Introduction
The penetration of Steril Aire into the coils goes to the heart of the understanding of Steril-Aire, its potential
and its effectiveness.
Granted that it is somewhat hard to get your head around how a light can travel through coils however the
results (peer reviewable) establish that this is in fact happening.
Ironically Steril Aire has consistently been proven in its ability to unblock coils where ALL other measures had
failed. In fact, it can and has been selected purely on its ability to unblock coils.
It is this unblocking and cleaning of a coil which is central to Indoor air quality and energy savings.
You cannot have Indoor Air Quality benefits without also achieving energy savings benefits when it comes to
coils. When coils are coated in Bio Film you will have poor heat transfer AND decreased air quality.
Relevant observations
1) UVC is invisible. The blue light is not UVC. You cannot stand on the air on side and see an invisible light
source.
2) The creators of Steril Aire spent 10 years trying to make Steril Aire work in the HVAC environment
before marketing it. In order for it to work they must penetrate the coil and clean all bio film on the
entire coil.
3) The Steril Aire product is patented because of its very high output @ 253.7 nanometres. This is the
secret to its ability to perform the job.
4) At 253.7 nanometres UVC has been scientifically proven to destroy DNA. Biofilm is made up of DNA
5) Bio film “attaches “to the coil surface and this supports the build-up of dirt etc. Steril Aire breaks down
the bio film allowing the bio film and dirt to fall away. This is how it cleans both Bio Film and dirt
( have a look in a condensate tray about a month after Steril Aire has been switched on and you will
see what I mean !!!)
6) Steril Aire returns coils to design conditions. Pre-testing shows that they typically are not at design
conditions, and this means they are inefficient. If a unit is 100KW and is not performing at design, it
will only offer the cooling capacity available eg 60 KW. This loss in capacity = more work for the
chillers to get the same effect= more energy consumed. Design conditions = a new installation= less
energy consumed
The scientific symptoms of a blocked / energy inefficient cooling coil.
- Reduced airflow. Airflow will be governed by the area of the coil which has the greatest blockage (build-up of
Biofilm) whether it is at the front, middle or back part of the coil. Biofilm will grow throughout the coil depth but
typically manual coil cleaning from both sides will push the biofilm deeper into the coil creating a blockage in the
centre of the coil. - Reduced cooling capacity as heat transfer is restricted by the biofilm build-up.
- Greater pressure drops measured between the air on and air off side of the coil
- Reduced chilled water Delta T’s measured by chilled water entering the coil and leaving the coil. A reduced Delta T
means that the biofilm blocking the coil is reducing heat transfer (The coil cannot extract heat from the air).
1-4 above can be clearly scientifically measured and this was done at Pacific Fair. This is one of the benefits of this product
from my perspective as it can be scientifically measured and you simply cannot create positive changes in these conditions
without also establishing energy saving claims.
Blocked Coil Case Study
Oasis Shopping Centre- Unblocking coils 300 mm thick on a 275 KW AHU
Sterl Aire was brought in after ALL attempts at restoring a coil were utilised.The AHU was going to removed
and a new one installed if Steril Aire didn’t work.Independent consultants created a contract which became
the basis of the PO. Essentially if they didn’t succeed they would not get paid
The independent consultant (Peter Lang) carried out the testing before Steril Aire and the testing after.
- 275 kw AHU with 2 coils approximately 300mm deep
- Steril-Aire was installed in January 2011.
- AHU 1.3B Original Design Airflow was 12315 l/s
- Independent Testing showed AHU was delivering 5816 l/s prior to the Emitters being switched on
(approx. 47% of design). - Objective was to achieve 70% design in 90 days.
- Steril-Aire achieved this in 60 days.
- AHU was not replaced and Steril Aire were paid
Page4
Penetrating coils and energy efficiency
Auckland Airport- Penetrating through the heating coils to clean the cooling coils
Auckland Airport provides an excellent insight into this issue and generally into Steril Aire. The
installation meant that Steril Aire needed to penetrate the heating coils BEFORE it could do its job on
the cooling coils. The results speak for themselves, enabled the Airport to receive a prestigious
energy saving award and were peer reviewed. It is important to note that this site was all about
energy savings.
Sent: Tuesday, 9 October 2012 1:40 PM
To: ‘Malcolm Cain’
Subject: RE: Steril-Aire UVC Technology
Hi Malcolm,
Apologies for the tardy response.
I am happy to confirm that the requirement at Auckland Airport was for the UVC to penetrate
through heating coils to the cooling coils due to their configuration. The results speak for
themselves in terms of visual cleanliness of the coils, the plate counts and the resultant energy
savings. Verification of the savings from the trial installs was also undertaken by Ivan Fraser,
chartered engineer, who went back to engineering first principles to confirm Steril-Aire results were
accurate.
Let me know if you need anything further.
Kind regards,
Martin
Martin Fryer
Sustainability Advisor
martin.fryer@aucklandairport.co.nz
+64 27417 1563 +64 9 255 9096
aucklandairport.co.nz
Penetrating Coils- Nambour Hospital
Nambour hospital had tried every method to clean the coils and was about to replace the coil in the unit
referenced below (as is standard without Steril Aire). This again shows the correlation between blocked coils
and energy performance.
The coil was 300 MM deep and the process was witnessed and verified by both the hospital and Haden Group.
Explanation of Energy Saving- Summary
Explanation of Energy Saving- Summary
By keeping the cooling coils free of bio-film, heat transfer efficiency is at its optimum and the air conditioning
plant will perform as designed. Better efficiency at the cooling coils means that the occupied space
temperature and humidity are achieved faster reducing the chiller or compressor run times
Pacific Fair Case Study
A study published in the ASHRAE Journal in 2006 concludes that “coil fouling increases coil pressure drop and reduces
airflow, reducing heat transfer from coil fins to lessen the amount of work a system can perform and reducing indoor
environmental quality”.
Source: “Study Verifies Coil Cleaning Saves Energy” by R. Montgomery
Pacific Fair Case Study
Continuous irradiation of cooling coils with Steril-Aire EmittersTM results in very clean cooling coils with high heat
transfer efficiency. This helps to achieve high chilled-water ΔTs.
Once high chilled-water ΔTs are realized, more tonnage of cooling will be accomplished per m³ of chilled-water
distributed
ΔT Results @ Pacific Fair
| Unit | Location | No Steril Aire | Steril Aire | % improvement |
| AHU 6 | Zone D | 3.90 deg C | 5.40 deg C | 38 % |
| AHU 5 | Zone D | 5.50 deg C | 7.90 deg C | 44 % |
| AHU 3 | Zone D | 6.60 deg C | 9.20 deg C | 39 % |
| AHU M2 | Arcade | 8.36 deg C | 11.02 deg C | 32 % |
| AHU M5 | Arcade | 7.81 deg C | 10.66 deg C | 36 % |
| AHU 38 | South West | 5.90 deg C | 10.41 deg C | 76 % |
| AHU 1 | South West | 6.73 deg C | 10.04 deg C | 49 % |