This is Part 1 of our 4-Part Article which details many ways to make your HVAC System quieter.  Al’s Plumbing, Heating & A/C, in Plano, Texas provides full service plumbing maintenance, repairs and replacements for every plumbing component in your home.  Al’s sells and installs Rheem Professional Series gas & electric water heaters, and tankless water heaters.  Al’s Plumbing, Heating & A/C is near your home in Plano, Allen, and Frisco.  We service homes in southern Collin County, TX & northeastern Dallas County, TX with no additional travel charge.

On A Side Note: 8 Companies Make 24 Different Brands Of Residential HVAC

Click Below For Our Article That Details The 8 HVAC Manufacturers — And The Brands Made By Each:

8 Companies Make 24 HVAC Systems Brands

How To Make Your HVAC System Quieter

HVAC Systems Make Assorted Noises — And What You Can Do To Minimize Them.

Image Source: Dreamstime

Shown: Central A/C or Heat Pump Outdoor Unit

Please Note: These Details Were Accurate As Of November 2021. 

All Details Are Subject To Change Without Notice.

The Outdoor Central Air Conditioner (or Heat Pump) — Makes Notably More Noise Than Indoor Equipment.

3 Components In Outdoor A/C Units Make Noise:

• Compressor (it’s what moves the refrigerant)
• Fan Blades
• Fan Motor

1 Factor Related To Outdoor A/C Units Creates Noise:

• Air Movement (turbulence)
• When any surface strikes air — it creates air movement/turbulence. 
• The turbulence creates sound/noise. 
• Less air turbulence = less noise.

Air Movement/Turbulence Noise — Is Affected By A Fan Blade’s Design:

• Shape & Size.
• Pitch/Angle.  Steeper pitch/angle = increased; air movement, air turbulence & noise.
• Rotation Speed.  Faster spinning blades = increased; air movement, air turbulence & noise.

EXAMPLE: Sickle-Shaped Fan Blades Are Quieter Because:

• Air moves over the entire fan blade (versus only the front edge).
• This increases air movement.
• That allows fan blades to spin slower.  **

• They have a thinner rear edge.  
• The rear edge of a fan blade is what creates air turbulence and noise.

• One manufacturer says sickle-shaped fan blades reduce noise: “by up to -7 decibels.”(dB). **
• -10 dB is perceived as 1/2 the noise by our ears.

*** Source:  https://www.multi-wing.net/blade-profiles/sickle-fan-blades/

Noise Level Comparison For 2 Different Brands/Models Of Central A/C Outdoor Unit

• We’re not peddling new central a/c in this article — rather we want you to know the significant noise difference between 2 different outdoor units.
• When buying new A/C — make your hvac system quieter by choosing a system that makes less noise.
• Noise level can be found in HVAC equipment marketing brochures.

• Slightly below within this article — we offer solutions to reduce the noise heard from your existing central a/c.
• The same solutions can be employed to reduce the noise heard from a newly installed  a/c.

The Way The A/C Outdoor Unit Is Made Has A Lot To Do With How Much Noise It Makes

These 3 Components Contribute The Most To An A/C Outdoor Unit Being Quieter:

• Scroll Compressor.
• Scroll compressors have 70% fewer moving parts.  This is why they’re quieter than piston compressors.

Source: https://airsquared.com/products/scroll-compressors/silent-series-scroll-compressors/

• Compressor Sound-Insulation.

• Sickle Shape Fan Blades.
• These blades can be up to 35% quieter.

EXAMPLE: A Comparison Of Noise Level For 2 Brand & Model Central A/C Outdoor Units

Note: Al’s Plumbing, Heating & A/C Doesn’t Sell Lennox Or Goodman HVAC Brands.

Note: Both Air Conditioners Show Are Single-Speed Operation.

• Goodman GSX 16 (up to SEER 16) noise level = 73 dB (average) *3
• Lennox HVAC ‎‎HXS 15 (up to SEER 15) noise level = 59 dB (average). *4

• Lennox HXS 15 creates -70% less noise than Goodman — as perceived by our ears. *4
• This is based on this standard guide: -10 dB = 1/2 the noise — as perceived by our ears.
• The Math: 1 dB = 5%.  -10 dB = -50%.

Compressors Are The Same:

• Both Have Copeland® (brand) Scroll Compressor.

Compressor Sound-Insulation Differs: 

• Lennox has an insulated compartment.
• Goodman has an insulated blanket.

Fan Blades Design Differs:

• Lennox has sickle-shaped fan blades — which can be up to 35% quieter.
• Goodman doesn’t have sickle-shaped fan blades.

Refrigerant Coils Differ:

• Lennox’s coil is described as “Provides Low Air Resistance”.  Less Resistance = Less Noise.

What’s Contributing To Lennox Being 35% Quieter: 

• Better compressor sound-insulation
• Superior fan blades’ design
• Superior (refrigerant) coil design.
• The fan blades and (refrigerant) coil design both create less air turbulence.  Less turbulence = less noise.

