“Healthy Environment, Healthy People” · “Healthy Environment, Healthy People” Results following Trial of High Intensity Ultra Violet Germicidal Irradiation for HVAC For Wellhouse
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The objective for this trial was to reduce the high level of microbial pathogens within the HVAC
system.
In order to help achieve this aim, UVC Emitters were installed into the above air handling unit on 17
July 2014 and Petri dish samples were taken from the coil surface of the AHU pre and post
commissioning of the UVC: pictures of the results are included in section 2 of the document. We
have also included details of the independent microbial testing results carried out by Tecomak
Prior to switching on the UVC, various measurements were taken related to the performance of the
AHU and these were repeated on 18 September 2014. The measurement process was carried out
using identical performance settings on each occasion, although the humidity and ambient air
temperatures were not the same, which limits the accuracy of data comparison from an energy
saving perspective.
Executive Summary After only 2 months of exposure to UVC, the key findings have been: Virtual elimination of mould from the cooling coil Petri dish samples have been taken from the coil surface before and after installation of UVC for comparison purposes and demonstrate the virtual elimination mould growth on the post UVC sample. The benefits realised by introducing UVC are:
Destroys mould and bio-film on coil surfaces
Destroys 99% of viruses and bacteria passing through the coil
Reduction in staff absence levels and improvement of patient care
Eliminates cooling coil maintenance, saving labour and associated material costs
Non-mechanical duct cleaning – Reduces mould in ducts, by destroying the food source
Increases the life of the coil by removing invasive cleaning methods
Extends the life of high performance (HEPA) filters downstream of the UVC
Reduces load on compressors and extends their life
Reduced pressure drop across the cooling coil There has been a 15% reduction in pressure drop across the surface of the cooling coil, which indicates that the obstruction caused by biofilm build-up on the coil components has been removed, allowing air to pass more freely through the air handling unit (AHU) and increasing the heat transfer efficiency of the unit. The following benefits will result:
Reduction in power required to drive fan motor
Reduction in compressor running hours (reducing compressor maintenance expense) (This will only be realised when all AHU’s supplied by the compressor have been treated with UVC)
Return the HVAC system back to “as specified” performance
Because the ambient air temperatures were not identical during the pre and post UVC visits, it has
not been possible to use Steril-Aire’s lifecycle tool to gauge a specific return on investment based
on energy savings. The temperature was over 28 ͦ C on the pre UVC visit and it may be difficult to
find a suitable time to replicate this, but, should you wish us to revisit the site to repeat the tests
with similar conditions, we will need to arrange this next year during the summer months.
Our experience with other clients is that a Return on Investment (ROI) can usually be achieved in
less than 24 months purely from an energy and maintenance saving perspective. Taking into
account health related benefits, the ROI is often achieved in under 12 months.
A snapshot comparison from the BMS with a similar AHU where UVC has not been installed has
been made, which shows the following improvements in performance.
Reading AHU 04 1/2/3
No UVC
AHU 03 4/5/6 UVC Installed
(July 2014) Difference
Pre Cooling Coil Temp ( ͦ C) 19.4 19.6 0.2
Off Frost Coil Temp ( ͦ C) 18.6 17.6 1.0
Frost Battery Temp ( ͦ C) 8.0 10.0 2.0
The AHU with UVC has a coolant supply temperature 2 degrees higher than the non-UVC AHU, but
has reduced the air off temperature by 1 degree more. Please see images below.
The NHS employs more than 1.7m people and treats over 1m patients every 36 hours. The 1st quarter absence figures for 2014 show a rate of 4.26%, which equates to approximately 10 days absence per person. A 1% reduction in absence would save the NHS over £22m per annum and introduction of UVC into the air conditioning system has shown reduction in absence rates of over 10%. Added to this is the significant cost of hospital acquired infections. The relatively low cost of installing UVC into an air handling unit would pay for itself, if it prevented a single patient from suffering from an infection.
NHS Absence Level Jan to March 2014 Report shows average absence level of 4.26%!
Health & Safety – Statutory Duty Companies have a statutory duty to provide a safe place to work and healthy working environment for all of its employees, including those employed on a temporary basis. Recirculation of air compromises this situation.
o “Airborne infectious particles can be disseminated through buildings including ventilation systems.”
o “Airborne infectious disease transmission
can be reduced using dilution ventilation, specific in-room flow regimes, room pressure differentials, personalised and source capture ventilation, filtration, and UVGI.”
Air Conditioned Environments Impact the Health of Building Occupants
o A study of 770 office staff found people
working in air-conditioned offices accounted for 17% of days off work compared with 9% in non air-conditioned buildings
* Air conditioning Air conditioning can use a huge amount of energy. In
fact, air conditioning can increase a building's energy
consumption and associated carbon emissions by up to
100%.
