-Up:

I agree. When I spoke to the Customer Service Rep, I clearing stated that the A/C Unit was working Ok and the technician verify that A/C air flow/cooling was working ok.

Bottom line is that Customer Service Rep concluded (their interpretation based on report) that warranty plan does not cover dirty coils, and totally ignored the vibration problem.

Do you have an idea about how much (an estimate) it would cost to get the coils clean? I as mention on my previous

Email that the technician estimated about $850 (to include 4 labor hours), he claimed that the entire unit must

be remove and remove all panels in order to the clean the coils, and if it took more than 4 hours, it could cost

more around $1000 to complete the job. I told him he was just cleaning coils not replacing the coils.

Reply:

I would not touch the coils before seeing myself that they are actually dirty and blocked with debris. This whole transaction sounds suspicious. I'd like to see some well-lit sharp focus photos of the cooling coil. Also, when the time comes to clean the coils, there are procedures for cleaning in place.

Reader Follow-Up:

The technician had a device (about two feet flexible tube with camera at the end) that he insert inside the area where the coils are located, where it shows the coils were dirty. I am sure the coils in any A/C unit after Long period time (5 to 7 years) could get.

I know for a fact that during a semi/annual A/C checkup or Service the technician don't inspect the coils, they just conduct an external checkup.

I agree with you that the whole transaction sounds suspicious to me also.

The company(where technician work for) make a quick $75 and Warranty Plan did not have pay for it.

Reply:

It's a disturbing topic - too often in the news we read reports of companies that sell insurance but who pull out all the stops to resist actually paying on a claim.

As you describe no ready access to the cooling coil, cleaning would require cutting and making a (reusable) access cover for an appropriate side of the unit; there are procedures for cleaning the coil in place that should be much less costly. If you choose that approach take some photos and send them along and we may be able to offer other comment.

Please keep me posted on how things progress, and send along photos if you can. Such added details can help us understand what's happening and often permit some useful further comment. What we both learn may help me help someone else. - Ed. 6/2/12

How do I diagnose & fix Roof Top A/C Condenser Vibrations & Noise

Roof Top A/C Condenser Vibrations

I live on the top floor of a 4 story 100 unit apartment building. There are 4 A/C condensers on my roof for the units below and at least two are creating an unbearable vibration and hum.

When the maintenance man went to install vibration pads under the units, I heard two very loud crashes and think he damaged the units even more as the vibrations are much worse.

Its sounds like a train in my apartment and I feel strong vibrations when sitting or even in bed. I even have two sets of vibration pads for my bed but it still is annoying.

The mechanical contractors are coming for the third time tomorrow to look at the units but I dont have a lot of faith in them. Looking at there permit history they do mostly kitchen and bath remodels and plumbing and maybe one or 2 A/C installs. Bldg management refuses to hire anyone else.

From researching online I know there are many many possible fixes but I dont think these guys will be open to anything more complicated than more pads or a sound blanket.

Any advice? Another neighbor just went through this and basically gave up but I dont think they had it as bad as mine.

btw should these units be on their own styrofoam/concrete pad. They wont let me on the roof but the set up on my roof section was described as 4 condenser units with each set of two condensers on a pair of 2x6s.

There are cheap rubber antivibration pads under the four corners of the units and under the 2x6s. thanks - On 2021-07-11 by Ballen

Reply by (mod) - Diagnose & Solve Noisy Roof Top A/C Condenser Vibrations

HVAC system noises are easily transmitted into a building by metal ductwork, pipes, or even the roof structure itself that can act as a giant speaker cone.

To solve noisy rooftop HVAC units including hum and vibration noise the onsite technician needs to

First decide if noises or vibration are abnormal - if normal, use normal sound isolating measures such as padding

For abnormal noises or vibration, trace the problem to its source, such as

A failing bearing on a motor or blower fan

A failing motor

An unsafe electrical condition

Loose mechanical parts or sheet metal or even something as simple as an access door that's not latching

For details see, and give copies to your technician of the following:

• HVAC NOISE-1 BANG BUZZ VIBRATE - banging, bearings, buzzing, thumping
  • BANGING A/C or heat pump
  • BANGING NOISE at AIR HANDLERS or in DUCT SYSTEMS
  • BEARING NOISES in HVAC equipment or motors
  • BUZZING SOUNDS & vibration sounds from A/C, heat pump or inverter or from other equipment in, or, or near buildings
  • BUZZING NOISE DIAGNOSIS - topic home

Vibrating roaring sound, then loud rattling knocking sound at A/C unit

My air conditioner, when it comes on, it makes a sound like a vibrating sound roar then it stops - (Sept 14, 2015) Anonymous said:

The air handler in my FL townhouse is making a loud rattling/knocking sound for 3 or 4 seconds about every 3rd or fourth time the compressor kicks in.