Lennox HXS 15 Has: *5 

• Copeland® (brand) Scroll Compressor.  Scroll compressors have fewer moving parts and make less noise than piston compressors. *5
• Insulated compressor Compartment.

• “Precision-Balanced, Direct-Drive Fan Motor. Delivers ultraquiet operation.” (as described in the brochure).
• Has: Sickle-Shaped fan blades. *5
• One fan blades manufacturer says sickle-shaped fan blades reduce noise: “by up to -7 decibels.”(dB). **
• -7 dB = -35% less noise, as perceived by our ears.

• “High-efficiency outdoor unit (refrigerant) coil Provides Low Air Resistance.” (as described in the brochure).

*5 Source: https://www.lennox.com/lib/legacy-res/pdfs/brochures/lennox_hsx15_air_conditioner.pdf

Goodman GSX 16 Has: *3 & *4

• Copeland® (brand) Scroll Compressor
• “Compressor sound-reduction Cover.

• “Direct-Drive Fan Motor provides quiet airflow across the condensing coil.” (as described in brochure).
• Does Not Have: Sickle-Shaped fan blades.

*3 Source: https://www.pickhvac.com/central-air-conditioner/goodman/

*4 Source: Source: https://www.amana-hac.com/pdfviewer.aspx?pdfurl=docs/default-source/default-document-library/cb-asx16bd154a0022fa6258827eff0a00754798.pdf?view=true    NOTE: Amana & Goodman A/C are identical.

Click Here To See A Sickle-Shaped Fan Blade: Sickle-Shaped Fan Blade

OR Copy This Link Into Your Browser: https://www.google.com/search? q=sickle+shaped+fan+blade&tbm=isch&hl=en&sa=X&ved=2ahUKEwjrvtLlv_zzAhUJTK0KHdwBDjcQBXoECAEQMg&biw=1087&bih=554#imgrc=itQgqlg4FJLn1M

Source: https://www.multi-wing.net/blade-profiles/sickle-fan-blades/

Tips To Make Your HVAC System Quieter — Exiting System

• TIP: Clean The Fan Blade (if needed).  Dirt buildup on fan blades increases air turbulence, and causes blades to become unbalanced.  Both problems result in increased noise.

• TIP: Clean Central A/C Outdoor Unit Coil (if needed).  When this coil is dirty — the A/C works harder and longer.  Both issues result in increased noise.
• TIP: A neglected central a/c increases cooling cost + it wears out sooner because it must work harder & longer than if it was maintained.

Click Here To See How Dirty The Coil In A/C Outdoor Unit Can Become: Very Dirty Outdoor A/C Unit Coil

• TIP: Purchase & Install A Compressor Sound-Insulator Cover To Any Central A/C (that doesn’t already have one).

Image Source: Amazon.com Embedded Link

Click On Image To; View Product, Read Details or Purchase From Amazon.com

Website Page Says: “Minimum 40%+ Reduction Of Compressor Noise”

• Tip: Clean Furnace Blower Fan (if needed).

Click Here To See How Dirty A Furnace Blower Can Get (likely due to operation without an air filter in place): Very Dirty Furnace Blower

Perhaps The Easiest Way To Reduce Noise Heard From An Outdoor HVAC Unit

Is With A Noise-Reducing Fence

(The Fence Below Is Made Specifically For This Purpose)

Image Source: Youtube Embedded Video

Click on the white arrow in the center of the image to view a video demonstrating the effectiveness of Quiet Fence™

Copy This Link Into Your Browser To Read About Quiet Fence™ Noise-Reducing Fence For Outdoor A/C or Heat Pump: https://quietfence.com/

Their Website Says: “Has The Same Technology That Sound-Recording Studios Use To Block And Absorb Noise At Its Source.”

• Quiet Fence™ is a 2-panel system that’s hinged in the center.
• Each panel is 43″ (h) X 24″ (w).  When fully open, width = 48″.
• Buy an additional Quiet Fence™ — to surround the entire outdoor a/c unit.

• Quiet Fence™:
• Creates a barrier that traps some noise.
• Minimizes sound’s directional travel.

• Can be freestanding on a patio.
• Sells 36″ stakes that push into the ground.

• Videos demonstrating the noise-reduction ability of Quiet Fence™  — are available on their website.
• One video says: “Quiet Fence™ reduced the noise from a Central A/C unit by -9 decibels (db)”.
• -10 db sounds seems like half the noise volume — as perceived by our ears.

NOTES:

• To reduce noise heard inside the house — place Quiet Fence panels between the A/C and the house (sitting against the house).
• Depending on the outdoor unit — it may have air vents on the backside (that faces the house) — though this is uncommon.

• The outdoor unit moves a tremendous amount of air — and will struggle if its airflow is restricted.
• Depending on the size of the outdoor a/c unit, more 2-panel Quiet Fence™ units may be required.
• A large outdoor A/C unit may be taller than 43″ high (though uncommon).  If so, a quiet fence would still block most noise.

