Air-cooled chillers are refrigeration systems using a vapor compression cycle to make cold water that absorbs heat from a building or process and rejects it to the outside air using air-cooled condenser coils. We design and develop innovative solutions to attenuate the sound and vibration from the system’s multiple noise sources, including compressors, condenser fans, radiated noise from refrigerant lines, vessels, unit casing, and structure-borne noise, manufacturing them to your exact specifications. In addition, we integrate and coordinate custom solutions for your specific location, grade, roof, and dunnage platform while balancing airflow and location concerns. Whether it’s as simple as a cover or as complex as a highly coordinated full enclosure, we have the ingenuity and expertise to achieve your goals.
Scroll down to explore our noise and vibration solutions for air-cooled chillers.
Screw Compressor Noise
Screw chillers have become the specified design of choice for most new construction projects because of their low first cost, high efficiency, and low maintenance expenses. Screw compressors generate moderate to loud overall noise levels and discrete tones that are extremely intrusive and annoying. Most screw models generate their fundamental tone at nominal 300 Hz frequency with strong harmonic frequencies at 600 Hz and 900 Hz.
Scroll Compressor Noise
Scroll compressors and their connected piping circuits radiate comparable overall sound pressure levels but are less tonal compared to screw machines.
Condenser Fan Exhaust Noise
Condenser fan exhaust noise is often a secondary contributing source except where receiver locations are elevated or in some cases directly above the chiller equipment. The condenser fan exhaust noise tone is around 63 Hz and below the human hearing range which drives dBA overall levels. Acoustical exhaust treatments must consider the negative impact on operational efficiency and unit power consumption.
Condenser Air Intake Noise
Condenser air intakes are the open sides and ends of the chiller where compressor radiated sound (lower region) and condenser fan sound (upper regions where condenser coils are located) flank horizontally outward from the unit. While this intake path is usually a lower priority contributing source, it can not be overlooked especially when noise reduction goals approach or exceed 8 dBA. Pressure drop is again a critical design consideration as most chillers can tolerate no more than total 0.15” to 0.25” w.g. pressure loss including system effects.
Screw Compressor Noise
Screw chillers have become the specified design of choice for most new construction projects because of their low first cost, high efficiency, and low maintenance expenses. Screw compressors generate moderate to loud overall noise levels and discrete tones that are extremely intrusive and annoying. Most screw models generate their fundamental tone at nominal 300 Hz frequency with strong harmonic frequencies at 600 Hz and 900 Hz.
Scroll Compressor Noise
Scroll compressors and their connected piping circuits radiate comparable overall sound pressure levels but are less tonal compared to screw machines.
Condenser Fan Exhaust Noise
Condenser fan exhaust noise is often a secondary contributing source except where receiver locations are elevated or in some cases directly above the chiller equipment. The condenser fan exhaust noise tone is around 63 Hz and below the human hearing range which drives dBA overall levels. Acoustical exhaust treatments must consider the negative impact on operational efficiency and unit power consumption.
Condenser Air Intake Noise
Condenser air intakes are the open sides and ends of the chiller where compressor radiated sound (lower region) and condenser fan sound (upper regions where condenser coils are located) flank horizontally outward from the unit. While this intake path is usually a lower priority contributing source, it can not be overlooked especially when noise reduction goals approach or exceed 8 dBA. Pressure drop is again a critical design consideration as most chillers can tolerate no more than total 0.15” to 0.25” w.g. pressure loss including system effects.
Building Reflection Noise
Published chiller equipment sound power levels are based on free field 360° spherical sound propagation. Considering no chillers can radiate spherically, there will always be contribution to overall receiver sound pressure levels from nearby reflective surfaces. Sound reflections from the roof or grade when combined with an adjacent vertical wall plane can add 3-5 dBA to the modeled or measured level at a receiver location. The closer the reflecting plane is to the source the greater the sound contribution will be.
Structure-Borne Noise
Any building structure that vibrates radiates airborne sound energy inside the space. Structure-borne unit vibration generated from chiller compressors and condenser fans can excite roof steel, metal decking and gypsum board partitions.
STA
2-5dB(A)
Standard
This is a treatment of the compressor circuits for chillers with Screw and Scroll Compressors. HUSH COVERS are used for the compressor housing, suction and discharge piping and oil separator vessels, depending on the type of unit and application.
Sample Installation Images
Standard Highlights
- Source Control using HUSH COVER™ removable sound blankets
- Model HC-500S-1 blanket construction
- “D” ring fastening bands with Velcro flaps
- The SL System treats only the scroll compressor to achieve a 2 to 3 dB(A) typical noise reduction
- The SC System treats chiller circuit parts, all compressors, suction lines, discharge pipes and oil separators to achieve a higher 4 to 5 dB(A) typical noise reduction
UNI
4-6+dB(A)
Unitary
The Unitary™ “SM” System is a top mounted, unit supported plenum style acoustically insulated stack constructed using HUSH GUARD™ sound panels. Condenser fan outlet noise can be reduced by 4 to 6 dB(A) with this treatment.
The Unitary™ “IM” System is an independently mounted, wind load rated plenum style acoustically insulated stack constructed using HUSH GUARD™ sound panels. Condenser fan outlet noise can be reduced by 4 to 6 dB(A) with this treatment alone.
Unitary™ SM-SB Systems (Silencer Bank) are available in both top mounted and independently supported constructions. This variation of the Unitary™ System design adds silencer modules to fit inside the HUSH GUARD™ plenum stack for increased performance and where noise sensitive receiver locations are elevated above the equipment. Baffle thickness, spacing and depth determine overall performance.