Key Cost Reduction Factors of Installing UVC Lights
No more manual cleaning of coil and drain pans with harmful chemicals and disinfectants
Returns coil capacity to “as built” Destroys mould, bacteria, and viruses, providing a healthier work environment Saves maintenance labour and associated material costs Reduces mould in ducts, by destroying the mould food source Increases the life of the coil by removing invasive cleaning methods Reduces load on compressors and extends their life Where used, extends the life of high performance filters downstream of the UVC
Images of Cooling Coil Pre UVC Emitters Post UVC Emitters
Bio pollutants cover metal surfaces with a thin, almost invisible layer of permeable materials, which can be impregnated with millions of tiny microscopic spores. This bio-mass can lead to a musty earth-like smell sometimes known as “Dirty Sock Syndrome”, a primary cause of offensive odours. Microbial growth on fin surfaces acts as insulation on the evaporator coils, which decreases system efficiency, and the pollutants are known to produce allergy-like symptoms, (refer to Section 4 – Indoor Air Quality for further information). Fouled coils generate an increase in the pressure drop across them, which, in turn, leads to increased fan kWh requirements and electricity consumption.
Introduction of UVC emitters will save between 10-20% of the energy required to run air conditioning. Biofilm can accelerate oxidation and corrosion of the cooling coil that is often caused by sulphuric acid secreted by common bacteria, significantly reducing HVAC equipment life. Removal of biofilm with UVC not only brings the HVAC equipment performance to the original equipment specification, it also prolongs the time frame for HVAC equipment replacement and capital investment.
Example of Contamination A badly contaminated coil was removed from its HVAC unit, taken outside and cleaned with high pressure hot water.
The coil was cut in half and you will notice that, although the outside edge of the coil is clean, the mould has been pushed towards the centre, reducing further the space for air to flow through the coil. Mould is a poor conductor and inhibits the heat transfer capability of the coil.
COIL INEFFICIENCY FROM biofilm & mould CONTAMINATION
HVAC EfficiencyDegradation caused by build up of Biofilm
Source: California Society for Healthcare Engineering May/June
The heat conductivity of aluminium is approximately 200 W/mK while that of biofilm is approximately 0.2 W/mK. As conductivity has fundamental implications on heat transfer, clean coils devoid of biofilm offer significant efficiency advantages. The limit of human visibility is 30 microns, so biofilms on coil surfaces are often not seen until they get to 50 - 150 microns thick. This means coils can look clean even when there is
contamination present.
American Society of Heating Refrigeration and
Air Conditioning Engineers
“Good maintenance including coil cleaning can
significantly improve energy efficiency and IAQ
performance of the HVAC&R systems in a building,
such as reported here of 10% to 15%.”
As a result of the non-invasive and thorough cleansing process that is attributed to UVC light, the delicate radiator fins of the cooling coil will not need to be subjected to harsh cleaning chemicals or power washing and will have their effective lifespan prolonged. UVC light penetrates right through the coil to the opposite side ensuring all elements of the external coil surfaces are constantly cleansed.
Water Conservation Air conditioning systems produce a lot of water, which is normally full of pollutants and is, consequently, ejected into the sewage system. Where it has been possible to install Steril-Aire’s UVC EmittersTM over the drain pan, the water is automatically purified and can be recycled for applications such as, cooling tower make up, irrigation systems, and internal “grey water” use.
Recycling HVAC Condensate Saves Money Increase condenser water supply temperature requiring less chiller energy per
ton of cooling Each °C increase of chilled water supply temp. can reduce chiller kW by 1 to 4% Improved chiller operating performance as the load is reduced Reduce trade effluent charges
1. Steril-Aire Emitters have been independently tested against all known competitors and the
results show that at standard AC operating temperatures, the Emitters are 5 times more powerful than the competitors’ UVC lamps. At the end of 1 year Steril-Aire’s Emitters are still 2.5 times more powerful than the competitors’ starting energy and come with one year’s warranty. Our UVC lamps do not generate OZONE. Crucially, the lamps will be installed at a suitable close proximity to the coils, (as per Steril-Aire’s registered Patent), to ensure full irradiation of the coils and to maximise efficiency of the UVC light in sterilising the airflow.
2. The UVC light package consists of a Power supply and housing specifically engineered for HVAC applications, manufactured to ISO Standard 9001:2000. The base is made from quality 304 stainless steel, to provide strength and to be rust-proof, and the top lamp support is made from a high quality polished specular-aluminium, which reflects the back part of the Emitter’s light out onto the coil, (providing significantly more light than stainless steel). “Plenum rated” wiring is UV stabilised and waterproof. The lamp plugs are fitted with boot kit protectors sufficient for up to 99% humidity). Emitter tubes are made from high quality SiO2 quartz crystal to ensure maximum irradiance. Optional Sleeved Emitters are hermetically encapsulated in a plastic sheath precluding glass contamination in the event of breakage. The sleeve comprises a highly engineered FEP resin coating of no less than 0.25mm thickness.
3. Power supplies are water resistant, internally grounded, will accept power at 50 or 60 hertz from 115-230 volts, are sound rated A, and have an operating temperature range of -18° to 50°C, plus a 5 year usage related warranty.
4. Air handling unit access doors will need to be fitted with mechanical interlock switches, factory wired to the UV disinfection package controller, to ensure that all UVC assemblies will be de-energized when any of the access doors are opened.
5. Radiometer controller kits can be installed (at additional cost) to enable the remote monitoring of the strength of UVC lamps in order to optimise tube replacement.