Quiet Fence™  information is provided as a service to our readers.

Al’s Plumbing, Heating & A/C does not receive compensation from Quiet Fence™.

Al’s does not endorse any specific brand of noise-reducing fence — only because we don’t have first-hand knowledge of all products available.

Heat Pumps Outdoor Units Make Additional Noises

NOTE: Skip This Section If You Don’t Have A Heat Pump.

Because Heat Pumps Extract Heat From Outdoor Air (and move the heat indoors) — They Frost Up During Winter.

During A Heat Pump Defrost-Cycle:

• A Heat Pump is a central A/C — that runs in reverse during winter.
• During winter, it removes heat from outdoor air — and pumps the heat into the furnace & house.

• While heating — a heat pump makes similar noise as a central a/c.
• Heat Pumps make notably more noise during their Defrost Cycle.
• The amount & frequency of Defrost-Cycles differs among different Heat Pump brands & models.

A. Some Heat Pump defrost whether it’s needed or not.  Defrost cycles are controlled by a timer. 

• This is because defrost-cycles are controlled by a timer — some heat pumps defrost when it’s not needed.
• When the timer reaches a preset time (typically 30–90 minutes) — the Heat Pump defrosts.
• During heat pump defrosting — the electric furnace comes on to provide heat.
• Needless defrosting + electric furnace heating during defrosting — wastes energy & makes a lot of unnecessary noise outdoors.

B. Some Heat Pump defrost — only when needed.   They defrost when frost build-up is detected.  Make your HVAC System quieter with this feature.

• They monitor the outdoor unit’s coil temperature and the outdoor temperature.
• Only when the difference between coil temp and outdoor temp reaches a preset amount — a defrost-cycle occurs.
• This technology eliminates unneeded defrost-cycles.

This Video Explains A Heat Pump Defrost Cycle

Image Source: Youtube Embedded Video

Click on the white arrow in the center of the image to view a video demonstrating a Heat Pump Defrost Cycle.

END OF HEAT PUMP SECTION

Make Your HVAC System Quieter

INDOOR HVAC NOISES

Image Source: Shutterstock

Shown: Example Of Metal HVAC Ductwork — Ductwork Connects The Furnace To The Return-Air Grilles & Supply-Air Vents.

Typical & Normal Indoor Noise From An HVAC System:

• The furnace’s blower fan (depending on where the furnace is located).
• A low volume, swooshing sound of moving air.

The Most Common Cause Of Increased HVAC Indoor Noise — Is A Clogged Furnace Air Filter 

NOTE: This Also Happens When Using An Air Filter Rated At MERV-14 or higher.

Why A Dirty Air Filter Makes A Furance More Noisey:

• The more surface-area that moving air strikes — the more turbulence/noise is created.
• More dirt in the filter = more surface-area.

• A clogged filter causes the furnace blower to work harder — to force air through a clogged filter.
• This will cause the furnace blower to make more noise.

• A dirty furnace filter reduces air-pressure on the supply side (coming from furnace) and increases air-pressure on the return air side (going to furnace).

• A furnace isn’t designed for a large air-pressure change at the filter.  More air-pressure change = blower motor works harder.

• Regardless of the reason — increased load on any electric motor — causes it to work harder and make more noise. 

Source:  https://www.plantservices.com/articles/2021/electric-motor-noise/

Image Source: Shutterstock

Shown: Dirty & Clogged Furnace Air Filter.

TIP: Check Your Furnace Filter On The 1st Day Of Each Month. 

If A Filter Looks Dirty, It Is — And It Needs To Be Replaced.

Furnace Filter Lifespan Varies By:

• How airtight the home is.  The older the home, the less airtight it is.  Older homes = more frequent air filter changes.
• Number of occupants.  More occupants = more frequent air filter changes.
• Number of shedding pets.  More shedding pets = more frequent air filter changes.

Source: https://www.resideo.com/us/en/corporate/newsroom/featured-articles/the-top-3-factors

Air-Movement Noise Is Mostly Heard At:

• Return-Air Grilles (air going to the furnace).
• Supply-Air Vents (cooled/heated air coming from the furnace).

Image Source: Shutterstock

Note: Return Air Grilles cannot be turned off.

Image Source: Embedded Amazon.com Link

Click On Image Above To; View Product, Read Details or Purchase from Amazon.com

A Supply-Air Vent can be turned off.

This is Part 1 of our 3-Part Article which detailed many ways to make your HVAC System quieter.  Al’s Plumbing, Heating & A/C, in Plano, Texas provides full-service plumbing maintenance, repairs and replacements for every plumbing component in your home.  Al’s sells and installs Rheem Professional Series gas & electric water heaters, and tankless water heaters.  Al’s Plumbing, Heating & A/C is near your home in Richardson, Garland, and northeast Dallas, Texas. We service homes in southern Collin County, TX & northeastern Dallas County, TX with no additional travel charge.