Sample Installation Images
Unitary Highlights
SM
- Source Control using HUSH GUARD™ modular acoustical panels
- Attenuates condenser fan exhaust
- 4 to 6 dB(A) typical reduction
- HGU panel construction
- Outperforms Low Noise Fans
- Minimal pressure loss impact
- Designed to be bolted to and supported by the chiller
SM-SB (Silencer Bank)
- Source Control using HUSH GUARD™ modular acoustical panels
- Silencers for increased attenuation of condenser fan noise
- Attenuation can vary from 6 to 12 dB(A) depending on splitter configuration
- HUSH GUARD™ type HGU panel construction
- Outperforms Low Noise Fans
- Minimal pressure loss impact
- Available in both "IM" Independently Mounted/Grade Mounted and Top Mounted/Unit Supported configurations
IM (Independently Mounted)
- Source Control using HUSH GUARD™ modular acoustical panels
- Attenuates condenser fan exhaust
- 4 to 6 dB(A) typical reduction
- HGU panel construction
- Outperforms Low Noise Fans
- Minimal pressure loss impact
- Wind Load rated
LOU
5-7dB(A)
Louver
The Louver™ System uses high performance type HUSH DUCT silencers up to 36” deep for direct bolting to the chiller cabinet/frame. Typical reductions of the condenser inlet noise are 3 to 5 dB(A). Greater reductions can be achieved when combined with other source treatments.
Sample Installation Images
Louver Highlights
- Source Control using HUSH DUCT silencers up to 36” deep
- Direct mounting of louvers to upper side intake coil area and/or lower open framing
- Galvanized steel construction
- Range is 350 FPM (ideal) to 600 FPM maximum
- Additional Hush Guard (hard) & Hush Flex (soft) panel options for blanking off openings and Chiller ends to treat breakout noise.
PRE
10-12dB(A)
Premium
Premium™ “SW” Systems are used for acoustical lining of block, brick, metal or other reflective barriers. The exterior grade construction is weather and UV resistant while absorbing specular sound reflections and dissipating reverberation build-up. HUSH QUILT™ panels can be supplied in roll form for contractor field installation or in factory fabricated finished panels.
Premium™ “OF” Systems are composite sound curtains used for chain link, shadow box or other louvered partially open barriers, fences and screens. These composite HUSH FLEX™ panels are finish fabricated with hanging grommets and Velcro® overlapping edges. The facings, Velcro, barrier layer and edge binding are all outdoor compatible. Average reductions are 10 to 12 dB(A) as long as the fence/panel height exceeds the chiller.
Sample Installation Images
Premium Highlights
- Path Control Treatment
- HUSH QUILT™ acoustical panel system (SW)
- HUSH FLEX™ acoustical curtain system (OF)
- Panels attached to block, brick, wood or other SOLID WALL (SW) Structure
- Panels attached to chain link or other OPEN FENCE (OF) Structure
- 10 to 12 dB(A) typical reduction
SUP
12-15dB(A)
Supreme
Supreme™ System perimeter sound barrier walls are enclosures constructed of HUSH GUARD™ panels with a wind load rated, PE stamped structural steel framework. Optimal system performance is for barriers that are 2-3’ taller than the equipment. Acoustical air intakes and discharge stacks may also be needed to manage the unit operating efficiency impact.
The Supreme(TM) System is a perimeter sound barrier solution designed to be independently supported, or supported by the unit dunnage, etc.
Sample Installation Images
Supreme Highlights
- Path Control Treatment
- HUSH GUARD™ modular acoustical barrier wall
- 12 to 15 dB(A) typical reduction
- HUSH GUARD™ panel construction
- Panels can be installed without a crane
- Superior weather resistant non- corrosion construction
- Performance is based on variations such as enclosure/wall height, distance to unit, and panel construction.
SUM
9-15dB(A)
SUMMIT
The Summit System for air-cooled chillers is a high-performance source-applied treatment of the chiller’s intakes and discharge fans using Hush Guard panels and Hush Duct Silencers. Hush Cover removable acoustic jackets provide additional source treatment of the chiller compressor(s) and refrigeration circuit(s).
Sample Installation Images
SUMMIT Highlights
- Three-part source-applied treatments include Hush Guard panels, Hush Duct Silencers, and Hush Cover removable acoustic jackets
- Specialized unit mounting and attachment allow the source-applied treatment to be supported from the unit (e.g., pad anchorage, etc.)
- Summit System to be unit supported after equipment coordination/approval. Our system integration is coordinated with the equipment/OEM as to not void unit warranty.
- For chillers up on dunnage or platforms, Hush Guard(TM) panels can be used to create an acoustic floor below the unit.
ULT
15-20+dB(A)
Ultimate
The Ultimate™ System is a complete, custom-designed enclosure with high performance integrated air intakes and discharge stacks. Reductions of up to 25+ dB(A) possible. This solution requires extensive coordination with the construction team and sign off by the chiller manufacturer to make sure the design is optimized to consider airflow and backpressure tolerance.
Sample Installation Images
Ultimate Highlights
- Path Control Treatment
- HUSH GUARD™ modular acoustical enclosure with roof
- Acoustical panels stacked between structural steel support columns
- Integrated HUSH DUCT™ acoustical air intake and condenser fan discharge silencer
- Critical attenuation projects