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AIR CONDITIONING & HEAT PUMP SYSTEMS
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BLOWER DOORS & AIR INFILTRATION
BLOWER FAN CONTINUOUS OPERATION
BLOWER FAN OPERATION & TESTING
BOOKSTORE - Air Conditioning "How To" Books
CAPACITORS for HARD STARTING MOTORS
CLEANING & Legionella BACTERIA
CHINESE DRYWALL HAZARDS
CONDENSATION or SWEATING PIPES, TANKS
DEFINITION of Heating & Cooling Terms
DEW POINT CALCULATION for WALLS
DEW POINT TABLE - CONDENSATION POINT GUIDE
DIAGNOSE & FIX AIR CONDITIONER / HEAT PUMP
DIAGNOSE & FIX HEATING PROBLEMS-BOILER
DIAGNOSE & FIX HEATING PROBLEMS-FURNACE
DUCTS - Asbestos
DUCT INSULATION, Asbestos Paper
DUCT INSULATION for SOUNDPROOFING
DUCT SYSTEM NOISES
DUCTS, Asbestos Transite Pipe
DUST, HVAC CONTAMINATION STUDY
ELECTRIC MOTOR OVERLOAD RESET SWITCH
EVAPORATIVE COOLING SYSTEMS
FAN LIMIT SWITCH
GAS EXPOSURE EFFECTS, TOXIC
GAS DETECTION INSTRUMENTS
HEAT LOSS (or GAIN) in buildings
HEAT LOSS (or GAIN) INDICATORS
HEAT LOSS R U & K VALUE CALCULATION
HEATING SMALL LOADS
INSPECTION CHECKLIST - OUTDOOR UNIT
INSPECTION LIMITATIONS, A/C SYSTEMS
LEED GREEN BUILDING CERTIFICATION
LOST COOLING CAPACITY
LOW VOLTAGE TRANSFORMER TEST
MOTOR OVERLOAD RESET SWITCH
MOLD in AIR HANDLERS & DUCT WORK
OPERATING COST, AIR CONDITIONER
OPERATING DEFECTS, AIR CONDITIONING
REPAIR GUIDE, AIR CONDITIONERS / HEAT PUMPS
REPAIR & DIAGNOSTIC FAQs for A/C
THERMOSTATS, HEATING / COOLING
THERMOSTATIC EXPANSION VALVES
WATER COOLED AIR CONDITIONERS
WINDOW / WALL AIR CONDITIONERS
WINDOW / WALL A/C SUPPORTS
Duct vibration dampeners or "vibration dampers": This article, part of our series "How to Inspect the Central Air Conditioning or Cooling System" describes the vibration damper (vibration dampener or vibration isolator) connecting the air handler unit supply plenum to the building supply duct and cites cases of asbestos-containing air conditioning or heating duct work that could send asbestos fibers into building air.
Green links show where you are. © Copyright 2013 InspectAPedia.com, All Rights Reserved. Author Daniel Friedman.
Thanks to reader Kenneth Meichtry, Building Maintenance Superintendent at General Services Agency, San Luis Obispo County, CA,for pointing out that the correct term for the HVAC component we illustrate here is vibration dampener.
A vibration dampener is a device designed to absorb rather than transmit vibration. In the case of heating furnaces and air conditioners, mechanical vibrations that occur in the air handler would be transmitted as annoying sounds throughout the building if a vibration dampener were not installed between the air handler unit itself and the metal ductwork to which it is connected. It would be equally accurate and more descriptive to refer to this device as a vibration isolator since what it's doing is isolating vibration in the vibrating part to avoid transmitting the vibration and thus annoying noise to other parts of the HVAC system or into the building.
On an air handler system or "blower unit", a fabric, currently often made of rubberized material, is installed as the vibration dampener. Vibrations in the air handler move the fabric without being transmitted into the metal ductwork.
In these articles we may include the less correct term "vibration damper" because it is very widely used among HVAC trades workers and because we want online searches for this noise-reducing component to enable our article to be found using either term: vibration damper or vibration dampener.
An additional HVAC noise source is of course an absent vibration dampener or one that is improperly connected or constructed. For example we observed an air handler connection to the supply duct trunk that had so little clearance space between the steel components that even though a vibration dampener had been squashed into that space, vibration and noise from the air handler was being transmitted to the duct system and into the building.
Inspect the vibration dampener to see that it is intact, not torn or damaged. If the blower is running you may feel air leakage around the damper if it is damaged or not properly installed.
Note that air blowing out of leaks in the HVAC supply duct system as well as air blowing into leaks in the return duct system can be a source of noises in the system including hisses, whistles, etc.
On older furnaces and some air conditioning systems you may see a white woven fabric used for the vibration damper material. It is possible that this material was made of asbestos fabric [better photos wanted].
Colors of asbestos vibration dampener cloth: If the vibration damper fabric is white or white-gray (un-coated asbestos fabric) or possibly silver (aluminized coated asbestos fabric) and woven of a coarse-woven fabric it may be an asbestos material, typically containing chrysotile asbestos fibers in a high percentage.
Look at the lower left corner of our close up photo of a silver-colored asbestos vibration damper at a warm air furnace (photo above right). See that little black round spot above the "D" in "Daniel" of our © notice?
That's where a technician has made a hole in the asbestos damper material in order to insert a thermometer to sense air temperature. The fibers released by such minor damage are probably below the limits of detection.
It is easy to distinguish asbestos fabric in the vibration dampener from other common damper materials which have been used as other fabrics are more finely woven (see photos on this page) and may be rubberized or coated canvas or on newer systems, vinyl-coated synthetic fabric.
Reports of actual asbestos lab tests of asbestos cloth vibration dampers confirms their composition:
The photograph of an asbestos cloth HVAC duct vibration damper shown at left, courtesy Jason Lee, was confirmed by Mr. Lee as containing 65% chrysotile asbestos.
OPINION-DF: Further testing or inspection may be in order, since if indeed asbestos material was used at this location, and especially if it is damaged, it could release asbestos fibers into building air. Do not tear, cut, or damage the material during your inspection.
If the vibration damper is missing, torn, leaky, or is made of asbestos, we recommend that it be replaced with modern materials. In some cases it may be less costly to simply replace an asbestos-suspect vibration damper than to pay to have it tested.
However if you want to test the vibration damper fabric, look inside the return plenum to the inside
of the fabric. Often we can find an individual thread sticking up above the metal clamp securing the fabric to the metal
plenum sides, easily clipped with no damage to the fabric itself.
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