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This article explains how to use the Wisconsin Protocol for cleaning air conditioners & heat pumps to avoid Legionella bacteria in air conditioners, how to clean air conditioning systems, Legionnaire's disease prevention & cleaning suggestions for air conditioning equipment and condensate trays, including condensate piping, traps, drains,
condensate pumps, and concerns for mold, Legionella bacteria, and other hazards associated with air conditioning
systems, cooling towers, and evaporative coolers.
This is a chapter of our
full document describing the inspection, maintenance, and repair of residential air conditioning systems (A/C systems) to inform home buyers, owners, and
home inspectors of common cooling system defects.
Comments and Advice on use of the Wisconsin Protocol for Cleaning A/C Equipment
The Wisconsin protocol for cleaning air conditioning condensate trays includes "This procedure calls for an initial shock treatment with 50 ppm free residual
(total) chlorine, addition of detergent to disperse bio-fouling, maintenance of 10 ppm chlorine for 24 hours,
and a repeat of the cycle until there is no visual evidence of biofilms.
To prevent exposure during cleaning and maintenance, wear proper personal protective equipment: a
Tyvek-type suit with a hood, protective gloves, and a properly fitted respirator with a high-efficiency particulate
(HEPA) filter or a filter effective at removing one-micron particles."
There is some suggestion that using chlorine products is more likely to damage the equipment by corrosion.
For example simply pouring bleach will produce chlorine gas and will corrode nearby aluminum fins on an evaporator or condenser coil.
This is a well known problem and there must be a collection of standard products offered to the HVAC industry.
OSHA's technical manual re Legionnaire's disease and has some (incomplete) details "disinfecting the cooling tower system
according to the Wisconsin Division of Health protocol for "Control of Legionella in Cooling Towers" or a similar process for
cleaning heat rejection systems that follows sound practices to minimize potential for Legionella growth."
A section in this document discusses the use of commercial biocides (looks questionable), traditional oxidizing agents (chlorine),
or bromine (effective and less corrosive).
In the case of Legionella, other measures like temperature control and cleaning frequency are cited as also important.
I would look for a disinfectant that would be broad spectrum but which also is assured not to damage the equipment,
maybe a bromine product.
Some history behind the "Wisconsin protocol" for cleaning air conditioning condensate trays may be in order.
By coincidence my associate Craig Balchunas (Poughkeepsie, NY) returned from a one day class on Legionella
where he spoke with one of the original contributors to the "Wisconsin Protocol".
He informs me that the protocol was an "off the cuff" exercise by a group of professionals in response to an
urgent protocol request from the Wisconsin DOH, that the protocol has not been tested scientifically, and that
there may be problems with corrosion damage to equipment when the protocol is followed.
Therefore we add that for any disinfection using corrosives (as I anticipated in my comment below)
since there is risk of damage to the equipment, you'll need to wash the disinfectant off thoroughly at the end of the procedure.
We also discussed UV lights as a disinfection method - a method I view with skepticism for
several reasons including questions about adequacy of exposure time in air systems and similarly,
because some pathogens find intermediate hosts (such as Legionella bacteria hiding in an amoeba) which protect them as they pass through the UV system.
At the end of the day, regular inspection and cleaning and control of blow-by of unwanted condensate droplets are what make the most sense to me.
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Thanks to Mark Cramer, Tampa Florida, for assistance in technical review of the "Critical Defects"
section and for the photograph of the deteriorating gray Owens Corning flex duct in a hot attic. Mr. Cramer is a Florida home inspector and
home inspection educator.
http://www.osha.gov/dts/osta/otm/otm_iii/otm_iii_7.html is OSHA"s technical manual re Legionnaire's disease
US EPA Safe Drinking Water Hotline: 800-426-4791
"Legionella in NY - How to Conduct a Legionella Risk Assessment", Mark Hodgson, LSC, Naperville IL & Diane Miskowski, MPH, EMSL Analytical, Inc., Westmont NY, Crown Plaza, White Plains, 8 May 2007. Course description:
"Guidelines for the control of Legionella in critical care hospitals in New York have been in place for two years. In October 2006, these guidelines
were extended to include nursing homes and long term care facilities. Join us for this 8 hour seminar to learn all you need to know to conduct
a Legionella health risk assessment, control it in your facility, and remediate it. This course will describe the ecology of the [Legionella] organism,
the epidemiology of the disease [Legionnaire's disease], a discussion of some recent outbreaks, and the proper sampling methods and analysis
of the bacteria. A significant amount of time will be spent discussing how to actually perform a Legionella risk assessment, and an
overview of cooling towers and potable water system design and how that contributes to growth of the [Legionella] organism. Discussion
will include where Legionella can be found in the engineered environment, and the use of biocides and other controls." -- Thanks to Craig Balchunas, AHI Accurate, LLC., a home inspection firm in Hyde Park, NY. - (800) 360-3998
"Legionella", a public information poster provided free by LA Testing, an California environmental testing lab - www.LATesting.com.
Thanks to Jon Bolton, an ASHI, FABI, and otherwise certified Florida home inspector who provided photos of failing Goodman gray flex duct in a hot attic.
Carson Dunlop, Associates, Toronto, have provided us with (and we recommend)
Carson Dunlop Weldon & Associates' Technical Reference Guide to manufacturer's model and serial number information for heating and cooling equipment ($69.00 U.S.).Thanks to Dave Burley, State of Vermont, for correspondence on this matter, 5/10/2007
Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 25th Ed., 2012, is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. Field inspection worksheets are included at the back of the volume. Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
Or choose the The Home Reference eBook for PCs, Macs, Kindle, iPad, iPhone, or Android Smart Phones. Special Offer: For a 5% discount on any number of copies of the Home Reference eBook purchased as a single order. Enter INSPECTAEHRB in the order payment page "Promo/Redemption" space.
Carson Dunlop, Associates, Toronto, have provided us with (and we recommend) Carson Dunlop Weldon & Associates' Technical Reference Guide to manufacturer's model and serial number information for heating and cooling equipment Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on any number of copies of the Technical Reference Guide purchased as a single order. Just enter INSPECTATRG in the order payment page "Promo/Redemption" space.
"Air Conditioning & Refrigeration I & II", BOCES Education, Warren Hilliard (instructor), Poughkeepsie, New York, May - July 1982, [classroom notes from air conditioning and refrigeration maintenance and repair course attended by the website author]