The A/H sits right outside the bedroom door, and it makes sleeping difficult.

The A/C tech says it is refrigerant surge and is caused by a bad install design.

The compressor sits in a platform on the ground level and the air handler is on the third floor. (bottom floor is garage.) Refrigerant lines go up into the attic and down to the air handler.

Tech says even a whole new system may not fix it as the units aren't designed to push the liquid up 3 floors.

There are over 100 units in the complex, but I haven't heard anyone else having this issue. Any solution? - (Sept 26, 2015) Kelly

Reply:

I would ask for help from a senior HVAC technician on-site.

You've answered the question yourself: if it were a design issue then every installation of the same design at your townhouses would behave the same way.

Vibration noises at scroll / rotary HVACR compressors

I have a new Goodman, 14 SEER, R22 scroll-compressor, Split-System HVAC unit that was purchased/installed in 2009 but not put into service and started until today.

The unit cools my home very well however the condensing unit is very noisy and has a great deal of vibration in the low side refrigerant line and the condensing coil is physical moving about a lot inside the housing in perfect time with the vibration.

The ambient temperature was/is 105F with the HS press @ 250psi and the LS Press @ 78psi which yields an evaporator coil temperature of around 43F.

The pressure readings are stable with no fluctuation what-so-ever. I am a certified tech with over 25 years of experience and I have never seen a unit do this before now. Anyone have any experience with this problem and/or any advice? Thanks a bunch, Jim 2016/06/04

Reply: studies report analysis of vibration in rotary compressors or scroll HVACR compressors

Jim

Look first for loose mounting bolts or screws anywhere on or in the compressor/condenser unit; also look for refrigerant tubing left un-insulated and in contact with a vibrating service. You probably already know those common noise sources and have perhaps more field experience than I do, so let's think and argue about this a bit.

Only a mechanical movement can cause vibration; we can probably exclude outside influences such as wind or nearby mechanicals on other systems;

Is the pad level and secure?

Can you take a mechanic's stethoscope and check components for vibration: seems to me we have either the compressor motor or the fan motor. I don't think that even a bad control such as a relay or TEV would vibrate at such a high frequency as to cause the noise you describe.

I'm speculating you'll trace the noise to the compressor motor itself: perhaps a sticking valve. I did some research on vibration in rotary compressors: you'll want to use Google Scholar to search for and find these articles:

Research on Vibration at Rotary Compressors

• Imaichi, Kensaku, M. Fukushima, S. Muramatsu, and N. Ishii. "Vibration analysis of rotary compressors." (1982). - you can read this directly at
  
  docs.lib.purdue.edu/cgi/viewcontent.cgi?article=1406&context=icec it's very technical, but the conclusions are worth noting.
  
  It makes me want to check the stability of the voltage being delivered to the unit; if that's ok it makes me suspect the motor itself is bad.
• Kim, Dae-Kyong, Kwang-Woon Lee, and Byung-Il Kwon. "Commutation torque ripple reduction in a position sensorless brushless DC motor drive." Power Electronics, IEEE Transactions on 21, no. 6 (2006): 1762-1768.
• Ishii, Noriaki, M. Fuhushima, K. Sano, and K. Sawai. "A study on dynamic behavior of a scroll compressor." (1986).
• Lee, Ho-Jung, and Kwang-Joon Kim. "Multi-dimensional vibration power flow analysis of compressor system mounted in outdoor unit of an air conditioner." Journal of sound and vibration 272, no. 3 (2004): 607-625.

The presence of these and other research papers to me as a non-engineer, suggest that vibration in rotary or scroll HVACR compressors is a known and studied problem.

For a catalog of different sorts of HVAC noises and what they may mean,

see NOISES, HVAC SOUND DESCRIPTIONS - Five groups of HVAC sounds, listed alphabetically from Banging to WuWuWu help track down the noise source & suggest repairs.

Question: vibration noise after fan replaced

I had my fan replaced on my outside condenser , heat pump. Now, there is more noise and vibration than before, I had to put foam between top grill and frame. It is a 4 ton unit and he put in a 1/2 HP 1075 rpm motor. He said it is because my last motor was a piece of crap. Does this sound like the right size motor. thanks 2016/09/15 Steve said:

Previous question error. He put in a 1/3 hp motor, not 1/2 hp, thanks

Reply:

Perhaps more noise and vibration from improper mounting or an unbalanced fan blade set? Look for loose parts first.

Unless the fan is running at the wrong speed, I would not expect fan vibration and noise to be due to motor size.

 

Very noisy and vibrating new Goodman Split System HVAC unit - expert tech seeks more info

I have a new Goodman, 14 SEER, R22 scroll-compressor, Split-System HVAC unit that was purchased/installed in 2009 but not put into service and started until today.

The unit cools my home very well however the condensing unit is very noisy and has a great deal of vibration in the low side refrigerant line and the condensing coil is physical moving about a lot inside the housing in perfect time with the vibration.

The ambient temperature was/is 105F with the HS press @ 250psi and the LS Press @ 78psi which yields an evaporator coil temperature of around 43F.

The pressure readings are stable with no fluctuation what-so-ever.

I am a certified tech with over 25 years of experience and I have never seen a unit do this before now.

Anyone have any experience with this problem and/or any advice? Thanks a bunch, Jim On 2016-06-04 by Jim

Reply by (mod)

Jim

Look first for loose mounting bolts or screws anywhere on or in the compressor/condenser unit; also look for refrigerant tubing left un-insulated and in contact with a vibrating service. You probably already know those common noise sources and have perhaps more field experience than I do, so let's think and argue about this a bit.

Only a mechanical movement can cause vibration; we can probably exclude outside influences such as wind or nearby mechanicals on other systems;

Is the pad level and secure?
Can you take a mechanic's stethoscope and check components for vibration: seems to me we have either the compressor motor or the fan motor. I don't think that even a bad control such as a relay or TEV would vibrate at such a high frequency as to cause the noise you describe.

I'm speculating you'll trace the noise to the compressor motor itself: perhaps a sticking valve. I did some research on vibration in rotary compressors: you'll want to use Google Scholar to search for and find these articles:

Imaichi, Kensaku, M. Fukushima, S. Muramatsu, and N. Ishii. "Vibration analysis of rotary compressors." (1982). - you can read this directly at http://docs.lib.purdue.edu/cgi/viewcontent.cgi?article=1406&context=icec it's very technical, but the conclusions are worth noting. It makes me want to check the stability of the voltage being delivered to the unit; if that's ok it makes me suspect the motor itself is bad.

Also

• Kim, Dae-Kyong, Kwang-Woon Lee, and Byung-Il Kwon. "Commutation torque ripple reduction in a position sensorless brushless DC motor drive." Power Electronics, IEEE Transactions on 21, no. 6 (2006): 1762-1768.
• Ishii, Noriaki, M. Fuhushima, K. Sano, and K. Sawai. "A study on dynamic behavior of a scroll compressor." (1986).
• Lee, Ho-Jung, and Kwang-Joon Kim. "Multi-dimensional vibration power flow analysis of compressor system mounted in outdoor unit of an air conditioner." Journal of sound and vibration 272, no. 3 (2004): 607-625.
  
  The presence of these and other research papers to me as a non-engineer, suggest that vibration in rotary or scroll HVACR compressors is a known and studied problem.
  

Followup by Jim

Thanks for the response and insight. The unit has quieted down significantly over the last 24 hours of operation with the condenser coil assembly now not having nearly as many moments in movement/vibration. These moments are also now more in synchronization with the enclosure movements.

The only changes I have made so far is in three (3) small refrigerant charge reductions based on superheat readings at the compressor return inlet.

I suspect there was/are possible refrigerant condensation fallout occurring inside the low pressure return line despite the pressure readings being stable with only very small fluctuations indicated in the high side discharge line.

The HS head pressure and LS pressure ratio is well within declared limits stated in the manufacturer's setup specification documentation.

I am considering adding a liquid line-trap loop in the low pressure piping near the evaporator outlet to see if it makes any difference in the vibration. I will post my findings. What is your opinion on my thoughts and direction? Thx, Jim

Reply by (mod)

Interesting; check that nothing remains loose.

Indeed refrigerant on the low side, as you know better than I, can at worst ruin a compressor and less bad, might cause ugly noises. Interesting and clever thing to try - slight charge reduction. Thanks for keeping me posted; working together makes us smarter.

Question: copper refrigerant pipe vibration noises indoors

I have two HVAC systems with heat pumps. The copper pipe (heat) that comes out of one unit vibrates alot and causes noises in the house.

It is an upstairs unit and I had the vibrating pipe ran up outside the house, into the attic and down to the upstairs unit.

It still vibrates and makes noises. Is there something that can deminish the vibration after it leaves the unit and before it reaches the house? (Feb 6, 2014) Lee Albro said:

Reply:

Lee, that vibration doesn't sound good - as it can cause a wear-leak, refrigerant loss, heat loss, or other equipment damage.

You could install foam insulation around the piping (it should be insulated anyway) where it passes through openings or needs buffering, but I'd suggest asking a service tech to diagnose and fix the vibration - hoping to avoid a more costly problem.